United Nations Scientific Committee on the Effects of Atomic Radiation

ATTACHMENT D-1

ESTIMATION OF THE POSSIBLE CONTRIBUTION OFINTAKES OF SHORT-LIVED RADIONUCLIDES TO
EFFECTIVE DOSE AND ABSORBED DOSES TO ORGANSFOR WORKERS AT THE FUKUSHIMA DAIICHINUCLEAR POWER STATIONUNSCEAR 2013 Report, Annex A, Levels and effects of radiation exposure due tothe nuclear accident after the 2011 great east-Japan earthquake and tsunami,
Appendix D (Assessment of doses to workers)

Content
This attachment describes the methodology and results of the Committee's assessment of thepossible contribution of intakes of short-lived radionuclides to internal exposure of workers at
the Fukushima Daiichi Nuclear Power Station. This assessment had been conducted for the
UNSCEAR 2013 Report, although this attachment describing the methods and results in detail
was issued subsequently.
Acknowledgements
The Committee would like to acknowledge the work done by G.Etherington (Public Health
England, United Kingdom) to address this issue and prepare this attachment.
Notes
The designations employed and the presentation of material in this publication do not imply theexpression of any opinion whatsoever on the part of the Secretariat of the United Nations
concerning the legal status of any country, territory, city or area, or of its authorities, orconcerning the delimitation of its frontiers or boundaries.
©

United Nations, January 2015. All rights reserved, worldwide.

This publication has not been formally edited.

Contents
I. INTRODUCTION .................................................................................................................. 3
II. METHOD ............................................................................................................................... 4
A. Generic intake scenarios ................................................................................................... 4
B. Estimation of intakes of short-lived radionuclides relative to the 131I intake ................... 5
C. Estimation of additional dose from intakes of short-lived radionuclides ......................... 8III. RESULTS............................................................................................................................... 9
IV. DISCUSSION AND CONCLUSIONS ................................................................................ 10
A. Additional contributions to effective dose for each scenario ......................................... 10
B. Additional contributions to absorbed doses to the thyroid for each scenario ................ 10
C. Additional contributions to dose from intakes of short-lived radionuclides .................. 11
REFERENCES ........................................................................................................................... 11I.

INTRODUCTION

1.
Internal exposures of workers at the Fukushima Daiichi Nuclear Power Station(FDNPS) were mainly determined using the results of measurements of the activities ofradionuclides in the body (in vivo monitoring). The radionuclides measured were typicallylimited to 131I, 134Cs and 137Cs. For a few workers, particularly those with higher assessedinternal exposures, the results of in vivo monitoring of the activities of 129mTe and 136Cs werealso reported.
2.
Delays in commencing in vivo monitoring with high energy resolution detectors meantthat some radionuclides with short half-lives that were likely to have been present in the body
early on had not been detected. In consequence, the contributions to dose from internal
exposure from these short-lived radionuclides had not been included in the doses reported by
TEPCO for FDNPS workers; see appendix D. The short-lived radionuclides of most interest in
this context are 132Te, 132I, 133I and 136Cs. Because of the short half-lives of these radionuclides,
their contributions to dose would have arisen mainly from intakes during the days immediately
following the shutdown of the reactors.
3.
In the absence of in vivo monitoring data for these short-lived radionuclides, theCommittee made estimates of the additional contributions to dose arising from intakes of eachof these radionuclides for three generic intake scenarios. This attachment describes themethodology used and the results of the assessment.
4.
For each scenario, the Committee estimated the magnitude of the intake of each shortlived radionuclide scaled to unit intake of 131I, using estimates of the relative amounts ofradionuclides released to the atmosphere during specified time periods. This procedure
implicitly assumed that the radionuclide content of the release at any particular time wasrepresentative of the radionuclide content of airborne radionuclides inhaled by workers at thattime. Reference values of dose coefficients specifying dose per unit intake for each of theshort-lived radionuclides, as well as for 131I, were then used to determine the additional
contribution to dose relative to the dose arising from 131I intake. (For the FDNPS workers forwhom independent assessments were performed, reported doses had been due almost entirely

ATTACHMENT D-1: ESTIMATION OF THE POSSIBLE CONTRIBUTION OF INTAKES OF SHORT-LIVED RADIONUCLIDES TO EFFECTIVE...

4

to 131I intakes; see appendix D, paragraphs D43 and D54.) The doses estimated in this way
were the committed effective dose and the committed absorbed doses to the thyroid, red bonemarrow and the colon.
5.
For each short-lived radionuclide, the estimated intake per unit 131I intake depended on
the assumed time period over which intakes took place, because the activities of the short-lived
radionuclides released decreased rapidly relative to 131I following reactor shutdown. For anindividual worker, the assumed intake period depended on their detailed work history while atthe FDNPS site, as well as on information on their use of protective measures to limit orprevent intakes. Such information included the times and administered amounts of any stableiodine provided to individual workers for prophylactic use; and the periods when items of
personal protective equipment such as respirators or face masks were being used effectively byeach worker. These types of information, where available, were used in the Committee’s
independent assessments of individual dose for selected workers that are described inappendix D. Unfortunately, the level of information of this type provided to the Committee wasvariable and incomplete.
6.
The aim of the assessment reported here was to provide estimates of the additional
contributions to dose that could have arisen from intakes of short-lived radionuclides for the
FDNPS workforce as a whole, rather than for individual workers. Therefore, the assessment
was performed using intake periods that provide realistic upper and lower bounds for theestimated additional contributions to dose for the two groups of workers identified inappendix D, that is “workers with the highest internal exposure” and “workers with lower
internal exposure”. These generic scenarios are presented and discussed in the next section.

7.

II.

METHODA.

Generic intake scenarios

The intake periods specified for the three scenarios were:(a) Scenario A: intakes took place continuously during the first 4.5 h of the release(05:00 to 09:30 JST on 12 March 2011) and then stopped;(b) Scenario B: intakes took place continuously from the start of the release at 05:00 JST
on 12 March 2011 until 00:00 JST on 1 May 2011 and then stopped;(c) Scenario C: intakes took place continuously from 05:00 JST on 12 March 2011 until
17:00 JST on 15 March 2011 and then stopped.

8.
Scenarios A and C provided the upper and lower bounds of the estimated additional
contributions to dose for the majority of the small group of workers with the highest internal
exposure, as identified in appendix D. This group was made up of those workers with reported
committed effective doses greater than 100 mSv. Work history information for 10 out of the
12 workers a within this group indicated there was reasonably good evidence that their intakescommenced on 12 March 2011. However, the available evidence did not allow a clear
conclusion to be drawn about whether intakes effectively ceased at some time during
12 March, or continued for a few more days. For all of the workers in this group for whoma

As a result of a reassessment of worker doses made in Japan, a thirteenth worker with a dose close to 100 mSv
was added to this group. This does not affect the assessment presented here.

ATTACHMENT D-1: ESTIMATION OF THE POSSIBLE CONTRIBUTION OF INTAKES OF SHORT-LIVED RADIONUCLIDES TO EFFECTIVE...

5

intakes probably commenced on 12 March, information on their work history and protective
measures taken indicated that intakes at a significant level had likely ceased by 15 March. (Forthe two remaining workers in this group, intakes could not have commenced until 18 March;
they both had assessed doses at the lower end of the range, close to 100 mSv.)
9.
The additional dose contribution from short-lived radionuclides is particularly sensitive
to the intake period, which was the reason for giving special attention to this issue for thisassessment. In the Committee’s earlier independent assessments of dose from 131I intakes andthe “Japanese” assessments performed by both Japan Atomic Energy Agency (JAEA) andNational Institute of Radiological Sciences (NIRS), a single 131I intake was assumed to havetaken place on 12 March 2011 for 9 out of the 10 workers. This was reasonable because theassessed doses were not very sensitive to the precise period of intake because of the relatively
long half-life of 131I in this context. For the remaining worker, the 131I intake was assumed tohave commenced on 11 March and ceased on 14 March. For the 17 Japanese assessments ofdoses to the 10 workers, 13 were based on an assumed single 131I intake on 12 March and 7 onan assumption that the 131I intake commenced on 11 March and variously ceased on 12, 13 or
14 March. These assumptions about intake period made for the earlier assessments ofindividual dose are not inconsistent with those in the generic scenarios used in this assessment.
10.
Scenarios A and B provided the upper and lower bounds of the estimated additional
contributions to dose for the group of workers with lower internal exposure, as identified inappendix D. For these workers, individual work history information was not available to theCommittee, and so the period of intake may have extended to later dates. However, for thoseworkers in this group who could not have received a radionuclide intake before about
19 March, the additional contributions to dose from intakes of short-lived radionuclides would
have been negligible. Such workers were therefore excluded from any consideration of dosefrom intakes of short-lived radionuclides.
B.

Estimation of intakes of short-lived radionuclides relative to the 131I
intake11.
Table D1-1 shows the estimated time-dependent releases to the atmosphere of theradionuclides 132Te, 131I, 132I, 133I, 133Xe b, 134Cs, 136Cs and 137Cs, during defined time periods in
March and April 2011 (see section II-A of appendix B). The releases of 131I, 134Cs and 137Cs arethose estimated by Terada et al. [Terada, 2012] who limited their assessment to theseradionuclides because they were deemed to be the most important. The estimates of thereleases of the short-lived radionuclides were derived from measurements of their levels in theenvironment (relative to longer-lived radionuclides) and from their relative inventories in thethree reactors.
12.
For scenario A, the values for each radionuclide from the first row of the table weretaken, covering the period from 05:00 to 09:30 JST on 12 March 2011. For scenario B, all of
the values in the table were summed for each radionuclide, covering the period from 05:00 JST
on 12 March 2011 to 00:00 JST on 1 May 2011. For scenario C, all values between 05:00 JST
on 12 March 2011 and 17:00 JST on 15 March 2011 were summed for each radionuclide.
Values for each radionuclide and scenario were normalized by dividing by the corresponding131
I activity.

b

Xenon-133 was not considered further because it is not deposited in the respiratory tract, and so would not havegiven rise to an internal exposure.

Table D1-1. Estimated time-dependent releases of radionuclides to the atmosphere during the accident at FDNPS
Data were taken from Terada et al. [Terada, 2012], but supplemented by estimates made for short-lived radionuclides—see section II-A of appendix B. The activities released are the products of
the release rates and the time periods given in table B5 of appendix B
Activity released (Bq)

Duration (h)
132

131

133

I
1.67E+14

Xe
2.96E+16132

I
1.79E+14133

I
2.15E+14

134

Cs
1.71E+13

136

Cs
5.00E+12137

Cs
1.67E+13Start
12 March 05:00

End
12 March 09:30

4.5

Te
1.79E+14

12 March 09:30

12 March 15:30

6

1.04E+14

1.02E+14

4.58E+17

1.04E+14

1.13E+14

1.05E+13

3.04E+12

1.02E+13

12 March 15:30

12 March 16:00

0.5

1.49E+15

1.50E+15

6.20E+15

1.49E+15

1.51E+15

1.54E+14

4.43E+13

1.50E+14

12 March 16:00

13 March 23:00

31

2.26E+15

2.60E+15

3.66E+18

2.26E+15

1.70E+15

2.68E+14

7.44E+13

2.60E+14

12 March 23:00

14 March 11:00

12

3.08E+14

4.32E+14

6.95E+16

3.08E+14

1.44E+14

4.44E+13

1.18E+13

4.32E+13

14 March 11:00

14 March 11:30

0.5

1.01E+15

1.50E+15

3.22E+15

1.01E+15

4.15E+14

1.54E+14

4.03E+13

1.50E+14

14 March 11:30

14 March 21:30

10

1.48E+14

2.30E+14

6.08E+16

1.48E+14

5.46E+13

2.36E+13

6.11E+12

2.30E+13

14 March 21:30

15 March 00:00

2.5

1.98E+15

3.25E+15

1.65E+16

1.98E+15

6.40E+14

3.33E+14

8.50E+13

3.25E+14

15 March 00:00

15 March 07:00

7

1.62E+15

2.45E+15

7.98E+17

1.62E+15

4.19E+14

2.86E+14

7.21E+13

2.79E+14

15 March 07:00

15 March 10:00

3

5.01E+15

9.00E+15

5.73E+17

5.01E+15

1.33E+15

9.24E+14

2.31E+14

9.00E+14

15 March 10:00

15 March 13:00

3

1.30E+14

2.40E+14

3.15E+17

1.30E+14

3.24E+13

2.46E+13

6.12E+12

2.40E+13

15 March 13:00

15 March 17:00

4

8.40E+15

1.60E+16

8.56E+17

8.40E+15

1.94E+15

1.64E+15

4.04E+14

1.60E+15

15 March 17:00

17 March 06:00

37

4.88E+14

7.77E+15

4.74E+17

4.88E+14

5.40E+14

1.14E+14

2.68E+13

1.11E+14

17 March 06:00

19 March 15:00

57

1.66E+15

2.34E+16

1.66E+15

4.32E+14

5.81E+14

1.24E+14

5.70E+14

19 March 15:00

21 March 03:00

36

2.37E+15

1.37E+16

2.37E+15

5.94E+13

1.27E+15

2.45E+14

1.24E+15

21 March 03:00

21 March 21:00

18

3.76E+14

2.52E+15

3.76E+14

4.77E+12

2.57E+14

4.68E+13

2.52E+14

21 March 21:00

22 March 23:00

26

1.51E+14

1.07E+16

1.51E+14

1.06E+13

1.25E+14

2.17E+13

1.22E+14

22 March 23:00

24 March 00:00

25

2.17E+14

1.78E+16

2.17E+14

8.30E+12

2.26E+14

3.70E+13

2.22E+14

24 March 00:00

25 March 00:00

24

5.42E+13

4.56E+15

5.42E+13

1.03E+12

7.03E+13

1.09E+13

6.91E+13

25 March 00:00

26 March 11:00

35

2.63E+13

1.96E+15

2.63E+13

1.89E+11

4.45E+13

6.48E+12

4.34E+13

26 March 11:00

28 March 10:00

47

3.44E+12

1.88E+14

3.44E+12

5.59E+09

8.32E+12

1.11E+12

8.18E+1228 March 10:00

29 March 21:00

35

4.76E+13

2.63E+14

4.76E+13

2.24E+09

1.66E+14

2.04E+13

1.64E+14

29 March 21:00

30 March 11:00

14

2.87E+13

2.10E+14

2.87E+13

8.34E+08

1.25E+14

1.46E+13

1.23E+1430 March 11:00

31 March 00:00

13

3.71E+14

2.34E+15

3.71E+14

6.23E+09

1.82E+15

2.05E+14

1.79E+15

31 March 00:00

31 March 22:00

221.76E+13

5.28E+14

1.76E+13

8.47E+08

1.01E+14

1.09E+13

9.97E+13

31 March 22:00

2 April 09:00

35

7.84E+12

6.30E+13

7.84E+12

4.48E+07

5.78E+13

5.92E+12

5.74E+13

2 April 09:00

4 April 09:00

48

2.64E+12

8.64E+13

2.64E+12

1.86E+07

2.81E+13

2.63E+12

2.79E+13

ATTACHMENT D-1: ESTIMATION OF THE POSSIBLE CONTRIBUTION OF INTAKES OF SHORT-LIVED RADIONUCLIDES TO EFFECTIVE...

Time period in 2011 (JST)6

Time period in 2011 (JST)End
7 April 17:00

7 April 17:00
13 April 23:00

132

131

132

I
6.21E+11133

I
2.09E+06

Cs
1.15E+13

Cs
9.36E+11

Cs
1.14E+13

1.05E+14

1.08E+12

2.13E+05

5.27E+13

3.36E+12

5.25E+13

1.86E+11

2.86E+14

1.86E+11

2.54E+03

7.12E+13

2.55E+12

7.16E+13

2.85E+16

1.24E+17

2.85E+16

9.56E+15

9.01E+15

1.77E+15

8.83E+1580

Te
6.21E+11I
5.60E+13

13 April 23:00

150

1.08E+12

1 May 00:00

409

Total release (Bq)

133

Xe

7.32E+18

134

136

137

ATTACHMENT D-1: ESTIMATION OF THE POSSIBLE CONTRIBUTION OF INTAKES OF SHORT-LIVED RADIONUCLIDES TO EFFECTIVE...

Start
4 April 09:00

Activity released (Bq)

Duration (h)7ATTACHMENT D-1: ESTIMATION OF THE POSSIBLE CONTRIBUTION OF INTAKES OF SHORT-LIVED RADIONUCLIDES TO EFFECTIVE...

C.

8

Estimation of additional dose from intakes of short-lived
radionuclides

13.
The relative contributions to the total dose from each radionuclide listed in table D1-1
were estimated by multiplying the intakes of each radionuclide relative to the 131I intake(determined as described above) by reference values of the dose coefficient for eachradionuclide. These dose coefficients specify committed effective dose per unit intake orcommitted absorbed dose to a specified organ per unit intake, as appropriate.
14.
The dose coefficients were selected (in the case of (b), (c) and (d) below) or evaluated(in the case of (a), below) using the following assumptions with regard to the physico-chemical
form and characteristics of the radionuclides to which the workers were exposed:(a) 131I and 133I comprised 50% elemental iodine vapour and 50% particulate material withan activity median aerodynamic diameter (AMAD) of 5 µm, the default value foroccupational exposure recommended by the International Commission on RadiologicalProtection [ICRP, 1994a];(b) 132Te, 132I and radiocaesium were in particulate form with an AMAD of 5 µm;(c) Particulate forms of 131I, 132I and 133I and radiocaesium were characterized byabsorption type F and gastro-intestinal uptake factor, f1 = 1 (0.99 by ICRP convention);(d) 132Te in particulate form was characterized by absorption type M and f1 = 0.1.
15.
For 132Te, ICRP provides different default f1 values for occupational and environmental
exposures to unknown chemical forms of tellurium. These are 0.3 and 0.1, respectively [ICRP,
1994b; ICRP, 1995]. The dose assessment was relatively insensitive to this value, and thedefault value for environmental exposure was chosen here.
16.
The resulting dose coefficients (dose per unit intake) for the intake of each radionuclide
by inhalation are given in table D1-2 [Birchall et al., 2007; ICRP, 2002].
17.
The relative contributions of each radionuclide to the total committed effective dose
and to the total committed absorbed dose for each organ were then normalized so that the total
relative dose was equal to unity; these values are given in section III, tables D1-3, D1-4 and
D1-5.
18.
For committed effective dose and committed dose to the thyroid, the dose from 131I
intake dominates and so the additional contributions to dose from the short-lived radionuclides
relative to the dose from 131I intake were then determined by normalizing to the latter dose.
These results are discussed in section IV.

ATTACHMENT D-1: ESTIMATION OF THE POSSIBLE CONTRIBUTION OF INTAKES OF SHORT-LIVED RADIONUCLIDES TO EFFECTIVE...

9

Table D1-2. Dose coefficients for intake of radionuclides by inhalation
The values are for radionuclides in the forms specified in section II. Values given for 131I and 133I are the averages of those forgaseous and particulate forms of iodine
Organ

Effective dose coefficient (Sv/Bq) or absorbed dose coefficient (Gy/Bq)
132

131

132

133

-

2.8E-09

1.55E-08

2.00E-10

3.05E-09

9.60E-09

1.90E-09

6.70E-09

Thyroid

6.4E-09

3.00E-07

1.90E-09

5.85E-08

9.00E-09

1.50E-09

6.30E-09

Red bone marrow

2.8E-10

7.40E-11

1.80E-11

3.60E-11

9.00E-09

1.40E-09

6.30E-09

Colon

6.4E-09

5.25E-11

1.80E-11

4.35E-11

1.00E-08

1.60E-09

7.40E-09

Te

Effective dose

Absorbed dose

I

I

I

134

Cs

136

Cs

137

Cs

III. RESULTS
19.
The relative contributions of each radionuclide to the committed effective dose andcommitted absorbed doses to the thyroid, red bone marrow and colon for the three genericintake scenarios, A, B and C, are shown in tables D1-3, D1-4 and D1-5, respectively. The
intake scenarios are described in section II.
Table D1-3. Scenario A. Fractional contributions to the committed effective dose and committed absorbed
doses to organs
Organ

Fractional contribution to total dose from each radionuclide
132

131

132

133

134

136

137

-

0.12

0.64

0.01

0.16

0.04

0.00

0.03

Thyroid

0.02

0.78

0.01

0.20

0.00

0.00

0.00

Red bone marrow

0.15

0.04

0.01

0.02

0.45

0.02

0.31

Colon

0.78

0.01

0.00

0.01

0.12

0.01

0.08

Te

Effective dose

Absorbed dose

I

I

I

Cs

Cs

Cs

Table D1-4. Scenario B. Fractional contributions to the committed effective dose and committed absorbed doses toorgansOrgan

Fractional contribution to total dose from each radionuclide
132

131

132

133

134

136

137

-

0.04

0.88

0.00

0.01

0.04

0.00

0.03

Thyroid

0.00

0.98

0.00

0.01

0.00

0.00

0.00

Red bone marrow

0.05

0.06

0.00

0.00

0.52

0.02

0.35

Colon

0.52

0.02

0.00

0.00

0.26

0.01

0.19

Te

Effective dose

Absorbed dose

I

I

I

Cs

Cs

Cs

Table D1-5. Scenario C. Fractional contributions to the committed effective dose and committed absorbed doses toorgansOrgan

Fractional contribution to total dose from each radionuclide
132

131

132

133

134

136

137

-

0.09

0.79

0.01

0.04

0.05

0.00

0.03

Thyroid

0.01

0.94

0.00

0.04

0.00

0.00

0.00

Red bone marrow

0.09

0.04

0.01

0.00

0.50

0.02

0.34

Colon

0.67

0.01

0.00

0.00

0.18

0.01

0.13

Te

Effective dose

Absorbed dose

I

I

I

Cs

Cs

Cs

ATTACHMENT D-1: ESTIMATION OF THE POSSIBLE CONTRIBUTION OF INTAKES OF SHORT-LIVED RADIONUCLIDES TO EFFECTIVE...

10

IV. DISCUSSION AND CONCLUSIONS
20.
Tables D1-3, D1-4 and D1-5 show the estimated contributions to total committed doses
from intakes of each radionuclide. Although the contribution to effective dose from 134Cs and137
Cs intakes was estimated to be 7–8% of the total for all three scenarios, assessments forindividual workers based on measurements of radionuclides in the body indicated acontribution to assessed effective dose of only around 1–2% (see tables D10, D11 and D13 of
appendix D). No obvious explanation could be provided for this discrepancy, but the finding
does indicate that caution should be employed when using data on the activities of theradionuclides released to the atmosphere to infer the content of radionuclide intakes byworkers.
21.
Because 131I intakes made such a dominant contribution to committed effective doses(98–99%), the estimated additional contributions to committed effective dose and committed
absorbed dose to the thyroid from intakes of the short-lived radionuclides were expressed as apercentage of the estimated committed dose from 131I intake. The contributions of committed
absorbed doses to the red bone marrow and colon to committed effective dose were small
compared with the contribution of the committed absorbed dose to the thyroid, and so thediscussion presented here is limited to the estimated additional contributions from intakes ofshort-lived radionuclides to the committed effective dose and committed absorbed dose to thethyroid.

A.

Additional contributions to effective dose for each scenario

22.
For scenario A, the data in table D1-3 indicate that 132I and 133I could have madeadditional contributions of 1% and 25%, respectively, relative to the contribution from 131I.
Tellurium-132 could have made a further additional contribution of 19%, relative to thecontribution from 131I.
23.
For scenario B, the data in table D1-4 indicate that 132I and 133I could have madeadditional contributions of 0.3% and 2%, respectively, relative to the contribution from 131I.
Tellurium-132 could have made a further additional contribution of 4%, relative to thecontribution from 131I.
24.
For scenario C, the data in table D1-5 indicate that 132I and 133I could have madeadditional contributions of 0.8% and 4% respectively, relative to the contribution from 131I.
Tellurium-132 could have made a further additional contribution of 11%, relative to thecontribution from 131I.

B.

Additional contributions to absorbed doses to the thyroid for eachscenario

25.
Iodine-131 is the main contributor to the total absorbed doses to the thyroid, with themain additional contribution arising from 133I. For scenarios A, B and C, the additional
contribution from the short-lived radionuclides is 28%, 2% and 6%, respectively, relative to thecontribution from 131I.

ATTACHMENT D-1: ESTIMATION OF THE POSSIBLE CONTRIBUTION OF INTAKES OF SHORT-LIVED RADIONUCLIDES TO EFFECTIVE...

C.

11

Additional contributions to dose from intakes of short-lived
radionuclides

26.
For the small number of FDNPS workers with the higher reported committed effective
doses (>100 mSv), assuming that intakes took place only on 12 March (scenario A) provided
an upper bound on the potential additional contribution to dose, while assuming that intakes
could have taken place continuously between 12 and 15 March (scenario C) provided a lower
bound. Thus, for this group of workers, the additional contribution to effective dose fromintakes of short-lived radionuclides could have been in the range 16–45% relative to thecontribution from 131I intakes, depending on the time pattern of intake. The corresponding
range for the additional contribution to absorbed dose to the thyroid is 6–28%.
27.
For other FDNPS workers with lower reported committed effective doses, the period of
intake may have extended to later dates and so the possible range on the additional
contributions to dose extends to lower values (scenario B). For these groups of workers, theadditional contribution to effective dose from intakes of short-lived radionuclides could be in
the range 6–45% relative to the contribution from 131I intakes, depending on the time pattern ofintake. The corresponding range for the additional contribution to absorbed dose to the thyroidis 2–28%. These estimates of the additional contributions to dose assume that intakes could
have commenced on 12 March. The additional contributions to dose from short-lived
radionuclides would have been negligible for all workers who commenced work at the FDNPS
after about 19 March.
28.
For those members of the FDNPS workforce who commenced work during the period
12–19 March, the typical additional contribution to effective dose from intakes of short-lived
radionuclides may be in the region of 20% relative to the contribution from 131I, although thisvalue is likely to be subject to large variations between individuals, mainly because ofvariations in the time period of intake.

References
Birchall, A., M. Puncher, J.W. Marsh et al. IMBA Professional Plus: a flexible approach tointernal dosimetry. Radiat Prot Dosim 125(1-4): 194-197 (2007).
ICRP. Human respiratory tract model for radiological protection. ICRP Publication 66. Annalsof the ICRP 24(1-3). International Commission on Radiological Protection, Pergamon
Press, Oxford, 1994a.
ICRP. Dose coefficients for intake of radionuclides by workers. ICRP Publication 68. Annalsof the ICRP 24(4). International Commission on Radiological Protection, Pergamon
Press, Oxford, 1994b.
ICRP. Age-dependent doses to members of the public from intake of radionuclides: Part 4.
Inhalation dose coefficients. ICRP Publication 71. Annals of the ICRP 25(3-4).
International Commission on Radiological Protection, Pergamon Press, Oxford, 1995.
ICRP. Database of dose coefficients: workers and members of the public. ICRP CD1.
International Commission on Radiological Protection, Pergamon Press, 2002.
Terada, H., G. Katata, M. Chino et al. Atmospheric discharge and dispersion of radionuclides
during the Fukushima Dai-ichi Nuclear Power Plant accident. Part II: verification of thesource term and analysis of regional-scale atmospheric dispersion. J Environ Radioact
112: 141-154 (2012).