ENVIRONMENTAL LETTERS , 9 ( 4 ) , 355-378 (1975)
ARE NUCLEAR SHIPMENTS REALLY SAFE?
William A. Brobst Division of Waste Management and Transportation U.S. Atomic Energy Commission Washington, D.C. 20545 ABSTRACT The transportation of nuclear materials is on t h e increase.
Although
nuclear shipments a r e only a very small f r a c t i o n of the Nation's hazardous materials shipments, they a t t r a c t a g r e a t deal of public a t t e n t i o n .
Ship-
ments of spent nuclear fuel and nuclear wastes a r e a p a r t i c u l a r concern. One of the many f e a r s t h a t people have about nuclear energy i s the p o s s i b i l i t y t h a t a nuclear shipment might scinehow go awry and c a G e a serious public hazard.
Primarily, they a r e worried t h a t a shipment o f
spent r e a c t o r fuel o r highly radioactive waste could be involved i n a serious r a i l or highway accident and dump i t s contents a l l over the countryside. Is t h a t r e a l l y possible?
How s a f e a r e those shipments? How many a r e
there? What do they look l i k e ? Are the packages tested? These and o t h e r Since public risk is the product of
questions a r e answered i n this paper.
the consequences of an accident and i t s probability, both aspects a r e presented so t h a t each of us can make up his own mind whether the risk from nuclear shipments is acceptable. INTRODUCT~ON
We live i n a world of hazards.
We a r e surrounded by t h r e a t s t o our
health, our welfare, and our economy. Amongst the many hazards we face is 355 Copyright 0 197s by hlnrcrl Dekkrr, InC. AII Rights Reserved. Neither this \Wrk 1101 any pJrt m3y be reproduced or Lransniittetl in any form or hy any means. electronic or n~echmical.including photocopyinp. microfilming. and recording, or hy m y inforimtion storage and retrieval system, without prrmission in writinp from the publisher.
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BROBST
the one involving the transportation of hazardous materials.
One of the
hazardous materials w i t h which we must concern ourselves is nuclear material Public s a f e t y i n the transportation of hazardous materials has been the subject of increasing emphasis:
An a r t i c l e i n t h e May 1970 i s s u e of
the Reader's Digest s t a t e d , "Transportation of hazardous materials on our roads, r a i l r o a d s , and waterways is a major and growing problem.
One of
every ten trucks r o l l i n g toward you on t h e highway today c a r r i e s explosives, flamnables, o r poison.
[ll
Questions have a r i s e n i n numerous public hearings on nuclear reactor operations with regard t o t h e adequacy of p u b l i c s a f e t y in t h e transportat i o n of nuclear materials t o and from nuclear reactors and fuel reprocessing plants.
This .paper presents a sumarized s t a t u s r e p o r t on t h e potential
hazards of shipping those nuclear materials.
Since t h e r e have been no
serious releases of nuclear materials i n transportation accidents during the 25-year l i f e of t h e Atomic Energy Commission, the paper is based on a
theoretical analysis of accident risks. WHAT IS SHIPPED? Nuclear power will play an increasingly important r o l e i n meeting the Nation's energy requirements.
As nuclear power increases, the quan-
t i t i e s of nuclear materials which must be shipped will a l s o increase. The operation of nuclear power reactors will usually require the transportation of three d i f f e r e n t types of materials t o and from reactor facilities.
Unirradiated ("cold" o r "fresh") nuclear reactor fuel elements
a r e transported from fuel f a b r i c a t o r s t o t h e reactor.
Irradiated ("spent")
fuel elements and nuclear wastes a r e shipped from reactor f a c i l i t i e s t o fuel reprocessing plants and t o disposal s i t e s .
Also, the radioactive
products of the spent fuel reprocessing plants c o n s i s t primarily of recycled nuclear fuel materials shipped t o fuel f a b r i c a t o r s o r processors and both high-level and low-level waste shipped t o disposal s i t e s .
SAFETY OF NUCLEAR SHIPMENTS
35 7
Other shipments of r a d i o a c t i v e materials are made i n support of nuclear power p l a n t operations.
For example, uranium concentrate, produced
from uranium ore, i s shipped from uranium m i l l i n g p l a n t s i n the western United States t o uranium conversion f a c i l i t i e s f o r conversion o f t h e urani-
um
concentrate t o uranium hexafluoride.
Uranium hexafluoride i s shipped
t o one o f the Atomic Energy Comnission (AEC) uranium enrichment f a c i l i t i e s . The enriched uranium hexafluoride i s then shipped t o other p l a n t s which convert the material t o uranium oxide which i s then f a b r i c a t e d i n t o f r e s h reactor fuel elements. THe Department of Transportation (DOT) has estimated [ Z ] t h a t there are n e a r l y 1,000,000
packages of nuclear materials shipped each year.
About 95 percent o f the shipments i n v o l v e small q u a n t i t i e s o f nuclear i s o topes f o r use i n industry, medicine, a g r i c u l t u r e , and education.
By com-
parison, the t o t a l number o f shipments o f nuclear materials t o and from nuclear power p l a n t s i n 1971 probably numbered only a few thousand.
[31
By t h e year 2000, however, the numbers o f shipments t o and from nuclear power p l a n t s w i l l probably increase by a t l e a s t 100 and perhaps as much as 1,000.
[4] Shipments o f nuclear materials are n o t r e a d i l y distinguishable from
shipments o f other hazardous m a t e r i a l s being transported i n r o u t i n e comnerce.
They look l i k e ordinary shipments.
They are u s u a l l y handled
and loaded i n an ordinary manner, using ordinary f r e i g h t handling equipment. They are transported on a worldwide basis, l i k e o t h e r shipments, i n the cargo compartment o f an airplane, i n a closed t r a i l e r o r r a i l r o a d boxcar, on "low boys" over highway, o r on heavy duty f l a t c a r s by r a i l . They are n o t r e a d i l y distinguishable, b u t there i s a difference. Nuclear materials, l i k e many other materials, have hazardous properties. These p r o p e r t i e s must be considered i n the transportation o f nuclear materials-considered from the viewpoints o f possible r a d i a t i o n exposure t o people; contamination o f property, and o v e r a l l e f f e c t on the environment.
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BROBST
As a r e s u l t of the depth of research studies of t h e hazards and experience i n t h e handling of nuclear materials, t h e i r properties a r e b e t t e r understood than the hazardous properties of most other hazardous materials being transported i n f a r g r e a t e r volume. The packaging requirements f o r nuclear materials a r e designed t o I
provide a high degree of protection and s a f e t y f o r personnel and materials, during both normal conditions of transportation and severe accidents. PRINCIPLES OF NUCLEAR SHIPMENT SAFETY Protection of the public and the transportation workers from radiation during the shipments of nuclear fuel and waste is achieved by a combination of limitations on b o t h t h e contents (according t o the q u a n t i t i e s and types of r a d i o a c t i v i t y ) and t h e package design.
Because shipments move i n routine
c m e r c e , and on conventional transportation equipment, they a r e , therefore, subject t o normal transportation accident environments [5] j u s t l i k e other nuclear cargo.
The shipper has e s s e n t i a l l y no control over t h e likelihood
of an accident involving his shipment.
He does have control over the con-
sequences of accidents by controlling the package design, contents , and external radiation levels.
Safety i n transportation does not depend upon
special handling o r special routing. I n the transportation of a l l types of hazardous m a t e r i a l s , t h e r e i s a difference between potential hazards and r e a l i z e d damage.
For hazardous
materials, a system of protection is used t o reduce the likelihood of the potential hazard from becoming a r e a l i t y .
A highly developed and sophis-
t i c a t e d system o f protection has evolved f o r the transportation of nuclear materials.
T h i s system is based upon a simple p r i n c i p l e - i f a package
contains enough r a d i o a c t i v i t y ("Type Bit quantity) t o present a s i g n i f i c a n t risk of injury o r large property l o s s i f released, then the package ("Type B" package) must be designed t o r e t a i n i t s contents during severe trans-
portation accidents.
[5,6J Lesser q u a n t i t i e s ("Type A" q u a n t i t i e s ) do
not require as much protection, b u t s t i l l must be packaged i n high q u a l i t y
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SAFETY OF NUCLEAR SHIPMENTS
"Type A" packaging.
In addition, a l l packages (Type A and B) a r e required
t o completely r e t a i n t h e i r contents during normal conditions of transportation The basic principles of s a f e t y a r e t r a n s l a t e d i n t o the Federal Government regulations. GOVERNMENT REGULATIONS
The transportation of nuclear materials i s s u b j e c t t o t h e regulations of both the DOT [7] and the AEC.
[S]
The DOT Hazardous Materials Regula-
tions a l s o provide f o r s a f e t y i n shipment of other more routinely shipped hazardous materials-materials which a r e flammable, unstable, poisonous , explosive, o r corrosive.
The same basic s a f e t y standards governing s h i p -
ments of nuclear materials i n t h e United S t a t e s a r e i n worldwide hse through
the regulations of the International Atomic Energy Agency.
[9]
In addition, the packages must provide adequate radiation shielding
t o l i m i t the radiation exposure t o transportation workers and the general public.
For spent f u e l , the package must have heat dissipation character-
i s t i c s t o p r o t e c t against overheating from radioactive decay heat.
For
both f r e s h and spent f u e l , package design must a l s o provide nuclear c r i t ical i t y s a f e t y under both normal transportation and severe accident condi tions. Package designs a r e reviewed by t h e AEC prior t o use i n order t o verify the adequacy o f the design parameters.
I f i t appears t h a t the
package will, i n f a c t , meet the regulatory requirements, [7,8] the AEC will issue a c e r t i f i c a t e of approval for the package. SHIPMENT INFORMATION DOT regulations specify the type o f information which must appear on b i l l s of lading and o t h e r shipping papers. labeled appropriately. transporting vehicle.
Packages a r e required t o be
Warning placards generally must be placed on t h e T h i s puts the c a r r i e r and emergency personnel on
notice t h a t they a r e handlinq shipments o f hazardous goods.
I t alerts
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BROBST
them t o t h e f a c t t h a t a p p l i c a b l e s t a t e and l o c a l r e g u l a t i o n s and ordinances need t o be followed. Q u a l i t y Assurance The adequacy o f the package design can be compromised o r circumvented by e r r o r s which occur d u r i n g f a b r i c a t i o n , maintenance, o r use o f t h e package.
The person loading and c l o s i n g the package c o u l d make errors.
Perhaps
one o r more b o l t s c o u l d be l e f t o u t o r n o t p r o p e r l y tightened; a gasket c o u l d be misplaced o r omitted; a brace o r "holddown" p i e c e could be l e f t off.
The chances o f such an e r r o r a r e l i m i t e d because o f t h e procedures
r e q u i r e d by t h e r e g u l a t i o n s f o r examination o f t h e package p r i o r t o each shipment, i n c l u d i n g t e s t s f o r leak tightness, where necessary.
Redundancy
of s a f e t y features on t h e package w i l l reduce the consequences o f such operational e r r o r s , should they occur. Use o f the wrong m a t e r i a l s o r e r r o r s i n f a b r i c a t i o n a l s o could r e s u l t i n a package f a i l i n g t o f u n c t i o n p r o p e r l y d u r i n g transportation.
Adequate
q u a l i t y assurance programs increase the l i k e l i h o o d t h a t such e r r o r s would be detected and corrected, p r i o r t o use.
The r e g u l a t i o n s [8] impose certain
qua1 i t y assurance requirements on package manufacturers.
The shipper i s
r e q u i r e d t o determine t h a t each package meets the approved design s p e c i f i cations. Types o f Radioactive Waste D i f f e r e n t types o f r a d i a t i o n have d i f f e r e n t p e n e t r a t i n g a b i l i t i e s . For example, alpha p a r t i c l e s have a very s h o r t range i n a i r and cannot even penetrate a p i e c e o f paper; beta p a r t i c l e s t r a v e l over a l a r g e r distance, b u t can s t i l l be shielded completely by l i g h t , low-density m a t e r i a l s such as aluminum; gama rays r e q u i r e t h i c k e r o r more dense s h i e l d i n g m a t e r i a l s such as l e a d and s t e e l .
The c h i e f hazard t o human
beings from alpha m a t e r i a l s would be from d e p o s i t i o n o f the m a t e r i a l s w i t h i n the body, so s p e c i a l care must be taken i n containment o f the alpha wastes. Beta-gamma wastes a l s o r e q u i r e maintenance o f c o n t a i n e r s h i e l d i n g .
SAFETY OF NUCLEAR SHIPMENTS
361
There a r e several d i f f e r e n t types of materials which may be found i n nuclear wastes.
Nuclear wastes which a r e shipped around the country t o
various processing, storage, o r burial s i t e s f a l l i n t o three general categories:
(1) low s p e c i f i c a c t i v i t y (LSA) wastes; ( 2 ) high-level wastes;
and ( 3 ) other wastes. Low s p e c i f i c a c t i v i t y wastes a r e those which contain such low concent r a t i o n s o r q u a n t i t i e s of r a d i o a c t i v i t y t h a t they do not present any s i g n i f i c a n t environmental hazards.
Even i f they were released f r m t h e i r
packages i n a transportation accident, they would not present much hazard t o the public.
Like any o t h e r f r e i g h t s p i l l e d a t t h e scene of an accident,
they would have t o be cleaned up because of t h e i r nuisance value.
Under
U.S. and international regulations, they require only normal i n d u s t r i a l
packaging f o r shipment and require no special r a i l c a r s o r other t r a n s p o r t vehicles.
LSA wastes may include such t h i n g s a s residues o r solutions
from chemical processing; building rubble, metal , wood, and f a b r i c scrap; glassware, paper, and p l a s t i c ; s o l i d o r liquid plant waste, sludges, and acids; and s l i g h t l y contaminated equipment o r objects. Alpha wastes, high-level wastes, and o t h e r wastes contain s u f f i c i e n t l y large amounts of radioactivity t h a t they have a s i g n i f i c a n t potential f o r injury o r property damage i f released t o the environment during a transaccident.
For t h a t reason, DOT and AEC regulations require t h a t they be
packaged such t h a t , even i n the event of a severe transportation accident, there would be no s i g n i f i c a n t r e l e a s e of radioactive materials outside of the containers.
The packages (Type B packages) must then be strong
enough t o withstand the types of impact and puncture forces and f i r e e f f e c t s which a r e often encountered i n severe accidents. High-level wastes a r e those s o l i d i f i e d wastes from the reprocessing of highly i r r a d i a t e d nuclear reactor f u e l s .
These wastes have such a high
radioactive content of long-lived isotopes t h a t they require long-term storage i n i s o l a t i o n and e s s e n t i a l l y perpetual s u r v e i l l a n c e of the storage
36 2
BROBST
sites.
The r a d i a t i o n l e v e l i s h i g h enough t o produce considerable heat,
and the m a t e r i a l must be h e a v i l y shielded.
The most comnon type o f high-
l e v e l waste shipments w i l l be the s o l i d i f i e d (process) waste from the nuclear fuel reprocessing plants. be shipped t o waste storage s i t e s .
Only s o l i d m a t e r i a l s o f t h i s type w i l l Shipments o f high-level l i q u i d wastes
are n o t presently allowed by the DOT, and are n o t p r a c t i c a l due t o problems i n designing s a f e containers f o r b u l k shipment o f such l i q u i d s . Alpha wastes u s u a l l y c o n s i s t o f materials which a r e contaminated w i t h alpha r a d i a t i o n em1t t e r s such as plutonium o r o t h e r transuranium nuclides. They have very low l e v e l s o f penetrating g a n a r a d i a t i o n and so do n o t r e q u i r e heavy shielding.
Alpha emitters have the p o t e n t i a l f o r causing
contamination o f objects o r people i f released from t h e i r packages.
If
the amount o f nuclear m a t e r i a l exceeds c e r t a i n l e v e l s o f concentration, the -1pha wastes must be packaged i n Type B packages, b u t o f a d i f f e r e n t type than the very heavy high-level waste packages.
The emphasis i n
packaging f o r t r a n s p o r t a t i o n i s containment, w i t h several containment b a r r i e r s provided i n the packaging system. Other wastes are predominantly of the beta-gamma type (e.g.,
fission
product, i n d u s t r i a l isotopes) which u s u a l l y requires some s h i e l d i n g material as a p a r t o f the package.
This waste may a l s o be a combination o f LSA,
alpha, and beta-gama types.
Beta-gama waste includes such things as
i r r a d i a t e d r e a c t o r s t r u c t u r a l components, h e a v i l y contaminated objects, concentrated s o l i d i f i e d sludges o r evaporator bottoms , and nonrecoverable r a d i o a c t i v e f u e l scrap.
Because o f the presence o f considerable q u a n t i t i e s
o f nuclear material, packages o f these materials must a l s o be capable o f r e s i s t i n g severe accident. Package I n t e q r i t y Before a s p e c i f i c type o f Type A package i s approved by the AEC for shipment o f nuclear materials, i t must be capable of withstanding, without leakage, a series o f " t o r t u r e t e s t " which produce damage conditions com-
363
SAFETY OF NUCLEAR SHIPMENTS
parable t o the actual damage a package might encounter i n a hypothetical severe t r a n s p o r t a t i o n accident.
The accident damage t e s t sequence s p e c i f i e d
i n the DOT and AEC regulations includes a 30-foot f a l l onto a s o l i d uny i e l d i n g surface, followed by a 40-inch drop onto a 6-inch diameter piston, followed by exposure f o r 30 minutes t o a 1475OF f i r e .
A water immersion
t e s t i s a l s o required. This t e s t sequence represents the type of damage which might occur t o a package i n a high-speed t r u c k accident o r t r a i n derailment, causing the package t o impact on a hard surface (such as a bridge abutment) and then t o smash through wreckage o r onto rocks, and then t o be d i r e c t l y involved i n a 2-4 hour cargo f i r e , and then t o r o l l down i n t o a r i v e r !
The regulations
therefore o f f e r a very high degree o f assurance t h a t a package w i l l n o t breach under severe accident conditions.
A s p e c i f i c s a f e t y analysis r e p o r t must be prepared f o r each package type and evaluated by the AEC before use.
Only i f the packaging has suc-
c e s s f u l l y passed such rigorous evaluations does the DOT authorize i t s use.
A t present, there are several hundred d i f f e r e n t types o f r a d i o a c t i v e material package designs t h a t have been authorized, ranging i n s i z e from small packages weighing a few pounds t o massive casks weighing over 100 tons. Packaging methods Fresh Fuel.
A " t y p i c a l " package f o r a " t y p i c a l " [16] l i g h t water reactor
f u e l i s a c r a d l e assembly consisting o f a r i g i d beam o r "strongback" and a clamping assembly which holds a few f u e l elements firmly t o the strongback. The strongback i s shock-mounted t o a s t e e l outer s h e l l .
Fresh f u e l elements
might a l s o be shipped i n s t e e l boxes which are positioned i n an outer wooden box by a cushioning material.
These packages, a l s o w i t h a f e w fuel elements
inside, would b e about 2 t o 3 f e e t i n diameter o r cross section, and about
17 f e e t long.
They would weigh from 1,000 t o 9,000 pounds.
t a i n e r s are shown i n Figures 1 and 2.
Typical con-
BROBST
364
OUTER WOODEN BOX CUSHIONING MATERIAL
FIGURE 1 BWR FUEL ELEMENT SHIPPING CONTAINER (GE MODEL RA-I)
Spent Fuel.
Because i r r a d i a t e d fuel elements a r e highly radioactive, t h e i r
containers must be very heavily shielded.
A typical "cask" used f o r ship-
p i n g spent fuel would weigh between 20 and 75 tons.
I t would be constructed
o f thick steel walls f i l l e d with a dense shielding material such as lead,
tungsten, or depleted uranium. 2-18 BWR elements.
Each cask would carry 1-7 PWR elements, or
The casks would be generally cylindrical i n shape, and
perhaps 5 f e e t i n diameter and 15 t o 18 f e e t long.
A recently designed
cask of this type is shown i n Figures 3 and 4. The cask must not only provide radiation shielding, b u t must also provide the means to dissipate the large amount of heat (perhaps 75,000 BTU/hr) produced by radioactive decay.
Nater i s usually used i n the
central cavity as a heat medium or primary coolant to transfer the decay heat from the fuel elements t o the body of the cask.
The heat i s usually
dissipated by natural processes t o the a i r through f i n s on the surface of the cask.
For some o f the larger casks, a i r may be forced over the fins
by blowers t o increase the cooling.
In other casks, heat exchanges w i t h
cooling coils r u n n i n g i n t o the body of the cask l i t e r a l l y pumps the heat
o u t and i n t o the atmosphere.
Reliable, redundant systems are used where
365
5AFETY OF NUCLFAR SHIPMEXTS
a
w
za
L
a
B
366
BROBST
SAFETY OF NUCLEAR SHIPPIENTS
367
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such mechanical systems a r e r e l i e d upon t o ensure adequate cooling. High-Level Nuclear Waste.
[12)
A t the present time, the AEC is planning on
long-term storage of a l l high-level wastes from c o m e r c i a l fuel reprocessing plants a t a Federal waste repository o r engineered storage f a c i l i t y . Some intermediate level f i s s i o n product wastes may be f u r t h e r treated f o r separation i n t o high-level and low-level components, t h e former of which would be destined f o r shipment t o a Federal storage f a c i l i t y , and t h e l a t t e r f o r shipment t o c o m e r c i a l burial f a c i l i t i e s . Shipping containers f o r high-level waste shipments will be very similar i n t h e i r basic design t o t h e shielded casks routinely used t o ship spent fuel assemblies from a nuclear power plant t o a fuel reprocessing s i t e . Spent fuel i s very s i m i l a r i n i t s overall shipping c h a r a c t e r i s t i c s t o c a n i s t e r s of high-level waste i n t h a t i t is highly radioactive and generates I n both cases, t h e shipping casks would be, e s s e n t i a l l y
considerable heat.
the same type-large s t e e l casks, lined with lead, s t e e l o r uranium.
The
high-level waste a c t u a l l y will be i n a burial capsule o r c a n i s t e r w i t h i n the outer shielded cask.
The waste is i n e r t , i m o b i l e , s o l i d material
rrhich i s nonexplosive, noncombustible, and cannot t u r n t o gaseous form and become airborne.
These high-level waste casks would be transported by r a i l
on conventional heavy duty f l a t c a r s ,
Highway load l i m i t s , r a t h e r than
s a f e t y reasons, will r e s t r i c t highway shipments. No d e t a i l e d cash designs have y e t been submitted by industry f o r AEC approval, since shipments t o a storage f a c i l i t y w i l l probably not begin u n t i l the e a r l y 1980's.
Low-Level Nuclear Waste.
[18] Under the DOT regulations, [7] low level s o l i d
waste is packaged depending on the amount of r a d i o a c t i v i t y i n the package. Typically, the waste is s o l i d i f i e d i n a mixture of vermiculite and cement i n Type A s t e e l drums. 500 and 800 pounds.
When f i l l e d , t h e individual drums weigh between
I f t h e drums contain Type B q u a n t i t i e s of waste, the
drums would require the addition of a Type B "overpack" ( i . e . , protective
SAFETY OF NUCLEAR SHIPMENTS
369
outer packaging) t o provide accident protection f o r the drums.
Low s p e c i f i c
a c t i v i t y wastes o r Type A q u a n t i t i e s of waste may be shipped i n drums w i t h out protective overpacks. Alpha waste is shipped e i t h e r i n a l a r g e accident proof box
Alpha Waste.
o r i n a bundle of 55-gallon drums encased i n some s o r t of outer protective container t o p r o t e c t such materials from impact and f i r e .
Special r a i l r o a d
cars already constructed have been used t o transport the s o l i d alpha wastes t o a storage f a c i l i t y .
Other methods and modes of transportation may be
used i n the future. NUMBER OF SHIPMENTS
Pattern of Shipments. i n the e a s t .
Shipments would be nationwide, with the predominance
Reactor locations a s of Dec. 31, 1973, a r e shown on Figure 5.
Fuel processing plants a r e located i n New York, I l l i n o i s , and South Carolina. Fuel f a b r i c a t o r s a r e scattered throughout the e a s t .
Comnercial waste burial
s i t e s a r e i n New York, Tennessee, I l l i n o i s , Nevada, Washington, and Kentucky. Fresh Fuel.
Each year, on the average, about 1/3 t o 1/5 of the fuel i n a
reactor i s replaced w i t h fresh fuel. w i t h 6 t o 16 packages per truck.
Fresh fuel is usually shipped by truck,
About 6 truckloads of fresh fuel elements
would be shipped t o a reactor each year.
For 100 reactors, t h a t ' s 600
truckloads per year nationwide. Spent Fuel.
A t present, a l l shipments of spent fuel a r e made under "exclu-
s i v e use" arrangement, by truck o r r a i l . i n the future.
Some barge shipments may be made
There would be about 10 r a i l shipments o r 40 truck shipments
annually from each reactor t o a fuel reprocessing plant.
For 100 reactors,
t h a t ' s 1,000 r a i l shipments o r 4,000 truck shipments per year. Radioactive Waste from Reactors.
About 4,000 cubic f e e t of low level 'waste
per year would be shipped from a BWR, and about 1,000 cubic f e e t per year from a PWR.
Most of the shipments would be made by truck.
About 2,000
drums of radioactive waste would be shipped, w i t h about 40 t o 50 drums per
370
BROBST
W
I I-
371
SAFETY OF NUCLEAR SHIPMENTS
truckload, f o r about 45 truckloads per year f o r a BWR.
For a PWR, t h e r e
rrould be about 500 drums and 10 truckloads per year. RADIOACTIVE WASTE FROM REPROCESSING PLANTS Hiqh-Level Waste.
The first shipments of high-level waste from reprocessing
plants a r e not expected u n t i l about 1983. shipments a Year.
By 2000, there will be 260 shipments per year, f o r the
three reprocessing plants. Low-Level Waste.
By 1985, there will be about 25
[18)
Each reprocessing p l a n t i s expected to produce about
20,000 cubic f e e t of low level waste per year.
There would be about 700
truckloads each year f o r three reprocessing plants. Alpha Waste.
Each reprocessing plant is expected t o produce about 5,000
cubic f e e t of alpha waste per year.
T h i s would be about 30 r a i l carloads
o r 150 truckloads each year f o r three reprocessing plants. ACCIDENTS Accidents occur i n a range of frequency and s e v e r i t y .
Most accidents
occur a t low vehicle speeds, b u t the s e v e r i t y of accidents i s g r e a t e r a t higher vehicle speeds.
Most severe accidents generally involve some
combination of impact, puncture, and f i r e e f f e c t s .
Even i f the hazardous
nature of the cargo is not a f a c t o r , accidents often r e s u l t i n i n j u r y , death, and cargo o r other property l o s s due t o comon causes. Truck Accidents.
In 1969, motor c a r r i e r s reported [13] a t o t a l of about
39,000 accidents, 20,000 i n j u r i e s , and 1,500 deaths.
The injury r a t e i s
about 0.5 i n j u r i e s per accident, and'the death r a t e is about 0.03 deaths per accident.
The accident r a t e f o r hazardous materials shipments was
about 1.7 accidents per million truck miles. Assuming 100,000 truck miles per y e a r of transportation f o r each nuclear power p l a n t , there would be about 0.09 i n j u r i e s per year and 0.005 deaths per year per reactor.
Those deaths and injuries would be from
conventional o r common causes not r e l a t e d t o the radioactive nature of the cargo.
372
BROBST
1
The nonnuclear property damage r a t e i s about $2,000 per truck accident. With 100,000 truck miles per year per reactor, t h i s would b e an average l o s s of about $300 per year per reactor due t o nonnuclear causes. Rail Accidents.
In 1969, the r a i l industry reported [14] about 8,500
accidents, 23,000 i n j u r i e s , and 2,300 f a t a l i t i e s .
The accident r a t e f o r
r a i l accidents was about 1.4 accidents per million c a r miles. There were about 2.7 i n j u r i e s per accident and about 0.27 deaths per accident.
Assuming about 15,000 r a i l c a r miles per y e a r per reactor, there
would be about 0.06 i n j u r i e s and 0.006 deaths per y e a r per reactor, from conventional and common causes. Nuclear Materials.
To d a t e , there have been no i n j u r i e s o r deaths of ra-
diological nature due t o the transportation of nuclear materials.
[5]
There have been a few cases of truck drivers being k i l l e d o r injured as a r e s u l t of a c o l l i s i o n o r overturn of vehicles carrying nuclear materials. In none of these cases, however, was there any r e l e a s e of nuclear materials from Type 6 packages.
121
In recent years, DOT has recorded [2] an average of 40 t o 50 incidents per year involving the transportation of nuclear materials. these incidents involved Type A- o r exempt packages.
Almost a l l of
In about 2/3 o f these
cases, t h e r e was no nuclear material released from the packages.
In a few
percent of the cases, t h e r e was s i g n i f i c a n t contamination requiring cleanup, w i t h cleanup costs r u n n i n g i n t o the thousands of d o l l a r s .
ACCIDENT RISK Principle of R i s k .
The significance o f radiological hazards during trans-
portation of nuclear m a t e r i a l s can be properly evaluated only by considering together the consequences of accidents and the p r o b a b i l i t i e s of those accidents.
One could compare the risks o f transportation of nuclear materials
i n several ways.
For example, one m i g h t compare the p r o b a b i l i t i e s of s h i p -
ment accidents; [15,16] one m i g h t compare the average c o s t of accidents by
373
SAFETY OF NUCLEAR SHIPIENTS
each mode a f transportation; one m i g h t compare d i r e c t transportation c o s t s , However, a l l of these p a r t i a l measures
which includes insurance premiums.
f o r comparing risk may be combined i n t o a s i n g l e contingency risk c o s t f a c t o r which i s the product of the probability of experiencing an accident involving nuclear materials and the probable c o s t of such an accident i f i t occurs.
In l a t e 1972, the AEC completed a study [17] of this type of
CM-
parison f o r nuclear reactor power p l a n t transportation. Accident Records.
In estimating the radiation risk from accidents involving
shipments of nuclear materials t o and from nuclear power plants, one must consider:
(1) the frequency and the s e v e r i t y of accidents; ( 2 ) the l i k e l i -
hood of package damage o r f a i l u r e ; ( 3 ) the nature, amount, and consequences o f releases of r a d i o a c t i v i t y during an accident; and (4) the capacity of
coping with such releases. The environmental e f f e c t s [5] which m i g h t occur i n transporting nuclear fuel and s o l i d wastes resulting from t h e operation of a "typical" power reactor has been evaluated. of:
[17]
The risk analysis covers transportation
(1) fresh fuel from a f a b r i c a t i o n plant t o a r e a c t o r by truck; ( 2 )
spent fuel from a reactor t o a fuel reprocessing p l a n t by truck, r a i l o r barge; and (3) s o l i d wastes from a reactor t o a radioactive burial s i t e by truck o r r a i l . .The range of known distances between various s i t e s must be considered.
Estimates may be made of radiation e f f e c t s on t h e environ-
ment under normal conditions of transportation and f o r credible severe accidents.
The potential accidents may be analyzed i n terms of s e v e r i t y
and predicted damage, and the probable consequences of releases.
Finally,
by combining the p r o b a b i l i t i e s of accidents w i t h the consequences, the overall risk of transportation accidents may be estimated. Normal Conditions.
According t o the AEC analysis, [17] truck drivers and
f r e i g h t handlers would normally receive an average of about 0.2 t o 0.3 millirem per shipment of fresh fuel.
No member of the general public i s
374
BROBST
l i k e l y t o r e c e i v e marc than about 0.005 m i l l i r e m p e r shipment.
Most of
the general p u b l i c ' s exposure would be n o n r e p e t i t i v e i n t h a t no s i n g l e member o f the general p u b l i c would be exposed t o those dose l e v e l s more than a few times per year.
The m o s t t h a t any one member o f the general
p u b l i c might g e t during a year would then be perhaps 0.01 m i l l i r e m o r about 1/50,000 o f h i s annual p e r m i s s i b l e exposure.
For spent f u e l shipments and r a d i o a c t i v e waste, each t r u c k d r i v e r could receive as much as 30 m i l l i r e m p e r shipment.
A few members o f t h e
general p u b l i c c o u l d r e c e i v e as much as one m i l l i r e m per shipment, o r about 1/500 o f h i s annual p e r m i s s i b l e exposure. ACCIDENT PROBABILITIES
A study o f accident p r o b a b i l i t i e s [16] showed t h a t t h e frequency o f severe accidents f o r both t r u c k and r a i l shipments i s about one f o r each one hundred m i l l i o n t r u c k m i l e s o r r a i l c a r miles.
The p r o b a b i l i t y of
extremely severe accidents i s about 100,000 times less.
Considering t h e
t o t a l number o f t r u c k m i l e s o r r a i l c a r m i l e s i n v o l v e d p e r r e a c t o r and estimating the p r e d i c t e d accident response o f packages, the study 1161 shows t h a t the p r e d i c t e d l i k e l i h o o d o f serious leakage a r i s i n g from accidents i n v o l v i n g packages o f nuclear m a t e r i a l s t o o r from a nuclear power p l a n t i n any one year i s about one i n f i v e m i l l i o n .
By comparison, the l i k e l i h o o d
o f serious i n j u r y due t o an automobile accident p e r person per year i s about one i n 500. The study [16] a l s o shows t h a t , i n the t r a n s p o r t a t i o n o f nuclear m a t e r i a l s , the p r o b a b i l i t y o f i n j u r y o r death due t o common accident causes i s a t l e a s t 100,000,000
times g r e a t e r than t h e p r o b a b i l i t y o f i n j u r y o r death
due t o r a d i o l o g i c a l consequences. ' Correspondingly, t h e t o t a l p r o p e r t y and cleanup l o s s from nonnuclear common causes i n t r a n s p o r t a t i o n accidents i s expected t o be about $300, o r about 2,500 times g r e a t e r than t h e probable
375
SAFETY OF NUCLEAR SHIPMENTS losses from r a d i o l o g i c a l contamination.
The t o t a l expected average loss
from contamination i n t r a n s p o r t a t i o n per r e a c t o r y e a r i s about 12 cents.
CONCLUSION On the basis of the studies r e f e r r e d to, i t appears t h a t the p r o b a b i l i t y
of death, i n j u r y , o r massive p r o p e r t y loss due t o t r a n s p o r t a t i o n o f r a d i o a c t i v e m a t e r i a l s i s (1) determinable, (2) n o t zero, and (3) very small. I n p r o j e c t i n g the t o t a l accident p r o b a b i l i t y f o r t r a n s p o r t a t i o n o f r a d i o a c t i v e m a t e r i a l s t o and from nuclear power p l a n t s , i t seems obvious t h a t the r a d i o l o g i c a l consequences of t h e t o t a l accident spectrum w i l l be several orders of magnitude beJow the more comnon nonradiological causes.
I t further
appears t h a t r a d i a t i o n doses t o t r a n s p o r t a t i o n workers and the general p u b l i c during the normal course o f t r a n s p o r t a t i o n w i l l be l i m i t e d t o a small f r a c t i o n of the t o t a l permissible annual dose, and then o n l y t o an extremely small segment o f t h e population.
The various s t u d i e s show c l e a r l y t h a t
the l i k e l i h o o d o f a catastrophic nuclear t r a n s p o r t accident i s so i n f i n i tesimal t h a t , f o r a l l p r a c t i c a l purposes, i t can be c o n f i d e n t l y s a i d t h a t one w i l l never happen. The r i s k i s small, b u t i s i t acceptable? confronts people w i t h a m u l t i t u d e o f r i s k s .
And t o whom? Modern l i f e We d o n ’ t l i v e i n a r i s k l e s s
society, nor c o u l d modern technological s o c i e t i e s e x i s t on t h a t basis. Each person has h i s own idea o f what r i s k s a r e acceptable t o him.
The
p u b l i c apparently judges the convenience of a i r t r a v e l t o be worth t h e r i s k t h a t r e s u l t s i n 200 f a t a l i t i e s p e r year; the convenience of d r i v i n g an automobile i s considered worth much higher l e v e l s o f r i s k . are a f r a i d o f a i r p l a n e s b u t r i d e motorcycles. ments a r e n o t e s p e c i a l l y r a t i o n a l .
Some people
Sometimes the p u b l i c judg-
About 49 m i l l i o n Americans continue t o
smoke c i g a r e t t e s d e s p i t e t h e c l e a r warning o f r i s k t o t h e i r h e a l t h p r i n t e d on each package.
Others smoke h e a v i l y b u t take a v i t a m i n p i l l every day
t o s t a y healthy.
Many people are a f r a i d o f t h e p o t e n t i a l hazards o f nuclear
376
BROBST
power, b u t risk their necks every day i n t h e hazardous r e a l i t y of highway travel.
Some say t h a t risks which they choose t o accept a r e acceptable,
b u t risks which others f o r c e on them a r e not.
In each case, the accept-
a b i l i t y is most l i k e l y t o be based on subjective emotional reactions-"gut" feelings-rather than a logical analysis of accident data o r other actual I
experience.
Few of us a r e a f r a i d of being b i t t e n by a venomous snake, o r
being attacked by a rhinocerous, i n t h e middle of Washington, D.C.,
but
t h a t probability is a l s o (1) determinable, ( 2 ) n o t zero, and (3) very small. Certainly laws and regulations themselves will not guarantee risk-free transportation.
We a r e a l l aware of the potential risks i n nuclear matters
if s a f e t y i s not given the very close a t t e n t i o n i t deserves.
Transportation
accidents and their potential e f f e c t s on shipping containers have been well studied.
These studies continue.
I t i s precisely because of this perceived
risk t h a t the AEC has always imposed s t r i n g e n t and overlapping p r o t e c t i v e measures in t h e i r concept of "defense i n depth." "assurance" a s an absolute.
However, one cannot claim
No s a f e t y system can nor should it be expected
to guarantee complete s a f e t y of a few individuals who by very exceptional circumstances, peculiar h a b i t s , unusual customs, extreme deviations from the typical individual g e t i n t o d i f f i c u l t i e s .
Even the normal i n d u s t r i a l safety
limits f o r a v a r i e t y of hazardous s t r e s s e s provide only reasonable protection f o r typical workers, and no more than t h a t . We tend t o r e a c t t o t h e problem of risk by making choices based on the magnitude of the risk, a s we perceive i t , and the b e n e f i t s t o be gained from accepting the risk. The National Academy of Sciences has s t a t e d , "Whether we regard a risk a s acceptable o r not depends on how avoidable i t i s , and how i t compares w i t h the r i s k s of a l t e r n a t i v e options and those normally accepted by
industry.". As a result of the s t u d i e s which have been done, i t is t h e
SAFETY OF NUCLEAR SHIPMENTS
377
AEC's opinion [la] t h a t , with regard t o nuclear shipments: a.
We have enough f a c t s and f i g u r e s on the hazards t o allow a more object i v e evaluation of the risk a c c e p t a b i l i t y than we might derive s o l e l y from "gut" f e e l i ng.
b.
The risk of public catastrophe has been eliminated by s t r i c t standards, engineering design s a f e t y , and operational care.
Whatever the conse-
quences of an accident a r e , the public hazard will be mnageable, and t h e nuclear e f f e c t s will be small compared t o t h e nonnuclear e f f e c t s . C.
The long-term public burden of not transporting nuclear materials i s l i k e l y t o be higher than the risks of c a r e f u l l y controlled transportat i o n , considering the various options available.
d.
The likelihood of death, i n j u r y , o r s e r i o u s property damage from the nuclear aspects of nuclear transportation is thousands of times l e s s than t h e likelihood of death, injury, o r s e r i o u s property damage from more common hazards, such a s automobile accidents, boating accidents, accidental poisoning, gunshot wounds, f i r e s , o r even f a l l s - a l l things which we can control, b u t apparently have accepted a s a way of l i f e without much p u b l i c support f o r reduction of risk.
REFERENCES 1.
Robinson, D. , "Danger! Hazardous Materials i n Transit," Reader's Digest, May 1970.
2.
Grella, A. W., "Accident Experiences i n the USA Involving Type B Packaging," IAEA/SM-147/19, Seminar on Test Requirements f o r Packaging f o r the Transport of Radioactive Materials, Vienna, Austria, 1971.
3.
Heinisch, R. , !Transportation of &.clear Fuel Material i n the United States, Nuclear Assurance Corporation, Atlanta, Georgia, 1970.
4.
Oak Ridge National Laboratory, Siting of Fuel Reprocessing P l m t s and Waste Management Facitities, ORNL-4451 , Clearinghouse f o r Federal S c i e n t i f i c and Technical Information, Springfield, Virginia 22101 , 1970.
BROBST
37a
5.
Brobst, W. A., " T r a n s p o r t a t i o n o f R a d i o a c t i v e Waste-Worth I t s S a l t ? " T h i r d I n t e r n a t i o n a l Symposium on Packaging and T r a n s p o r t a t i o n of Radioa c t i v e M a t e r i a l s , August 1971 ; CONF-710801.
6.
Gibson, R., 1966.
7.
Department o f T r a n s p o r t a t i o n , Hazardous Materia2 ReguZations, T i t l e 49, Code o f Federal Regulations, P a r t s 170-189.
8.
Atomic Energy Commission; Packaging of Radioactive Materials f o r Transportation, T i t l e 10, Code o f Federal Regulations, P a r t 71.
9.
I n t e r n a t i o n a l Atomic Energy Agency, ReguZations for t h e Safe IR.ansport of Radioactive Materials, S a f e t y S e r i e s No. 6, 1967.
The Safe Transport of Radioactive Material, Pergamon Press,
10.
I n t e r n a t i o n a l Atomic Energy Agency, Notes on Certain Aspects of t h e Regulations, S a f e t y S e r i e s No. 7, 1961.
11.
Brobst, W. A. , "Tests on T r a n s p o r t Packaging f o r R a d i o a c t i v e M a t e r i a l s , " IAEA/SM-147/18, Seminar on T e s t Requirements f o r Packaging f o r t h e T r a n s p o r t o f R a d i o a c t i v e M a t e r i a l s , Vienna, A u s t r i a , 1971.
12.
Shappert, L. B. , e t al., A Guide for t h e Design, Fabrication, and Operation of Shipping Casks for &clear Applications. ORNL-NSIC 68, Clearinghouse f o r Federal S c i e n t i f i c and T e c h n i c a l I n f o r m a t i o n , Springf i e l d , V i r g i n i a 22101, 1970.
13.
Federal Highway A d m i n i s t r a t i o n , 1969 Accidents of Large Motor .Carriers of Property, Department o f T r a n s p o r t a t i o n , Dec. 1970.
14.
Federal R a i l r o a d A d m i n i s t r a t i o n , S m a q and Analysis of Accidents on Railroads i n the United S t a t e s , A c c i d e n t B u l l e t i n , KO. 138, U. S. Department o f T r a n s p o r t a t i o n , Washington, D.C. ; 1970.
15.
Leimkuhler, F. F., Trucking of Radioactive Materials: Safety versus Economy f o r Highway Trmsportation, The Johns Hopkins Press, B a l t i m o r e , Maryland, 1963.
16.
Brobst, W. A., "The P r o b a b i l i t y o f T r a n s p o r t a t i o n Accidents," Department o f Defense E x p l o s i v e s S a f e t y Seminar, November 10, 1972; a v a i l a b l e from D i v i s i o n o f Waste Management and T r a n s p o r t a t i o n , USAEC, Washington, D.C. 20545.
17.
Atomic Energy Commission, Environmental Survey of Transportation of Radioactive Materials t o and from Nuclear Power PZants., USAEC, D i r e c t o r a t e o f R e g u l a t o r y Standards, Washington, D.C., December 1972.
18.
Atomic Energy Commission, Everything You Always wanted t o Know About Shipping High Level &clear Waste, September, 1973; WASH-1264, U.S. Government P r i n t i n g O f f i c e , Washington, D.C. 20402 ($0.65).
I
ARE NUCLEAR SHIPMENTS REALLY SAFE?
William A. Brobst Division of Waste Management and Transportation U.S. Atomic Energy Commission Washington, D.C. 20545 ABSTRACT The transportation of nuclear materials is on t h e increase.
Although
nuclear shipments a r e only a very small f r a c t i o n of the Nation's hazardous materials shipments, they a t t r a c t a g r e a t deal of public a t t e n t i o n .
Ship-
ments of spent nuclear fuel and nuclear wastes a r e a p a r t i c u l a r concern. One of the many f e a r s t h a t people have about nuclear energy i s the p o s s i b i l i t y t h a t a nuclear shipment might scinehow go awry and c a G e a serious public hazard.
Primarily, they a r e worried t h a t a shipment o f
spent r e a c t o r fuel o r highly radioactive waste could be involved i n a serious r a i l or highway accident and dump i t s contents a l l over the countryside. Is t h a t r e a l l y possible?
How s a f e a r e those shipments? How many a r e
there? What do they look l i k e ? Are the packages tested? These and o t h e r Since public risk is the product of
questions a r e answered i n this paper.
the consequences of an accident and i t s probability, both aspects a r e presented so t h a t each of us can make up his own mind whether the risk from nuclear shipments is acceptable. INTRODUCT~ON
We live i n a world of hazards.
We a r e surrounded by t h r e a t s t o our
health, our welfare, and our economy. Amongst the many hazards we face is 355 Copyright 0 197s by hlnrcrl Dekkrr, InC. AII Rights Reserved. Neither this \Wrk 1101 any pJrt m3y be reproduced or Lransniittetl in any form or hy any means. electronic or n~echmical.including photocopyinp. microfilming. and recording, or hy m y inforimtion storage and retrieval system, without prrmission in writinp from the publisher.
356
BROBST
the one involving the transportation of hazardous materials.
One of the
hazardous materials w i t h which we must concern ourselves is nuclear material Public s a f e t y i n the transportation of hazardous materials has been the subject of increasing emphasis:
An a r t i c l e i n t h e May 1970 i s s u e of
the Reader's Digest s t a t e d , "Transportation of hazardous materials on our roads, r a i l r o a d s , and waterways is a major and growing problem.
One of
every ten trucks r o l l i n g toward you on t h e highway today c a r r i e s explosives, flamnables, o r poison.
[ll
Questions have a r i s e n i n numerous public hearings on nuclear reactor operations with regard t o t h e adequacy of p u b l i c s a f e t y in t h e transportat i o n of nuclear materials t o and from nuclear reactors and fuel reprocessing plants.
This .paper presents a sumarized s t a t u s r e p o r t on t h e potential
hazards of shipping those nuclear materials.
Since t h e r e have been no
serious releases of nuclear materials i n transportation accidents during the 25-year l i f e of t h e Atomic Energy Commission, the paper is based on a
theoretical analysis of accident risks. WHAT IS SHIPPED? Nuclear power will play an increasingly important r o l e i n meeting the Nation's energy requirements.
As nuclear power increases, the quan-
t i t i e s of nuclear materials which must be shipped will a l s o increase. The operation of nuclear power reactors will usually require the transportation of three d i f f e r e n t types of materials t o and from reactor facilities.
Unirradiated ("cold" o r "fresh") nuclear reactor fuel elements
a r e transported from fuel f a b r i c a t o r s t o t h e reactor.
Irradiated ("spent")
fuel elements and nuclear wastes a r e shipped from reactor f a c i l i t i e s t o fuel reprocessing plants and t o disposal s i t e s .
Also, the radioactive
products of the spent fuel reprocessing plants c o n s i s t primarily of recycled nuclear fuel materials shipped t o fuel f a b r i c a t o r s o r processors and both high-level and low-level waste shipped t o disposal s i t e s .
SAFETY OF NUCLEAR SHIPMENTS
35 7
Other shipments of r a d i o a c t i v e materials are made i n support of nuclear power p l a n t operations.
For example, uranium concentrate, produced
from uranium ore, i s shipped from uranium m i l l i n g p l a n t s i n the western United States t o uranium conversion f a c i l i t i e s f o r conversion o f t h e urani-
um
concentrate t o uranium hexafluoride.
Uranium hexafluoride i s shipped
t o one o f the Atomic Energy Comnission (AEC) uranium enrichment f a c i l i t i e s . The enriched uranium hexafluoride i s then shipped t o other p l a n t s which convert the material t o uranium oxide which i s then f a b r i c a t e d i n t o f r e s h reactor fuel elements. THe Department of Transportation (DOT) has estimated [ Z ] t h a t there are n e a r l y 1,000,000
packages of nuclear materials shipped each year.
About 95 percent o f the shipments i n v o l v e small q u a n t i t i e s o f nuclear i s o topes f o r use i n industry, medicine, a g r i c u l t u r e , and education.
By com-
parison, the t o t a l number o f shipments o f nuclear materials t o and from nuclear power p l a n t s i n 1971 probably numbered only a few thousand.
[31
By t h e year 2000, however, the numbers o f shipments t o and from nuclear power p l a n t s w i l l probably increase by a t l e a s t 100 and perhaps as much as 1,000.
[4] Shipments o f nuclear materials are n o t r e a d i l y distinguishable from
shipments o f other hazardous m a t e r i a l s being transported i n r o u t i n e comnerce.
They look l i k e ordinary shipments.
They are u s u a l l y handled
and loaded i n an ordinary manner, using ordinary f r e i g h t handling equipment. They are transported on a worldwide basis, l i k e o t h e r shipments, i n the cargo compartment o f an airplane, i n a closed t r a i l e r o r r a i l r o a d boxcar, on "low boys" over highway, o r on heavy duty f l a t c a r s by r a i l . They are n o t r e a d i l y distinguishable, b u t there i s a difference. Nuclear materials, l i k e many other materials, have hazardous properties. These p r o p e r t i e s must be considered i n the transportation o f nuclear materials-considered from the viewpoints o f possible r a d i a t i o n exposure t o people; contamination o f property, and o v e r a l l e f f e c t on the environment.
358
BROBST
As a r e s u l t of the depth of research studies of t h e hazards and experience i n t h e handling of nuclear materials, t h e i r properties a r e b e t t e r understood than the hazardous properties of most other hazardous materials being transported i n f a r g r e a t e r volume. The packaging requirements f o r nuclear materials a r e designed t o I
provide a high degree of protection and s a f e t y f o r personnel and materials, during both normal conditions of transportation and severe accidents. PRINCIPLES OF NUCLEAR SHIPMENT SAFETY Protection of the public and the transportation workers from radiation during the shipments of nuclear fuel and waste is achieved by a combination of limitations on b o t h t h e contents (according t o the q u a n t i t i e s and types of r a d i o a c t i v i t y ) and t h e package design.
Because shipments move i n routine
c m e r c e , and on conventional transportation equipment, they a r e , therefore, subject t o normal transportation accident environments [5] j u s t l i k e other nuclear cargo.
The shipper has e s s e n t i a l l y no control over t h e likelihood
of an accident involving his shipment.
He does have control over the con-
sequences of accidents by controlling the package design, contents , and external radiation levels.
Safety i n transportation does not depend upon
special handling o r special routing. I n the transportation of a l l types of hazardous m a t e r i a l s , t h e r e i s a difference between potential hazards and r e a l i z e d damage.
For hazardous
materials, a system of protection is used t o reduce the likelihood of the potential hazard from becoming a r e a l i t y .
A highly developed and sophis-
t i c a t e d system o f protection has evolved f o r the transportation of nuclear materials.
T h i s system is based upon a simple p r i n c i p l e - i f a package
contains enough r a d i o a c t i v i t y ("Type Bit quantity) t o present a s i g n i f i c a n t risk of injury o r large property l o s s i f released, then the package ("Type B" package) must be designed t o r e t a i n i t s contents during severe trans-
portation accidents.
[5,6J Lesser q u a n t i t i e s ("Type A" q u a n t i t i e s ) do
not require as much protection, b u t s t i l l must be packaged i n high q u a l i t y
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SAFETY OF NUCLEAR SHIPMENTS
"Type A" packaging.
In addition, a l l packages (Type A and B) a r e required
t o completely r e t a i n t h e i r contents during normal conditions of transportation The basic principles of s a f e t y a r e t r a n s l a t e d i n t o the Federal Government regulations. GOVERNMENT REGULATIONS
The transportation of nuclear materials i s s u b j e c t t o t h e regulations of both the DOT [7] and the AEC.
[S]
The DOT Hazardous Materials Regula-
tions a l s o provide f o r s a f e t y i n shipment of other more routinely shipped hazardous materials-materials which a r e flammable, unstable, poisonous , explosive, o r corrosive.
The same basic s a f e t y standards governing s h i p -
ments of nuclear materials i n t h e United S t a t e s a r e i n worldwide hse through
the regulations of the International Atomic Energy Agency.
[9]
In addition, the packages must provide adequate radiation shielding
t o l i m i t the radiation exposure t o transportation workers and the general public.
For spent f u e l , the package must have heat dissipation character-
i s t i c s t o p r o t e c t against overheating from radioactive decay heat.
For
both f r e s h and spent f u e l , package design must a l s o provide nuclear c r i t ical i t y s a f e t y under both normal transportation and severe accident condi tions. Package designs a r e reviewed by t h e AEC prior t o use i n order t o verify the adequacy o f the design parameters.
I f i t appears t h a t the
package will, i n f a c t , meet the regulatory requirements, [7,8] the AEC will issue a c e r t i f i c a t e of approval for the package. SHIPMENT INFORMATION DOT regulations specify the type o f information which must appear on b i l l s of lading and o t h e r shipping papers. labeled appropriately. transporting vehicle.
Packages a r e required t o be
Warning placards generally must be placed on t h e T h i s puts the c a r r i e r and emergency personnel on
notice t h a t they a r e handlinq shipments o f hazardous goods.
I t alerts
360
BROBST
them t o t h e f a c t t h a t a p p l i c a b l e s t a t e and l o c a l r e g u l a t i o n s and ordinances need t o be followed. Q u a l i t y Assurance The adequacy o f the package design can be compromised o r circumvented by e r r o r s which occur d u r i n g f a b r i c a t i o n , maintenance, o r use o f t h e package.
The person loading and c l o s i n g the package c o u l d make errors.
Perhaps
one o r more b o l t s c o u l d be l e f t o u t o r n o t p r o p e r l y tightened; a gasket c o u l d be misplaced o r omitted; a brace o r "holddown" p i e c e could be l e f t off.
The chances o f such an e r r o r a r e l i m i t e d because o f t h e procedures
r e q u i r e d by t h e r e g u l a t i o n s f o r examination o f t h e package p r i o r t o each shipment, i n c l u d i n g t e s t s f o r leak tightness, where necessary.
Redundancy
of s a f e t y features on t h e package w i l l reduce the consequences o f such operational e r r o r s , should they occur. Use o f the wrong m a t e r i a l s o r e r r o r s i n f a b r i c a t i o n a l s o could r e s u l t i n a package f a i l i n g t o f u n c t i o n p r o p e r l y d u r i n g transportation.
Adequate
q u a l i t y assurance programs increase the l i k e l i h o o d t h a t such e r r o r s would be detected and corrected, p r i o r t o use.
The r e g u l a t i o n s [8] impose certain
qua1 i t y assurance requirements on package manufacturers.
The shipper i s
r e q u i r e d t o determine t h a t each package meets the approved design s p e c i f i cations. Types o f Radioactive Waste D i f f e r e n t types o f r a d i a t i o n have d i f f e r e n t p e n e t r a t i n g a b i l i t i e s . For example, alpha p a r t i c l e s have a very s h o r t range i n a i r and cannot even penetrate a p i e c e o f paper; beta p a r t i c l e s t r a v e l over a l a r g e r distance, b u t can s t i l l be shielded completely by l i g h t , low-density m a t e r i a l s such as aluminum; gama rays r e q u i r e t h i c k e r o r more dense s h i e l d i n g m a t e r i a l s such as l e a d and s t e e l .
The c h i e f hazard t o human
beings from alpha m a t e r i a l s would be from d e p o s i t i o n o f the m a t e r i a l s w i t h i n the body, so s p e c i a l care must be taken i n containment o f the alpha wastes. Beta-gamma wastes a l s o r e q u i r e maintenance o f c o n t a i n e r s h i e l d i n g .
SAFETY OF NUCLEAR SHIPMENTS
361
There a r e several d i f f e r e n t types of materials which may be found i n nuclear wastes.
Nuclear wastes which a r e shipped around the country t o
various processing, storage, o r burial s i t e s f a l l i n t o three general categories:
(1) low s p e c i f i c a c t i v i t y (LSA) wastes; ( 2 ) high-level wastes;
and ( 3 ) other wastes. Low s p e c i f i c a c t i v i t y wastes a r e those which contain such low concent r a t i o n s o r q u a n t i t i e s of r a d i o a c t i v i t y t h a t they do not present any s i g n i f i c a n t environmental hazards.
Even i f they were released f r m t h e i r
packages i n a transportation accident, they would not present much hazard t o the public.
Like any o t h e r f r e i g h t s p i l l e d a t t h e scene of an accident,
they would have t o be cleaned up because of t h e i r nuisance value.
Under
U.S. and international regulations, they require only normal i n d u s t r i a l
packaging f o r shipment and require no special r a i l c a r s o r other t r a n s p o r t vehicles.
LSA wastes may include such t h i n g s a s residues o r solutions
from chemical processing; building rubble, metal , wood, and f a b r i c scrap; glassware, paper, and p l a s t i c ; s o l i d o r liquid plant waste, sludges, and acids; and s l i g h t l y contaminated equipment o r objects. Alpha wastes, high-level wastes, and o t h e r wastes contain s u f f i c i e n t l y large amounts of radioactivity t h a t they have a s i g n i f i c a n t potential f o r injury o r property damage i f released t o the environment during a transaccident.
For t h a t reason, DOT and AEC regulations require t h a t they be
packaged such t h a t , even i n the event of a severe transportation accident, there would be no s i g n i f i c a n t r e l e a s e of radioactive materials outside of the containers.
The packages (Type B packages) must then be strong
enough t o withstand the types of impact and puncture forces and f i r e e f f e c t s which a r e often encountered i n severe accidents. High-level wastes a r e those s o l i d i f i e d wastes from the reprocessing of highly i r r a d i a t e d nuclear reactor f u e l s .
These wastes have such a high
radioactive content of long-lived isotopes t h a t they require long-term storage i n i s o l a t i o n and e s s e n t i a l l y perpetual s u r v e i l l a n c e of the storage
36 2
BROBST
sites.
The r a d i a t i o n l e v e l i s h i g h enough t o produce considerable heat,
and the m a t e r i a l must be h e a v i l y shielded.
The most comnon type o f high-
l e v e l waste shipments w i l l be the s o l i d i f i e d (process) waste from the nuclear fuel reprocessing plants. be shipped t o waste storage s i t e s .
Only s o l i d m a t e r i a l s o f t h i s type w i l l Shipments o f high-level l i q u i d wastes
are n o t presently allowed by the DOT, and are n o t p r a c t i c a l due t o problems i n designing s a f e containers f o r b u l k shipment o f such l i q u i d s . Alpha wastes u s u a l l y c o n s i s t o f materials which a r e contaminated w i t h alpha r a d i a t i o n em1t t e r s such as plutonium o r o t h e r transuranium nuclides. They have very low l e v e l s o f penetrating g a n a r a d i a t i o n and so do n o t r e q u i r e heavy shielding.
Alpha emitters have the p o t e n t i a l f o r causing
contamination o f objects o r people i f released from t h e i r packages.
If
the amount o f nuclear m a t e r i a l exceeds c e r t a i n l e v e l s o f concentration, the -1pha wastes must be packaged i n Type B packages, b u t o f a d i f f e r e n t type than the very heavy high-level waste packages.
The emphasis i n
packaging f o r t r a n s p o r t a t i o n i s containment, w i t h several containment b a r r i e r s provided i n the packaging system. Other wastes are predominantly of the beta-gamma type (e.g.,
fission
product, i n d u s t r i a l isotopes) which u s u a l l y requires some s h i e l d i n g material as a p a r t o f the package.
This waste may a l s o be a combination o f LSA,
alpha, and beta-gama types.
Beta-gama waste includes such things as
i r r a d i a t e d r e a c t o r s t r u c t u r a l components, h e a v i l y contaminated objects, concentrated s o l i d i f i e d sludges o r evaporator bottoms , and nonrecoverable r a d i o a c t i v e f u e l scrap.
Because o f the presence o f considerable q u a n t i t i e s
o f nuclear material, packages o f these materials must a l s o be capable o f r e s i s t i n g severe accident. Package I n t e q r i t y Before a s p e c i f i c type o f Type A package i s approved by the AEC for shipment o f nuclear materials, i t must be capable of withstanding, without leakage, a series o f " t o r t u r e t e s t " which produce damage conditions com-
363
SAFETY OF NUCLEAR SHIPMENTS
parable t o the actual damage a package might encounter i n a hypothetical severe t r a n s p o r t a t i o n accident.
The accident damage t e s t sequence s p e c i f i e d
i n the DOT and AEC regulations includes a 30-foot f a l l onto a s o l i d uny i e l d i n g surface, followed by a 40-inch drop onto a 6-inch diameter piston, followed by exposure f o r 30 minutes t o a 1475OF f i r e .
A water immersion
t e s t i s a l s o required. This t e s t sequence represents the type of damage which might occur t o a package i n a high-speed t r u c k accident o r t r a i n derailment, causing the package t o impact on a hard surface (such as a bridge abutment) and then t o smash through wreckage o r onto rocks, and then t o be d i r e c t l y involved i n a 2-4 hour cargo f i r e , and then t o r o l l down i n t o a r i v e r !
The regulations
therefore o f f e r a very high degree o f assurance t h a t a package w i l l n o t breach under severe accident conditions.
A s p e c i f i c s a f e t y analysis r e p o r t must be prepared f o r each package type and evaluated by the AEC before use.
Only i f the packaging has suc-
c e s s f u l l y passed such rigorous evaluations does the DOT authorize i t s use.
A t present, there are several hundred d i f f e r e n t types o f r a d i o a c t i v e material package designs t h a t have been authorized, ranging i n s i z e from small packages weighing a few pounds t o massive casks weighing over 100 tons. Packaging methods Fresh Fuel.
A " t y p i c a l " package f o r a " t y p i c a l " [16] l i g h t water reactor
f u e l i s a c r a d l e assembly consisting o f a r i g i d beam o r "strongback" and a clamping assembly which holds a few f u e l elements firmly t o the strongback. The strongback i s shock-mounted t o a s t e e l outer s h e l l .
Fresh f u e l elements
might a l s o be shipped i n s t e e l boxes which are positioned i n an outer wooden box by a cushioning material.
These packages, a l s o w i t h a f e w fuel elements
inside, would b e about 2 t o 3 f e e t i n diameter o r cross section, and about
17 f e e t long.
They would weigh from 1,000 t o 9,000 pounds.
t a i n e r s are shown i n Figures 1 and 2.
Typical con-
BROBST
364
OUTER WOODEN BOX CUSHIONING MATERIAL
FIGURE 1 BWR FUEL ELEMENT SHIPPING CONTAINER (GE MODEL RA-I)
Spent Fuel.
Because i r r a d i a t e d fuel elements a r e highly radioactive, t h e i r
containers must be very heavily shielded.
A typical "cask" used f o r ship-
p i n g spent fuel would weigh between 20 and 75 tons.
I t would be constructed
o f thick steel walls f i l l e d with a dense shielding material such as lead,
tungsten, or depleted uranium. 2-18 BWR elements.
Each cask would carry 1-7 PWR elements, or
The casks would be generally cylindrical i n shape, and
perhaps 5 f e e t i n diameter and 15 t o 18 f e e t long.
A recently designed
cask of this type is shown i n Figures 3 and 4. The cask must not only provide radiation shielding, b u t must also provide the means to dissipate the large amount of heat (perhaps 75,000 BTU/hr) produced by radioactive decay.
Nater i s usually used i n the
central cavity as a heat medium or primary coolant to transfer the decay heat from the fuel elements t o the body of the cask.
The heat i s usually
dissipated by natural processes t o the a i r through f i n s on the surface of the cask.
For some o f the larger casks, a i r may be forced over the fins
by blowers t o increase the cooling.
In other casks, heat exchanges w i t h
cooling coils r u n n i n g i n t o the body of the cask l i t e r a l l y pumps the heat
o u t and i n t o the atmosphere.
Reliable, redundant systems are used where
365
5AFETY OF NUCLFAR SHIPMEXTS
a
w
za
L
a
B
366
BROBST
SAFETY OF NUCLEAR SHIPPIENTS
367
U
a W
P
--
d""
such mechanical systems a r e r e l i e d upon t o ensure adequate cooling. High-Level Nuclear Waste.
[12)
A t the present time, the AEC is planning on
long-term storage of a l l high-level wastes from c o m e r c i a l fuel reprocessing plants a t a Federal waste repository o r engineered storage f a c i l i t y . Some intermediate level f i s s i o n product wastes may be f u r t h e r treated f o r separation i n t o high-level and low-level components, t h e former of which would be destined f o r shipment t o a Federal storage f a c i l i t y , and t h e l a t t e r f o r shipment t o c o m e r c i a l burial f a c i l i t i e s . Shipping containers f o r high-level waste shipments will be very similar i n t h e i r basic design t o t h e shielded casks routinely used t o ship spent fuel assemblies from a nuclear power plant t o a fuel reprocessing s i t e . Spent fuel i s very s i m i l a r i n i t s overall shipping c h a r a c t e r i s t i c s t o c a n i s t e r s of high-level waste i n t h a t i t is highly radioactive and generates I n both cases, t h e shipping casks would be, e s s e n t i a l l y
considerable heat.
the same type-large s t e e l casks, lined with lead, s t e e l o r uranium.
The
high-level waste a c t u a l l y will be i n a burial capsule o r c a n i s t e r w i t h i n the outer shielded cask.
The waste is i n e r t , i m o b i l e , s o l i d material
rrhich i s nonexplosive, noncombustible, and cannot t u r n t o gaseous form and become airborne.
These high-level waste casks would be transported by r a i l
on conventional heavy duty f l a t c a r s ,
Highway load l i m i t s , r a t h e r than
s a f e t y reasons, will r e s t r i c t highway shipments. No d e t a i l e d cash designs have y e t been submitted by industry f o r AEC approval, since shipments t o a storage f a c i l i t y w i l l probably not begin u n t i l the e a r l y 1980's.
Low-Level Nuclear Waste.
[18] Under the DOT regulations, [7] low level s o l i d
waste is packaged depending on the amount of r a d i o a c t i v i t y i n the package. Typically, the waste is s o l i d i f i e d i n a mixture of vermiculite and cement i n Type A s t e e l drums. 500 and 800 pounds.
When f i l l e d , t h e individual drums weigh between
I f t h e drums contain Type B q u a n t i t i e s of waste, the
drums would require the addition of a Type B "overpack" ( i . e . , protective
SAFETY OF NUCLEAR SHIPMENTS
369
outer packaging) t o provide accident protection f o r the drums.
Low s p e c i f i c
a c t i v i t y wastes o r Type A q u a n t i t i e s of waste may be shipped i n drums w i t h out protective overpacks. Alpha waste is shipped e i t h e r i n a l a r g e accident proof box
Alpha Waste.
o r i n a bundle of 55-gallon drums encased i n some s o r t of outer protective container t o p r o t e c t such materials from impact and f i r e .
Special r a i l r o a d
cars already constructed have been used t o transport the s o l i d alpha wastes t o a storage f a c i l i t y .
Other methods and modes of transportation may be
used i n the future. NUMBER OF SHIPMENTS
Pattern of Shipments. i n the e a s t .
Shipments would be nationwide, with the predominance
Reactor locations a s of Dec. 31, 1973, a r e shown on Figure 5.
Fuel processing plants a r e located i n New York, I l l i n o i s , and South Carolina. Fuel f a b r i c a t o r s a r e scattered throughout the e a s t .
Comnercial waste burial
s i t e s a r e i n New York, Tennessee, I l l i n o i s , Nevada, Washington, and Kentucky. Fresh Fuel.
Each year, on the average, about 1/3 t o 1/5 of the fuel i n a
reactor i s replaced w i t h fresh fuel. w i t h 6 t o 16 packages per truck.
Fresh fuel is usually shipped by truck,
About 6 truckloads of fresh fuel elements
would be shipped t o a reactor each year.
For 100 reactors, t h a t ' s 600
truckloads per year nationwide. Spent Fuel.
A t present, a l l shipments of spent fuel a r e made under "exclu-
s i v e use" arrangement, by truck o r r a i l . i n the future.
Some barge shipments may be made
There would be about 10 r a i l shipments o r 40 truck shipments
annually from each reactor t o a fuel reprocessing plant.
For 100 reactors,
t h a t ' s 1,000 r a i l shipments o r 4,000 truck shipments per year. Radioactive Waste from Reactors.
About 4,000 cubic f e e t of low level 'waste
per year would be shipped from a BWR, and about 1,000 cubic f e e t per year from a PWR.
Most of the shipments would be made by truck.
About 2,000
drums of radioactive waste would be shipped, w i t h about 40 t o 50 drums per
370
BROBST
W
I I-
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SAFETY OF NUCLEAR SHIPMENTS
truckload, f o r about 45 truckloads per year f o r a BWR.
For a PWR, t h e r e
rrould be about 500 drums and 10 truckloads per year. RADIOACTIVE WASTE FROM REPROCESSING PLANTS Hiqh-Level Waste.
The first shipments of high-level waste from reprocessing
plants a r e not expected u n t i l about 1983. shipments a Year.
By 2000, there will be 260 shipments per year, f o r the
three reprocessing plants. Low-Level Waste.
By 1985, there will be about 25
[18)
Each reprocessing p l a n t i s expected to produce about
20,000 cubic f e e t of low level waste per year.
There would be about 700
truckloads each year f o r three reprocessing plants. Alpha Waste.
Each reprocessing plant is expected t o produce about 5,000
cubic f e e t of alpha waste per year.
T h i s would be about 30 r a i l carloads
o r 150 truckloads each year f o r three reprocessing plants. ACCIDENTS Accidents occur i n a range of frequency and s e v e r i t y .
Most accidents
occur a t low vehicle speeds, b u t the s e v e r i t y of accidents i s g r e a t e r a t higher vehicle speeds.
Most severe accidents generally involve some
combination of impact, puncture, and f i r e e f f e c t s .
Even i f the hazardous
nature of the cargo is not a f a c t o r , accidents often r e s u l t i n i n j u r y , death, and cargo o r other property l o s s due t o comon causes. Truck Accidents.
In 1969, motor c a r r i e r s reported [13] a t o t a l of about
39,000 accidents, 20,000 i n j u r i e s , and 1,500 deaths.
The injury r a t e i s
about 0.5 i n j u r i e s per accident, and'the death r a t e is about 0.03 deaths per accident.
The accident r a t e f o r hazardous materials shipments was
about 1.7 accidents per million truck miles. Assuming 100,000 truck miles per y e a r of transportation f o r each nuclear power p l a n t , there would be about 0.09 i n j u r i e s per year and 0.005 deaths per year per reactor.
Those deaths and injuries would be from
conventional o r common causes not r e l a t e d t o the radioactive nature of the cargo.
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BROBST
1
The nonnuclear property damage r a t e i s about $2,000 per truck accident. With 100,000 truck miles per year per reactor, t h i s would b e an average l o s s of about $300 per year per reactor due t o nonnuclear causes. Rail Accidents.
In 1969, the r a i l industry reported [14] about 8,500
accidents, 23,000 i n j u r i e s , and 2,300 f a t a l i t i e s .
The accident r a t e f o r
r a i l accidents was about 1.4 accidents per million c a r miles. There were about 2.7 i n j u r i e s per accident and about 0.27 deaths per accident.
Assuming about 15,000 r a i l c a r miles per y e a r per reactor, there
would be about 0.06 i n j u r i e s and 0.006 deaths per y e a r per reactor, from conventional and common causes. Nuclear Materials.
To d a t e , there have been no i n j u r i e s o r deaths of ra-
diological nature due t o the transportation of nuclear materials.
[5]
There have been a few cases of truck drivers being k i l l e d o r injured as a r e s u l t of a c o l l i s i o n o r overturn of vehicles carrying nuclear materials. In none of these cases, however, was there any r e l e a s e of nuclear materials from Type 6 packages.
121
In recent years, DOT has recorded [2] an average of 40 t o 50 incidents per year involving the transportation of nuclear materials. these incidents involved Type A- o r exempt packages.
Almost a l l of
In about 2/3 o f these
cases, t h e r e was no nuclear material released from the packages.
In a few
percent of the cases, t h e r e was s i g n i f i c a n t contamination requiring cleanup, w i t h cleanup costs r u n n i n g i n t o the thousands of d o l l a r s .
ACCIDENT RISK Principle of R i s k .
The significance o f radiological hazards during trans-
portation of nuclear m a t e r i a l s can be properly evaluated only by considering together the consequences of accidents and the p r o b a b i l i t i e s of those accidents.
One could compare the risks o f transportation of nuclear materials
i n several ways.
For example, one m i g h t compare the p r o b a b i l i t i e s of s h i p -
ment accidents; [15,16] one m i g h t compare the average c o s t of accidents by
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SAFETY OF NUCLEAR SHIPIENTS
each mode a f transportation; one m i g h t compare d i r e c t transportation c o s t s , However, a l l of these p a r t i a l measures
which includes insurance premiums.
f o r comparing risk may be combined i n t o a s i n g l e contingency risk c o s t f a c t o r which i s the product of the probability of experiencing an accident involving nuclear materials and the probable c o s t of such an accident i f i t occurs.
In l a t e 1972, the AEC completed a study [17] of this type of
CM-
parison f o r nuclear reactor power p l a n t transportation. Accident Records.
In estimating the radiation risk from accidents involving
shipments of nuclear materials t o and from nuclear power plants, one must consider:
(1) the frequency and the s e v e r i t y of accidents; ( 2 ) the l i k e l i -
hood of package damage o r f a i l u r e ; ( 3 ) the nature, amount, and consequences o f releases of r a d i o a c t i v i t y during an accident; and (4) the capacity of
coping with such releases. The environmental e f f e c t s [5] which m i g h t occur i n transporting nuclear fuel and s o l i d wastes resulting from t h e operation of a "typical" power reactor has been evaluated. of:
[17]
The risk analysis covers transportation
(1) fresh fuel from a f a b r i c a t i o n plant t o a r e a c t o r by truck; ( 2 )
spent fuel from a reactor t o a fuel reprocessing p l a n t by truck, r a i l o r barge; and (3) s o l i d wastes from a reactor t o a radioactive burial s i t e by truck o r r a i l . .The range of known distances between various s i t e s must be considered.
Estimates may be made of radiation e f f e c t s on t h e environ-
ment under normal conditions of transportation and f o r credible severe accidents.
The potential accidents may be analyzed i n terms of s e v e r i t y
and predicted damage, and the probable consequences of releases.
Finally,
by combining the p r o b a b i l i t i e s of accidents w i t h the consequences, the overall risk of transportation accidents may be estimated. Normal Conditions.
According t o the AEC analysis, [17] truck drivers and
f r e i g h t handlers would normally receive an average of about 0.2 t o 0.3 millirem per shipment of fresh fuel.
No member of the general public i s
374
BROBST
l i k e l y t o r e c e i v e marc than about 0.005 m i l l i r e m p e r shipment.
Most of
the general p u b l i c ' s exposure would be n o n r e p e t i t i v e i n t h a t no s i n g l e member o f the general p u b l i c would be exposed t o those dose l e v e l s more than a few times per year.
The m o s t t h a t any one member o f the general
p u b l i c might g e t during a year would then be perhaps 0.01 m i l l i r e m o r about 1/50,000 o f h i s annual p e r m i s s i b l e exposure.
For spent f u e l shipments and r a d i o a c t i v e waste, each t r u c k d r i v e r could receive as much as 30 m i l l i r e m p e r shipment.
A few members o f t h e
general p u b l i c c o u l d r e c e i v e as much as one m i l l i r e m per shipment, o r about 1/500 o f h i s annual p e r m i s s i b l e exposure. ACCIDENT PROBABILITIES
A study o f accident p r o b a b i l i t i e s [16] showed t h a t t h e frequency o f severe accidents f o r both t r u c k and r a i l shipments i s about one f o r each one hundred m i l l i o n t r u c k m i l e s o r r a i l c a r miles.
The p r o b a b i l i t y of
extremely severe accidents i s about 100,000 times less.
Considering t h e
t o t a l number o f t r u c k m i l e s o r r a i l c a r m i l e s i n v o l v e d p e r r e a c t o r and estimating the p r e d i c t e d accident response o f packages, the study 1161 shows t h a t the p r e d i c t e d l i k e l i h o o d o f serious leakage a r i s i n g from accidents i n v o l v i n g packages o f nuclear m a t e r i a l s t o o r from a nuclear power p l a n t i n any one year i s about one i n f i v e m i l l i o n .
By comparison, the l i k e l i h o o d
o f serious i n j u r y due t o an automobile accident p e r person per year i s about one i n 500. The study [16] a l s o shows t h a t , i n the t r a n s p o r t a t i o n o f nuclear m a t e r i a l s , the p r o b a b i l i t y o f i n j u r y o r death due t o common accident causes i s a t l e a s t 100,000,000
times g r e a t e r than t h e p r o b a b i l i t y o f i n j u r y o r death
due t o r a d i o l o g i c a l consequences. ' Correspondingly, t h e t o t a l p r o p e r t y and cleanup l o s s from nonnuclear common causes i n t r a n s p o r t a t i o n accidents i s expected t o be about $300, o r about 2,500 times g r e a t e r than t h e probable
375
SAFETY OF NUCLEAR SHIPMENTS losses from r a d i o l o g i c a l contamination.
The t o t a l expected average loss
from contamination i n t r a n s p o r t a t i o n per r e a c t o r y e a r i s about 12 cents.
CONCLUSION On the basis of the studies r e f e r r e d to, i t appears t h a t the p r o b a b i l i t y
of death, i n j u r y , o r massive p r o p e r t y loss due t o t r a n s p o r t a t i o n o f r a d i o a c t i v e m a t e r i a l s i s (1) determinable, (2) n o t zero, and (3) very small. I n p r o j e c t i n g the t o t a l accident p r o b a b i l i t y f o r t r a n s p o r t a t i o n o f r a d i o a c t i v e m a t e r i a l s t o and from nuclear power p l a n t s , i t seems obvious t h a t the r a d i o l o g i c a l consequences of t h e t o t a l accident spectrum w i l l be several orders of magnitude beJow the more comnon nonradiological causes.
I t further
appears t h a t r a d i a t i o n doses t o t r a n s p o r t a t i o n workers and the general p u b l i c during the normal course o f t r a n s p o r t a t i o n w i l l be l i m i t e d t o a small f r a c t i o n of the t o t a l permissible annual dose, and then o n l y t o an extremely small segment o f t h e population.
The various s t u d i e s show c l e a r l y t h a t
the l i k e l i h o o d o f a catastrophic nuclear t r a n s p o r t accident i s so i n f i n i tesimal t h a t , f o r a l l p r a c t i c a l purposes, i t can be c o n f i d e n t l y s a i d t h a t one w i l l never happen. The r i s k i s small, b u t i s i t acceptable? confronts people w i t h a m u l t i t u d e o f r i s k s .
And t o whom? Modern l i f e We d o n ’ t l i v e i n a r i s k l e s s
society, nor c o u l d modern technological s o c i e t i e s e x i s t on t h a t basis. Each person has h i s own idea o f what r i s k s a r e acceptable t o him.
The
p u b l i c apparently judges the convenience of a i r t r a v e l t o be worth t h e r i s k t h a t r e s u l t s i n 200 f a t a l i t i e s p e r year; the convenience of d r i v i n g an automobile i s considered worth much higher l e v e l s o f r i s k . are a f r a i d o f a i r p l a n e s b u t r i d e motorcycles. ments a r e n o t e s p e c i a l l y r a t i o n a l .
Some people
Sometimes the p u b l i c judg-
About 49 m i l l i o n Americans continue t o
smoke c i g a r e t t e s d e s p i t e t h e c l e a r warning o f r i s k t o t h e i r h e a l t h p r i n t e d on each package.
Others smoke h e a v i l y b u t take a v i t a m i n p i l l every day
t o s t a y healthy.
Many people are a f r a i d o f t h e p o t e n t i a l hazards o f nuclear
376
BROBST
power, b u t risk their necks every day i n t h e hazardous r e a l i t y of highway travel.
Some say t h a t risks which they choose t o accept a r e acceptable,
b u t risks which others f o r c e on them a r e not.
In each case, the accept-
a b i l i t y is most l i k e l y t o be based on subjective emotional reactions-"gut" feelings-rather than a logical analysis of accident data o r other actual I
experience.
Few of us a r e a f r a i d of being b i t t e n by a venomous snake, o r
being attacked by a rhinocerous, i n t h e middle of Washington, D.C.,
but
t h a t probability is a l s o (1) determinable, ( 2 ) n o t zero, and (3) very small. Certainly laws and regulations themselves will not guarantee risk-free transportation.
We a r e a l l aware of the potential risks i n nuclear matters
if s a f e t y i s not given the very close a t t e n t i o n i t deserves.
Transportation
accidents and their potential e f f e c t s on shipping containers have been well studied.
These studies continue.
I t i s precisely because of this perceived
risk t h a t the AEC has always imposed s t r i n g e n t and overlapping p r o t e c t i v e measures in t h e i r concept of "defense i n depth." "assurance" a s an absolute.
However, one cannot claim
No s a f e t y system can nor should it be expected
to guarantee complete s a f e t y of a few individuals who by very exceptional circumstances, peculiar h a b i t s , unusual customs, extreme deviations from the typical individual g e t i n t o d i f f i c u l t i e s .
Even the normal i n d u s t r i a l safety
limits f o r a v a r i e t y of hazardous s t r e s s e s provide only reasonable protection f o r typical workers, and no more than t h a t . We tend t o r e a c t t o t h e problem of risk by making choices based on the magnitude of the risk, a s we perceive i t , and the b e n e f i t s t o be gained from accepting the risk. The National Academy of Sciences has s t a t e d , "Whether we regard a risk a s acceptable o r not depends on how avoidable i t i s , and how i t compares w i t h the r i s k s of a l t e r n a t i v e options and those normally accepted by
industry.". As a result of the s t u d i e s which have been done, i t is t h e
SAFETY OF NUCLEAR SHIPMENTS
377
AEC's opinion [la] t h a t , with regard t o nuclear shipments: a.
We have enough f a c t s and f i g u r e s on the hazards t o allow a more object i v e evaluation of the risk a c c e p t a b i l i t y than we might derive s o l e l y from "gut" f e e l i ng.
b.
The risk of public catastrophe has been eliminated by s t r i c t standards, engineering design s a f e t y , and operational care.
Whatever the conse-
quences of an accident a r e , the public hazard will be mnageable, and t h e nuclear e f f e c t s will be small compared t o t h e nonnuclear e f f e c t s . C.
The long-term public burden of not transporting nuclear materials i s l i k e l y t o be higher than the risks of c a r e f u l l y controlled transportat i o n , considering the various options available.
d.
The likelihood of death, i n j u r y , o r s e r i o u s property damage from the nuclear aspects of nuclear transportation is thousands of times l e s s than t h e likelihood of death, injury, o r s e r i o u s property damage from more common hazards, such a s automobile accidents, boating accidents, accidental poisoning, gunshot wounds, f i r e s , o r even f a l l s - a l l things which we can control, b u t apparently have accepted a s a way of l i f e without much p u b l i c support f o r reduction of risk.
REFERENCES 1.
Robinson, D. , "Danger! Hazardous Materials i n Transit," Reader's Digest, May 1970.
2.
Grella, A. W., "Accident Experiences i n the USA Involving Type B Packaging," IAEA/SM-147/19, Seminar on Test Requirements f o r Packaging f o r the Transport of Radioactive Materials, Vienna, Austria, 1971.
3.
Heinisch, R. , !Transportation of &.clear Fuel Material i n the United States, Nuclear Assurance Corporation, Atlanta, Georgia, 1970.
4.
Oak Ridge National Laboratory, Siting of Fuel Reprocessing P l m t s and Waste Management Facitities, ORNL-4451 , Clearinghouse f o r Federal S c i e n t i f i c and Technical Information, Springfield, Virginia 22101 , 1970.
BROBST
37a
5.
Brobst, W. A., " T r a n s p o r t a t i o n o f R a d i o a c t i v e Waste-Worth I t s S a l t ? " T h i r d I n t e r n a t i o n a l Symposium on Packaging and T r a n s p o r t a t i o n of Radioa c t i v e M a t e r i a l s , August 1971 ; CONF-710801.
6.
Gibson, R., 1966.
7.
Department o f T r a n s p o r t a t i o n , Hazardous Materia2 ReguZations, T i t l e 49, Code o f Federal Regulations, P a r t s 170-189.
8.
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9.
I n t e r n a t i o n a l Atomic Energy Agency, ReguZations for t h e Safe IR.ansport of Radioactive Materials, S a f e t y S e r i e s No. 6, 1967.
The Safe Transport of Radioactive Material, Pergamon Press,
10.
I n t e r n a t i o n a l Atomic Energy Agency, Notes on Certain Aspects of t h e Regulations, S a f e t y S e r i e s No. 7, 1961.
11.
Brobst, W. A. , "Tests on T r a n s p o r t Packaging f o r R a d i o a c t i v e M a t e r i a l s , " IAEA/SM-147/18, Seminar on T e s t Requirements f o r Packaging f o r t h e T r a n s p o r t o f R a d i o a c t i v e M a t e r i a l s , Vienna, A u s t r i a , 1971.
12.
Shappert, L. B. , e t al., A Guide for t h e Design, Fabrication, and Operation of Shipping Casks for &clear Applications. ORNL-NSIC 68, Clearinghouse f o r Federal S c i e n t i f i c and T e c h n i c a l I n f o r m a t i o n , Springf i e l d , V i r g i n i a 22101, 1970.
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14.
Federal R a i l r o a d A d m i n i s t r a t i o n , S m a q and Analysis of Accidents on Railroads i n the United S t a t e s , A c c i d e n t B u l l e t i n , KO. 138, U. S. Department o f T r a n s p o r t a t i o n , Washington, D.C. ; 1970.
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Leimkuhler, F. F., Trucking of Radioactive Materials: Safety versus Economy f o r Highway Trmsportation, The Johns Hopkins Press, B a l t i m o r e , Maryland, 1963.
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Brobst, W. A., "The P r o b a b i l i t y o f T r a n s p o r t a t i o n Accidents," Department o f Defense E x p l o s i v e s S a f e t y Seminar, November 10, 1972; a v a i l a b l e from D i v i s i o n o f Waste Management and T r a n s p o r t a t i o n , USAEC, Washington, D.C. 20545.
17.
Atomic Energy Commission, Environmental Survey of Transportation of Radioactive Materials t o and from Nuclear Power PZants., USAEC, D i r e c t o r a t e o f R e g u l a t o r y Standards, Washington, D.C., December 1972.
18.
Atomic Energy Commission, Everything You Always wanted t o Know About Shipping High Level &clear Waste, September, 1973; WASH-1264, U.S. Government P r i n t i n g O f f i c e , Washington, D.C. 20402 ($0.65).
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