I

upwr

RADIATION EXPOSURE INSIDE REINFORCED CONCRETE BUILDINGS AT NAGASAKI W. A. Rhoades,* R. L. Childs,? and D. T. Ingersolls effects so that many individuals received only radiation injuries. The buildings studied were located at ground ranges of about 500 m, and the resulting radiation doses were such that a mixture of long-term survivals and fatalities was found in each building. (Unless otherwise noted, all ranges in this study refer to ground ranges, i.e., to the distance horizontally from a point at ground level directly under the weapon.) The first building studied was the main building of the Chinzei School, located southwest of the weapon detonation. This building consisted of four stories and a basement. The other building was the south wing of the Shiroyama School, located west of the detonation. The Shiroyama School consisted of only three floors, and all of the persons were located on the second and third floors. (Additional details regarding the buildings and occupant locations will be cited in later sections.) Early postwar studies did not attempt to calculate radiation doses in such heavily shielded buildings, and adequate mathematical procedures, computer power, and software were not available until recently for such a calculation. However, the early records and postwar studies were quite helpful in providing the construction details that allowed accurate analytical models of the buildings to be assembled and used in this study. More recently, an extensive reassessment of atomic weapon radiation dosimetry was conducted (Roesch 1987), commonly called “DS86,”in which sophisticated analyses were performed for occupants of residential dwellings located at substantially greater ground ranges. While the analysis methods and dosimetry results for the wood-frame houses are not directly relevant to this study, the radiation sources and environmental conditions in the vicinity of the concrete buildings were obtained from DS86. The penetration of external radiation into the buildings was calculated using the method of discrete ordinates. This proven method has been used for many years, but significant extensions to existing computer codes were needed to accommodate the large scale and complex features of the concrete buildings, and to allow a full three-dimensional representation. The resulting computer code, the Three-Dimensional Oak Ridge Discrete Ordinates Radiation Transport Code (TORT) (Rhoades and Childs 1987), provides the state-of-theart capabilities to solve this difficult problem and con-

Abstract-In this study, the radiation doses to occupants of two reinforced concrete buildings at Nagasaki, who survived the immediate effects of the nuclear weapon detonation, are determined using state-of-the-art radiation transport techniques. The radiation doses at all locations in the buildings are calculated using the Three-Dimensional Oak Ridge Discrete Ordinates Radiation Transport Code which was constructed especially for this task. This code represents a new and unique capability that has been previously reported. This study resulted in case-by-case lists of doses to occupants and an uncertainty analysis. These data have been used in a companion study as the basis for determining a new value of the dose producing a 50% risk of fatality. Health Phys. 63(5):510-521; 1992 Key words: atomic bomb survivors; dosimetry; radiation effects; Nagasaki

INTRODUCTION AT THE END of World War 11, American researchers compiled records of the locations and surroundings of people exposed to the nuclear weapon detonations at Hiroshima and Nagasaki. Detailed medical histories of those who survived the initial blast were also kept, and the incidence of radiation effects can be determined from those records. It is the purpose of this study to calculate the radiation dose to certain survivors, from which a companion study (Levin et al. 1992) determines the corresponding value of the LD50 parameter, i.e., the dose at which the risk of fatality is 50%.

MATERIALS AND METHODS The cases studied here are for persons located inside two reinforced concrete buildings at Nagasaki. These heavy, earthquake-proof structures protected their occupants from most of the blast and thermal * Engineering Physics and Mathematics Division, Oak Ridge National Laboratory, P.O. Box 2008, Building 6025, MS-6363, Oak Ridge, TN 37831-6363; Computing and Telecommunications Division, Oak Ridge National Laboratory, P.O. Box 2008, Building 6025, MS-6363, Oak Ridge, TN 37831-6363; *Engineering Physics and Mathematics Division, Oak Ridge National Laboratory, P.O. Box 2008, Building 6025, MS-6363, Oak Ridge, TN 37831-6363. (Manuscript received 23 September 1991; revised manuscript received 27 April 1992, accepted 27 April 1992) 00 17-9078/92/$3.00/0 Copyright 0 1992 Health Physics Society 510

Radiation inside concrete buildings at Nagasaki 0 W. A. RHOADES ET AL.

tains numerous features and flexibilities that make it useful for a wide diversity of applications. The validity of the TORT method for calculating the transport of radiation into concrete buildings was tested by constructing a model of such a building at the Tower Shielding Facility in Oak Ridge and exposing it to radiation from a reactor (Muckenthaler et al. 1985). Neutron and gamma fluences measured inside the building were compared with TORT results to give a quantitative assessment of the accuracy of the method (Rhoades et al. 1985). That original analysis prompted further improvements in the TORT method summarized in the TORT document (Rhoades and Childs 1987) and in other publications cited therein. The validity of the TORT method was also tested by performing an analysis of the Chinzei School using an established Monte Carlo code (Cramer and Slater 1990). While the TORT results agreed well with the Monte Carlo results, the Monte Carlo analysis proved to be extremely difficult and costly and generated dose data at only a single location within the building. This provided further evidence that the Monte Carlo method alone was not viable for calculating the large number of dose points needed for our study. Radiation transport calculations The radiation transport calculations within the concrete buildings required the determination of radiation emission from the weapon, the resulting fluence outside the buildings, nuclear models of the structures, and the penetration of fluence into the structures. The calculation of radiation emission and external fluence was thoroughly analyzed as part of DS86 (Roesch 1987) and the resulting fluence data were used directly for this study. As the DS86 document describes, the prompt radiation leakage from the weapon was calculated by a group headed by Whalen (Roesch 1987) using hydrodynamics and radiation transport codes, and Pace calculated the penetration of radiation through the air and ground environment to the vicinity of the buildings. Gritzner and associates (Roesch 1987) determined the delayed fluence from debris in the cloud that rose above the weapon using codes that described air heating, hydrodynamics, and radiation transport through the disturbed air. For our study, the prompt and delayed fluences in the vicinity of the buildings were folded onto a Cartesian surface surrounding each building. The resulting surface fluences were then used as boundary sources for the three-dimensional transport calculations performed within the buildings. Gritzner5(1 986) also supplied data from which it was deduced that 70% of the delayed fluence arrived at the site of the selected buildings after the shock wave. This is an important parameter because the shock wave destroyed all of the internal walls (US. SBS 1947), and threw the individuals to the floor. Accordingly, “early

*

Personal communication (1986), M. L. Gritzner, Science Applications International Corporation, P.O. Box 235 1, La Jolla, CA 92038.

511

fluence” arriving before the shock wave was attenuated more by the building structure than “late fluence,” and the occupant locations were different. These effects were incorporated explicitly into our analysis. We constructed TORT especially for the task of calculating the radiation penetration into the building (Rhoades and Childs 1987). Briefly, TORT uses a form of the Boltzmann equation to determine the fluence of particles traveling in specific directions, within specified energy bands, averaged over each cell of a finite space mesh. Performing numerical quadrature over the discrete directions results in the average scalar fluence in each mesh cell. TORT is based on methods in widespread use since the 1960s, especially in the DOT 4 and DORT codes and their predecessors (Rhoades and Childs 1982; Rhoades and Childs 1988). Numerous comparisons of various discrete ordinates, Monte Carlo, and experimental results were performed in order to verify TORT for this application. The results of this extensive verification are presented elsewhere (Rhoades et al. 1989).”The analytical results and experimental data were also used to select the appropriate input parameters and numerical flux models needed to obtain sufficient accuracy. At specific locations for persons in the buildings, either radiation streaming through the windows, penetration through the roof and overhead floors, or both may dominate. Careful selection of the numerical flux model, the spatial mesh, and the directional quadrature was made in order to achieve the desired accuracy and reliability within the limits of available computer resources. The final calculations were performed using a new nodal numerical procedure, more than 120,000 spatial mesh cells, and an Sl0 directional quadrature having 140 discrete directions. Also, the code verification study determined that the use of a PI Legendre expansion of the scattering cross-sectionswas sufficient. The nuclear cross-sectiondata were taken from the “DABL-69” set (Ingersoll et al. 1989). The data are derived from Version 5 of the Evaluated Nuclear Data Files and are given in 46 neutron energy groups and 23 gamma-ray groups. The DABL-69 library was constructed specifically for applications of this type, i.e., weapon radiation sources and shielded structures. The adequacy of the energy group boundaries and the energy weighting was determined as part of the library development effort (Ingersoll et al. 1989). The building calculations used the five nuclide mixtures listed in Table 1. The concrete and earth compositions, taken from the DS86 study, are appropriate to construction in Nagasaki. The air composition, also from the DS86 study, has been carefully adjusted to the correct moisture content. The wood and plaster compositions are from standard references, as discussed in the detailed report (Rhoades et al. 1989). Available from the National Technical Information Service, U S . Department of Commerce, 5285 Port Royal Road, Springfield, VA 22161.

Health Physics

512

November 1992, Volume 63, Number 5

Table 1. Librarv nuclide selections and material compositions. Library ID numbers Nuclide

IH

‘OB “B Carbon I4N ‘60 23Na Magnesium 27A Silicon 3’P Sulfur Argon Potassium Calcium Chromium 55Mn Iron Nickel Chlorine Titanium

Atomic densities (atoms/b cm-’)

69-group

Concrete

1 49 55 61 67 75 85

8.488 x 2.21 x 10-6 8.94 X 9.681 X

91 97 103 I09 115 127 133 139

4.907 X 2.836 X 1.277 X 3.112 X lo-’ 4.698 X

157 163 169 187 121 145

-

4.852 X lo-’ 1.158 X

Earth

Air

3.521 X

1.311 X lo-‘

-

-

1.806 X 3.857 X lo-’ 2.556 X low4

-

3.676 X lo-’ 1.052 X -

1.189 X

2.198 X

4.931 X 3.113 X

1.510 X 2.267 X

-

5.794 x 10-6 1.645 X 6.721 X 1.026 X lo-‘

1.796 X 8.247 X

-

7.512 X 1.034 X

Fig. 1. Chinzei School main building before the attack, looking northwest.

Dosimetry Individual doses were obtained by folding the fluence values calculated in each mesh cell and each energy group with energy-dependent response functions representing various dose effects. The resulting spacedependent responses were then interpolated between adjacent mesh cells to yield the dose at specific locations. The simplest response function used in this study is the “free-in-air tissue kerma” (FIA) taken from the DS86 study (Roesch 1987). This function represents

X

-

1.426 X

-

-

2.377

-

-

-

Wood

-

Plaster 3.247 X lo-’

-

4.870 X lo-’ -

-

-

-

-

-

-

-

-

the kinetic energy of charged particles liberated by the effect of radiation on a small, isolated sample of tissue. The other response functions represent the kerma in either small intestine tissue (SI) or bone marrow (BM). They are calculated by initiating adjoint Monte Carlo histories at appropriate locations in a manikin representing a young adult and then tabulating the escaping histories as a function of energy (Kerr and Eckerman 1985). By performing the calculations separately for each component of the incident radiation, the contribution of each to the total dose was obtained individually. The various contributions were then added to obtain the total. No attempt was made to account for a “quality factor” describing the effectiveness of neutrons, relative to gammas. Instead, the total gamma and neutron doses were obtained separately, as will be Seen in later seetions.

CHINZEI SCHOOL MODEL AND RESULTS Building model The main building of the Chinzei School at Nagasaki (Fig. 1) was a four-story rectangular structure with a half-basement under the center of the building. The exterior walls were 25 cm of reinforced concrete, built to withstand earthquakes, while the floors were of similar construction and 12 cm thick. All floors were supported by heavy concrete beams resting on concrete pillars. The fourth-floor attic extended from the south

Radiation inside concrete buildings at Nagasaki 0 W. A. RHOADES ET AL.

end of the building to just past the center, leaving room for a high-ceiling auditorium at the north end. The roof over the attic was of tile construction, supported by a wooden framework resting on wooden posts. The roof over the auditorium was of concrete slab construction, supported by a steel truss system. The entire roof and fourth-floor structure collapsed at the time of the shock wave passage.' Since photographs indicate that the roofing material was scattered relatively uniformly after the blast, it was assumed to provide the same protection to the people on the lower floors that it provided in its original position. The exterior dimensions of the building, exclusive of the basement, were roughly 70 m long by 17 m wide by 15 m high. The building sat on a hill about 18.3 m above sea level and the first floor was taken to be at 61 cm above ground level. The building was located southwest of the hypocenter (the surface location directly under the detonation) at the location indicated as " 18" in Fig. 2. The hypocenter was taken to be 468 m from the center of the building in a direction 39 degrees clockwise from the south-to-north axis of the building. Since the epicenter (the detonation position) was at an altitude of 503 m above sea level, the weapon radiation was incident on the building from an upward angle of 47 degrees from the horizontal. Fig. 3 shows two views of our computer model of Chinzei School: One view corresponding to the orientation of the incident radiation and the other view corresponding to the viewpoint of the photograph shown in Fig. 1. The exterior source calculation was based on a level air/ground interface; thus the hill could not be simulated exactly. At the given ground range of the building, the primary effect of the hill was to slightly reduce the slant range, i.e., the distance from the weapon to the building, relative to the flat-terrain model. In order to ensure the correct air and distance attenuation of the weapon radiation while maintaining the correct air/ground environment, the building was moved inward toward the hypocenter to preserve the actual slant range, which yielded an adjusted ground range of 448 m. This perturbed the angle of the incident radiation by only about 1.3 degrees, too little to be of concern. The model used in the transport calculations is described in detail in a full technical document (Rhoades et al. 1989). Construction information was obtained from the records of several postwar studies. All walls, windows, doors, floors, beams, and pillars were modeled explicitly. In order to keep the mesh size within acceptable bounds, some internal features were represented as smeared between adjacent mesh boundaries, with density factors adjusting the effective mass of material to the correct value. It was found that the placement and size of the windows were the most important construction details, and those details were

' Personal communication (1987), R. L. Stohler, Dikewood Division, Kaman Sciences, 6400 Uptown Blvd. NE, Suite 300E,Albuquerque, NM 871 10.

513

Fig. 2. Nagasaki target area; aerial photograph looking north. (Chinzei School is at area 18; Shiroyama School is at area 16.)

(b)

Fig. 3. Building model for Chinzei School as viewed from: (a) direction of incident radiation and (b) viewpoint of photograph in Fig. 1.

5 14

Health Physics

deduced directly from the photographs. The level of interior and exterior detail in our final building model is demonstrated in the computer-generated drawings given in Fig. 3. Two types of internal wall construction were represented: heavy, solid-concrete walls and light-construction walls similar to those found in conventional American homes. The heavy construction, represented as 14.0 cm of reinforced concrete, was used for all of the basement walls and for the walls adjacent to the stairwells on the upper floors. Photographs indicate that most of these walls survived the blast at least partially intact. The details of the stairsteps and floor penetrations were not modeled. The other internal walls were of light construction. Based on data supplied by Ken-,' these were represented as 1.12 cm of plaster and 3.0 cm of wood. The layout of the basement and first two floors is illustrated in Fig. 4. The locations of individuals and the estimated uncertainty in the coordinates are listed in Table 2. In this coordinate system, the origin is located at the center of the building on the top surface of the first floor, X

'Personal communication (1986), G. D. Ken, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 3783 1.

- , -17.4

0

17.4

34.8

17.4

34 8

174

34 a

X (m) 50 cm above first floor: 9.5

->

E O

-9.5

-34.8

0

X (m) 50 cm above basement floor:

-34.8

-17.4

lies along the northward axis of the building, and Y lies along the westward axis. The positions of occupants are plotted as small upright triangles in Fig. 4. Records indicate that all of the occupants were thrown about by the blast, so gamma dose arriving after the shock wave was calculated with personnel 30 cm above the floor, rather than at the height listed in the table. The locations and uncertainties were determined by Stohler' using various files from postwar studies. The criteria for selecting these cases were, briefly, those cases: 1) for whom adequate medical records existed; 2) whose locations at the time of the detonation could be established; and 3) who did not die on the first day due to nonradiation consequences. Additional discussion of this selection process is given in the companion article (Levin et al. 1992). Dose results: Contour plots and selected locations Fig. 4 shows spatial contours of the common logarithms (base 10) of the FIA dose. The source in these plots is from the direction of the lower right corner. Table 2. Position data for Chinzei School cases (X,Y,Z positions; X,Y uncertainty). X Case position number (cm)

50 cm above second floor:

-34.8

November 1992, Volume 63, Number 5

0

X (m) Source Direction

\

Fig. 4. Chinzei School dose distribution. Contour labels refer to common logarithm of dose in cGy units. (Note: Most other information in this paper is given by Gy units.)

1 2 3 4 5 11 12 16 17 101 102 103 104 13 92 112 115 37 32 26 27 30 40 43 46 88 89 90 93 95 97 94 96 6 18 49 54

-90.00 -225.00 135.00 210.00 85.00 2,960.00 2,155.00 1,495.00 3,270.00 -2,090.00 -2,090.00 -2,090.00 -2,090.00 1,140.00 -410.00 -740.00 -420.00 2,810.00 2,400.00 1,580.00 1,555.00 1,670.00 2,975.00 2,425.00 1,060.00 -3,080.00 -3,200.00 -2,980.00 -3,200.00 -2,960.00 -3,070.00 -3,320.00 -3,295.00 2,345.00 185.00 1,450.00 1.640.00

Y 2 position position (cm) (cm) 125.00 325.00 -700.00 -455.00 -755.00 -730.00 -275.00 -470.00 -720.00 385.00 480.00 565.00 665.00 540.00 -445.00 -70.00 -215.00 -700.00 -630.00 -480.00 -260.00 -675.00 540.00 360.00 275.00 525.00 730.00 730.00 525.00 525.00 730.00 0.00 -295.00 -280.00 -370.00 730.00 730.00

-290.52 -290.52 -290.52 -290.52 -290.52 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 90.00 90.00 90.00 410.52 410.52 410.52 410.52 410.52 410.52 410.52 410.52 410.52 410.52 410.52 410.52 410.52 410.52 410.52 440.52 30.00 90.00 410.52 410.52

X uncertainty (cm)

Y uncertainty (cm)

90.00 90.00 30.00 30.00 30.00 60.00 60.00 60.00 60.00 30.00 30.00 30.00 30.00 60.00 30.00 90.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 60.00

90.00 90.00 30.00 30.00 30.00 60.00 60.00 60.00 60.00 60.00 60.00 30.00 60.00 30.00 30.00 60.00 90.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 60.00

-

-

-

-

Radiation inside concrete buildings at Nagasaki 0 W. A. RHOADES ET AL.

The plots clearly show the effects of streaming through both front and back windows, shadowing by the structure, and other transport features in general agreement with expected results. None of the “ray effects” that sometimes distort discrete ordinates transport through air are observed. It may also be of interest to look at details of the dose at three selected locations: An “exterior” point, i.e., a point calculated at the origin of the building, but without the building materials present; Point 1 (Table 3), 155 cm above the center of the first floor; and Point 3 (Table 3), 155 cm above the first floor, in front of a window facing the weapon. The dose contributions from the following source components will be listed: Prompt gamma dose leaking directly from the weapon; Air/ground capture gamma dose from leakage neutrons; Early delayed gamma dose (reaching the building before the shock wave); Late delayed gamma dose (reaching the building after the shock wave); Building capture gamma dose due to neutron capture in the building; and Prompt neutron dose due to weapon leakage. The FIA dose response for the key locations just identified is tabulated in Table 3. It can be seen that the doses in the building range from the surely-lethal 25.86 Gy to a survivable 2.08 Gy. The attenuation differs for the various sources due to spectral and directional effects. The late delayed gammas are more penetrating than the early delayed gammas due to the assumption that the light-construction walls have been removed by the shock wave. The total attenuation for the composite radiation dose ranged from about 4 near the windows, largely dependent upon window size and position, to about 50 in the building interior. Gammas

Table 3. Free-in-air doses from various sources outside the building, near a window facing the source, and deep inside the first floor of Chinzei School.

10.83 26.95 18.81 43.89 0 100.48

2.95 8.10 4.06 9.53 0.25 24.89

Point 1, center of first floor (GY) 0.16 0.59 0.29 0.83 0.1 1 1.98

3.35

__ 0.97

0.10

103.83

25.86

2.08

Exterior Point 3, near (Gy) window (Gy) Prompt gamma Air/ground capture gamma Early delayed gamma Late delayed gamma Building capture gammas All gammas (subtotal) Prompt neutron Total

515

were attenuated much more than neutrons. Capture gamma dose actually exceeded neutron dose in the center of the building. Certain low-level sources, e.g., delayed neutrons, were not included in the dose calculations due to their negligible effect as indicated in the DS86 study. Dose results: Occupant locations Tables of gamma, neutron, and total FIA dose to each of the personnel are listed in Table 4. Tables 5 and 6 list the corresponding data for the other response functions. The “case number” designation is for the purpose of coordination with a companion study (Levin et al. 1992). SHIROYAMA SCHOOL MODEL AND RESULTS Building model The south wing of the Shiroyama School at Nagasaki was a three-story rectangular structure built of

Table 4. Chinzei personnel exposure, free-in-air. Positional uncertainty

Dose (Gy) Case number Gamma Neutron

Total

0.213 0.227 3.458 1.794 3.188 17.778 6.597 10.342 18.767 1.775 2.019 2.493 3.605 3.841 4.378 2.354 2.543 34.774 27.140 15.699 11.923 27.407 7.472 12.142 10.311 3.831 3.094 5.850 3.683 3.577 5.130 5.916 5.100 7.155 4.477 13.074 12.108

0.221 0.236 3.524 1.840 3.257 18.382 6.937 10.790 19.277 1.885 2.164 2.689 3.876 4.092 4.538 2.456 2.633 35.828 28.073 16.300 12.366 28.296 7.825 12.527 10.612 4.065 3.274 6.170 3.892 3.814 5.392 6.314 5.363 7.506 4.684 13.518 12.619

1 2 3 4 5 11 12 16 17 101 102 103 104 13 92 112 115 37 32 26 27 30 40 43 46 88 89 90 93 95 97 94 96 6 18 49 54

0.008 0.009 0.066 0.046 0.069 0.604 0.340 0.448 0.510 0.110 0.145 0.197 0.271 0.250 0.160 0.103 0.090 1.055 0.933 0.601 0.443 0.889 0.353 0.385 0.301 0.233 0.181 0.320 0.208 0.237 0.262 0.398 0.263 0.351 0.207 0.445 0.512

Gamma Neutron Total 6.5 35.9 12.9 16.6 15.2 56.1 10.5 23.6 30.8 6.1 12.6 11.2 27.2 4.7 12.3 14.5 28.4 13.9 27.8 14.6 5.9 22.9 19.0 7.2 3.8 2.6 12.6 13.3 3.6 4.0 24.1 8.2 5.8

-

11.2 40.2 3.1 9.6 2.8 33.6 7.3 17.1 21.0 13.9 20.1 12.5 13.2 7.1 12.8 21.8 24.5 8.7 14.9 14.7 6.2 13.8 10.2 3.1 5.9 4.0 10.9 10.3 3.8 5.7 20.0 10.6 5.1

-

6.7 36.0 12.7 16.4 14.9 55.3 10.3 23.4 30.5 6.5 13.1 11.3 26.2 4.8 12.3 14.8 28.2 13.8 27.4 14.6 5.9 22.6 18.6 7.1 3.8 2.7 12.5 13.2 3.6 4.1 23.9 8.3 5.8

-

-

-

516

November 1992, Volume 63, Number 5

Health Physics

Table 6. Chinzei personnel exposure, bone marrow.

Table 5. Chinzei personnel exposure, small intestine. Positional uncertainty

Dose (Gy) Case number Gamma Neutron 1 2 3 4 5 11 12 16 17 101 102 103 104 13 92 112 I15 37 32 26 27 30 40 43 46 88 89 90 93 95 97 94 96 6 18 49 54

0.144 0.154 2.324 1.191 2.128 11.496 4,096 6.545 12.346 1.063 1.196 1.465 2.129 2.343 2.701 1.405 1.555 22.735 17.638 10.093 7.638 17.785 4.792 7.924 6.768 2.833 1.969 3.669 2.325 2.220 3.252 3.570 3.211 4.482 2.750 8.554 7.747

Dose (Gy)

I07 \

1/01

Total

Case number Gamma Neutron

Gamma Neutron Total

0.007 0.008 1.033 0.025 0.034 0.267 0.170 0.204 0.226 0.073 0.089 0.111 0.139 0.140 0.098 0.060 0.058 0.446 0.405 0.291 0.231 0.391 0.209 0.216 0.167 0.129 0.112 0.161 0.121 0.131 0.139 0.188 0.140 0.173 0.1 15 0.232

0.151 0.162 2.357 1.216 2.162 11.763 4.266 6.749 12.572 1.136 1.285 1.576 2.268 2.484 2.799 1.466 1.613 23.181 18.043 10.384 7.870 18.176 5.001 8.140 6.935 2.512 2.081 3.829 2.446 2.331 3.391 3.758 3.351 4.653 2.865 8.785

6.5 36.1 13.5 17.2 16.0 57.3 11.1 24.3 31.0 6.0 12.0 11.0 29.7 4.5 12.6 14.9 28.4 14.4 28.6 14.7 6.5 23.8 19.9 7.7 3.8 2.7 12.4 14.2 3.6 3.9 24.3 ~. 7.8 6.4

0265

8 012

-

-

9.2 31.6 2.5 6.7 2.1 24.9 4.1 12.8 15.5 10.6 14.4 8.8 9.1 5.4 9.6 16.3 20.8 6.3 11.0 10.4 4.5 9.0 7.2 2.6 5.2 2.6 6.6 7.8 2.0 4.1 13.0 .. 7.6 3.7

-

6.6 35.9 13.3 17.0 15.8 56.6 10.8 23.9 30.7 6.3 12.2 10.8 28.4 4.6 12.5 15.0 28.2 14.3 28.2 14.6 6.5 23.5 19.4 7.5 3.9 2.7 12.1 13.9 3.5 3.9 23.8 ~

.

7.8 6.3

-

-

-

-

-

reinforced concrete. The roof and floors were all of slab construction, supported by a framework of concrete beams and girders resting on pillars. The east end of the building faced the blast directly, and Fig. 5, taken soon after the attack, shows that it was heavily damaged. The exterior dimensions of the building were 56 m long by 9 m wide by 13 m high. The building sat on a hill about 24.4 m above sea level,’ and the first floor was taken to be 6 1 cm above ground level. The building was located west of the hypocenter at the location indicated by “16” in Fig. 2. For the purpose of this study, the hypocenter was taken to be 5 15 m from the center of the building in a direction 4.5 degrees clockwise from the west-to-east axis of the building and the epicenter was at an upward angle of approximately 44 degrees from the horizontal. A view of the building from the direction of the incident radiation is shown in Fig. 6. As in the Chinzei study, the slant range between the weapon and the elevated building was preserved by artificially moving the building inward to a ground range of 49 1 m.

.

I 2 3 4 5 11 12 16 17 101 102 103 104 13 92 112 115 37 32 26 27 30 40 43 46 88 89 90 93 95 97 94 96 6 18 49 54

0.161 0.172 2.591 1.33 1 2.375 12.891 4.634 7.374 13.799 1.212 1.366 1.674 2.429 2.659 3.06 1 1.603 1.766 25.438 19.770 11.343 8.594 19.931 5.389 8.883 7.580 2.696 2.218 4.139 2.623 2.494 3.662 4.057 3.623 5.062 3.119 9.579 8.711

0.008 0.009 0.043 0.033 0.045 0.361 0.225 0.275 0.307 0.092 0.113 0.143 0.182 0.181 0.125 0.077 0.073 0.61 1 0.552 0.388 0.304 0.531 0.268 0.280 0.2 16 0.167 0.142 0.212 0.156 0.170 0.181 0.250 0.183 0.229 0.149 0.303 0.347

Positional uncertainty (%\ \.-,

Total Gamma Neutron Total 6.5 9.4 6.6 0.169 32.6 35.9 0.181 36.1 13.4 2.6 13.2 2.634 7.2 16.9 1.364 17.1 2.420 15.8 2.3 15.6 26.7 56.2 13.252 57.1 11.0 4.6 10.7 4.859 13.7 23.7 7.650 24.1 16.7 30.6 14.106 30.9 6.0 11.0 6.3 1.304 15.2 12.3 1.479 12.1 9.4 10.8 1.817 11.0 2.61 1 29.2 9.9 27.8 4.5 5.6 4.6 2.840 12.5 10.1 12.4 3.186 17.1 14.9 1.680 14.8 21.2 28.1 1.839 2.84 14.3 6.8 14.1 26.049 11.9 27.9 20.321 28.4 11.2 14.6 11.731 14.7 6.4 4.8 6.3 8.898 20.462 23.6 10.0 23.3 5.657 19.7 7.6 19.1 7.6 2.6 7.4 9.163 7.797 3.8 5.3 3.9 2.7 2.8 2.7 2.863 2.360 12.4 7.2 12.1 8.3 13.7 4.350 14.0 2.779 3.6 2.3 3.5 2.663 3.9 4.4 4.0 14.2 23.7 3.843 24.2 4.306 7.8 8.2 7.9 3.805 6.3 3.9 6.2 5.291 3.268 9.883 9.058 -

Fig. 5. Shiroyama School complex after attack, looking southwest.

Radiation inside concrete buildings at Nagasaki 0 W. A. RHOADES ET AL.

517

The geometric model was constructed from the same record sources as the Chinzei model. External walls were 30.5 cm of solid concrete, while the floors and roof were 14-cm concrete slabs. The external stairwells on the north side were modeled, but the details of the stairsteps and floor penetrations were not. Enough of the passageway to the north buildings was modeled to give proper shielding to the northwest corner of the building. The exterior and interior appearance of the final model is shown in Fig. 6. The interior walls were entirely of light construction, represented by the same materials used in the Chinzei model. Enough information was available from the references to locate them with confidence. No information as to internal windows and doors was available, however, and those features were not modeled. The interior floor plan layout is shown in Fig. 7. The locations of occupants and uncertainties in the location coordinates were determined in the same manner as the Chinzei data. The locations and coordinate uncertainty are shown in Table 7. In this coordinate system, the origin is located at the center of the building, at the top surface of the first floor; X lies along the eastward axis of the building, and Y lies along the northward axis (the stairwells are ignored in this placing). The positions are plotted in Fig. 7. Dose results: Contour plots and selected locations Spatial contours of the common logarithm of FIA dose are shown in Fig. 7. The source is from the right side of the figure, directed toward a wall with no windows. An area of low dose can be seen immediately behind the wall. The effect of radiation streaming through the open windows on the south wall and across the room is evident in all of the plots as is the complicated nature of the contours around the passageway and stairwells. As in the case of the Chinzei School, the doses at three key locations will be examined: An “exterior” point; Point 1 (Table 8), deep inside the second floor; and Point 5 (Table 8), near a window at the east end of the building. The FIA doses from various source components are listed in Table 8. The attenuation factors for both neutrons and gammas are lower than the corresponding Chinzei factors, due partly to the presence of only two layers of concrete above the occupants and partly to the fact that all of the individuals in the building were exposed directly to the windows in the south wall. Accordingly, doses were generally higher.

Fig. 6. Model of Shiroyama School south wing showing: (a) direction of incident radiation and (b) interior detail.

48

cm above third floor:

-

4.8

85

E

> o

9

-4 8 -28.0

-14.0

0

14.0

cm above second floor:

48

85

-

4.8

I

E

> o -4.8

-26.0

-14.0

0

140

X (m)

Dose results: Occupant locations Tables of gamma, neutron, and total FIA dose to each of the personnel are shown in Table 9. Tables 10 and 1 1 list the corresponding data for the other response functions.

28.0

X (m)

Source

Direction

-

28.0

Fig. 7. Shiroyama School dose distribution. Contour labels refer to common logarithm of dose in cGy units. (Note: Most other information in this paper is given in Gy units.)

518

Health Physics

Table 7. Position data for Shiroyama School cases (X,Y,Z positions; X,Y Uncertainty). X Case position number (cm) 12 19 75 95 98 18

58 69 76 103 104 I05 36 62 Ill

117 39 80 81 82 106 112 52 113 42 56 65 I I4 94 110 10 17 30 31 53 88 21 23 32 44 48 27 43 46 47 86 91 38 41 51 54 90 101

78 87 109 1 I8 40 49 73

190.00 225.00 130.00 435.00 645.00 -290.00 -240.00 -470.00 -415.00 -470.00 -195.00 -690.00 -1,310.00 -1,030.00 - I ,045.OO 390.00 790.00 -680.00 -670.00 1,100.00 665.00 460.00 2,125.00 2,700.00 1,560.00 1,315.00 1,325.00 1,180.00 115.00 275.00 -810.00 -365.00 -390.00 -265.00 -250.00 -I 10.00 - I ,3 10.00 -1,700.00 -1,250.00 - 1,440.00 -1,545.00 -2,600.00 -2,4 15.00 -2,400.00 -2,600.00 -2,615.00 -2,235.00 -120.00 2,520.00 2,340.00 2,120.00 -2,2 10.00 1,685.00 -645.00 -645.00 -1 15.00 645.00 -1,010.00 -820.00 1,425.00

Y Z position position (cm) (cm) -135.00 456.24 -345.00 456.24 50.00 456.24 75.00 456.24 -105.00 456.24 75.00 456.24 -360.00 456.24 -360.00 456.24 -225.00 456.24 60.00 456.24 -230.00 456.24 60.00 456.24 25.00 456.24 25.00 456.24 - 135 .OO 465.24 -375.00 456.24 -290.00 456.24 -185.00 456.24 -360.00 456.24 55.00 456.24 -290.00 456.24 -275.00 456.24 55.00 822.00 55.00 822.00 20.00 822.00 20.00 822.00 -390.00 822.00 20.00 822.00 -135.00 822.00 -135.00 822.00 -380.00 822.00 -135.00 822.00 -380.00 822.00 -380.00 822.00 -160.00 822.00 -170.00 822.00 -350.00 822.00 -375.00 822.00 65.00 822.00 -365.00 822.00 20.00 822.00 -270.00 822.00 -30.00 822.00 205.00 822.00 205.00 822.00 -25.00 822.00 210.00 822.00 -370.00 822.00 75.00 822.00 75.00 822.00 270.00 822.00 -25.00 822.00 -170.00 822.00 - 170.00 822.00 -370.00 822.00 45.00 822.00 0.00 822.00 -360.00 822.00 -45.00 822.00 25.00 822.00

X uncertainty (cm) 60.00 60.00 30.00 60.00 60.00 30.00 60.00 60.00 60.00 60.00 60.00 60.00 90.00 60.00 60.00 60.00 30.00 60.00 60.00 60.00 60.00 90.00 60.00 30.00 60.00 60.00 30.00 60.00 60.00 60.00 30.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 30.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 30.00 60.00 30.00 30.00 30.00

Y uncertainty (cm) 60.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 60.00 30.00 30.00 30.00 60.00 60.00 60.00 30.00 60.00 60.00 30.00 60.00 30.00 30.00 60.00 60.00 30.00 30 .OO 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 60.00 60.00 60.00 60.00 60.00 60.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 60.00 30.00 60.00 60.00

November 1992, Volume 63, Number 5

Table 8. Free-in-air doses from various sources outside the building, near a window, and deep inside the second floor of Shirovama School. Point 1, center Exterior Point 5, near of second floor (GY) window (GY) (GY) 3.28 0.24 Prompt gamma 7.70 8.95 1.42 Air/ground capture gamma 22.30 14.07 5.48 0.45 Early delayed gamma 32.83 12.86 I .76 Late delayed gamma 0.22 Building capture gammas 0 0.23 All gammas (subtotal) 76.90 30.80 4.09

-

Prompt neutron

2.30-

Total

79.20

1.15

0.15 __

31.95

4.24

EVALUATION OF UNCERTAINTIES The uncertainty in each individual dose can be considered to be a composite of the following contributions: External fluence-the total uncertainty in calculating the fluence at the exterior boundary of the building; Building transport-the uncertainty in calculating the fluence at an interior point, given the external fluence; Position-the uncertainty due to errors in locating the position of the individual at the time of the attack; and Response function-the uncertainty in calculating the appropriate kerma, given the fluence and position. In the DS86 document, the uncertainty in delayed radiation dose due to uncertainty in the external fluence is estimated as 14%, and that value would apply to this study as well (Roesch 1987). In a discussion on 29 October 1986, Woolson also estimated an uncertainty of 15% for the prompt dose, based on comparisons with integral measurements.** (These, like all uncertainties quoted herein, are 1-sigma values, i.e., at the 67% confidence level.) Lillie (Lillie et al. 1987) performed a theoretical estimate of the prompt uncertainty, arriving at approximately 17% for locations at the ranges of interest here. Additionally, the calculation of dose inside the buildings is affected by aspects of the external fluence that are not included in that estimate, for example, uncertainties in directional distribution and energy spectrum. Based on a sensitivity study for these and other such effects, we estimate 20% uncertainty in our calculations due to external fluence uncertainty (Lillie et al. 1988). The building transport uncertainty was estimated by variations of procedural adjustments within the TORT code, by comparison with independent calcu-

** W. A. Woolson, Science Applications International Corporation, P.O. Box 2351, L a Jolla, CA 92038.

Radiation inside concrete buildings at Nagasaki 0 W. A. RHOADES ET AL.

Table 9. Shiroyama personnel exposure, free-in-air. Case number Gamma Neutron 12 19 75 95 98 18 58 69 76 103 104 105 36 62 111 117 39 80 81 82 106 112 52 113 42 56 65 114 94 110 10 17 30 31 53 88 21 23 32 44 48 27 43 46 47 86 91 38 41 51 54 90 101 78 87 109 118 40 49 73

83.477 16.687 6.038 6.538 7.598 5.163 16.987 12.755 10.145 5.423 8.299 5.575 5.165 5.217 6.402 10.127 9.884 7.994 15.644 6.415 12.744 13.273 18.851 8.466 16.517 18.357 17.405 18.182 18.476 18.000 25.200 17.627 24.222 24.028 16,457 16.064 24.316 23.881 15.066 16.970 15.615 16.082 14.758 13.514 14.292 15.310 12.541 17.022 12.683 17.157 2 1.680 12.466 16.317 17.600 21.586 14.806 16.480 15.587 16.801 18.029

0.384 0.606 0.253 0.302 0.353 0.228 0.575 0.420 0.428 0.257 0.395 0.249 0.243 0.216 0.284 0.435 0.437 0.387 0.556 0.299 0.533 0.514 0.6 12 0.5 10 0.525 0.564 0.6 17 0.590 0.607 0.644 0.718 0.588 0.701 0.767 0.587 0.521 0.705 0.689 0.458 0.590 0.479 0.583 0.504 0.490 0.503 0.497 0.468 0.6 13 0.602 0.650 0.720 0.445 0.562 0.624 0.734 0.429 0.563 0.558 0.506 0.547

Table 10. Shiroyama personnel exposure, small intestine.

Positional uncertainty,

Dose, (GY)

(%\ \

Total 8.731 17.293 6.290 6.840 7.952 5.391 17.563 13.175 10.574 5.680 8.693 5.824 5.408 5.433 6.686 10.561 10.322 8.381 16.200 6.7 15 13.277 13.787 19.463 8.976 17.042 18.92 1 18.022 18.772 19.083 18.644 25.9 18 18.216 24.923 24.795 17.044 16.586 25.021 24.570 15.524 17.561 16.094 16.665 15.263 14.005 14.795 15.808 13.009 17.635 13.286 17.807 22.400 12.91 1 16.879 18.224 22.320 15.235 17.043 16.146 17.307 18.577

I

Gamma Neutron Total 11.6 15.6 3.9 6.2 7.3 2.6 14.7 27.2 24.1 7.3 10.5 2.9 10.2 8.3 11.9 24.0 16.2 13.9 18.9 7.4 21.9 13.9 7.3 6.8 4.9 4.4 13.0 2.9 1.7 3.2 4.4 3.2 10.7 9.3 3.5 4.5 8.2 4.6 3.8 14.2 3.1 9.2 5 .O 5 .O 2.9 4.9 5.2 10.9 11.5 4.1 9.7 9.1 5.1 2.8 12.9 3.8 3.5 7.8 4.1 5.3

12.6 7.1 3.7 7.7 6.6 3.5 7.6 14.1 13.1 9.1 10.3 3.4 9.1 9.1 13.6 11.4 12.5 12.6 9.4 5.0 9.8 7.0 15.3 3.1 4.3 4.4 8.1 4.4 5.2 4.2 6.2 4.0 12.1 6.5 4.4 7.6 8.8 7.8 3.9 7.8 4.4 5.6 3.2 2.1 3.3 4.6 4.0 8.6 4.0 1.5 17.4 8.2 9.3 3.9 7.4 4.2 4.0 8.5 8.2 7.8

519

11.7 15.3 3.9 6.3 7.3 2.6 14.5 26.8 23.7 7.4 10.5 3.0 10.2 8.4 11.9 23.5 16.1 13.8 18.6 7.3 21.4 13.6 7.5 6.6 4.9 4.4 12.8 3.0 1.8 3.2 4.4 3.2 10.7 9.2 3.5 4.6 8.2 4.7 3.8 14.0 3.1 9.1 5 .O 4.9 2.9 4.9 10.8 11.2 4.0 10.0 9.1 5.2 2.8 12.7 3.8 3.5 7.8 4.2 5.3

Positional uncertainty,

Dose, (GY) Case number Gamma Neutron 12 19 75 95 98 18 58 69 76 103 104 105 36 62 111 117 39 80 81 82 106 112 52 113 42 56 65 114 94 110 10 17 30 31 53 88 21 23 32 44 48 27 43 46 47 86 91 38 41 51 54 90 101 78 87 109 118 40 49 73

5.243 10.696 3.8 15 4.075 4.748 3.228 10.932 8.308 6.429 3.388 5.159 3.497 3.226 3.266 4.004 6.469 6.190 5.004 10.057 3.989 8.055 8.473 12.330 5.3 18 10.723 1.2000 11.315 1.826 11,992 11.629 16.505 11.438 15.890 15.599 10.584 10.346 15.898 15.610 9.803 11.012 10.190 10.422 9.599 8.742 9.293 10.038 8.046 10.922 8.093 11.134 14.086 8.005 10.479 11.394 13.979 9.587 10.637 9.983 10.980 11.777

0.196 0.267 0.152 0.169 0.189 0.138 0.250 0.200 0.202 0.146 0.196 0.144 0.138 0.134 0.158 0.214 0.222 0.190 0.244 0.174 0.247 0.236 0.302 0.265 0.270 0.284 0.298 0.294 0.294 0.304 0.317 0.279 0.310 0.332 0.28 1 0.264 0.303 0.299 0.235 0.270 0.236 0.256 0.235 0.23 1 0.23 1 0.229 0.225 0.290 0.297 0.3 13 0.337 0.219 0.285 0.290 0.321 0.233 0.283 0.268 0.256 0.277

(%I Total 5.439 10.963 3.967 4.245 4.937 3.366 11.183 8.508 6.63 1 3.534 5.355 3.642 3.365 3.400 4.162 6.682 6.412 5.194 10.301 4.162 8.301 8.709 12.633 5.583 10.993 1.2284 11.613 12.120 12.286 11.933 16.822 11.717 16.200 15.931 10.865 10.610 16.202 15.909 10.038 11.?82 10.426 10.678 9.835 8.973 9.524 10.267 8.271 11.212 8.389 11.447 14.422 8.224 10.764 11.684 14.301 9.821 10.92 1 10.250 11.236 12.054

Gamma Neutron Total 11.5 16.3 4.0 6.0 7.4 2.3 15.3 28.0 25.1 7.1 10.8 3.0 10.5 8.7 11.7 24.8 16.9 13.8 19.5 7.8 23.2 14.4 7.1 7.1 5.2 4.3 13.2 2.9 1.7 3.3 4.2 3.3 10.3 9.5 3.7 4.5 8.0 4.5 4.2 14.5 3.1 9.4 5.4 5.2 3.0 5.0 4.1 10.9 12.1 4.3 9.6 9.4 5.2 2.8 13.1 3.8 3.7 7.8 3.9 5.2

8.2 4.7 2.1 4.0 3.9 2.0 4.6 9.2 8.7 4.7 6.1 1.8 5.2 4.6 7.8 7.5 7.3 8.5 6.5 2.5 5.9 4.5 9.7 2.3 2.6 2.4 5.4 2.8 2.9 2.7 4.0 2.4 8.3 4.3 2.5 3.8 6.1 5.1 2.2 5.0 2.7 3.8 2.1 1.4 2.1 3.1 2.9 5.2 2.9 1.o 10.8 4.9 5.2 2.5 5.0 2.3 2.3 4.8 4.9 4.9

11.4 16.0 4.0 5.9 7.3 2.3 15.1 27.6 24.6 7.0 10.6 3.0 10.3 8.6 11.5 24.2 16.5 13.6 19.2 7.5 22.7 14.2 7.2 6.9 5.1 4.3 13.0 2.9 1.7 3.3 4.2 3.3 10.2 9.4 3.6 4.5 8.0 4.5 4.1 14.2 3.1 9.3 5.3 5.1 2.9 5.0 4.1 10.8 11.8 4.2 9.7 9.3 5.2 2.8 12.9 3.7 3.7 7.7 3.9 5.2

520

Health Physics

Table 11. Shirovama Dersonnel exDosure. bone marrow. Dose, (GY) Case number Gamma Neutron Total 12 19 75 95 98 18 58 69 76 I03 I04 105 36 62 111

I17 39 80 81 82 106 112 52 1 I3 42 56 65 1 I4 94 I10 10 17 30 31 53 88 21 23 32 44 48 27 43 46 47 86 91 38 41 51 54 90 101

78 87 109 118 40 49 73

5.918 12.011 4.304 4.609 5.365 3.648 12.265 9.304 7.240 3.830 5.832 3.950 3.648 3.69 1 4.524 7.274 6.986 5.650 t1.286 4.514 9.072 9.526 13.816 6.012 12.033 13.448 12.689 13.266 13.455 13.060 18.468 12.834 17.776 17.483 11.896 1.1625 17.795 17.472 10.997 12.350 11.423 11.692 10.766 9.815 10.422 11.241 9.048 12.274 9.1 15 12.495 15.797 9.001 1 I .782 12.790 15.677 10.765 11.951 1 1.224 12.305 13.200

0.257 0.36 1 0.195 0.2 19 0.246 0.176 0.340 0.267 0.270 0.188 0.259 0.186 0.178 0.171 0.204 0.283 0.292 0.252 0.330 0.224 0.330 0.317 0.400 0.346 0.355 0.375 0.396 0.389 0.391 0.406 0.429 0.372 0.419 0.45 1 0.374 0.348 0.4 13 0.406 0.309 0.363 0.313 0.346 0.3 I4 0.308 0.309 0.307 0.299 0.386 0.392 0.416 0.450 0.290 0.375 0.388 0.435 0.304 0.374 0.356 0.338 0.366

6.175 12.372 4.498 4.828 5.61 1 3.825 12.604 9.571 7.509 4.0 I8 6.091 4.136 3.826 3.861 4.728 7.556 7.278 5.902 11.616 4.737 9.402 9.843 14.215 6.358 12.388 13.823 13.085 13.655 13.846 13.466 18.897 13.206 18.195 17.934 12.270 11.973 18.208 17.878 11.305 12.713 11.736 12.038 11.081 10.123 10.731 11.548 9.346 12.660 9.507 12.911 16.247 9.291 12.157 13.178 16.1 12 1 1.069 12.325 11.579 12.643 13.565

Positional uncertainty, (V.\ I'"I

Gamma Neutron Total 11.5 16.1 4.0 6.1 7.4 2.4 15.2 27.8 24.9 7.1 10.7 3.0 10.4 8.6 11.7 24.6 16.7 13.8 19.4 7.1 22.9 14.3 7.1 7.0 5.1 4.3 13.1 2.9 1.7 3.3 4.2 3.3 10.3 9.4 3.6 4.5 8.0 4.5 4.1 14.4 3. I 9.3 5.3 5.2 2.9 5.0 4.1 10.9 12.0 4.2 9.6 9.3 5.2 2.8 13.0 3.8 3.7 7.8 3.9 5.2

9.0 5.3 2.4 4.6 4.4 2.2 5.2 10.2 9.6 5.5 6.8 2.1 5.8 5.2 8.7 8.2 8.2 9.3 7.1 2.9 6.7 5.1 10.6 2.4 2.9 2.7 5.9 3.1 3.3 3.0 4.5 2.7 9.1 4.8 2.9 4.5 6.7 5.6 2.5 5.6 3.0 4.2 2.3 1.5 2.4 3.4 3.3 5.9 3. I 1.1 11.9 5.5 5.9 2.7 5.6 2.7 2.6 5.5 5.5 5.4

11.4 15.8 3.9 6.0 7.2 2.4 14.9 27.3 24.3 7.0 10.6 3.0 10.2 8.5 11.6 24.0 16.4 13.6 19.1 7.5 22.3 14.0 7.2 6.8 5.1 4.3 12.9 2.9 1.7 3.3 4.2 3.3 10.3 9.3 3.6 4.5 8.0 4.5 4.0 14.1 3.1 9.2 5.2 5.1 2.9 4.9 4.0 10.8 11.6 4.1 9.7 9.2 5.2 2.8 12.8 3.7 3.6 7.7 4.0 5.2

lations, and by comparison with the experimental building constructed and tested at Oak Ridge (Muck-

November 1992, Volume 63, Number 5

enthaler 1985; Rhoades et al. 1985; Rhoades et al. 1989). In the building experiment, the gamma dose uncertainty in areas touched by streaming through the windows was typically about 17%, and that value was adopted as representative of the transport uncertainty in the present study. A formal estimate of the effect of uncertainty in personnel location was made. As each position was determined, an estimate of the uncertainty in the horizontal coordinates was determined, as listed in previous tables. The variation in each dose due to displacement by that amount was calculated, resulting in a mean uncertainty of 14%. The effect of uncertainty in the FIA response function has been estimated as 2% for gammas and 5% for neutrons. The gamma dose predominates in these calculations, so the 2% value is also applicable to the combined total. The internal doses, i.e., the SI and BM doses, are susceptible to other uncertainties, however. The Monte Carlo calculation that resulted in the response functions had statistical convergence on the order of 2% (Rhoades et al. 1989). Uncertainty in modeling the human form apply, and cross-section uncertainty is a contributor. This study did not consider the directional asymmetry of organ response, but that is also a significant effect (Roesch 1987). The DS86 document lists several examples of variation due to horizontal rotation, of which the kerma in bone marrow of a standing male is most applicable to this study. The data listed fall within a range of &3% for prompt gamma dose and &5% for delayed gammas. The 1sigma uncertainty would be expected to be less than the complete range of data, of course. Studies related to the DS86 report suggested a 6% uncertainty in dose to the bone marrow due to these various effects, and that value is accepted for the present use. All uncertainties except uncertainty in the external source have a relatively random effect from position to

Table 12. Overall dose uncertainty (%). FIA dose

Internal dose

Random uncertainty Building transport process Position Response function, including orientation efects Total random uncertainty

17 14

17 14

2 22

6 -

Correlated uncertainty External fluence

20

20

Overall uncertainty Composite

30

30

23

Note: These uncertainties combine as squares since they are statistically independent of each other.

Radiation inside concrete buildings at Nagasaki 0 W. A. RHOADES ET AL,

position. Furthermore, the types of uncertainty are relatively independent of each other. Accordingly, they have been combined as independent to give the composite random uncertainties in Table 12. The source uncertainty is relatively independent of the other types of uncertainty, although it tends to apply to all positions equally. Accordingly, it contributes to the total uncertainty as shown in the table. From these data, presuming that internal dose is a better indicator of mortality risk than FIA dose, we conclude that 23% of the observed case-to-case randomness would be due to errors in dose calculation. The overall uncertainty in individual doses, considering the 20% source uncertainty, would be 30%. It should be noted, however, that the total uncertainty in a collective parameter such as LD50 will be different from the uncertainty in each individual case and can only be derived from an appropriate statistical analysis.

SUMMARY The objective of this study was to determine the radiation doses to occupants of two reinforced concrete buildings during the World War I1 nuclear attack on Nagasaki. Previous work had determined the fluence in the vicinity of the buildings. This study constructed radiation models of the buildings, calculated the radiation inside the buildings, and determined the dose to each occupant. A parallel effort determined the locations of the occupants and the physical injuries from the radiation exposure. The dose calculation centered about a three-dimension discrete ordinates code, TORT, constructed especially for this study. As reported elsewhere (Rhoades et al. 1989), the validity of TORT was tested in comparisons with various alternate methods of calculation and with an experimental simulation of the concrete buildings. Code input parameters and numerical flux models were varied in order to find the most suitable combinations to achieve the desired accuracy. The construction of analytical models of the buildings was particularly difficult, since the buildings were heavily damaged by the attack and were later demolished. Various postwar records and photographs were pieced together to form the best composite. Of all the details, the size and positioning of the windows were the most important, and the existence of high-quality glossy photographs helped in modeling them correctly. An uncertainty analysis indicated random case-tocase uncertainties of 22% in FIA dose and 23% in SI or BM dose. An overall uncertainty of 30% for all dose types was estimated, including the consistent 20% uncertainty in the external fluence. The use of numerous cases in deducing a single parameter like the LD50 would mitigate the effect of the random component,

52 1

thus driving the uncertainty in that parameter toward the 20% value.

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Radiation exposure inside reinforced concrete buildings at Nagasaki.

In this study, the radiation doses to occupants of two reinforced concrete buildings at Nagasaki, who survived the immediate effects of the nuclear we...
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