Society for Radiological Protection
Journal of Radiological Protection
J. Radiol. Prot. 34 (2014) N41–N46
doi:10.1088/0952-4746/34/2/N41
Note
Assessment of radiation doses in the UK from the Fukushima Daiichi Nuclear accident J Brown PHE-CRCE, Chilton, Didcot, Oxon OX11 0RQ, UK E-mail: [email protected] Received 24 October 2013, revised 5 February 2014 Accepted for publication 26 February 2014 Published 14 April 2014 Abstract
PHE has undertaken a simple dose assessment for members of the public living in the UK at the time of the accident at the Fukushima Daiichi nuclear power station in March 2011. PHE reported that there was no public health risk to the UK from the release of material from the accident in a statement made on 29 March 2013. This assessment confirms the initial estimate of the doses which were about the same as a person in the UK would receive in an hour from natural background. Keywords: Fukushima, radiation doses, UK
1. Introduction
On 11 March 2011 an earthquake of magnitude 9.0 occurred near Honshu, Japan that created a tsunami. The earthquake and subsequent tsunami led to the loss of off-site and on-site electrical power and compromised safety systems at the Fukushima Daiichi Nuclear Power Plant. Severe core damage to three of the six nuclear reactors on the site occurred that resulted in a release of radioactivity to the atmosphere and sea. The majority of the releases to atmosphere occurred during the period 12–22 March, with the highest releases between 14 and 17 March. Increased levels of radioactivity in the environment were measured in the UK but, due to the large distance between the UK and Japan, these were extremely small and not of concern to public health. Public Health England (PHE) has undertaken a simple dose assessment for members of the public living in the UK at the time of the accident at the Fukushima Daiichi nuclear power station. The estimated doses, based on the measurements made, can be compared with those from other sources of radiation exposure in the UK. The dose assessment is summarised in this note. 0952-4746/14/020041+06$33.00
c 2014 IOP Publishing Ltd
Printed in the UK
N41
J. Radiol. Prot. 34 (2014) N41
Note
2. Environmental monitoring data for the UK
Public Health England (formerly the Health Protection Agency at the time of the accident in 2011) runs a small programme of routine environmental monitoring of a range of radionuclides in air and milk across the UK. On 29 March, routine air monitoring stations at the PHE sites at Glasgow and Chilton, Oxfordshire detected very low levels of iodine-131 (131 I) in air (Hammond et al 2012). PHE increased the frequency of air monitoring at its four air monitoring stations and also took a number of other environmental samples for analysis. Other routine environmental monitoring is undertaken by the Environment Agency (EA), Scottish Environment Protection Agency (SEPA) and Northern Ireland Environment Agency (NIEA) (Environment Agency et al 2012). PHE collated the air monitoring and other environmental monitoring data in surface water, rainwater and ground deposition on behalf of EA, SEPA and NIEA after the accident and published it on the HPA website until the middle of July 2011. The measurements made in the UK following the accident are compiled in the annual Radioactivity in Food and the Environment (RIFE) report, 2011 (Environment Agency et al 2012). Measurements of radionuclides in milk were also made by the Food Standards Agency (FSA) as part of their normal surveillance programme and these data are also included in the RIFE report. The locations where air monitoring was carried out across the UK are shown in figure 1. A summary of all the monitoring locations and types of sample taken in the UK after the accident can be found in the 2011 RIFE report (Environment Agency et al 2012). These included a few measurements made in rainwater, the majority of which did not contain levels of radionuclides distinguishable from background levels in the UK. The highest activity concentrations in air were measured for the volatile fission products iodine-131 (131 I), caesium-137 (137 Cs) and caesium-134 (134 Cs); lower levels of tellurium-132 (132 Te) were also detected. The highest recorded 131 I activity concentration was about 850 µBq m−3 in the period 21–28 March. The highest total caesium (137 Cs + 134 Cs) activity concentration in air was in the period 3–9 April but was lower at 270 µBq m−3 . Measurements made of activity concentrations in air showed very similar levels across the UK. This is expected as the accident happened more than 9000 km away from the UK. All the measurements made across the UK were therefore used to provide a robust estimate of the variation of the activity concentrations of each radionuclide as a function of time for the whole period when radionuclides were detected. Figure 2 shows the weekly average activity concentrations in air measured across the UK. It was expected that UK food, including milk, would not be significantly affected by releases from the accident. At the time of the accident the majority of dairy cows in the UK were not grazing on pasture and, in most of the milk samples collected, radionuclides were not detectable in milk. However, in a few samples collected in England, very low levels of 131 I were detected. Measurements of radionuclides in grass and soil samples were made by PHE. These were used to obtain deposition levels for 131 I of 2.5 Bq m−2 and 1.7 Bq m−2 based on measurements made on 30 and 31 March, respectively in Oxfordshire. The highest measurement was taken as being representative of the total deposition and any further contributions to the total deposition after the end of March were assumed to be small. This assumption is supported by the rapid decrease in activity concentrations in air after the end of March. It was not possible to distinguish the measured deposition of 137 Cs (0.6 Bq m−2 ) from normal background levels (Hammond et al 2012); no 134 Cs was measured above detection limits in grass and soil. Table 1 shows the activity concentrations in the environment used for the dose assessment. N42
J. Radiol. Prot. 34 (2014) N41
Note
Figure 1. Air monitoring locations in the UK.
3. Assessment of radiation doses
Radiation doses were estimated for the main exposure pathways; inhalation of airborne radioactivity, ingestion of food and external irradiation from radionuclides deposited on the ground. Surface water and rainwater samples were collected at several locations across the UK and 131 I was detected in a few rainwater samples with a maximum activity concentration of about 1 Bq l−1 . The potential ingestion doses from drinking rainwater for a period of 2 days at this activity concentration, e.g. whilst camping, were also considered. Doses from external irradiation from material on the ground were estimated using a model and the deposition measurements (Kowe et al 2007). Account was taken of the time people spend indoors and the protection offered by buildings. N43
J. Radiol. Prot. 34 (2014) N41
Note
Figure 2. Weekly activity concentrations in air measured across the UK following the accident at the Fukushima Daiichi nuclear power station.
Activity concentrations used in the dose assessment. (Notes: NM not measured. NC not distinguishable from normal background levels in the UK/no evidence that levels in the environment were due to the accident.) Table 1.
Radionuclide Sample type
131 I
132 Te
134 Cs
137 Cs
Time integrated activity concentration in air (Bq s m−3 ) Rainwater (Bq l−1 ) Deposition (Bq m−2 ) Milk (Bq l−1 )
500a
10
70
80
1 3 0.3
NM NM NM
NC NC NC
NC NC NC
a Particulate measured. Particulate form assumed to be 20% of total activity concentration with
remainder in gaseous form (Masson et al 2011) which is comparable to the values reported following the Chernobyl accident (Morrey et al 1988).
The highest measured activity concentration in milk (see table 1) was used with PHE’s foodchain model (Brown and Simmonds 1995) to estimate the variation of activity concentrations with time after the accident. The model was also used to estimate activity concentrations in green vegetables, as some varieties could have been growing outdoors at the time of the accident. Table 2 shows the estimated committed effective doses for different age groups and exposure pathways. N44
J. Radiol. Prot. 34 (2014) N41
Note
Table 2. Estimated dosesa,b (Sv) for 1 and 10 year old children and adults.
Exposure pathway
1 year old
10 year old
Adult
Inhalationc Ingestiond
2 × 10−8 3 × 10−9 2 × 10−7 1 × 10−10
2 × 10−8 2 × 10−9 4 × 10−8 1 × 10−10
1 × 10−8 2 × 10−9 1 × 10−8 1 × 10−10
2 × 10−7
6 × 10−8
3 × 10−8
Green vegetables Milk
External dose from deposition Total
a Values have been rounded to 1 significant figure. b The doses estimated are committed effective doses. c Inhalation doses are calculated by multiplying the activity concentration in air (table 1) by a
breathing rate and an inhalation dose coefficient for the radionuclide/age group being considered (ICRP 1996). d Ingestion doses are calculated by multiplying the activity concentration in food (table 1) by an ingestion rate and an ingestion dose coefficient for the radionuclide/age group being considered (ICRP 1996).
The committed effective doses1 estimated for people living in the UK due to the accident at the Fukushima Daiichi nuclear power station are 2.0×10−7 Sv or lower. Watson et al (2005) estimated that the average annual dose for the UK population is 2.7 × 10−3 Sv which is four orders of magnitude higher. To give context, these doses are so small that they are about the same as a person in the UK would receive in an hour from natural background. The ingestion doses that have been calculated are cautious and likely to be over estimates. In particular, the estimated doses from ingestion of milk, which are the main contributor to the total dose for children, are based on levels in milk only observed at a few farms across the UK. Across the majority of the country, there would not have been any doses arising from this exposure pathway as cows were not grazing pasture outdoors. The potential doses to individuals consuming rainwater for a few days after the release from the accident reached the UK are estimated to be between about 1×10−8 and 1×10−7 Sv. These doses are also extremely low. Radiation doses have also been estimated for people living in Ireland (McGinnity et al 2012). Doses to adults of 2.6 × 10−7 Sv have been reported. These doses are also extremely low but are higher than those estimated for adults in the UK. This is because the maximum activity concentrations in air and milk were used and assumed to be constant for a 2 month period; no account was taken of the reduction of activity concentrations with time. PHE reported that there was no public health risk to the UK from the release of radioactive material from the accident at the Fukushima Daiichi nuclear power plant in a statement made on 29 March 2013 and subsequently. Doses ‘equivalent to around 1/10 000 of that received from natural radiation’ were estimated (14 April 2013). This assessment confirms the initial estimate of the doses made.
Acknowledgment
The author would like to thank Dr A Eslava-Gomez for her significant contribution to this study. 1 The committed effective dose is the committed dose to age 70 from inhalation during the period when activity
concentrations in air were elevated following the Fukushima Daiichi accident and from ingestion of food over the first year plus doses arising from external irradiation in the first year after the accident. N45
J. Radiol. Prot. 34 (2014) N41
Note
References Brown J and Simmonds J R 1995 FARMLAND: a dynamic model for the transfer of radionuclides through terrestrial foodchains NRPB Report NRPB-R273 (London: HMSO) Environment Agency, Northern Ireland Environment Agency, Food Standards Agency and Scottish Environment Protection Agency 2012 Radioactivity in Food and the Environment 2011 RIFE-17 (Bristol, Belfast, London, Stirling: EA, NIEA, FSA, SEPA) Hammond D, Pritchard R J and Davidson M 2012 Environmental radioactivity surveillance programme: results for 2011 including monitoring following the Fukushima Dai-ichi accident in Japan Report HPA-CRCE-041 (Chilton, UK: HPA) ICRP 1996 Age-dependent doses to members of the public from intake of radionuclides. Pt.5: compilation of ingestion and inhalation dose coefficients ICRP Publication 72; Ann. ICRP 26 (1) (Oxford: Pergamon) Kowe R, Carey A D, Jones J A and Mobbs S F 2007 GRANIS: a model for the assessment of external photon irradiation from contaminated media of infinite lateral extent Report HPA-RD-032 (Chilton, UK: HPA) Masson O et al 2011 Tracking of airborne radionuclides from the damaged Fukushima Dai-Ichi nuclear reactors by European networks Environ. Sci. Technol. 45 7670–7 McGinnity P et al 2012 Assessment of the Impact on Ireland of the 2011 Fukushima Nuclear Accident Radiological Protection Institute of Ireland, RPII 12/01 Morrey M, Brown J, Williams A J, Crick M J, Simmonds R J and Hill D M 1988 A preliminary assessment of the radiological impact of the Chernobyl reactor accident on the population of the European Community Radiation Protection EUR 11523 Watson J S, Jones L A, Oatway B W and Hughes S J 2005 Ionising radiation exposure of the UK population: 2005 review Report HPA-RPD-001
N46
Copyright of Journal of Radiological Protection is the property of IOP Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
Journal of Radiological Protection
J. Radiol. Prot. 34 (2014) N41–N46
doi:10.1088/0952-4746/34/2/N41
Note
Assessment of radiation doses in the UK from the Fukushima Daiichi Nuclear accident J Brown PHE-CRCE, Chilton, Didcot, Oxon OX11 0RQ, UK E-mail: [email protected] Received 24 October 2013, revised 5 February 2014 Accepted for publication 26 February 2014 Published 14 April 2014 Abstract
PHE has undertaken a simple dose assessment for members of the public living in the UK at the time of the accident at the Fukushima Daiichi nuclear power station in March 2011. PHE reported that there was no public health risk to the UK from the release of material from the accident in a statement made on 29 March 2013. This assessment confirms the initial estimate of the doses which were about the same as a person in the UK would receive in an hour from natural background. Keywords: Fukushima, radiation doses, UK
1. Introduction
On 11 March 2011 an earthquake of magnitude 9.0 occurred near Honshu, Japan that created a tsunami. The earthquake and subsequent tsunami led to the loss of off-site and on-site electrical power and compromised safety systems at the Fukushima Daiichi Nuclear Power Plant. Severe core damage to three of the six nuclear reactors on the site occurred that resulted in a release of radioactivity to the atmosphere and sea. The majority of the releases to atmosphere occurred during the period 12–22 March, with the highest releases between 14 and 17 March. Increased levels of radioactivity in the environment were measured in the UK but, due to the large distance between the UK and Japan, these were extremely small and not of concern to public health. Public Health England (PHE) has undertaken a simple dose assessment for members of the public living in the UK at the time of the accident at the Fukushima Daiichi nuclear power station. The estimated doses, based on the measurements made, can be compared with those from other sources of radiation exposure in the UK. The dose assessment is summarised in this note. 0952-4746/14/020041+06$33.00
c 2014 IOP Publishing Ltd
Printed in the UK
N41
J. Radiol. Prot. 34 (2014) N41
Note
2. Environmental monitoring data for the UK
Public Health England (formerly the Health Protection Agency at the time of the accident in 2011) runs a small programme of routine environmental monitoring of a range of radionuclides in air and milk across the UK. On 29 March, routine air monitoring stations at the PHE sites at Glasgow and Chilton, Oxfordshire detected very low levels of iodine-131 (131 I) in air (Hammond et al 2012). PHE increased the frequency of air monitoring at its four air monitoring stations and also took a number of other environmental samples for analysis. Other routine environmental monitoring is undertaken by the Environment Agency (EA), Scottish Environment Protection Agency (SEPA) and Northern Ireland Environment Agency (NIEA) (Environment Agency et al 2012). PHE collated the air monitoring and other environmental monitoring data in surface water, rainwater and ground deposition on behalf of EA, SEPA and NIEA after the accident and published it on the HPA website until the middle of July 2011. The measurements made in the UK following the accident are compiled in the annual Radioactivity in Food and the Environment (RIFE) report, 2011 (Environment Agency et al 2012). Measurements of radionuclides in milk were also made by the Food Standards Agency (FSA) as part of their normal surveillance programme and these data are also included in the RIFE report. The locations where air monitoring was carried out across the UK are shown in figure 1. A summary of all the monitoring locations and types of sample taken in the UK after the accident can be found in the 2011 RIFE report (Environment Agency et al 2012). These included a few measurements made in rainwater, the majority of which did not contain levels of radionuclides distinguishable from background levels in the UK. The highest activity concentrations in air were measured for the volatile fission products iodine-131 (131 I), caesium-137 (137 Cs) and caesium-134 (134 Cs); lower levels of tellurium-132 (132 Te) were also detected. The highest recorded 131 I activity concentration was about 850 µBq m−3 in the period 21–28 March. The highest total caesium (137 Cs + 134 Cs) activity concentration in air was in the period 3–9 April but was lower at 270 µBq m−3 . Measurements made of activity concentrations in air showed very similar levels across the UK. This is expected as the accident happened more than 9000 km away from the UK. All the measurements made across the UK were therefore used to provide a robust estimate of the variation of the activity concentrations of each radionuclide as a function of time for the whole period when radionuclides were detected. Figure 2 shows the weekly average activity concentrations in air measured across the UK. It was expected that UK food, including milk, would not be significantly affected by releases from the accident. At the time of the accident the majority of dairy cows in the UK were not grazing on pasture and, in most of the milk samples collected, radionuclides were not detectable in milk. However, in a few samples collected in England, very low levels of 131 I were detected. Measurements of radionuclides in grass and soil samples were made by PHE. These were used to obtain deposition levels for 131 I of 2.5 Bq m−2 and 1.7 Bq m−2 based on measurements made on 30 and 31 March, respectively in Oxfordshire. The highest measurement was taken as being representative of the total deposition and any further contributions to the total deposition after the end of March were assumed to be small. This assumption is supported by the rapid decrease in activity concentrations in air after the end of March. It was not possible to distinguish the measured deposition of 137 Cs (0.6 Bq m−2 ) from normal background levels (Hammond et al 2012); no 134 Cs was measured above detection limits in grass and soil. Table 1 shows the activity concentrations in the environment used for the dose assessment. N42
J. Radiol. Prot. 34 (2014) N41
Note
Figure 1. Air monitoring locations in the UK.
3. Assessment of radiation doses
Radiation doses were estimated for the main exposure pathways; inhalation of airborne radioactivity, ingestion of food and external irradiation from radionuclides deposited on the ground. Surface water and rainwater samples were collected at several locations across the UK and 131 I was detected in a few rainwater samples with a maximum activity concentration of about 1 Bq l−1 . The potential ingestion doses from drinking rainwater for a period of 2 days at this activity concentration, e.g. whilst camping, were also considered. Doses from external irradiation from material on the ground were estimated using a model and the deposition measurements (Kowe et al 2007). Account was taken of the time people spend indoors and the protection offered by buildings. N43
J. Radiol. Prot. 34 (2014) N41
Note
Figure 2. Weekly activity concentrations in air measured across the UK following the accident at the Fukushima Daiichi nuclear power station.
Activity concentrations used in the dose assessment. (Notes: NM not measured. NC not distinguishable from normal background levels in the UK/no evidence that levels in the environment were due to the accident.) Table 1.
Radionuclide Sample type
131 I
132 Te
134 Cs
137 Cs
Time integrated activity concentration in air (Bq s m−3 ) Rainwater (Bq l−1 ) Deposition (Bq m−2 ) Milk (Bq l−1 )
500a
10
70
80
1 3 0.3
NM NM NM
NC NC NC
NC NC NC
a Particulate measured. Particulate form assumed to be 20% of total activity concentration with
remainder in gaseous form (Masson et al 2011) which is comparable to the values reported following the Chernobyl accident (Morrey et al 1988).
The highest measured activity concentration in milk (see table 1) was used with PHE’s foodchain model (Brown and Simmonds 1995) to estimate the variation of activity concentrations with time after the accident. The model was also used to estimate activity concentrations in green vegetables, as some varieties could have been growing outdoors at the time of the accident. Table 2 shows the estimated committed effective doses for different age groups and exposure pathways. N44
J. Radiol. Prot. 34 (2014) N41
Note
Table 2. Estimated dosesa,b (Sv) for 1 and 10 year old children and adults.
Exposure pathway
1 year old
10 year old
Adult
Inhalationc Ingestiond
2 × 10−8 3 × 10−9 2 × 10−7 1 × 10−10
2 × 10−8 2 × 10−9 4 × 10−8 1 × 10−10
1 × 10−8 2 × 10−9 1 × 10−8 1 × 10−10
2 × 10−7
6 × 10−8
3 × 10−8
Green vegetables Milk
External dose from deposition Total
a Values have been rounded to 1 significant figure. b The doses estimated are committed effective doses. c Inhalation doses are calculated by multiplying the activity concentration in air (table 1) by a
breathing rate and an inhalation dose coefficient for the radionuclide/age group being considered (ICRP 1996). d Ingestion doses are calculated by multiplying the activity concentration in food (table 1) by an ingestion rate and an ingestion dose coefficient for the radionuclide/age group being considered (ICRP 1996).
The committed effective doses1 estimated for people living in the UK due to the accident at the Fukushima Daiichi nuclear power station are 2.0×10−7 Sv or lower. Watson et al (2005) estimated that the average annual dose for the UK population is 2.7 × 10−3 Sv which is four orders of magnitude higher. To give context, these doses are so small that they are about the same as a person in the UK would receive in an hour from natural background. The ingestion doses that have been calculated are cautious and likely to be over estimates. In particular, the estimated doses from ingestion of milk, which are the main contributor to the total dose for children, are based on levels in milk only observed at a few farms across the UK. Across the majority of the country, there would not have been any doses arising from this exposure pathway as cows were not grazing pasture outdoors. The potential doses to individuals consuming rainwater for a few days after the release from the accident reached the UK are estimated to be between about 1×10−8 and 1×10−7 Sv. These doses are also extremely low. Radiation doses have also been estimated for people living in Ireland (McGinnity et al 2012). Doses to adults of 2.6 × 10−7 Sv have been reported. These doses are also extremely low but are higher than those estimated for adults in the UK. This is because the maximum activity concentrations in air and milk were used and assumed to be constant for a 2 month period; no account was taken of the reduction of activity concentrations with time. PHE reported that there was no public health risk to the UK from the release of radioactive material from the accident at the Fukushima Daiichi nuclear power plant in a statement made on 29 March 2013 and subsequently. Doses ‘equivalent to around 1/10 000 of that received from natural radiation’ were estimated (14 April 2013). This assessment confirms the initial estimate of the doses made.
Acknowledgment
The author would like to thank Dr A Eslava-Gomez for her significant contribution to this study. 1 The committed effective dose is the committed dose to age 70 from inhalation during the period when activity
concentrations in air were elevated following the Fukushima Daiichi accident and from ingestion of food over the first year plus doses arising from external irradiation in the first year after the accident. N45
J. Radiol. Prot. 34 (2014) N41
Note
References Brown J and Simmonds J R 1995 FARMLAND: a dynamic model for the transfer of radionuclides through terrestrial foodchains NRPB Report NRPB-R273 (London: HMSO) Environment Agency, Northern Ireland Environment Agency, Food Standards Agency and Scottish Environment Protection Agency 2012 Radioactivity in Food and the Environment 2011 RIFE-17 (Bristol, Belfast, London, Stirling: EA, NIEA, FSA, SEPA) Hammond D, Pritchard R J and Davidson M 2012 Environmental radioactivity surveillance programme: results for 2011 including monitoring following the Fukushima Dai-ichi accident in Japan Report HPA-CRCE-041 (Chilton, UK: HPA) ICRP 1996 Age-dependent doses to members of the public from intake of radionuclides. Pt.5: compilation of ingestion and inhalation dose coefficients ICRP Publication 72; Ann. ICRP 26 (1) (Oxford: Pergamon) Kowe R, Carey A D, Jones J A and Mobbs S F 2007 GRANIS: a model for the assessment of external photon irradiation from contaminated media of infinite lateral extent Report HPA-RD-032 (Chilton, UK: HPA) Masson O et al 2011 Tracking of airborne radionuclides from the damaged Fukushima Dai-Ichi nuclear reactors by European networks Environ. Sci. Technol. 45 7670–7 McGinnity P et al 2012 Assessment of the Impact on Ireland of the 2011 Fukushima Nuclear Accident Radiological Protection Institute of Ireland, RPII 12/01 Morrey M, Brown J, Williams A J, Crick M J, Simmonds R J and Hill D M 1988 A preliminary assessment of the radiological impact of the Chernobyl reactor accident on the population of the European Community Radiation Protection EUR 11523 Watson J S, Jones L A, Oatway B W and Hughes S J 2005 Ionising radiation exposure of the UK population: 2005 review Report HPA-RPD-001
N46
Copyright of Journal of Radiological Protection is the property of IOP Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
