SOURCES, EFFECTS AND RISKSOF IONIZING RADIATION
United Nations Scientific Committee on the
Effects of Atomic Radiation
UNSCEAR 2016
Report to the General Assembly,
with Scientific Annexes

UNITED NATIONSNew York, 2017

NOTE
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ANNEX A
METHODOLOGY FOR ESTIMATING PUBLICEXPOSURES DUE TO RADIOACTIVEDISCHARGES

19

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 21

Contents
I.

INTRODUCTION ................................................................................................................................... 23

II. GENERAL CONSIDERATIONS .......................................................................................................... 24
A. Dosimetric quantities ................................................................................................................ 24
B. Integration times ........................................................................................................................ 29
C. End points considered .............................................................................................................. 30
D. Discharges considered.............................................................................................................. 31
III. DESCRIPTION OF THE METHODOLOGY ...................................................................................... 32
A. Assessment of doses from discharges to atmosphere.................................................. 34
B. Assessment of doses from discharges to a freshwater environment ................................. 48
C. Assessment of doses from discharges to a marine environment ............................. 64
IV. GLOBALLY DISPERSED RADIONUCLIDES ................................................................................... 70
A. Tritium ............................................................................................................................................ 70
B. Carbon-14 ...................................................................................................................................... 71
C. Iodine-129 ..................................................................................................................................... 72
D. Krypton-85 .................................................................................................................................... 72
V. LIMITATIONS OF THE MODELS AND DATA USED ................................................................... 73
A. Discharges to atmosphere ...................................................................................................... 74
B. Discharges to freshwater and marine environments .................................................... 75
C. Global modelling ........................................................................................................................ 76
D. Comparison of the current and previous methodologies ........................................... 77
VI. APPLICATION OF THE METHODOLOGY ...................................................................................... 78
VII. CONCLUSIONS ..................................................................................................................................... 90
VIII. ACKNOWLEDGEMENTS .................................................................................................................... 91
TABLES ........................................................................................................................................................... 97
REFERENCES ............................................................................................................................................... 127
Electronic attachments (http://www.unscear.org/unscear/en/publications/2016.html)
1. Comparison of the Committee’s earlier and current methodologies
2. Summary of the Committee’s pre-2010 methodologies and their development
3. Population densities around uranium mines and nuclear power sites
4. Sensitivity studies in support of the methodology development
5. Electronic workbooks that implement the current methodology

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 23

I. INTRODUCTION
1.
For many years the Committee has had a methodology for assessing the radiation exposures of thegeneral public from discharges of radionuclides to the environment, where the term discharge refers toauthorized releases from normal operations. The methodology does not apply for accidental releases.
Every few years, the Committee has updated its estimates of the global radiological impact of thevarious types of nuclear installation, using this methodology and the latest available information on thelevel and nature of discharges. The most recent versions of the methodology, which in turn were built
on earlier versions, were published in annex A of the UNSCEAR 2000 Report [U6] and annex B of the
UNSCEAR 2008 Report [U10]. Although used successfully for many years, the Committee decided at
its fifty-sixth session in 2008 to review and, where appropriate, update its methodology [U10] as part ofits strategic plan for 2009–2013, with a view to subsequently updating its assessments of the levels ofradiation exposure from energy production.
2.
The global impact of energy production was one of the Committee’s thematic priorities identified
in its strategic plan for 2014−2019 (see [U12]). The Committee decided to specifically assess the global
radiological impact of discharges from both nuclear and non-nuclear sources of electrical energy
production, and thus to review its methodology so that it could be used to:(a) Evaluate the radiation levels worldwide to which people are usually exposed as a consequenceof electricity generation;(b) Assess the typical variations in exposure worldwide to different sources of radioactive
discharges;(c) Identify sources of possible concern for public exposure;(d) Allow users to derive benchmarks for comparison purposes and to derive relationships fortheir investigative work;(e) Analyse temporal trends in the contributions of different sources to overall public exposure.
3.
The Committee recognizes that it is impractical to carry out a full site-specific assessment foreach site of electricity generation in the world that discharges radionuclides to the environment.
However, it decided that, where possible, its approach should be able to take into account differencesamong regions of the world. It also decided that the methodology should be robust, transparent andapplicable to the different electrical energy sources, and that it should build on the experience gained inapplying the previous methodology. One change agreed was that for ease of application to different
electrical energy sources and to all parts of the nuclear fuel cycle, the methodology should provide
estimates of the doses 1 per unit discharge of key radionuclides to different environments. With
information on the discharges from the various facilities, these factors could then be used to estimate
doses per unit electrical energy produced (see annex B).
1

Where the word “dose” is used in this annex without qualification, it should be taken to mean effective dose to an individual orcollective effective dose to a population, according to context, unless otherwise stated.

24 UNSCEAR 2016 REPORT

4.
The methodology is thus designed to assess individual and collective doses from unit discharge ofeach of the key radionuclides to atmosphere, lakes, rivers and seas. The individuals considered arethose living in the area local to the point of discharge with behaviour indicative of most people living inthat area; the doses to these characteristic individuals are referred to here as “characteristic individual
doses” and are not to be confused with those to the so-called “representative person” (previously
termed by the International Commission on Radiological Protection, ICRP, as the “critical group”) used
for radiation protection purposes [I13]. The Committee agreed that, where possible, estimates should beavailable for collective doses as a function of distance from the point of discharge and of the levels of
individual dose that make up these collective doses. The Committee also agreed to take account ofsome differences among geographical regions, notably on population densities. For ease of applicationand transparency, the methodology has been implemented through a series of Excel® workbooks, whichshould also facilitate any future updates of the Committee’s assessments.
5.
The Committee intends to use the methodology to conduct its worldwide assessments of theradiological impact of discharges of radionuclides. The methodology aims to provide best estimates ofradiation doses, in contrast to other established methodologies (e.g. [I2]) which aim to ensure that doses
are not underestimated and thus adopt cautious parameter values and assumptions. The Committee’s
methodology only applies to continuous routine releases to the environment and is not intended to becomprehensive, covering all situations and other uses (such as for estimating the risks of radiationinduced health effects).
6.
This scientific annex describes the methodology to assess doses from discharges to atmosphere,
freshwater bodies and sea, together with the approach adopted for globally dispersed radionuclides. The
limitations of the models and data used are also discussed. An appendix provides detailed informationon the implementation of the methodology, including the end points considered, the relevant
mathematical equations and model parameters, a specification of the series of Excel® workbooks that
implement the methodology, information on how the workbooks can be used to assess exposures fromdifferent types of discharge, and a description of how progeny of radionuclides were treated and quality
assurance conducted. In addition more detailed supporting information and the workbooks themselves
are provided in electronic attachments, which can be downloaded only from the UNSCEAR website(http://www.unscear.org/unscear/en/publications/2016.html).

II. GENERAL CONSIDERATIONS

A. Dosimetric quantities
7.
Although for strict scientific purposes other quantities are appropriate, the Committee has formany years used two protection quantities, namely effective dose and collective effective dose for its
evaluations of levels and trends of exposures. These have the advantage of simplifying comparison ofdoses from different types of radiation and different distributions of dose within the body, and of
averaging over age and sex; moreover, many regulatory authorities keep records in terms of thesequantities. The quantity effective dose is based on another underlying radiation protection quantity, theequivalent dose, which takes into account the inferred differences in biological effectiveness ofdifferent types of radiation by applying defined radiation weighting factors to the absorbed dose to an

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 25

organ or tissue. Equivalent doses to different organs and tissues are then combined using defined tissue
weighting factors, which take into account the inferred differences in detriment from irradiation of theparticular organ or tissue, averaged over the sex and age distributions of typical populations. This
enables external and internal exposures from a source of radiation to be added to produce an overall
effective dose 2 from that source, which can then be compared with effective doses from other sources.
In this annex, the definition of effective dose used to express both individual and collective doses isgenerally that of Publication 60 of the ICRP [I10]. Although ICRP made some modifications to theweighting factors in the definition of effective doses in its 2007 recommendations [I13], it has not yet
published a full set of dose coefficients for external and internal exposure and so the Committee has
used the previous values, unless otherwise stated.
8.
It is important to note that there are differences between the quantities of individual and collective
dose, although they are calculated in similar ways. In this methodology and any related studies, thecollective (effective) dose is always estimated for a defined population over a specified period of time.
The collective dose used here is the product of the mean effective dose to a specified population from aparticular source, and the number of people in that population, integrated over a defined period of time.
In other words, a collective dose is the dose received by all members of a particular population
combined, over a defined period of time. When evaluating collective doses, the population and time
period should always be specified and any underlying assumptions—such as the population remaining
the same over the time period—should be acknowledged. The Committee has used the quantity,collective dose, for many years to compare the radiation exposures of populations from different
sources of ionizing radiation, or following different protection measures. In particular, the quantity
provides a convenient basis for comparing the impacts of radioactive discharges from nuclear and othersources of electrical energy, and for incorporation by analysts into measures of economic utility fordecision-aiding. However, collective dose should only be used for comparative purposes; it isinappropriate to use it for quantifying exposure in epidemiological studies or for making risk
projections. Specifically, the Committee has stated that it does not recommend the aggregation of very
low doses over extended time periods to large numbers of individuals to estimate absolute numbers ofradiation-induced health effects within a population exposed to incremental doses at levels equivalent
to or lower than normal natural background levels [U13].
9.
The Committee decided to retain its previous approach where collective dose was estimated for
local, regional and global components. The spatial variation in collective dose can be estimated fordischarges to atmosphere because (a) dispersion can be expressed as a function of distance from thedischarge point and (b) data on the distribution of population density are also available as a function of
distance. However, for aquatic discharges, when using a simple generic approach, it is not possible todetermine collective doses as a function of distance. Because people over a wide area may all obtain
their drinking water and fish from the same water body, there is not a simple relationship between
distance from the discharge point and dose. A simplified approach is therefore used based on adischarge to a single water body so that, for aquatic discharges, less spatial resolution in collective
doses is possible than for discharges to atmosphere.
10. The Committee considered that the assessment of characteristic individual doses is also useful inaddressing the thematic priority in its strategic plan mentioned above. As noted previously, as far as
possible, the dose estimates are based on best estimates of parameter values. For example, fordischarges to atmosphere, the characteristic individual dose estimated is the dose to someone living
2
For both individual and collective doses, the effective doses estimated here are the sum of the effective doses from external
exposure received during the period of interest and the committed effective doses from intakes by inhalation and ingestion during
the same period.

26 UNSCEAR 2016 REPORT

5 km from the discharge point who is assumed to obtain a proportion of their food from this location,rather than a more cautious assumption of living 1 km or less from the discharge point. For aquatic
discharges, the characteristic individual dose estimated is the dose to someone assumed to be living in
the area near to the discharge location and to obtain part of their food—and in the case of discharges tofreshwater bodies, their drinking water—from the receiving water body.
11. In this regard, for estimating characteristic individual doses, the Committee considered it to be
more realistic to assume that only a proportion of their food consumed was locally produced (locally
produced food is that grown by the individual or bought fresh from local markets) rather than an
approach often used for regulatory purposes of assuming all their food consumed was 100% locally
produced. There is little information on how much locally produced food people consume. In France, acomprehensive investigation was carried out to determine the amount of locally produced food thatpeople ate [B3]. This showed that rural populations in France consumed more locally produced foodthan urban populations, as would be expected, and that there was a significant variation for different
foods. For example, for milk consumption in France as a whole, only 3% was found to be locally
produced but in rural areas, the figure was 30%, on average. For leafy vegetable consumption in France
as a whole, just over 25% was found to be locally produced but in rural areas the figure was 70%. For
cereal consumption in France, the percentage locally produced was very low, at 0.1% both for thecountry as a whole and for rural areas. While recognizing that there are likely to be wide variations inpractice across the world, the Committee agreed that a simple assumption of 25% of the food consumed
being locally produced was reasonable for its generic methodology and that this value be used for bothterrestrial and aquatic foods. This value is consistent with the value used in the Committee’s recent
assessment of doses in Japan following the nuclear accident at the Fukushima-Daiichi nuclear power
station [U12].
12. The methodology employs published dose coefficients to estimate doses from external andinternal exposure. The dose coefficients used for internal exposure are those for adult members of the
public and are the committed effective doses to 70 years of age per unit intake of radionuclide given by
ICRP [I14]. The dose coefficients for external exposure from radionuclides in the air or deposited on
the ground following discharges to air or water bodies were selected from literature sources relevant tothe situation being considered. The main dose coefficients used for internal and external exposure aresummarized in table 1 both for radionuclides that are discharged and for their key progeny, whereappropriate (see also the appendix). It should be noted that for dose coefficients for internal exposure
the contribution of short-lived progeny is included in the dose coefficient assigned to the parent.
However, for the dose coefficients for external exposure the dose coefficients are for the parent alone
and any contribution from short-lived progeny has to be added separately using the values given intable 1(b). Except for isotopes of argon (e.g. 41Ar), krypton (e.g. 85Kr), xenon (e.g. 133Xe, 135Xe and138Xe) and radon (e.g. 222Rn), which are all gases, the discharges are assumed to be particulate with adefault size of 1 µm AMAD. The dose coefficients for tritium in the form of tritiated water (HTO) andof organically bound tritium (OBT) are provided for use with the “specific activity” model for tritium inthe environment described in chapter III. The chemical form assumed for each element is generally thedefault type for public exposure given in ICRP Publication 72 [I12].

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 27

Table 1. Radionuclide-specific dose coefficients for internal exposure from inhalation andingestion and for external exposure from the plume and deposition
Values are given to one decimal place only as this is considered sufficient for this purpose(a) Radionuclides discharged
Radionuclide

ProgenyaLungabsorption
typeb
[I12]

3

Committed effective dosecoefficients for adults to age
70 years for internal exposurec

Effective dose coefficients forexternal exposured

Inhalation
Dinh(Sv/Bq)[I14]

Ingestion
Ding(Sv/Bq)
[I14]

Plume
Dex,cloud(Sv/(Bq s/m3))[E2, P2](Sv/(Bq /m2))e
[P2]

0

0

Deposition
Dex,deposit

H

—

M

4.5 × 10−11

0

C

—

M

2.0 × 10

5.8 × 10

2.6 × 100M

1.4 × 10

7.7 × 10−18

3.1 × 10

0

14

S

35 f

−9
−9

−10
−10

−18

41

Arf

—

n/a

0

0

6.2 × 10−14

0

54

Mn

—

M

1.5 × 10−9

7.1 × 10−10

3.9 × 10−14

5.2 × 10−14

58

Co

—

M

1.6 × 10−9

7.4 × 10−10

4.5 × 10−14

5.0 × 10−9

60

Co

—

M

1.0 × 10−8

3.4 × 10−9

1.2 × 10−13

2.0 × 10−7

65

Zn

—

M

1.6 × 10−9

3.9 × 10−9

2.8 × 10−14

9.0 × 10−9

85

Krf

—

n/a

0

0

9.9 × 10−17

0

90

Sr

90

Y

M

3.6 × 10

2.8 × 10

9.8 × 100RhM

2.8 × 10

7.0 × 10

0

0

c

−8

−8

−17

106

Ru

129

I

—

F

3.6 × 10−8

1.1 × 10−7

2.8 × 10−16

3.1 × 10−9

I

—

F

7.4 × 10−9

2.2 × 10−8

1.7 × 10−14

2.4 × 10−10

133

Xef

—

n/a

0

0

1.2 × 10−15

0

135

Xe

f

135

Cs

n/a

0

0

−14

1.0 × 10

0

138

Xef

138

Cs

n/a

0

0

5.4 × 10−14

0

134

Cs

—

F

6.6 × 10−9

1.9 × 10−8

7.1 × 10−14

6.2 × 10−8

137

Csc

137m

F

4.6 × 10−9

1.3 × 10−8

9.3 × 10−17

4.6 × 10−13

210

Pb

M

1.1 × 10−6

6.9 × 10−7

4.5 × 10−17

2.5 × 10−10

210

Po

—

M

3.3 × 10−6

1.2 × 10−6

3.9 × 10−19

1.2 × 10−13

222

Rnf,g

Po 214Pb, 214Bi, 214Po

n/a

4.8 × 10−9

n/a

n/a

n/a

226

Ra

—

M

3.5 × 10

2.8 × 10

2.8 × 10

3.8 × 10−9

230

Th

—

S

1.4 × 10−5

2.1 × 10−7

1.5 × 10−17

0

232

Th

Ra, 228Ac, 228Th, 212Pb

S

2.5 × 10−5

2.3 × 10−7

7.2 × 10−18

8.7 × 10−11

234

U

—

M

3.5 × 10−6

4.9 × 10−8

6.1 × 10−18

5.5 × 10−11

238

UTh, 234mPa

M

2.9 × 10−6

4.5 × 10−8

2.5 × 10−18

1.9 × 10−11

239

Pu

—

M

5.0 × 10−5

2.5 × 10−7

3.5 × 10−18

3.5 × 10−11

240

Pu

—

M

5.0 × 10−5

2.5 × 10−7

3.4 × 10−18

1.5 × 10−11

241

Am

—

M

4.2 × 10−5

2.0 × 10−7

6.7 × 10−16

7.9 × 10−9

c

106

131 d

Ba

218

228

234

−8

−6

−9

−7

−16

28 UNSCEAR 2016 REPORT(b) Radionuclides considered to have different chemical forms in the environment or as progeny ofothersRadionuclide

Lung absorption typeb[I12]

Committed effective dosecoefficients for adults to age 70
years for internal exposurec

Effective dose coefficients forexternal exposured

Inhalation
Dinh(Sv/Bq)[I14]

Ingestion
Ding(Sv/Bq)
[I14]

Plume
Dex,cloud(Sv/(Bq s/m3))[E2, P2]

Deposition
Dex,deposit(Sv/(Bq /m2))e
[P2]
0

HTO

n/a

1.8 × 10−11

1.8 × 10−11

0

OBT

n/a

4.1 × 10

4.2 × 10

0

Y

—

—

—

7.9 × 10

0

106

Rh

—

—

—

9.4 × 10−15

5.5 × 10−15

135

Csf

F

6.9 × 10−10

2.0 × 10−9

9.5 × 10−18

2.4 × 10−11

138

Csf

F

2.4 × 10−11

9.2 × 10−11

1.2 × 10−13

3.9 × 10−12

Ba

—

—

—

2.7 × 10−14

1.7 × 10−7

212

Pb

—

—

—

5.7 × 10−15

4.7 × 10−12

214

Pb

M

1.4 × 10−8

1.4 × 10−10

1.1 × 10−14

5.6 × 10−13

210

Bi

—

—

—

2.6 × 10−16

2.2 × 10−11

214

Bi

—

1.4 × 10−8

1.1 × 10−10

7.1 × 10−14

2.5 × 10−12

214

Po

n/a

0

0

3.8 × 10−18

1.9 × 10−23

218

Po

n/a

0

0

4.2 × 10−19

2.3 × 10−18

228

Ra

M

2.6 × 10−6

6.9 × 10−7

0

0

228

Ac

F

2.5 × 10

228

Th

S

234

Th
Pa

90

137m

234m

−11

−11

0
−16

4.3 × 10−14

4.0 × 10

1.7 × 10−11

4.0 × 10−5

7.2 × 10−8

8.1 × 10−17

6.9 × 10−11S

7.7 × 10−9

3.4 × 10−9

2.9 × 10−16

1.3 × 10−11

n/a

0

0

1.2 × 10−15

1.1 × 10−14

−8

−10

a

The progeny considered in the methodology are listed. For further details see the appendix; The symbol “—” means either thatthe progeny are not considered or that the progeny are stable isotopes.

b

This refers to the rate of absorption from the lung. The symbols relate to fast (F), medium (M) or slow (S) absorption.

c

For these radionuclides with short-lived progeny, the dose coefficients for internal exposure for the parent include thecontribution from the progeny and coefficients are not given separately for the progeny.
dIn all cases the dose coefficients for external exposure are for the parent only and the contribution from progeny has to beconsidered separately.

eIntegrated effective dose to 100 years following a continuous deposition rate of 1 Bq/(m2 s) for one year. The Petoussi-Henss etal. values are not used directly but are modified to allow for changes in external dose with time [G2].
fConsidered for discharges to atmosphere only.

g

See section III.A.3 for more information on the treatment of radon inhalation.

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 29

B. Integration times
13. The methodology is applicable to discharges that can be assumed to be continuous and takes into
account (a) the build-up of long-lived radionuclides in the environment and (b) the continued exposure
to long-lived radionuclides after discharges have ceased. This is done by considering a year’s dischargeof a radionuclide, its dispersion in the environment and the subsequent exposures of people over many
years; the resulting dose rates are then integrated to various times. Using these integrals, it is also
possible to consider that the discharges may continue for many years from the same site. This isbecause the integrated dose to say 100 years from one year’s discharge is numerically equal to the dosein the 100th year from a continuous discharge at a constant rate. The Committee agreed that 100 years
was generally a reasonable assumption for the length of continuous discharge for estimating
characteristic individual doses as it covers the lifetime of individual power plants and also thepossibility that additional power plants may be constructed on the same site. Separate considerations
apply for the disposal of waste residues (mill tailings) from uranium and coal mining operations as
discussed below.
14. Collective dose rates can be integrated to infinity (referred to as the collective dose commitment) to
take account of all possible future doses from a discharge. However collective dose rates are generally
integrated to shorter times; values ranging from 80 to 10,000 years have been used in the Committee’s
past reports, see electronic attachments 1 and 2 (collective doses integrated to various times are sometimes
referred to as truncated collective doses). For most radionuclides, integrating collective dose rates to
100 years gives a significant proportion of the collective dose commitment [S9]. However, some relatively
long-lived, environmentally mobile radionuclides (3H, 14C, 85Kr and 129I) become globally dispersed andcan continue to contribute to the integrated collective doses for many years. For both 3H and 85Kr (halflives 12.6 years and 10.7 years, respectively), the integrated collective dose does not increase beyond
100 years. However, for 14C (half-life 5,730 years), the integrated collective dose increases by a factor of
more than five between 1,000 and 10,000 years; however the additional collective dose is then negligible
if the integration is continued to 1,000,000 years. For the very long-lived 129I (half-life 15.7 million years),
the integrated collective dose increases by about a factor of six between 1,000 and 10,000 years and by afactor of over 150 between 10,000 and 1,000,000 years (based on table 70 of [U5]). However, fordischarges from nuclear sites, the integrated collective dose from 14C rather than that from 129I dominates
the total integrated collective dose and so most of the collective dose will be received in the first
10,000 years [S9, U5]. Also, when comparing options explicit consideration of collective doses at longtimes is often not necessary because the collective doses at these times are all similar and moreovercomprise extremely low levels of individual dose [S9, U5].
15. In general, the uncertainties associated with estimating collective doses increase with integration
time, for example, because of possible major changes in environmental conditions and population
dynamics. The integrated collective dose to 500 years from a continuous discharge over one year hasoften been used to provide an upper estimate of the highest future annual collective dose rate if thepractice, and hence discharge, were to continue at a constant rate for that number of years [L1].
Five hundred years is used because it is assumed to be the maximum duration of the generation ofelectrical energy by nuclear power. An integration time of 10,000 years was used in the Committee’s
assessments conducted before the year 2000. Ten thousand years is consistent with the duration of thewarm period between glacial periods [L1] and therefore the maximum number of years over which any
reasonable assumptions about the nature of the global environment can be made.
16. When comparing the radiological impact of different sources, it is important not to introduce any
bias when choosing integration times for collective dose. For example, choosing a short time (e.g. of afew hundred years) for nuclear power generation would mean that a significant portion of the integrated

30 UNSCEAR 2016 REPORT

collective dose is not included. For non-nuclear energy production, notably that using fossil fuels, themajor radionuclides discharged are from the 238U decay chain, particularly 226Ra and its progeny
including 222Rn. These radionuclides do not become dispersed globally and so once discharged to theenvironment need to be considered only for relatively short timescales; a few hundred years is sufficient
to allow for the ingrowth of the radiologically significant radionuclide, 210Po.
17. The conventional mining and milling of uranium ore gives rise to various waste residues, which
are referred to as mill tailings. These contain enhanced levels of naturally occurring radionuclides andthe radon is emitted from the mill tailings for many years following disposal because of the longradioactive half-life of the parent 238U. In assessing the radiological impact of mill tailings, it isnecessary to allow for the number of years over which the emissions will continue. Previously, theCommittee estimated collective doses from mill tailings assuming that the emissions of radon continued
for 10,000 years [U6]. Since the year 2000, improvements have been made to the treatment of milltailings and the rehabilitation of areas where mill tailings had been disposed of. As discussed in thecompanion report on radiation exposures from electricity generation (see annex B), enhanced levels ofradon emissions may continue for periods of less than 100 years. The Committee therefore agreed thatthe best estimate of the period of radon emissions from mill tailings should be reduced to 100 years, butthat the effect of considering periods of 500 years and 10,000 years should also be evaluated. The sameconsiderations also apply to the disposal of mine spoil or ash from coal used for electricity generation.

C. End points considered
18. Taking account of the considerations discussed in sections A and B above, the Committee hasdeveloped its methodology to estimate the following characteristic individual doses (expressed as
effective doses, in sieverts, Sv) from each radionuclide discharged continuously at a rate of 1 Bq/s:(a) For discharges to atmosphere, the characteristic individual dose in the 100th year (as noted
above, the dose in the 100th year of continuous discharge is equal to the integrated dose to
100 years from 1 year’s discharge) at 5 km from the discharge point (annual individual doses arealso calculated at 50, 300, 750 and 1,250 km from the discharge point for use in estimatingcollective doses);(b) For discharges to freshwater bodies, the characteristic individual dose in the 100th year;(c) For discharges to a marine environment, the characteristic individual dose in the 100th year.
19. In addition, integrated collective doses (man Sv) from each radionuclide discharged continuously
at a rate of 1 Bq/s for a year are calculated as follows:(a) For discharges to atmosphere, collective doses are integrated to 100 years (this is equivalent tothe collective dose in the 100th year of continuous discharge) in the following distance bands:
0−100 km (local), 100–500 km, 500–1,000 km and 1,000–1,500 km. The results for 100–1,500 km
are summed to constitute regional components of collective dose;(b) For discharges to freshwater bodies, the collective dose is integrated to 100 years. It should be
noted that for freshwater bodies, instantaneous mixing in a single water volume is assumed and,with this assumption, it is not possible to distinguish between local and regional components ofcollective dose;ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 31(c) For discharges to a marine environment, local and regional components of collective dose areintegrated to 100 years;(d) For globally circulating radionuclides only (3H, 14C, 85Kr and 129I), the global collective dose is
integrated to 100, 500 and 10,000 years.
20. The results can be scaled to obtain the characteristic individual and collective doses for specificdischarges and sources. In chapter III, results are calculated for discharges from different geographicalregions of the world, considering different population distributions (generic, nuclear coastal and nuclear
inland). Results are also calculated for a generic discharge location situated in a region of very low
population density, which may apply to sites of uranium mines and mill tailings.

D. Discharges considered
1.

Electrical energy production

21. One of the aims of the methodology is to allow exposures from discharges of radionuclides toatmosphere and water bodies to be assessed for a range of facilities associated with electricity
generation, covering both nuclear and non-nuclear power production. The methodology could also be
broadly used to assess routine discharges from other sources, but—as noted earlier—it is not intended
for site-specific or regulatory purposes. The assessment of exposures due to electricity generation
requires adequate and representative discharge data from the various facilities for input into the models
that implement the methodology. For example, discharges from the nuclear facilities involved in power
production and the fuel cycle listed in table 2 could be considered.
Table 2. Types of nuclear facility for which the methodology may be relevantLife-cycle stage
Front end

Facility types
Uranium mine with mill
Enrichment and fabrication

Nuclear reactor operation

Nuclear power reactors (e.g. pressurized water reactors,
boiling water reactors, fast breeder reactors, gas cooled
reactors, heavy water cooled reactors, and light-watercooled, graphite-moderated reactors)
Research reactors

Back end

Reprocessing
Decommissioning
Waste management

22. There are also a number of non-nuclear means of electrical energy production that may haveassociated discharges of naturally occurring radionuclides because of the materials used in construction
or at some point in their production cycle. The Committee decided that these should also be covered by
the methodology and they are considered in annex B. These could include the use of: (a) fossil fuels(coal, gas and oil); (b) geothermal sources; and (c) solar power, wind and biomass.

32 UNSCEAR 2016 REPORT2.

Radionuclides discharged

23. The radionuclides covered by the methodology are listed in table 1 and are considered by theCommittee to give rise to most of the doses from radioactive discharges from different energy sources.
This list of radionuclides includes those that have been demonstrated to give rise to the highest
integrated collective doses in previous assessments [C3, U6]. Naturally occurring radionuclides are also
covered by the methodology in order to assess the radiological impact of discharges from mining andmilling of primary materials, fuel production, and non-nuclear forms of electrical energy production [N4].
24. Although the methodology is designed to use data on discharges of individual radionuclides, inmany cases discharge data are provided only for groups of radionuclides as a whole. For example,
discharges may be given for “total alpha” and then this value will need to be apportioned among therelevant radionuclides included in the methodology (e.g. 239,240Pu, 241Am). For discharges specified as
total beta/gamma or particulate there may be many radionuclides that could be discharged, with themost important for nuclear power plants generally being 60Co, 90Sr, 134Cs and 137Cs but with significant
contributions from others such as 54Mn or for United Kingdom gas cooled reactors only 35S. In using themethodology, it will be necessary to specify a fraction of the discharge for each relevant radionuclide
and also which representative radionuclides to consider as defaults for the sum of discharges from any
radionuclides not included in table 1.
25. The methodology is designed to allow different assumptions to be made about the state ofequilibrium between components of the decay chains of the naturally occurring radionuclides. Accountis taken of the time necessary for ingrowth to occur and differences between the importance ofingrowth of progeny for different types of discharge and for different exposure pathways. Where
appropriate, the contribution of progeny is taken into account according to the following assumptions:(a) Where the progeny are short-lived compared to the parent, their contribution is not considered
explicitly but is generally included with the parent, for example, contributions from 90Y and137m
Ba are included in the dose coefficients for intakes by inhalation and ingestion for 90Sr and137
Cs, respectively;(b) Where the progeny are long-lived compared to the parent, their contribution is not consideredfurther if, over a period of 100 years, there is unlikely to be sufficient ingrowth of the progeny.
Examples where this is the case are 239Pu/235U, 240Pu/236U, and 241Am/237Np;(c) The key radionuclides in the decay chains of the naturally occurring radionuclides are
considered separately and other progeny are only considered if they make a significant
contribution to exposures or if it is reasonable to assume that they would be discharged insecular equilibrium with the parent.
Further information for specific radionuclides and exposure pathways and details of how this is appliedin practice are given in the appendix.

III. DESCRIPTION OF THE METHODOLOGY
26. When radionuclides are discharged to the environment there are various ways in which people canbe exposed to radiation. Figure I illustrates the more important exposure pathways.

Figure I. Exposure pathways following discharge of radioactive material to the environment

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 33

34 UNSCEAR 2016 REPORT

A. Assessment of doses from discharges to atmosphere
27. This section describes the methodology for estimating characteristic individual and local andregional components of collective dose to the public from a discharge of radionuclides to atmosphere.
The appendix gives full details of all of the equations used. The exposure pathways included in themethodology for discharges to atmosphere are:(a) Internal exposure from inhalation of radionuclides in the plume;(b) External exposure (beta and gamma emitters) from radionuclides in the plume;(c) External exposure from deposited radionuclides;(d) Internal exposure from ingestion of radionuclides incorporated in food.
28. Other exposure pathways such as internal exposure from inhalation of resuspended radionuclides
deposited on the ground and from inadvertent ingestion of soil are also possible. However a review ofthe literature indicated that the doses from these exposure pathways are negligible compared with thosefrom the exposure pathways listed above for continuous discharges of radionuclides to atmosphere [J5].
29. Characteristic individual doses are calculated for a member of the public assumed to be living at a
distance of 5 km from the point of discharge. Local and regional components of collective dose fromdischarges to atmosphere are derived directly by multiplying individual doses calculated at the
midpoints of distance bands or annuli (of 0–100, 100–500, 500–1,000 and 1,000–1,500 km) around thepoint of discharge by data specific to each geographical region on the number of people within eachannulus. Region-specific or generic values are used for parameters in the dose calculation as discussed
in the following sections.

1.

Population distribution

30. The Committee’s previous approach was based on simplified assumptions regarding population
density around nuclear sites representative of the situation in the 1980s. Given the importance of
population information in determining the overall magnitude of collective doses, and that there havebeen significant changes in population patterns throughout the world, the Committee decided to update
the information on population density. For comparison purposes and to examine the effect of different
population densities, four different sets of population data are considered in the methodology. As adefault case for comparison purposes, the calculation of collective dose from discharges to atmosphereis based on information on population densities for 2010 weighted by the population in eachgeographical region [F1]. The population distribution used for the default case is given in table 3 where
the same population density is used for each annulus (the population is the assumed density multipliedby the area of the annulus). In addition to values by region, a world-average population distribution has
been obtained as an average of the values for each region weighted by the populations in each region.
The regions considered in the methodology are those used by the United Nations Environment
Programme (UNEP), illustrated in figure II below.

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 35

Table 3. Default population distributions for different geographical regions
UNEP region

Population density,
weighteda (km−2)

Population within each annulus
0–100 km100–500 km

500–1,000 km

1,000–1,500 km

Africa1

7.9 × 106

2.5 × 107

5.9 × 108

1.9 × 10

3.1 × 108

Asia and Pacific

2.8 × 102

8.8 × 106

2.1 × 108

6.6 × 108

1.1 × 109

Europe1.3 × 102

4.0 × 106

9.7 × 107

3.0 × 108

5.0 × 108

Latin America and Caribbean

1.4 × 102

4.3 × 106

1.0 × 108

3.2 × 108

5.3 × 108

North America

3.2 × 101

1.0 × 106

2.4 × 107

7.6 × 107

1.3 × 108

West Asia

1.0 × 102

3.2 × 106

7.7 × 107

2.4 × 108

4.0 × 108

World averageb

1.6 × 102

5.0 × 106

1.2 × 108

3.8 × 108

6.3 × 108a

The population densities are taken from FAO [F1] and are values for each region weighted as described in this reference.

b

The world-average value is the average of the values for each region weighted by the population in each region.

Figure II. The geographical regions used in the methodology (taken from UNEP [U3])31. For nuclear power stations, a more specific analysis of population data is possible. In
collaboration with the Metadata and Socio-Economics Unit of UNEP/DEWA/GRID-Geneva, 3 ageographic information system has been used to express the number of people living within specified
distance bands around each station. Details of the approach and data used are given in electronic
attachment 3; in essence, the numbers of people living within different distances (100, 500, 1,000 and
1,500 km) around the site of each operating nuclear power station have been analysed. These data havebeen used to derive simplified averages by UNEP region for the population in each annulus. The
averages have been estimated separately for inland sites and for sites located on the coast, where thepopulation distribution is likely to be affected by the presence of a large body of water (see table 4).
Again a world-average value has also been calculated using all the available data. Because there were,at the time of analysis, no significant operating nuclear power stations in West Asia and only a coastal
3

United Nations Environment Programme (UNEP) Division of Early Warning and Assessment (DEWA) Global Resource
Information Database network (GRID) http://www.grid.unep.ch/.

36 UNSCEAR 2016 REPORTsite for Africa, no population densities are given for these in table 4. The results for the default
population distribution in table 3 could be used to consider nuclear sites in these regions if needed.
Table 4. Population distribution around operating nuclear power stations as a function of UNEP
region and location
Based on information provided by UNEP for the year 2008

UNEP regiona

Population within each annulusb
0–100 km100–500 km

500–1,000 km

1,000–1,500 km

COASTAL
Africa6

3.9 × 10

1.1 × 106

8.7 × 106

3.4 × 107

Asia and Pacific8.3 × 106

8.8 × 107

2.0 × 108

3.5 × 108

Europe3.3 × 106

6.4 × 107

1.3 × 108

1.5 × 108

Latin America and Caribbean

3.6 × 106

6.2 × 107

4.8 × 107

4.3 × 107

North America

4.7 × 106

4.0 × 107

7.0× 107

6.7 × 107

n/a

n/a

n/a

n/a

5.6 × 106

6.6 × 107

1.4 × 108

2.0 × 108

n/a

n/a

West Asia
World averagec

INLAND
African/an/aAsia and Pacific7

1.9 × 108

2.0 × 108

4.6 × 10

5.0 × 108

Europe

4.6 × 106

8.9 × 107

1.8 × 108

1.8 × 108

Latin America and Caribbean

4.6 × 106

1.5 × 107

3.7 × 107

3.4 × 107

North America

3.0 × 106

3.9 × 107

7.7 × 107

8.5 × 107

n/a

n/a

n/a

n/a

West Asia
World averagec

4.6 × 106

7.2 × 107

1.5 × 108

1.5 × 108aNote that at the time of analysis there were no significant operating nuclear power stations in West Asia or inland in Africa (seefigure II for definition of UNEP regions) and hence population data are not presented for these regions.

b

Data are presented to one decimal place, which is considered sufficient for this purpose.

c

The world-average is the average of the population in each annulus for all nuclear sites for which data are available.

32. The other case considered in the methodology is for uranium mines and mill tailings sites. Mostof these facilities are situated in areas of very low population densities, as illustrated in electronic
attachment 3. Therefore, the methodology also considers a population distribution with a density of
5 km−2 to gain insight into the effect on collective doses. Using this low population density out to1,500 km results in estimated collective doses from atmospheric discharges that are about two orders ofmagnitude lower than those estimated using the population distributions in tables 3 and 4. The low
value for population density should therefore only be used where appropriate and where it can beassumed to apply over the integration period for the collective dose.
33. There are two main approaches to assessing collective doses from ingestion of terrestrial foods.
The first uses information on the distribution of agricultural production to obtain an overall collective
dose from the production but with no indication of the individual doses that make up the collective
dose. The second approach, which the Committee adopted here, assumes that people obtain their food

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 37

from the area where they live. This enables both individual and collective doses to be estimated.
However, as discussed earlier, in many parts of the world it is not realistic to assume that people derive
all their food from local produce. This is particularly so within a small area that has a high population
density, and therefore low agricultural production. The Committee therefore decided that collective
doses from ingestion (where it is assumed that 100% of the food is obtained from the area considered)should only be calculated for distances of at least 100 km. For the characteristic individual dose, basedon an individual living at a distance of 5 km from the site, 25% of their food is assumed to be locally
produced as discussed earlier (paragraph 11).

2.

Dispersion in the atmosphere

34. In previous assessments, the Committee adopted a simple generic atmospheric dispersion model.
It considered the uncertainties associated with this approach in some detail in its 2000 Report [U6].
Given the generic nature of its assessment objectives, the Committee concluded that the long-term
sector-averaged Gaussian model was likely to provide an appropriate level of accuracy. Crawford et al.
[C5] acknowledge that simple Gaussian models continue to be used because they produce results that
often agree fairly well with measured data and because their results are relatively easy to obtain. The
Committee has decided to retain this approach.
35. The variation in activity concentration in air, Ca(x), with downwind distance beyond 1 km isapproximately given by the following equation:

Ca ( x) = D1 ⋅ Q ⋅ x − n(1)where D1 is the annual average dilution factor at 1 km (s/m3), Q is the discharge rate (Bq/s), x is thedownwind distance (km) and n is an empirically-determined index. The Committee agreed to retain theparameter values used in the UNSCEAR 2000 Report, in which a value of 5.3 × 10−7 s/m3 was found tobe the best approximation for D1 with a value for n of 1.42 for all radionuclides except noble gases,
tritium and carbon-14 [U6]. The dilution factor, D1, was found to be relatively insensitive to changes inthe values of parameters, except for wind speed and release height. The value of n was, however, foundto be dependent upon deposition velocity and inversion height. For noble gases, which do not deposit, avalue of n equal to 1.2 is retained. This value is also retained for tritium because, although tritium
rapidly exchanges with water in the soil and vegetation, it is quickly re-emitted to the atmosphere.
Carbon-14 also exchanges with carbon in soil and vegetation and partially returns to atmospherethrough plant and soil respiration. A value for n of 1.4 is therefore used for this radionuclide.
36. As part of the development of the current methodology, the activity concentrations estimatedusing this simple relationship were compared with the results obtained using a more complex Gaussianmodel, for a uniform wind rose (for which activity concentrations were averaged over 12 sectors) thatallowed for depletion of the plume but not radioactive decay. The results were found to be very similar(less than a factor of two difference).
37. A reduction factor is now included in the methodology to allow for the radioactive decay of shortlived radionuclides, notably radon, during dispersion over distances of hundreds of kilometres. Thisfactor is based on a mean wind speed, ua, of 2 m/s [I2].
38. The deposition rate of radionuclides at a specified distance (in Bq/(m2 s) is determined by theapplication of a simple “effective deposition velocity” that allows for both wet and dry deposition onvegetation, soil and other surfaces. An annual-average deposition rate of 0.002 m/s [U6] is used for all38 UNSCEAR 2016 REPORT

radionuclides, with the exception of the noble gases, tritium and 14C for which a value of zero isapplied. As noted above, tritium and 14C exchange with the soil and vegetation; however, this ismodelled using a specific activity approach (as discussed below). Because these radionuclides are
returned to atmosphere, the deposition rate is not used and the effective deposition velocity is taken to
be zero, even for 14C which is partly retained on the ground. This is consistent with the use of thegeneric approach to the modelling of dispersion applied in the UNSCEAR 2000 Report [U6] and, withthe application of a value of n of 1.42, 1.4 or 1.2 in equation 1. The use of these parameters ensures that
there is a balance between the activity discharged and the activity deposited within a distance of around2,000 km, thereby ensuring that the relevant exposures are included in the estimation of collective dose.
39. The calculated activity concentrations in air at ground level depend to some extent on the heightfrom which the discharge takes place and whether the discharge is from a point source or a wide area.
The heights of stacks from which discharges take place (i.e. point sources) vary considerably. The
discharges from uranium mine and mill tailings, on the other hand, take place at ground level over awide area. Electronic attachment 4 discusses the variation in estimated activity concentrations in air
with stack height and the differences for point and area sources. The differences in the concentration
profiles with stack height lessen with distance from the stack. For the case illustrated in electronic
attachment 4, where a uniform wind rose is assumed together with Pasquill Category D conditions for
65% of the time and all other categories for the rest of the time, the estimated concentration in air for aground-level discharge is about a factor of three higher than that from a 100 m stack at a distance of
5 km, and less than a factor of two higher than from a 30 m stack. Larger and smaller differences would
be seen for the individual Pasquill categories but this comparison applies to the annual average that isneeded for assessing routine continuous discharges. At a downwind distance of 100 km, the differencein concentrations for a ground-level discharge and one from a 100 m stack is about a factor of two. For
point and area sources, the differences in estimated activity concentrations at these distances are small.
The ratio of the time-integrated activity concentrations in air for an area source to that for a point sourceis 0.9 at 5 km and is 1 beyond 10 to 20 km (see electronic attachment 4). Given these findings, theCommittee agreed that, for its generic methodology, it was reasonable to adopt a single stack height of
30 m and to consider all discharges to atmosphere as point sources.

3.

Behaviour of radionuclides in a terrestrial environment

40. Radionuclides discharged to atmosphere may be transferred to plants by a number of processes,
primarily direct deposition onto the surface of plants and uptake by their roots from material depositedon the soil. The most important processes for the transfer of radionuclides through the terrestrial
environment are illustrated in figure III.

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 39

Figure III. The important processes for transfer of radionuclides through the terrestrial environment

41. There have been significant developments in the modelling of the transfer of radionuclides
through the terrestrial environment in recent years, partly as a result of studies following the Chernobyl
accident, see for example [C1]. The standard compilations of the concentration factors, linking different
parts of the environment, e.g. soil and plants, and other relevant parameters have been reviewed andupdated as part of international coordinated research activities [C1, I5].
42. For the purposes of this methodology, the Committee used the dynamic food-chain model
FARMLAND [B6], as implemented in PC-CREAM [S8], to derive integrated activity concentrations infood (fresh weight) per unit deposition rate; these are the activity concentrations integrated to 100 years
for continuous deposition at a rate of 1 Bq/(m2 s) for one year. These estimated concentrations takeaccount of the various environmental transfer, migration and loss processes illustrated in figure III andradioactive decay. Values of radionuclide transfer parameters for terrestrial environments were selectedfrom international compilations of data [I1, I5], supplemented by additional data [S8]. Expert
judgement was used to select values appropriate for the Committee’s purposes which are not overly
cautious. The values selected are intended to be appropriate for a range of environments and climates.
The FARMLAND model uses a standard approach to estimate the transfer of radionuclides throughterrestrial food chains and has been found to be in good agreement with measured data [S8]. In a
comparison exercise carried out as part of the IAEA EMRAS II (Environmental Modelling for40 UNSCEAR 2016 REPORT

Radiation Safety) programme [I6], the results obtained from FARMLAND were found to be in good
agreement with those results from other models. The derived activity concentrations applied in theCommittee’s methodology are summarized in table 5 and full details of the model and parameter values
can be found in Brown and Simmonds [B6] and Smith and Simmonds [S8].
Table 5. Activity concentrations in foodstuffs integrated to 100 years for continuous deposition at
a rate of 1 Bq/(m2 s) for one year [S8]Integrated activity concentration in food (fresh weight) (Bq/kg per Bq/(m2 s))
Radionuclidea

Cereals(Ccereal,unit)

Vegetables & fruits(Cveg,unit)

Milk & dairy products(Cmilk,unit)

Meat & offal(Cmeat,unit)

35

S

3.7 × 105

1.2 × 105

1.4 × 106

6.0 × 10654

Mn

8.6 × 104

1.3 × 105

9.0 × 104

1.9 × 10558

Co

5.3 × 104

9.3 × 104

3.9 × 105

7.4 × 10560

Co

1.1 × 105

1.5 × 105

2.3 × 106

1.3 × 10765

Zn

1.8 × 105

2.2 × 105

7.0 × 105

5.8 × 106

90

Sr

7.1 × 105

7.3 × 105

1.5 × 106

3.3 × 105

106

Ru

9.8 × 103

1.0 × 105

1.1 × 103

9.7 × 105129

I

6.0 × 105

2.3 × 105

3.1 × 105

2.1 × 105131

I

4.2 × 104

4.1 × 104

5.8 × 104

2.5 × 104

134

Cs

4.9 × 105

1.4 × 105

2.5 × 105

1.2 × 106

135

Csa

7.0 × 105

3.3 × 105

3.0 × 105

1.6 × 106

137

Cs

5.9 × 105

2.2 × 105

3.0 × 105

1.5 × 106

138

Csa

8.5 × 100

1.7 × 102

1.3 × 10−2

1.3 × 10−3

210

Pb

4.1 × 104

1.4 × 105

1.2 × 104

2.4 × 104

212

Pba

1.6 × 102

3.2 × 103

2.1 × 102

8.5 × 10−1

214

Pba

7.0 × 100

1.4 × 102

6.6 × 10−1

1.1 × 10−4

214

Bia

5.4 × 100

1.0 × 102

1.4 × 100

1.7 × 10−2

210

Po

4.9 × 103

9.5 × 104

8.2 × 104

1.1 × 105226

Ra

2.6 × 105

3.0 × 105

1.7 × 105

3.3 × 104

228

Raa

8.8 × 104

1.3 × 105

7.4 × 104

1.4 × 104

228

Tha

5.4 × 103

1.0 × 105

1.5 × 102

1.2 × 103

230

Th

7.9 × 103

1.1 × 105

1.7 × 102

2.2 × 103232

Th

7.9 × 103

1.1 × 105

1.7 × 102

2.2 × 103

234

Tha

3.4 × 103

6.6 × 104

1.1 × 102

6.6 × 101

234

U

5.6 × 104

1.5 × 105

5.7 × 104

2.8 × 105238

U

5.6 × 104

1.5 × 105

5.7 × 104

2.8 × 105

239

Pu

1.0 × 104

1.1 × 105

1.6 × 102

8.8 × 103

240Pu

1.0 × 104

1.1 × 105

1.6 × 102

8.8 × 103

241

Am

1.5 × 104

1.1 × 105

8.5 × 101

4.7 × 103

Included as progeny only.

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 41

43. The dispersion of 3H and 14C in the environment is more complex than that of other radionuclides
owing to the role of hydrogen and carbon in biological systems. These radionuclides therefore need to
be treated differently from other radionuclides. As previously, the Committee has assumed theseradionuclides reach equilibrium rapidly with their corresponding stable element, and used an approachbased on their specific activity.
44. The specific-activity model for tritium is based on the assumption that tritium behaves ashydrogen in the environment so that tritium discharged to atmosphere exchanges with the hydrogen inwater in air, soil, plants and animals. The concentration of tritiated water (HTO) and organically boundtritium (OBT) in plants is determined on the basis of the water content in plants and a partition factor
that takes account of the presence of exchangeable hydrogen in the dry weight of the plant [I5]. Fulldetails of the approach are given in the appendix. The concentrations of HTO and OBT in animal
products are determined using concentration factors that relate the concentrations in these products to
those in feed, drinking water and inhaled air.
45. The specific activity (or activity concentration) of 14C in elemental or stable carbon is determinedfrom the discharge by taking account of dispersion in the atmosphere and the concentration of stablecarbon in the atmosphere. The concentration of 14C, expressed in Bq/kg of stable carbon, is assumed tobe the same in plants as in air. The following equation is used to calculate the concentration of 14C interrestrial foods, Cf,C-14(x), at distance x from the discharge point:C=( x ) Cair,14C ( x ) ⋅f ,14 C

Sp
Sair

(2)

where Cair,C-14 (x) is the activity concentration of 14C in air at distance x (Bq/m3), Sp is the concentrationof stable carbon in the crop of interest (grams of carbon per kg fresh weight of crop) and Sair is theconcentration of stable carbon in air (grams of carbon per cubic metre of air).
Similarly the concentration of 14C in animal products, Cf,C-14 at distance x from the discharge point isgiven by:

C f ,14 C ( x ) =f C ⋅ Cpasture,14C ( x ) ⋅ S aSp(3)

where fc is the fraction of feed containing 14C (assumed to be 1 in the methodology), Cpasture,C-14 (x) is theconcentration of 14C in pasture at distance x from the discharge point (derived as for crops using
equation (2)), Sa is the concentration of stable carbon in the animal product (grams of carbon per
kilogram fresh weight) and Sp is the concentration of stable carbon in the pasture (grams of carbon per
kilogram fresh weight of pasture).
46. The values of the model parameters forming part of the specific-activity model for 3H and 14C aresummarized in table 6 (see the appendix for more information). The symbols used here and in the
workbooks are those used in the IAEA publication describing this model for ease of reference.

42 UNSCEAR 2016 REPORT

Table 6. Parameters and their values associated with the specific-activity model for 3H and 14C(taken from [I5])
Parameter

Symbol

Value

Unit

Stable carbon concentration in air

Sair

0.2

g of C/m3

Stable carbon concentration in cereals (fresh weight)

Sp

390

g of C /kg

Stable carbon concentration in vegetables (fresh weight)

Sp30

g of C /kg

Stable carbon concentration in pasture (fresh weight)

Sp

100

g of C /kg

Stable carbon concentration in cow meat (fresh weight)

Sa

200

g of C /kg

Stable carbon concentration in cow milk (fresh weight)

Sa65

g of C /kg

Fraction of feed containing 14C

fc

1

—

Fractional water content of cereals (fresh weight)

WCp

0.12

L/kg

Fractional water content of vegetables (fresh weight)

WCp

0.92

L/kg

Fractional water content of pasture (fresh weight)

WCp

0.76

L/kg

HTO:H2O water vapour pressures

γ

0.909

—

Absolute humidityHa

6 × 10−3

L/m3

Relative humidity

RH

0.7

—

Empirical constant

CRs-a

0.3

—

Concentration ratio for HTO intake through milk

CRa,HTO

0.87(Bq/kg fresh weight)per (Bq/L)

Concentration ratio for HTO intake through meat

CRa,HTO

0.66(Bq/kg fresh weight)per (Bq/L)

Water equivalent factora, cereals

WEQp

0.56

L/kg

Water equivalent factor, vegetables

WEQp

0.51

L/kg

Water equivalent factor, pasture

WEQp

0.56

L/kg

Rp

0.54

—

Concentration ratio for OBT intake, milk

CRa,OBT

0.24(Bq/kg fresh weight) per(Bq/kg dry weight)

Concentration ratio for OBT intake, meat

CRa,OBT

0.4(Bq/kg fresh weight) per(Bq/kg dry weight)

Partition factorba

The water equivalent factor is the mass (kg) of water produced per unit mass (kg) of dry matter combusted.

b

The ratio of the concentration of non-exchangeable organically-bound tritium in combustion water to that in tissues (e.g. leaves).

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 43

4.

External and internal exposure(a) External exposure
47. The Committee considers that its previous methodology [U6] for estimating the dose fromexternal exposure due to immersion by assuming a semi-infinite cloud of radionuclides is still
appropriate. It acknowledges some limitations with this approach, most notably where activity
concentrations in air are likely to be non-uniform over a distance of a few hundred metres to one
kilometre from the point of discharge. However, given the distances over which the Committee’s
assessments are made, the application of dose coefficients for external exposure used previously, whichwere based on [E2], is unlikely to be a source of significant error. The dose coefficients applied in theCommittee’s methodology are presented in table 1.
48. The annual characteristic individual dose from immersion in the plume, HE(ex,cloud),i forradionuclide, i (Sv/a) is estimated at a series of distances, x (m), from the discharge point by assuming
100% occupancy (the fraction of the time that is spent at a particular location) at locations at thosedistances (Oann (s/a)) and applying the relevant dose coefficients for external exposure due to immersion
in the plume, Dex, cloud,i from table 1 (Sv per (Bq s/m3)). Account is then taken of the fraction of timespent outdoors, Oout (dimensionless) and the shielding effect of buildings, Lcloud (dimensionless) as
shown in equation (4) and discussed below.

H E (ex,cloud),i=( x ) Cair,i ( x ) ⋅ Dex,cloud,i ⋅ Oann ⋅ ( Oout + (1 − Oout ) ⋅ Lcloud )(4)

Where Cair,i (x) is the activity concentration of radionuclide i in air (Bq/m3) at location x. The annual
individual dose from external exposure due to deposited material, HE(ex,deposit),i (x) (Sv/a) at a distancex (m) from the discharge point is calculated from the time-integrated activity concentration (to100 years) of the radionuclide i on soil at the location of interest, di ( x) (Bq s/m2), the length of thedischarge, tdischarge (s/a) the relevant dose coefficient for external exposure due to deposition, Dex,deposit,i(Sv/ Bq s/m2), the fraction of time spent outdoors, Oout (dimensionless) and the dimensionless location
factor that takes account of the shielding effect of buildings, as shown in equation (5) and discussed
below.

H E ( ex,deposit ),i ( x=) di ( x ) ⋅ tdischarge ⋅ Dex,deposit,i ⋅ ( Oout + (1 − Oout ) ⋅ Ldeposit )(5)

49. The Committee’s previous methodology applied the dose coefficients for external exposure fromradionuclides deposited on soil provided by Beck [B1]. An alternative approach was used for theCommittee’s 2013 Report of the levels of radiation exposure due to the nuclear accident at the
Fukushima-Daiichi nuclear power station [U12] based on the model published by Petoussi-Henss et al.
[P2]. The effective dose coefficients calculated using this more recent model [P2] were similar to orwithin a factor of two of those used previously. For the sake of simplicity and consistency with its
2013 Report [U12], the Committee decided to apply dose rate coefficients for external exposure, edep(nSv/h per kBq/m2) from Petoussi-Henss et al. These values are based on calculations using a voxel
phantom and the latest definition of effective dose [I13] (the use of the previous definition of effective
dose in the methodology would make little difference to the calculated effective doses for external
exposure). Where data for particular radionuclides were not available, the data set was supplemented byfactors derived from the United States Federal Guidance Report No. 12 [E2].

44 UNSCEAR 2016 REPORT

50. Petoussi-Henss et al. [P2] modelled the geometry as an infinite mono-energetic plane sourceshielded by a soil layer of depth 0.5 g/cm2. Such an assumption gives a good description of theradiation field after wet deposition on the ground and after dry deposition following the first rainfall[I15, J1]. With this geometry, the air kerma from a 137Cs (137mBa) source is reduced by a factor of 0.67
compared to a plane source on the ground–air interface. The effective dose coefficients were derived
assuming a constant density of air of 1.2 × 10−3 g/cm3 and a soil density of 1 g/cm3, which is considered
to be representative of the upper 2 cm of soil [P2].
51. In order to model the reduction of gamma dose rates because of migration into the soil, theCommittee adopted an attenuation function r(t) derived empirically from data on the migration of 137Cs[G2]:

 ln2  ln2 r ( t )= p1 ⋅ exp  −t  + p2 ⋅ exp  −t T1 
 T2 

(6)

where p1, and p2 are dimensionless parameters with values derived empirically, T1 and T2 are the initialand final times, respectively, following deposition and t is the time after the deposition of interest. The
parameter values in this function were determined from gamma-spectrometric analyses of over 400 soil
samples taken during 1986–2003 in the areas of Germany (specifically Bavaria), the RussianFederation, Sweden and Ukraine affected by deposition from the accident at the Chernobyl nuclear
power plant in 1986 (e.g. [G2, J3, L2, S2]). For the purposes of the Committee’s methodology,
parameter values derived for areas distant from the Chernobyl plant were applied, namely p1 was taken
to be 0.5 and p2 to be 0.5; T1 was assumed to be 1.5 years while T2 was assumed to be 50 years. Thus
the relationship below with T = 100 years was applied to the value of the dose coefficient from
deposition ( edep ) given in [P2]:
t

t 


ln 2 
− li +t
T1 

edep = =edep ⋅ er ( t ) dt edep ⋅  p1e 

0
0


∫

( − lit )∫+ p2 eln 2  − li +
t
T2  





dt

(7)

Substituting for p1, p2, T1, T2 in the above equations and changing from a decay constant to a half-life,
the effective dose (Sv) from external exposure in year 100, edep, is given by: ln 2 ln 2   ln 2 ln 2  


−
+
−
+
T
T 



0.5
0.5
1 − e  t1/2 1.5   +1 − e  t1/2 50   =edep edep ⋅ 
ln
2
ln
2
ln
2
ln
2





+
 t + 50  t1/2 1.5 
1/2


(8)

This can be simplified to ln 2 ln 2   ln 2 ln 2   



−
+
−
+
T
T
0.75t1/2
25t1/2 t1/2 1.5   t1/2 50   



=
+
1− e
1− e
edep edep ⋅ (t1/2 + 1.5) ln 2  (t1/2 + 50) ln 2 




 


As an example, for caesium-137 and caesium-134 the following values can be calculated:(9)

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 45()

edep 137 Cs+137m Ba = 1.55∙× 10−7 Sv/(Bq/m2)()

edep 134 Cs = 6.23∙× 10−8 Sv/(Bq/m2)

(10)

(11)

52. Despite differences in climate, little variation in indoor occupancies has been found between
countries and there is no evidence of a significant difference due to climate [A1]. Studies show thatindoor occupancies range from around 84 to 91% [G1, O2]. The Committee considered that values ofbetween 70% (for an outdoor worker) and 90% (for pensioners and indoor workers) were appropriate
for a Japanese population [U12]. In accordance with its previous methodology, the Committee assumed
an indoor occupancy factor of 80% [U6]. In equations (4) and (5) above the outdoor occupancy Oout isused; this is simply a fractional value and is 1 − 0.8 = 0.2.
53. People indoors receive some protection from external exposure due to gamma-emitting
radionuclides in the plume as it passes overhead. The reduction in ambient dose equivalent rate depends
on the nature and structure of the building as well as on the energy of the radiation. A number of studiesof the shielding effect of various types of buildings have been published, particularly following theChernobyl accident [E2]. For example, the work of Le Grand [L1] and Jacob and Meckbach [J1, J2]
indicated that shielding factors (i.e. the ratio of the ambient dose equivalent rate indoors to that
outdoors) for radiation from airborne radionuclides ranged from 0.01 to 0.7 for single-family houses invarious European countries. For multi-storey buildings the shielding factor varies with storey, with thelowest values in the basement and first storey and the highest value for the top storey. Le Grand [L1]estimated that shielding factors appropriate for an airborne plume with photon energy of 0.68 MeV
ranged from 0.01 to 0.1 for the ground floor and from 0.09 to 0.4 for the upper floors of buildings. For
its methodology, the Committee has selected a shielding factor of 0.2 for radionuclides in the plume,
being within the range applicable to single and multi-storey buildings.
54. The UNSCEAR 1982 Report [U4] provided an overview of shielding factors appropriate fordeposited radionuclides, with values ranging from 0.05 in office buildings, 0.2 in masonry homes, and
0.4 in wooden buildings. This information was based on work by Burson and Profio, which showed arange of shielding factors depending on the nature of the building, with the lowest factors being forbasements of large multi-storey buildings [B8]. The United States Nuclear Regulatory Commission[N6] and others have suggested a generic shielding factor of 0.5 for regulatory purposes, which it
considers appropriate for photon energies above a few hundred kiloelectronvolts [E2]; for photons oflower energy, use of such a value may considerably overestimate the dose equivalent [K6]. In theirassessment of the radiation exposure of the population of the United States of America [N3, S1], theNational Council on Radiation Protection and Measurements (NCRP) applied a shielding factor of
0.59 (±6%) for terrestrial gamma radiation, which it considered to be appropriate for photon energies ofgreater than a few hundred kiloelectronvolts.
55. Location factors are used to express the ratio of external exposures in terms of ambient dose
equivalent rate at a specific location to the ambient dose equivalent at the location for which calculated
or measured ambient dose equivalent was obtained (for example, this might be between the exposures
outdoors in an urban and a rural environment). This is a broader term than shielding factor which justallows for the reduction of ambient dose equivalent from being indoors. For the purposes of thismethodology, the two terms can be considered to be equivalent, because it is the reduction in external
exposures from being indoors that is relevant. Golikov et al. evaluated the location factors for gamma
radiation in air in rural and urban environments in the Russian Federation five years after the Chernobyl
accident [G2]. In urban areas, they derived location factors for living areas that varied from 0.01 for a
multi-storey house to 0.09 for a wooden house, while they estimated the factor for buildings where

46 UNSCEAR 2016 REPORT

people work to be around 0.02. In rural areas, location factors for living areas ranged from 0.02 (for a
multi-storey house) to 0.13 (for a single-storey wooden building). This work formed the basis for thetime-dependent location factors used in the Committee’s 2013 Report on the levels and effects ofradiation exposure due to the nuclear accident at the Fukushima-Daiichi nuclear power station [U12].
Three different time-dependent location factors were used for that assessment: (a) for paved externalsurfaces, (b) for non-paved external surfaces, and (c) for inside buildings. This time dependence isimportant when assessing exposures due to an accident. However, for routine releases it is the dose in
the 100th year of continuous discharge that is of interest and the effect of using a time-dependent
location factor is small compared to differences in location factors for different building types. These
results also show a greater degree of shielding from deposited radionuclides than from radionuclides in
the plume, and this is reflected in the Committee’s choice of values for its methodology. In accordancewith its previous methodology [U6], the Committee has used a shielding (location) factor of 0.1 toallow for the reduction in ambient dose equivalent from external exposure due to deposited material
while indoors. This value was chosen as representative of occupancy in a single-storey building andwas considered to be reasonably consistent with the result that would be obtained if an approach basedon time-dependent location factors had been used.

(b) Internal exposure from inhalation
56. As previously, the Committee uses a standard approach to assess the internal exposure frominhalation of radionuclides in the air following discharges to atmosphere. This approach uses theestimated activity concentration of a radionuclide in air (section III.A.2 above), an appropriate
breathing rate and the relevant dose coefficient for intake by inhalation (table 1).
57. The Committee continues to use a nominal adult breathing rate of 20 m3/d [U7] in its
methodology to maintain consistency with previous assessments, recognizing differences between thisvalue and that used by ICRP to derive dose coefficients. As discussed earlier, the Committee considers
that the dose coefficients for inhalation given in ICRP Publication 119 [I14] using the ICRP model ofthe respiratory tract [I11] continue to be appropriate (table 1). No account is taken of any reduction in
activity concentrations in air when people are indoors because the Committee considers this to be asecond-order effect that will not have a significant effect on the estimated doses.
58. A different approach is needed for the inhalation of isotopes of radon. In the UNSCEAR 2006
Report, the Committee considered a number of issues related to the assessment of doses from theinhalation of radon and its short-lived progeny [U9]. It concluded that it should continue to use a value
for the radon dose coefficient of 9 nSv per (Bq h)/m3 for this methodology, with equilibrium factors(the ratio between the activity of the short-lived radon progeny and the activity that would be atequilibrium with the radon parent) of 0.6 for radon outdoors and 0.4 for radon indoors (indoor
occupancy being 80% as discussed earlier) to calculate annual effective doses from inhalation of radonand its short-lived progeny (see the appendix for more details).

(c) Internal exposure from ingestion
59. Members of the public may be exposed through ingestion of food that contains radionuclides
resulting from discharges to atmosphere. As indicated in section III.A.3, radionuclides discharged toatmosphere may be transferred to human food by a number of routes. The annual effective dose fromthe ingestion of food, f, containing radionuclide, i, at distance x (m) from the discharge point in regionr, (HE(ing),f,r,i (x)) (Sv/a) is given by equation (12):ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 47

H E ( ing ), f ,r ,i ( x=
) C f ,i ( x ) ⋅ Ding,i ⋅ Flocal ⋅ I f ,r(12)

where Ding,i (Sv/Bq) is the effective dose coefficient for ingestion of radionuclide i as given in table 1;
Flocal is the fraction of food that is locally produced (dimensionless); If,r is the average consumption rateof food f in region r (kg or L per year) as discussed below; Cf,i is the activity concentration ofradionuclide i in terrestrial food f at distance x from the discharge point (Bq/kg) given by:C=
C f ,unit,i ⋅ di ( x )f ,i ( x )(13)where Cf,unit,i is the activity concentrations in foodstuffs integrated to 100 years for continuous deposition
at a rate of 1 Bq/(m2 s) for one year (Bq/kg per Bq/(m2 s)) given in table 5 and di ( x) is the deposition rate
at distance x of radionuclide i (Bq /(m2 s)). The food contamination monitoring and assessment
programme (GEMS/Food) database for 2012 — part of the WHO Global Environment Monitoring
System — formed the basis for the population-weighted consumption rates used by the Committee tocalculate doses from ingestion for each UNEP region [W2]. For the Committee’s methodology, the World
Health Organization (WHO) combined the data for specified food groups and reconfigured them for the
UNEP regions and subregions (figure II). The resulting values of If,r for terrestrial foods are presented intable 7. World-average values have also been derived; these are the averages of the values for each region
weighted by the population densities given in table 3. As discussed in paragraph 11, for the estimation ofcharacteristic individual doses, it is assumed that only 25% of foods consumed are produced locally (Flocal
is 0.25). However in estimating collective doses, people are assumed to obtain 100% of their food fromthe area where they live (Flocal is 1.0), this assumption is considered reasonable because collective doses
are estimated for areas of 30,000 km2 or more.
Table 7. Annual average per caput consumption rates of terrestrial foods by UNEP region
Annual average per caput consumption ratea (kg) for each food type
UNEP region

Cereals

Vegetables andfruit

Milk and dairy
products

Meat and offal

Africa

130

220

31

17

Asia and Pacific

140

240

45

30

Europe

110

280

120

65

Latin America and Caribbean

110

210

77

63

North America

88

260

120

100

West Asia

140

180

43

34

World averageb

130

230

65

44

a

Values are rounded to two significant figures in order not to imply great precision.

b

World-average values are the averages of the values for each region weighted by the population densities given in table 3.

60. The Committee considered that the inclusion of all food groups and all 13 regions in the WHO
GEMS/Food [W2] would imply a level of accuracy that was inconsistent with other aspects of therevised methodology. Although the dietary data in GEMS/Food were based on clusters of countries
with similar dietary habits, this clustering would not have been consistent with other information for
UNEP regions used to calculate doses (e.g. population distribution and energy production). Therefore, asimplified approach was used based on the UNEP regions shown in figure II; any differences in intakes
and hence doses because of this simplification were deemed commensurate with those due to othersimplifying assumptions made in the methodology.

48 UNSCEAR 2016 REPORT

61. As discussed in section III.A.3, activity concentrations in foods integrated to 100 years forcontinuous deposition at a rate of 1 Bq/(m2 s) for one year have been determined using combined foodand radionuclide-specific transfer parameters. These estimated concentrations take account of a rangeof physical processes that do not depend on the chemical element (such as interception by plantsurfaces) and biochemical factors that do depend on the chemical element, such as root uptake andtransfers from animal feed to meat and milk. For tritium and carbon-14, combined transfer parameters
are defined per unit activity concentration in air based on a specific-activity approach. The intake ofradionuclides is then determined using the population-weighted food consumption rates for the different
geographical regions. This is a slightly different approach from that used previously by the Committee,
where simple global average intakes were used, (see electronic attachments 1 and 2); however, theoverall difference in the resulting dose estimates is not significant.
62. A limited sensitivity analysis was carried out to determine the applicability of the generic foodchain model for different regions of the world and whether the foods and related consumption rates
were appropriate. This analysis is outlined in electronic attachment 4 and the Committee concluded that
it was reasonable to use the food-chain model and the consumption data by geographical region for the
purposes of assessing worldwide exposures.

B. Assessment of doses from discharges to a freshwater environment
63. The extent of dispersion of radionuclides in freshwater bodies varies significantly depending on
characteristics of the water body, particularly the volume of the body into which the discharge occurs
and the water flows. However, the Committee decided that there would be value in developing genericdose-calculation factors that provide an estimate of the integrated activity concentrations in water froma discharge of each radionuclide for a year, allowing for dispersion within different types of water
body. An approach for estimating individual doses and for calculating regional components ofcollective dose was developed on this basis. (As discussed previously, for discharges to rivers using thesimple, generic approach adopted in the methodology, it is not possible to distinguish between local andregional components of collective dose).
64. The following exposure pathways are considered for discharges to freshwater bodies (seefigure I):(a) Internal exposure from ingestion of radionuclides in drinking water;(b) External exposure (beta and gamma emitters) from radionuclides in sediments deposited on
the riverbank;(c) Internal exposure from ingestion of radionuclides incorporated into freshwater fish;(d) Internal exposure from ingestion of radionuclides incorporated into terrestrial foods because of
irrigation.
65. Other exposure pathways such as internal exposure from inadvertent ingestion of water andsediment, external exposure when swimming or boating, and external exposure from radionuclides
deposited on irrigated land, are also possible. However, the exposure pathways above have been foundto be the largest contributors to individual and collective doses following continuous discharges towater bodies [J5]. The external exposure pathway, (b) above, is included only in the calculation ofcharacteristic individual dose. This pathway is unlikely to be a significant contributor to collective
doses from aquatic discharges from nuclear power stations and reprocessing plants, as demonstrated by

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 49

past assessments (e.g. [J6]). Individual doses are estimated from individual consumption rates andoccupancy data, while collective doses from ingestion are calculated using region-specific data on total
fish catches, water abstraction and agricultural production. Thus, the resulting individual and collective
dose estimates are not directly linked in the way that they are for discharges to atmosphere. In effect,collective doses from discharges to a freshwater body are based on the total usage of water or total
amount of produce from the generic water body, irrespective of the location of people.
66. The Committee’s methodology initially considered three types of environment for assessing doses
arising from aquatic discharges to freshwater bodies: (a) lakes, (b) small rivers and (c) large rivers.
However, the Committee agreed that the dispersion of aquatic discharges from facilities on the shoresof a large lake can be assessed using the same approach as for large rivers. Given the differences incharacteristics and hence dispersion in different rivers and lakes throughout the world, the Committee
agreed that the distinction between lakes and large rivers was a second-order effect and did not need tobe considered further for its purposes. It should be noted that the Committee’s methodology does not
apply to closed lake systems, i.e. those without rivers feeding into or out of the lake.
67. Two types of river are defined to allow for the range of discharge conditions that may occur. For
example, inland nuclear facilities (with the exception of mines and mills) are assumed to discharge intolarge rivers, and non-nuclear facilities and mines into small rivers. The dimensions and flow rates
associated with a range of rivers into which nuclear and other facilities discharge were reviewed inorder to select appropriate parameter values for the Committee’s methodology.

1.

Dispersion of radionuclides in freshwater bodies

68. The Committee’s methodology for deriving activity concentrations of radionuclides following
their discharge into freshwater bodies assumes that complete mixing occurs immediately. This is a
simplification because for rivers complete dilution would occur over some tens of kilometres
downstream, the actual distance depending on the width of the river, which is in turn related to thevolumetric flow rate. Nevertheless, significant mixing does occur over relatively short distances. As an
illustration of this, table 8 shows results from using the NCRP screening model, which is designed forthe purpose of demonstrating compliance with environmental standards for discharges of radionuclides[N2]. The table indicates that the activity concentration in unfiltered water assuming complete mixingof the radionuclide across the total width of the river essentially equals the actual activity concentrationin unfiltered water in the plume (i.e. the value of the partial mixing correction factor approaches one)for rivers up to a width of around 100 m at a downstream distance of around 5 km. For wider rivers, thevalue of the correction factor would be of the order of one to five at this distance; complete mixing
would, however, occur over a distance of around 100 km for such rivers. Specific information isavailable for the Techa–Iset–Tobol–Irtysh–Ob river system in the Russian Federation [N5]. This is acomplex river system and complete mixing does not occur until some distance downstream. (At 27 km
downstream there was not complete mixing with nearly a factor of 5 variation in measured
concentrations at different locations across the river.) However, the abstraction point for drinking water
is likely to be at some distance downstream from the discharge point and fish will be caught over large
sections of the river. Given this and the generic nature of the revised methodology, the distances overwhich collective doses are calculated, and other uncertainties associated with the approach, theCommittee considered it unlikely that assuming complete mixing would significantly affect thecollective dose estimate. Although the dose to an individual obtaining their drinking water from theimmediate vicinity of a source would depend on the location of the abstraction point relative to thepoint of discharge, because of the generic nature of the approach, assuming complete mixing is also
appropriate for individual dose estimation.

50 UNSCEAR 2016 REPORT

Table 8. Correction factors to complete mixing in a river plume as a function of downstream
distance from the point of discharge for different river widths [N2]
The correction factor for partial mixing represents the ratio of the activity concentration in water in the plume to the activity
concentration in water if, at the same point, complete mixing in the total width of the river were assumed. Complete mixing
would give a value of 1aPartial mixing correction factor at various river widthsa

Distance downstream
(km)

10 m

50 m

100m

200 m

400 m

0.1

3.2

6

8

10

12

1

1

2.4

3.2

5

8

5

1

1

1.6

2.6

3.6

10

1

1

1

1.9

3

50

1

1

1

1

1.4

100

1

1

1

1

1

Values are rounded to one decimal place.

69. For the purposes of the Committee’s methodology, the activity concentrations of radionuclides inriver water are therefore derived assuming that the discharged radionuclides are dispersed uniformly
across the river. Under these conditions, the activity concentrations in water depend upon thevolumetric flow rate of the river alone, which, in turn, is primarily determined by the width of the river.
Thus, it is assumed that, for all freshwater pathways, the activity concentration in unfiltered freshwater
is given by:

Cuw,i = Qi / F(14)

where Cuw,i is the activity concentration of radionuclide, i, in unfiltered water at the discharge point(Bq/m3); Qi is the discharge rate of radionuclide, i, (Bq/s) and F is the volumetric flow rate of the riverat the point of discharge (m3/s). The activity concentrations of radionuclides in filtered water are
determined from the suspended sediment load and the radionuclide-specific partition factors for
freshwater environments. These activity concentrations are then used, for example, to derive activity
concentrations of radionuclides in freshwater fish. To derive activity concentrations of radionuclides indrinking water, a water treatment factor is applied.
70. For the large river (and as noted earlier, for lakes), a width of 240 m and flow rate of 1,000 m3/s
are assumed for the purposes of the methodology. Table 9 gives some illustrative flow rates and otherdimensions for a range of rivers of different sizes throughout the world. The values assumed for a large
river are consistent with the data for major sections of the Rhône, Loire, Danube and Rhine; these arerivers into which a number of nuclear installations discharge radionuclides. They are also similar toother major rivers throughout the world, as shown in table 9, although some rivers have greater flows,
notably the Amazon.

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 51

Table 9. Flow rates and dimensions of some typical rivers and those assumed in the methodology
River

Country

Flow rate(m3/s)

Length in
specifiedcountry (km)

Width
(m)

Depth
(m)

5 × 102

6

AmazonaPeru, Columbia, Brazil

2.0 × 105

6.9 × 103Danubeb

Germany, Austria, Slovakia,
Hungary, Croatia, Serbia,
Bulgaria, Romania,
Moldova, Ukraine

3 × 103

3 × 103

Gangesa

India, Bangladesh

1.6 × 104

2.5 × 103

Kennet (tributary of Thames)

United Kingdom

1 × 101

3.3 × 101

17

1

LoirecFrance

7.8 × 102

5.6 × 102

2.6 × 102

3

Mississippia

United States of America

1.6 × 104

3.7 × 103

Niled,eEgypt

1.8 × 103

1.5 x 103

Paraná f

Brazil, Paraguay, Argentina

1.7 × 104

4.8 × 103

Pearl

Chinag

2.2 × 103

2.2 × 103

RhônecFrance1.2 × 103

4.0 × 102

2 × 102

7

ThamesUnited Kingdom

5 × 10

2.3 × 1050

2

Yangtze

g

China

4

3.2 × 10

6.3 × 10

Yellow

Chinag2.1 × 103

5.5 × 103h12

1.8 × 104

3

ASSUMED VALUES IN THE METHODOLOGY
Methodology—small riveri

1 × 101

1 × 102

30

1

Methodology—large riveri

1 × 103

5 × 102240

4aMilliman and Farnsworth (2011) [M2].

bMaringer (2000) [M1].

cSmith and Simmonds (2009) [S8].

dWahaab and Badawy (2004) [W1].

eHamza (2014) [H1].

fEncyclopaedia Britannica (Parana-River) [E3].

g

Information provided by the Chinese delegation.

hHilton et al. (2003) [H4].

i

The dimensions of the small river are similar to those of the River Kennet in the United Kingdom; those of the large river are
similar to those of major sections of the Rhône and Loire in France and other rivers.

71. For the small river, a flow rate of 10 m3/s (width of 30 m and depth of 1 m) is assumed in themethodology. This is similar to that of the River Kennet in the United Kingdom.
72. The measured suspended sediment loads of the Colorado and Mississippi Rivers have been shownto vary by three or more orders of magnitude [H2, S10]. However, a value of 5 × 10−4 t/m3 is considered
to be appropriately representative within this range and is assumed for large rivers; this also agrees withother data presented for the Colorado River [V1].

52 UNSCEAR 2016 REPORT

73. The suspended sediment loads of small rivers also vary by several orders of magnitude,
depending on flow rate. For low flow rates, values in the range 2 to 5 × 10−5 t/m3 may be considered tobe typical (see, for example, Hejduk and Banasik [H3]). A value of 2 × 10−5 t/m3 was adopted for the
purposes of this methodology.

2.

Behaviour of radionuclides in a freshwater environment(a) Transfers in freshwater environments
74. The key element-specific parameters that account for the transfer of radionuclides in an aquatic
environment are concentration factors that relate the concentrations of elements in fish to theirconcentrations in water, and partition coefficients that relate the distribution of elements between
sediment and water. Standard compilations of these data [I3, I5] have also been updated since theCommittee’s assessments were issued in the UNSCEAR 2000 and 2008 Reports [U6, U10, U11].
75. The activity concentration of a radionuclide in an aquatic food is derived by applying anequilibrium concentration factor, defined as the ratio of the concentration of the radionuclide in theaquatic food (fresh weight) at equilibrium to its concentration in water (Bq/kg per Bq/L) (note in somecompilations of data the term “bioaccumulation factor” is used for these values). The most recent
international compilation of concentration factors for freshwater environments [I5] provides transfer
parameter values appropriate for equilibrium conditions. Where the available data permit, ranges ofobserved values are presented together with mean values. Those mean values have been used for the
purposes of this methodology supplemented by data from other sources, where necessary; the values
adopted by the Committee for this methodology are given in table 10.
76. The transfer of radionuclides between the water column and suspended and bottom sediments
depends on both the characteristics of the water body and the chemical and physical characteristics ofthe radionuclides themselves. The partition coefficient, Kd, relates to the partitioning of radionuclides
between the solid and aqueous phases and is expressed as the ratio of the activity of a radionuclide perunit dry weight of sediment at equilibrium to the activity of that radionuclide per unit volume of water(Bq/kg per Bq/L) (this can also be referred to as a distribution coefficient). The most recent
international compilation of Kd values for freshwater environments is presented in [I5], although theCommittee also used values from other sources, where data were not available in [I5]. The data used
are given in table 10 and are intended to represent generic best estimates, recognizing that Kd values
vary depending on the characteristics of the water body.

Table 10. Values of radionuclide-specific parameters used in the model for freshwater environments
Radionuclide3

H (HTO and OBT)

Concentration factor for freshwater fish,
Bfish (L/kg) (fresh weight)

1.0 × 100 [N2]

Activity concentrations in sediment (dry weight) in the
100th year of continuous discharge at 1 Bq/s (Bq/kg)
Small river[S8]

Large river
[S8]

0

0

C

4.0 × 10 [I5]5.0 × 1035

S

8.0 × 102 [N2]

54

Mn

58

5

−4

−6

Partition coefficient, Kd(m3/t)

1.0 × 1000 [I2]

5.0 × 100

1.0 × 10

5.0 × 100 [I2]2.0 × 10−2

1.8 × 10−4

5.4 × 10−1

2.0 × 102 [B4]2.4 × 102 [I5]3.1 × 100

2.0 × 10−3

3.6 × 10−1

7.9 × 104 [I5]Co

7.6 × 101 [I5]2.3 × 100

1.9 × 10−3

5.4 × 10−1

4.4 × 104 [I5]60

Co

7.6 × 101 [I5]2.3 × 100

1.9 × 10−3

5.4 × 10−1

4.4 × 104 [I5]65Zn

3.4 × 103 [I5]4.9 × 10−2

4.0 × 10−4

5.4 × 10−1

5.0 × 102 [I2]90Sr

2.9 × 100 [I5]1.2 × 10−1

7.5 × 10−4

8.1 × 10−1

1.2 × 103 [I5]

106

Ru

5.5 × 101 [I5]2.0 × 100

1.9 × 10−3

5.4 × 10−1

3.2 × 104 [I5]129I

3.0 × 101 [I5]4.0 × 10−1

1.4 × 10−3

8.1 × 10−1

4.4 × 103 [I5]131I

3.0 × 101 [I5]4.0 × 10−1

1.4 × 10−3

8.1 × 10−1

4.4 × 103 [I5]

134

Cs

2.5 × 103 [I5]1.8 × 100

1.9 × 10−3

8.1 × 10−1

2.9 × 104 [I5]

137

Cs

2.5 × 103 [I5]1.8 × 100

1.9 × 10−3

8.1 × 10−1

2.9 × 104 [I5]

210

Pb

2.5 × 101 [I5]8.3 × 10−1

1.7 × 10−3

5.4 × 10−1

1.0 × 104 [K1]

212

Pb

2.5 × 101 [I5]6.3 × 10−1

1.5 × 10−3

5.4 × 10−1

1.0 × 104 [K1]

214

Pb

2.5 × 101 [I5]1.3 × 10−3

2.1 × 10−4

5.4 × 10−1

1.0 × 104 [K1]

210

Po

3.6 × 101 [I5]2.2 × 100

1.9 × 10−3

5.4 × 10−1

4.0 × 104 [S3]

226

Ra

4.0 × 100 [I5]6.4 × 10−1

1.6 × 10−3

5.4 × 10−1

7.4 × 103 [I5]

228

Th

6.0 × 100 [I5]4.0 × 100

2.0 × 10−3

3.0 × 10−1

1.9 × 105 [I5]

230

Th

6.0 × 100 [I5]4.0 × 100

2.0 × 10−3

3.0 × 10−1

1.9 × 105 [I5]

232

Th

6.0 × 100 [I5]4.0 × 100

2.0 × 10−3

3.0 × 10−1

1.9 × 105 [I5]

234

Th

6.0 × 100 [I5]3.9 × 100

2.0 × 10−3

3.0 × 10−1

1.9 × 105 [I5]234U

9.6 × 10−1 [I5]5.0 × 10−3

4.9 × 10−5

3.0 × 10−1

5.0 × 101 [I2]238U

9.6 × 10−1 [I5]5.0 × 10−3

4.9 × 10−5

3.0 × 10−1

5.0 × 101 [I2]ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 53

14

Water treatment factor
FWT
[B7]a

a

Concentration factor for freshwater fish,
Bfish (L/kg) (fresh weight)

Activity concentrations in sediment (dry weight) in the
100th year of continuous discharge at 1 Bq/s (Bq/kg)
Small river[S8]

Large river[S8]

Water treatment factor
FWT
[B7]a

Partition coefficient, Kd(m3/t)

239

Pu

3.0 × 101 [I2]4.1 × 100

2.0 × 10−3

2.7 × 10−1

2.4 × 105 [I5]

240

Pu

3.0 × 101 [I2]4.1 × 100

2.0 × 10−3

2.7 × 10−1

2.4 × 105 [I5]

241

Am

2.4 × 102 [I5]3.5 × 100

2.0 × 10−3

2.7 × 10−1

1.2 × 105 [I5]

The water treatment factors used are based on flocculation, coagulation, clarification and rapid sand filtration. Where data were not given for a specific element in Brown et al. [B7], an analogue approach was used.

54 UNSCEAR 2016 REPORTRadionuclide

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 55(b) Transfers from fresh water to terrestrial environments
77. The irrigation of crops with fresh water may lead to the transfer of radionuclides from a
freshwater to a terrestrial environment. This exposure pathway was not included in the Committee’s
previous methodology but, given the importance of irrigation of crops throughout the world, theCommittee decided that it should be considered. In general terms, the rate at which radionuclides
present in fresh water are deposited on crops and soil is estimated from information on the rate ofirrigation and the length of the crop-growing season. This information is then used to estimate theresultant activity concentrations of radionuclides in terrestrial crops from their activity concentrations infresh water and the derived calculation factors for their activity concentrations in food per unit
deposition rate.
78. There are many different types of irrigation. The most important for the transfer of radionuclides
to crops is sprinkler or spray irrigation because radionuclides in the water will be deposited directly on
the surface of the plants. Other types of irrigation where water is deposited on the surface of the soil
give rise to lower transfers and so were not included in the Committee’s methodology. Although there
are obvious differences in the behaviour of radionuclides that are deposited on the surface of plants
during sprinkler irrigation and that of radionuclides deposited by wet and dry deposition from theatmosphere, the Committee considered that the differences in the overall transfers to plants are asecond-order effect in the context of the objectives of the methodology. Therefore, the values of thetransfer factors for deposition from the atmosphere are assumed to apply also to irrigation. These
parameters include the transfers from plant surfaces and from uptake from the soil. The Committee
recognizes that there may be some overestimation in assuming that the rate of uptake from irrigationwater is equivalent to that from deposition from the atmosphere, given that greater losses from plantsurfaces may be anticipated for the higher deposition rates characteristic of irrigation.
79. The Food and Agriculture Organization of the United Nations (FAO) publishes statistics on water
resources in its AQUASTAT database [F4]. The information indicates that 40% of global foodproduction involves irrigation. Data are available on the overall rates of abstraction of water by source(whether from surface or groundwater). Information is available on the overall rate of water abstracted
for irrigation, but not on the fraction of irrigation water that is drawn from each source. In the absenceof this information, it is assumed that the fraction of water used for irrigation of the total amountabstracted is the same for both sources. Using data from the AQUASTAT database, the fraction of
surface water withdrawn for irrigation and the area irrigated per unit volume of water was obtained foreach region as shown in table 11, which also gives world-average values. The appendix describes how
these values are used in the methodology.
80. From this table, it is clear that, with the exception of West Asia, there is only limited abstractionof water from surface water.
81. The International Commission on Irrigation and Drainage provides data on the area of land under
different types of irrigation for 45 countries [I7]. The Committee has used these data to derive thefraction of land under sprinkler/spray irrigation for each region and an average for the world (seetable 12). The values in this table are for various times between 1999 and 2012.
82. The fractions given in table 12 are used in the methodology together with the calculated activity
concentrations of radionuclides in water and the abstraction rate for irrigation to derive concentrationsof radionuclides in foods and hence to estimate individual and collective doses. The Committee agreed
that irrigation should only be considered for vegetables and grain and only for large rivers. For small

56 UNSCEAR 2016 REPORT

rivers with low abstraction rates, it is unlikely that there is significant irrigation. Although other crops
are likely to be irrigated, the most important are leafy vegetables and grain [F4]. The irrigation of
pasture is important in some parts of the world (such as parts of the United States) but it is rare in othermajor areas with significant cattle production, such as Brazil and Argentina, and so it is not included in
the methodology.
Table 11. The fraction of water for irrigation withdrawn from surface waters and the total area
irrigated per unit volume of surface water available
Parameter
RegionFraction of water for irrigation withdrawn
from surface waters (dimensionless)Area irrigated per unit volume ofwithdrawn water (m2 a /m3)

Africa2.7 × 10−2

6.0 × 10−1

Asia and Pacific9.4 × 10−2

7.9 × 10−1

Europe1.2 × 10−2

1.9 × 100

Latin America and Caribbean

1.0 × 10−2

8.2 × 10−1

North America

2.4 × 10−2

1.3 × 100

West Asia

5.7 × 10−1

4.7 × 10−1

World average

3.9 × 10−2

8.5 × 10−1

Table 12. Fraction of irrigated land that is spray-irrigated (based on information from [I7]
RegionFraction

Africa0.2

Asia and Pacific

0.1

Europe0.4

Latin America

0.2North America

0.5West Asia

0.3

World average

0.2(c) Specific activity models for tritium and carbon-14 in fresh water
83. The Committee has adopted a specific-activity approach for assessing the transfer of tritium andcarbon-14 in a freshwater environment. This is the same approach as it used previously and as
described for a terrestrial environment. The assumption that equilibrium conditions exist, which is
implicit in the specific-activity model, is considered to be a good approximation for most aquaticcompartments in the model [E1, K5]. The model adopted is that described in [I5] in which activity
concentrations of tritium in fish are determined on the basis of the HTO concentration in the watercolumn and the fractional water content of fish. The fractional water content is found to be 0.78 L/kg
for most fish that form part of the human diet [I5]. The concentration of organically bound tritium(OBT) is also taken into account. The relevant equations and parameter values used in the methodology
are given in the appendix.

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 57

84. A specific activity approach is also applied to estimate the total tritium concentration in soil waterby taking account of the activity concentration of tritium in irrigation water, the rate of irrigation andthe effect of mixing with water reaching the soil from precipitation [C1]. The equations and dataapplied are presented in the appendix.
85. For discharges to aquatic bodies, the specific activity of dissolved inorganic carbon is assumed to
be in equilibrium within the part of the environment of interest. The methodology includes a simplified
approach based on a dynamic model developed by Sheppard et al. [S4, S5] with some modification to
apply it to irrigation based on the approach outlined in [C1]. The equations and parameter values
applied are given in the appendix.

3.

External and internal exposure(a) External exposure from radionuclides in riverbank sediments
86. Annual individual doses from external exposure during occupancy of riverbanks are calculatedusing the time-integrated activity concentrations of radionuclides in sediments, the dose coefficients forexternal exposure from surface deposits and the amount of time spent on riverbanks. This exposure
pathway is only considered for the calculation of the characteristic individual dose.
87. For discharges to fresh water bodies, activity concentrations of radionuclides in sediments at a
distance of 5 km downstream from the discharge point are used for the purpose of calculating
characteristic individual doses from external exposure due to radionuclides in riverbank sediments. It is
assumed that there will be continual cycling of radionuclides from the aquatic environment intoriverbank sediments taking account of build-up over the 100 year integration period. Dose coefficientsfor external radiation exposure from surface deposits (Sv/s per Bq/m2) from the United States Federal
Guidance Report No. 12 [E2] are used in the Committee’s revised methodology. However, these dosecoefficients apply to an infinite surface (assuming a surface deposit only); for river banks, a geometry
factor is applied to allow for the finite size of the source of external exposure. Apostoaei et al. [A2]have discussed appropriate geometry factors (these depend upon the surface area of the sediment on theriver bank, as represented by the width of the sediment on the bank, and upon the radionuclide). They
recommend that factors for 137Cs are applicable in general. The Committee agreed to apply a geometry
factor of 0.2 based on the values given by Apostoaei et al. for riverbank sediments with a width of afew metres. In addition, the Committee agreed that the methodology should use an annual occupancy
factor of 50 hours for the calculation of the characteristic individual dose.

(b) Internal exposure from ingestion
88. Three sources of internal exposure via ingestion are considered in the methodology: drinking
water; freshwater fish and irrigated terrestrial foods. In estimating the characteristic individual doses, it
is assumed that only 25% of the food is locally produced (see section II, paragraph 11).

58 UNSCEAR 2016 REPORTDrinking water
89. As described above, the activity concentrations of radionuclides in unfiltered fresh water are
assumed to be a function of the volumetric flow rate of the river, which is, in turn, directly related to thetype of river assumed. In order to derive activity concentrations in drinking water, element-specificwater treatment factors are applied. These are similar to those presented in the UNSCEAR 2000 Report[U6], updated with information included in the most recent edition of the WHO Drinking Water
Guidelines [W3]. The WHO provides indicators of the performance of a number of common watertreatment methods for a range of radionuclides.
90. Different treatment techniques are applied across the world and have different effectiveness.
Based on information used for the WHO Drinking Water Guidelines [W3], the Committee assumed
that—for most countries with high human development indices—flocculation, coagulation, clarification
and rapid sand filtration are used. As there are insufficient data available on the techniques employed inless developed countries, the Committee decided to apply a single set of water-treatment factors basedon the data for countries with high human development indices. The fractions of each radionuclide
removed by standard water-treatment processes assumed in the methodology are shown in table 10.
91. Previously, the Committee used a value of 500 litres per year (1.4 litres per day) [U6, U7, U9] forthe worldwide average individual rate of ingestion of drinking water. The Committee has reconfirmedthat this value should be retained because it is appropriate for average individual consumption rather
than the somewhat higher values typically used for protection purposes.
Freshwater fish
92. Individual doses from the ingestion of freshwater fish are calculated using the activity
concentrations of radionuclides in fish and the per caput consumption rate; collective doses arecalculated using the activity concentrations and fish-catch data. Information on fish-catch data for eachregion in 2007 was obtained from [F3]. The total fish catch for each region was divided by the size ofthe population for the same region to derive per caput consumption rates, which were used to estimatecharacteristic individual doses. Table 13 shows the resulting annual per caput consumption rates offreshwater fish for each region and a world-average value.
Table 13. Annual per caput consumption of freshwater fish by region
These values represent the total intakes of freshwater fish; the factor of 25% to account for local consumption of food isapplied subsequently when calculating characteristic individual doses

RegionAnnual consumption (kg)Africa2.7

Asia and Pacific

7.8

Europe3.4

Latin America and Caribbean

1.6

North America

4.5West Asia

1.3

World average

5.7

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 59

93. For the calculation of collective doses, the Committee has derived generalized fish-catch
information for a range of rivers using data from FAO [F4]. Aquaculture (e.g. the intensive farming of
freshwater fish) is excluded from consideration because a large proportion of fish reared in aquaculture
come from lakes and ponds [F4].
94. Typical values for the quantity of freshwater fish caught per unit distance and volume of water fortypical small and large rivers have been derived for use in the Committee’s methodology for eachregion separately and as a world average. From the FAO data, information was derived on the catch offreshwater fish including and excluding that obtained from aquaculture, plus the annual fish catch foreach river in a country. Using information on the length and volume of the relevant stretch of eachriver, annual fish catches per unit length and per unit volume were calculated and the results are shownin table 14. Based on this information, generic values for small and large rivers were adopted for use in
the methodology. It is therefore assumed that one tonne of freshwater fish is caught annually perkilometre from small rivers (of length less than 500 km) and that ten tonnes are caught annually perkilometre from large rivers (length greater than 500 km). Because of the volumes of water assumed forthe two river sizes, which also differ by a factor of 10, the freshwater catch per unit volume isindependent of river size.

60 UNSCEAR 2016 REPORT

Table 14. Freshwater fish-catch data for a range of rivers
Data taken from FAO [F1] unless otherwise stated

CountryCountry-wide annual fish catchRiver

Annual fish catchfor the river(s)Excludingaquaculture (t)RiverAnnual fish catch
Per unit length, excluding
aquaculture (t/km)

Includingaquaculture (t)Excludingaquaculture (t)Australia

4.0 × 103

1.2 × 103

All rivers

China

1.9 × 107

1.6 × 106Pearl

2.8 × 104

1.4 × 103

Egypta9.4 × 105

2.3 × 105

Nile

2.3 × 105

1.5 × 103

France4.4 × 104

2.6 × 103

Loire

1.0 × 103

5.6 × 102

4.3 × 108

2.0 × 10−6

1.9 × 100Rhône

1.5 × 103

4.0 × 102

6.3 × 108

2.0 × 10−6

3.9 × 100

All rivers

2.6 × 103
7.9 × 103

5.6 × 104

2.1 × 104

DanubeJapan

6.7 × 104

2.5 × 104

All rivers

Romania

1.6 × 104

5.7 × 103Danube5.7 × 103

Sudanb

8.1 × 104

7.9 × 104

Nile

5.4 × 104

Nile tributaries(incl. Blue andWhite Nile)

2.5 × 104

ThamesUnited States

1.6 × 104

2.5 × 105

2.5 × 103

1.4 × 104

Volume (m3)Per unit volume, excluding
aquaculture (t/m3)

6.2 × 10−1

Germany

United Kingdom

Length in specified
country (km)

2.3 × 109

1.0 × 10−5

2.0 × 101
1.5 × 102

3.0 × 10-1
5.0 × 102

2.1 × 108

4.0 × 10−5

1.6 × 101
1.4 × 101

4.0 × 102

3.2 × 109

2.0 × 10−6

1.4 × 101

2.3 × 102

2.3 × 102

2.5 × 107

9.0 × 10−6

9.8 × 10−1

Kennet (tributaryof Thames)

6.0 × 100

3.3 × 101

6.1 × 105

9.0 × 10−6

1.7 × 10−1

All rivers

2.5 × 103

All riversaAdditional data obtained from Hamza [H1].

bData for 2012 from internal report published by the Sudan Ministry of Animal Resources and Fisheries [S11].

8.0 × 10−1
3.4 × 10−1

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 61

Irrigated foods
95. As discussed in section III.B.2(b), the ingestion of irrigated foods is included in the methodology
for the estimation of both characteristic individual and collective doses. In the calculation of individual
doses from this pathway, it is assumed that cereals and vegetables are irrigated. For the assessment ofcollective doses, it is assumed that only cereals are irrigated, because these represent the bulk of
irrigated crops intended for human consumption [F4].
96. As illustrated in table 15 [C1], there are variations in irrigation rate which are likely to depend tosome extent upon factors such as the type of crop and the climate. A single value for a daily irrigation
rate was considered to be appropriate for the purposes of this methodology. The United States NCRP in
its screening methodology uses a value of 5 L/m2 for the volume of irrigation water applied per unit
area for a period of 150 days annually[N2]. The FAO AQUASTAT database [F4] contains data for awide range of countries on irrigation water withdrawals and/or requirements, and on the total areas ofirrigated crops harvested. These data could then be used to indicate values of daily irrigation rates in
L/m2 assuming a total irrigation period of 150 days in a year. Table 16 illustrates the range of irrigation
rates thus obtained from the FAO data. The irrigation rate varies from country to country and althoughsome of the highest values are for arid areas of the world, some countries that are generally arid (e.g.
Peru) do not have particularly high estimated irrigation rates. From the data in tables 15 and 16 a single
value for the daily irrigation rate of 4 L/m2 was adopted for the methodology.
Table 15. Irrigation rates averaged over the growing season for various crops and climates [C1]Country or area

Crop type

Daily irrigation rate (L/m2)
Min

CanadaFrance(Loire Valley)

India

Republic of Korea

ForageAverage

Reference
Max

0

[C6]

Garden vegetables

0

1.8

Fruit

2

6

Garden vegetables

2

6

Grain

0

2.4

Maize

0.8

2.8

Banana

2.6

Gram

1.8

Ground nut

6.3

Improved jowar

2.0

Pigeon pea

1.6

Rice

0.9

Sugar cane

4.1

Turmeric

2.1

Wheat

4.3

Rice

5

[C4]

[P1]

8

[J4]

62 UNSCEAR 2016 REPORTCountry or area

Crop type

Daily irrigation rate (L/m2)
Min

United States(California)

Average

ReferenceMax

Alfalfa

4.9

7.1

Barley2.4

3.2

Fruit orchards

3.9

4.9

Garden vegetables

4.2

5.2

Hay

3.2

5.4

Oats, rye

2.0

2.5

Pasture3.7

4.4

Grapes

1.7

[U14]

[B5]

Table 16. Effective irrigation rates obtained from data in the FAO AQUASTAT database [F4]Country

Daily irrigation rate (L/m2)

Algeria

5.2

Argentina

3.5

Australia

3.3

Bangladesh

2.8

Brazil1.9

Canada

4.1

China

1.8

Egypt

5

France1.4

Greece

2.8

India

2.8

Indonesia

2.3

Japan

8.6

Kenya

3.2

Peru

3.5

Qatar

7.3

Russian Federation

6.5

Spain

4.5

United States

5.1

97. Collective doses from irrigation are determined by assuming that, on average, the fraction ofwater abstracted for irrigation from the type of river of interest, in a given geographical region, is thesame as the fraction of water abstracted for irrigation purposes from all surface waters (rivers, lakes andso on). The fraction of water abstracted for irrigation and the amount of land irrigated per unit volume
of water, was derived from information in the FAO AQUASTAT database [F4]. This information,
together with the annual yields of cereals [F1] (given in table 17), the integrated activity concentrationsof radionuclides in cereals for unit deposition rate (given in table 5), and the percentage of irrigation

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 63

that is sprinkler irrigation (see table 12 and section III.B.2(b)), is used to calculate collective doses from
irrigation. Table 17 shows the parameter values used in the methodology for the estimation of collective
doses in different regions from the irrigation of cereals; world-average values are also given.
Table 17. Parameter values used in the model for the irrigation of cereals
RegionAnnual cereal yield(kg/m2)aFraction of surface waterused for irrigationb
Firr,surface

Area irrigated per unit
volume of water
withdrawnb
Airr,unit (m2 a/m3)

Africa2.3 × 10−1

2.7 × 10−2

6.0 × 10−1

Asia and Pacific

2.9 × 10−1

9.4 × 10−2

7.9 × 10−1

Europe

3.6 × 10−1

1.2 × 10−2

1.9 × 100

Latin America and Caribbean

3.3 × 10−1

1.0 × 10−2

8.2 × 10−1

North America

3.0 × 10−1

2.4 × 10−2

1.3 × 100

West Asia

2.9 × 10−1

5.7 × 10−1

4.7 × 10−1

World average

3.0 × 10−1

3.9 × 10−2

8.5 × 10−1aFrom FAO 2010 [F1].

bFrom FAO 2014a [F3].

4.

Individual and collective doses

98. Annual characteristic individual doses arising from the ingestion of drinking water and freshwater
fish are calculated using the derived activity concentrations of radionuclides in water and fish, therelevant consumption rates, and the dose coefficients for ingestion (see table 1). Because the activity
concentrations in unfiltered fresh water are assumed to be a function of the river flow rate alone, these
individual dose estimates are directly related to the type of river assumed.
99. Collective doses are calculated using the total abstraction rate of drinking water and the total catchof fish associated with the freshwater body. The abstraction rate of drinking water is assumed to be afraction of that abstracted for municipal use. The abstraction rate was derived from FAO statistics
which indicate that around 1–10% of domestic water is used for drinking [F1]. Since not all municipal
water will be for domestic use, the lower end of this range is applied in this methodology. The total
amount of water abstracted depends on the size of the water body with smaller amounts removed fromsmall rivers than from large rivers; the water flow is also inversely related to this size. This means that,
although for small rivers the activity concentrations per unit discharge are higher than for large rivers,
the amount of water abstracted is lower and therefore—using the Committee’s methodology—thecollective doses from drinking water are estimated to be essentially independent of river size.
100. The irrigation pathway is considered using generic irrigation rates and transfer factors appropriate
for a terrestrial environment. Characteristic individual doses from this pathway are determined using
region-specific population-weighted consumption rates and the assumption that 25% of the food islocally produced. Collective doses are determined from information on the region-specific proportionof water abstracted from surface waters for irrigation purposes, the area irrigated and the annual yieldof cereal products.

64 UNSCEAR 2016 REPORT101. Collective doses from the consumption of water and freshwater fish are calculated on the basis of
the total abstraction of water and fish-catch data, respectively, and are thus related to the river as awhole and cannot be divided into local and regional components.

C. Assessment of doses from discharges to a marine environment
102. As indicated above, the Committee decided to develop generic dose calculation factors that takeaccount of dispersion within different types of water bodies. The approach used for assessing doses
from discharges into a marine environment is based on a simple two-box compartment model, thecharacteristics of which are broadly representative of areas where discharges into a coastal environment
occur (see figure IV, which is based on [C2]). The larger compartment (referred to as the regional box)
could also be used to assess the dispersion of radionuclides discharged into the deep sea from oil andgas platforms, if required.
103. The following exposure pathways are considered for discharges to a marine environment (seefigure I):(a) External exposure from radionuclides (beta and gamma emitters) in sediments;(b) Internal exposure from ingestion of radionuclides incorporated into marine foods.
The first pathway is considered for the calculation of characteristic individual doses only; a review ofprevious studies assessing collective dose indicated that this pathway provided less than 1% of thecollective dose. Similar to discharges to atmosphere and freshwater environments, other exposure
pathways (e.g. inadvertent ingestion of water or sediments, and exposures during swimming) are
possible; however, the ingestion of marine foods has been found to be the most important exposure
pathway in published assessments of collective doses (for example, see [J5]).
Figure IV. Simple two-box compartment model representing a marine environment
Q is the discharge rate (Bq/a); λl,r is the effective rate of transfer between the local and regional compartments (a−1), taking
into account exchange between the compartments; λr,g is the effective rate of transfer between the regional and global
oceans (a−1), taking into account exchange between the compartments; λs,l and λs,r are the rates of transfer to sediment for
the local and regional compartments, respectively (a−1), and li is the radioactive decay constant for radionuclide, i, (a−1)

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 65

104. Figure IV illustrates the simplified approach used to model the movements of radionuclides between
marine compartments. The model considers inputs (such as discharges and incoming transfers ofradionuclides) and losses (such as radioactive decay, sedimentation and outgoing transfers ofradionuclides). This allows the activity concentrations in the local and regional compartments to be
determined. The equations and parameter values associated with this approach are presented in the
appendix. The model includes transfer to other marine areas but any contribution to collective doses fromthe global oceans is only considered for the long-lived radionuclides (3H, 14C and 129I) in a separate global
circulation model as discussed below. The size of the regional compartment and the related transfer
parameters have been chosen to ensure that the model is a reasonable representation. A comparison with amore complex multi-compartmental marine model [S7, S8], which has been validated against
measurement data, has shown that the simple model is adequate for the purpose of this methodology.
105. The dimensions and characteristics applied in the methodology are presented in table 18.
Table 18. Characteristics of the marine compartment model
Marine compartment

Characteristic
Volume (m )
3

Local

Regional

1 × 101 × 1015

9Effective rate of transfer between compartments (a−1):
Local to regional, λ l,r2 × 101

Regional to global, λr, g1

Depth (m)

10

1 000

Suspended sediment load, SSL (t/m3)

2 × 10−4

1 × 10−7

Sedimentation rate, SR (t m−2 a−1)

1 × 10−4

1 × 10−5

10

1 000

Length of coastline (km)OTHER PARAMETERS
Volume of global oceans, Vg (m3)

1 × 1018

Volumetric exchange between local and regional compartments,∆Vl,r (m3/a)

2 × 1010

Volumetric exchange between regional compartment and global oceans,∆Vr,g (m3/a)

1 × 1015

106. The transfer of radionuclides between water and sediments is dependent on a combination offactors that relate to the characteristics of the water body and of individual radionuclides. The key
radionuclide-independent parameters are the suspended sediment load and sedimentation rate, which
are determined by the nature of the coastal or marine compartment. Values have been chosen from therange of those associated with European waters [S7]. Sedimentation is also dependent upon theradionuclide-dependent partition factor (Kd) for a coastal or marine environment; these values havebeen derived from [I3].
107. The purpose of the local marine compartment is to allow doses to a characteristic individual livingin the area and collective doses to the local population to be calculated. The selected dimensions of thelocal marine compartment allow tidal, bathymetric and sedimentary conditions to be broadly
homogenous throughout the compartment and have been selected so that the compartment issufficiently large to represent a source of shellfish for the local population. The dimensions of the local

66 UNSCEAR 2016 REPORT

marine compartment are typical of those used in the MARINA II project for European waters [S7]. The
dimensions of the regional marine compartment are significantly larger than those generally adopted forsite-specific modelling: approximately equivalent to the size of the north-east Atlantic. This again
reflects the purpose of the methodology; the regional marine compartment is intended to represent thesource of exposure for the regional component of collective dose, which is assumed to extend for a
distance of around 1,500 km from the point of discharge.
108. The depth of the sea in the regional marine compartment is assumed to be 1,000 m, which is thedepth down to which fish are assumed to be caught.
109. The sensitivity of the calculated activity concentrations of radionuclides in water to changes in thevolume of the local compartment and movements between the local and regional compartments wasinvestigated. The calculated activity concentrations in water in the local compartment (assuming
constant transfer rates between the local and regional compartments) decrease proportionally as thevolume of the local compartment increases. A water transfer rate of 20–40 a−1 is typical of those foundin European waters based on the volume exchange rates and water volumes given in [S8]. The
Committee adopted a volume of 1 × 109 m3 with a water transfer rate of 20 a−1 for the local marine
compartment as being reasonably representative of coastal conditions into which nuclear sites are
known to discharge.
110. The values of the sedimentation rate and suspended sediment load adopted for the local
compartment are typical of values for local compartments around the United Kingdom (e.g. the southwestern part of the North Sea) [S7]. The values adopted for the regional compartment correspond to thenorth-east Atlantic [S7], considered to be typical of large deep oceans.

1.

Radionuclide transfers in a marine environment

111. The key element-specific parameters that take account of the transfer of radionuclides from waterto other parts of a marine environment are (a) concentration factors, which relate concentrations ofelements in fish and shellfish to their concentrations in water, and (b) partition coefficients, which
express the distribution of elements between sediment and water. The most significant international
compilation of concentration factors (also referred to as bioaccumulation factors) and partition
coefficients, Kd, for coastal and deep-sea environments is presented in [I3]. Following a critical reviewof the data, these values have been adopted and applied in the present methodology, and are given intable 19.

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 67

Table 19. Radionuclide-specific parameters used in the marine model[I3]

Dose coefficient forexternal exposure
from surface
deposita,
Dex,deposit(Sv/s per Bq/m2) [E2]H

0

1 × 100

1 × 101 × 100

0

1 × 100

1 × 100

14

C

2 × 104

2 × 104

2 × 104

1.3 × 10−20

1 × 103

2 × 10335

S

1 × 100

1 × 100

3 × 100

1.3 × 10−20

5 × 10−1

1 × 100

54

Mn

1 × 103

5 × 103

5 × 104

7.9 × 10−16

2 × 106

2 × 108

58

Co

7 × 102

7 × 103

2 × 104

9.3 × 10−16

3 × 105

5 × 10760

Co

7 × 102

7 × 103

2 × 104

2.3 × 10−15

3 × 105

5 × 107

65

Zn

1 × 103

3 × 105

8 × 104

5.4 × 10−16

7 × 104

2 × 105

90

Sr+ 90Y

3 × 100

5 × 100

1 × 101

1.6 × 10−18

8 × 100

2 × 102106

Ru + 106Rh

2 × 100

1 × 102

5 × 102

3.5 × 10−16

4 × 104

1 × 103

129

I

9 × 100

3 × 100

1 × 101

2.0 × 10−17

7 × 101

2 × 102131

I

9 × 100

3 × 100

1 × 101

3.6 × 10−16

7 × 101

2 × 102

134

Cs

1 × 102

5 × 101

6 × 101

1.5 × 10−15

4 × 103

2 × 103137

Cs+ 137mBa

1 × 102

5 × 101

6 × 101

5.8 × 10−16

4 × 103

2 × 103210

Pb

2 × 102

9 × 104

5 × 104

2.1 × 10−18

1 × 105

1 × 107212

Pb

2 × 102

9 × 104

5 × 104

1.4 × 10−16

1 × 105

1 × 107

214

Pb

2 × 102

9 × 104

5 × 104

2.4 × 10−16

1 × 105

1 × 107

210

Po

2 × 103

2 × 104

2 × 104

8.1 × 10−21

2 × 107

2 × 107

226

Ra

1 × 1021 × 1021 × 102

6.1 × 10−18

2 × 103

4 × 103228

Ra

1 × 1021 × 1021 × 1020

2 × 103

4 × 103

228

Th

6 × 1021 × 103

1 × 103

2.1 × 10−18

3 × 106

5 × 106

230

Th

6 × 1021 × 103

1 × 103

6.4 × 10−19

3 × 106

5 × 106

232

Th

6 × 1021 × 103

1 × 103

4.6 × 10−19

3 × 106

5 × 106

234

Th

6 × 1021 × 103

1 × 103

7.5 × 10−18

3 × 106

5 × 106

234

U

1 × 100

1 × 101

3 × 101

5.9 × 10−19

1 × 103

5 × 102

238

U

1 × 100

1 × 101

3 × 101

4.2 × 10−19

1 × 103

5 × 102239

Pu

1 × 1022 × 102

3 × 103

2.8 × 10−19

1 × 105

1 × 105

240Pu

1 × 1022 × 102

3 × 103

6.0 × 10−19

1 × 105

1 × 105

241

Am

1 × 102

4 × 1021 × 103

2.3 × 10−17

2 × 106

2 × 106

Concentration factor (L/kg) (fresh weight)
Radionuclide

Fish
Bfish
[I3]

3

a

Crustaceans
BcrustMolluscs
Bmolluscs[I3]

Partition coefficient (L/kg)(dry weight sediment)
Ocean
marginKd,local [I3]Open ocean
Kd,regional[I3]

These dose coefficients are for the parent only; the contribution from short-lived progeny is added separately (see appendix).

68 UNSCEAR 2016 REPORT

2.

External and internal exposure(a) External exposure from radionuclides in beach sediments
112. Annual characteristic individual doses due to external exposure from occupancy of beaches are
estimated on the basis of the modelled activity concentrations of each radionuclide in sediments, therelevant dose coefficients for external exposure from surface deposits and the amount of time spent on
the beach.
113. The activity concentration of each radionuclide in sediments is estimated using the activity
concentration in water, the relevant partition coefficient Kd, an assumed average thickness of sedimentof 5 cm and an assumed density of sediment of 1.2 t/m3 [I2]. The dose coefficients for external
exposure from surface deposits are taken from [E2] for each radionuclide. A factor of 0.5 is applied tothe dose coefficients to account for the geometry of the radionuclide distribution on a marine shoreline[E2]. The estimates of effective dose include contributions from beta and gamma irradiation of the skinfrom radionuclides in the sediment. Any additional dose from irradiation of the skin due to directcontact with sediment is not included in the methodology because it is deemed not a major contributor
to the overall characteristic individual doses.
114. An average individual beach occupancy rate of around four days per year is assumed, based ondata for the Nord-Cotentin area of France [R1]. Because this exposure pathway is unlikely to be asignificant contributor to collective doses from nuclear installations [J6], it is not included in theestimation of collective dose.

(b) Ingestion of marine foods
115. Annual individual doses from ingestion of radionuclides in marine foods are estimated from themodelled activity concentration of each radionuclide in fish and shellfish (comprising crustaceans andmolluscs) harvested from the relevant marine compartment, the region-specific or world-average annual
consumption of the food (for adults) and the relevant dose coefficient for ingestion of eachradionuclide. Information on the annual consumption of marine fish, crustaceans and molluscs was
obtained from WHO [W2] and the values used are given in table 20.
Table 20. Per caput annual consumption of marine foods by region
Based on data provided by WHO [W2]Regiona

Per caput annual consumption of food (kg)Fish

Crustaceans

Molluscs

Africa

6.6

0.1

0a

Asia and Pacific

6.9

1.4

2.4

Europe

13

0.9

1.0

Latin America and Caribbean

5.9

0.6

0.4

North America

8.2

2.8

1.4

West Asia

4.5

0.3

0a

World average

7.5

1.1

1.6

Consumption rate is less than 2× 10−2 kg/a and treated as 0.

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 69

116. Activity concentrations of radionuclides in aquatic foods are estimated from the product of themodelled activity concentrations in water and concentration factors that relate the activity
concentrations in sea food to those in water (see table 19). In order to apply this approach, it wasnecessary to make some assumptions about the origin of the food and therefore the activity
concentrations in water that are appropriate to adopt. Thus, it was necessary to make an assumption
about the proportions of fish and shellfish that are derived from each compartment in the model.
117. One approach applied to estimate doses to individuals is to assume that a certain proportion offish and shellfish is derived from the local and regional marine compartments. The proportions assumed
would depend upon the purpose of the assessment. In a similar manner to that used for terrestrial andfreshwater foods, it is assumed in the Committee’s methodology that the characteristic individual
obtains 25% of their fish consumption from the local compartment, with the remaining fraction
obtained from the regional compartment. All of the crustaceans and molluscs are assumed to beobtained from the local compartment.
118. The respective local and regional components of collective dose from marine discharges are
estimated using (a) data on the average crustacean-catch and mollusc-catch per unit length of coastline
appropriate for the local compartment, and (b) data on the average fish-catch per unit volume
appropriate for the regional compartment. Catch data for fish, crustaceans and molluscs were derived
from the FAO FishStatJ software [F2], which comprises the FAO databases on capture and aquaculture
for major fishing areas from 1955 to 2012. The area of sea and length of coastline associated with eachof the major fishing areas were determined using a geographical information system (ArcGIS,
version 10) and then used to estimate the relevant values for the UNEP geographical regions employedin the methodology; world-average values were also derived. The edible fraction of the catch of fish,
crustaceans and molluscs is assumed to be 0.5, 0.35 and 0.15, respectively [S6]. Table 21 shows thecatch data for estimating collective doses for the different regions.
Table 21. Annual catch of fish, crustaceans and molluscs used for estimating collective doses fromdischarges to marine environments [F2]Annual catch
Mass of fish
per unit area of sea(kg/km2)

Mass of crustaceans
per unit length of coastline(kg/km)Mass of molluscs
per unit length of coastline(kg/km)Africa2 × 102

4 × 103

5 × 103

Asia and Pacific

2 × 1021 × 104

5 × 104

Europe2 × 1021 × 103

5 × 103

Latin America and Caribbean

9 × 101

7 × 103

1 × 104

North America

6 × 101

7 × 103

7 × 103

West Asia

2 × 102

5 × 103

5 × 103

World average

1 × 102

8 × 103

3 × 104

Region

70 UNSCEAR 2016 REPORT(c) Individual and collective doses
119. Annual individual doses arising from the ingestion of marine fish and shellfish are estimatedusing the modelled activity concentrations of radionuclides in water and fish, the per caput annual
consumptions given in table 20 and the dose coefficients for ingestion of the relevant radionuclides
given in table 1.
120. To estimate collective doses, region-specific information on the catch of fish and shellfish per unit
area of sea or length of coastline are applied from table 21.

IV. GLOBALLY DISPERSED RADIONUCLIDES
121. The Committee has periodically assessed public exposure to long-lived globally dispersedradionuclides discharged from nuclear power and reprocessing plants since 1982. The radionuclides ofparticular interest are 3H, 14C, 85Kr and 129I. The features of the approaches used and the evolution of theCommittee’s approach are summarized in electronic attachment 2. The estimated collective doses per unit
discharge integrated to various times after discharge are summarized in table 22 at the end of this section.

A. Tritium
122. The Committee’s previous approach to estimating the doses from the global circulation of tritium
discharged from nuclear installations [U6] was based on a comparison of models developed by Kelly et
al. [K2], NCRP [N1], Bergman et al. [B2] and Killough and Kocher [K4]. The relevant concentration oftritium for each compartment of the Committee’s model was determined from the total amount oftritium in the compartment divided by the volume of water represented in the compartment. The
concentration in humans was then estimated from the modelled concentration of tritium and therelevant fractional intake from each compartment of the model.
123. The global collective dose from discharges to the near-surface atmosphere within the 30°–50°
latitude band of the northern hemisphere was estimated by the Committee using the model developedby Killough and Kocher [K4]. This gave a global collective dose per unit discharge of tritium of
2.3 man Sv/PBq [U6]. The global collective dose arising from discharges to the ocean estimated by
NCRP [N1] and Bergman et al. [B2] was around one tenth of that arising from discharges toatmosphere. A value of 0.2 man Sv/PBq was therefore adopted in the UNSCEAR 2000 Report [U6] forthe collective dose per unit discharge of tritium to the ocean. The Committee still considers theseestimates to be appropriate for a world population of 10 billion.
124. The approach used by the Committee to estimate the collective dose commitment is summarized
as follows [S8]:S (t ) =∑ c ∑ p I c (t ) ⋅ f p ,c ⋅ Rc ⋅ U p ⋅ P(15)

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 71

where S(t) is the collective dose commitment truncated at time t (man Sv); Ic(t) is the time-integrated
activity concentration in compartment c at time t ((Bq a)/kg); fp,c is the fraction of the individual’s
intake of water due to pathway p; Rc is the total consumption rate by an individual of water fromcompartment c (kg/a); Up is the dose per unit intake from pathway p (Sv/Bq); and P is the number ofpeople in the exposed population. This model was implemented in the PC-CREAM 08 computer
system [S8] and has been used to derive values for the global collective doses from unit discharges oftritium for the Committee’s methodology. An important factor in the collective dose estimation is theassumed number of people in the world population. The estimate of the United Nations for this for
1 December 2014 was 6.4 billion (6.4 × 109) [U2]. The value for the global population of 10 billion
used in the Committee’s methodology is equivalent to the United Nations’ median estimate of the
projected population for 2060 [U1] and is deemed reasonable as a rounded value for collective doses
integrated into the future.

B. Carbon-14
125. Carbon-14 is the largest contributor to the collective dose from global dispersion of long-lived
radionuclides discharged from reprocessing of nuclear fuel and is a significant contributor to that resulting
from operation of nuclear reactors. A 23-compartment model [T1] (see figure VI, annex A of the
UNSCEAR 2000 Report [U6]) was applied by the Committee to estimate the activity per unit mass ofcarbon in each environmental compartment over time. Once mixing had been achieved, a specific-activity
approach was used to estimate the collective dose commitments from 14C, assuming that the specificactivity of 14C in the carbon ingested by humans was the same as that in the compartments that directly
related to the intake of food (i.e. ground vegetation for terrestrial foods and surface water compartments
for marine foods). The collective dose commitment per unit discharge to atmosphere, truncated at
10,000 years, was estimated to be 109,000 man Sv/PBq. The model can be used to estimate collective
doses for discharges to any compartment; the collective doses from unit discharge to the surface waters ofoceans were found to be about the same as those from unit discharges to atmosphere, but doses from unit
discharges to deep oceans were around 20% lower [U6]. Killough and Rohwer [K3] found that theestimates from six models differed by a factor of only 1.5, suggesting a remarkable level of agreement(although it has not been possible to fully validate any of the models against global measurements). Thishas been attributed to the long half-life of 14C relative to its rate of movement in the environment, whichmakes calculated dose commitments insensitive to the detailed structure of the models [K3].
126. The Committee has therefore not modified its approach to the estimation of collective dose
commitment from 14C from that used in 2000. The approach to derive the collective dose commitment
is implemented in PC-CREAM 08 and is summarized as follows [S8]:=S (t )∑∑ I (t ) ⋅ f
c

c

p

p ,c

⋅ Rc ⋅ U p ⋅ P(16)

where S(t) is the collective dose commitment truncated at time t (man Sv); Ic(t) is the time-integrated
activity concentration in compartment c at time t (Bq a/kg); fp,c is the fraction of the individual’s intake
of carbon from pathway p; Rc is the total intake rate of stable carbon (kg/a); Up is the dose per unit
intake from pathway p (Sv/Bq); and P is the size of the exposed population. As before for tritium, theworld population is assumed to be 10 billion.

72 UNSCEAR 2016 REPORT

C. Iodine-129
127. The Committee used the global circulation compartment model for 129I developed by Titley et al.
[T1] for the assessment it presented in the UNSCEAR 2000 Report (see figure VII, annex A [U6]). The
inventories of stable iodine in the compartments of the model and the transfers between thecompartments were estimated from environmental measurements and the requirement that the total
mass of iodine in the environment was balanced. Iodine intakes by humans from each modelcompartment were estimated from the average inhalation and food consumption rates combined withthe concentrations of stable iodine in the atmosphere and foods respectively, or using a specific-activity
approach. Five exposure pathways were considered as follows, with the values of individual intakes ofstable iodine used given in brackets: inhalation (0.29 µg/d); deposition from the atmosphere onto crops
followed by ingestion by humans or by dairy or beef cattle subsequently ingested by humans (6.6 µg/d);
ingestion of surface water (5.3 µg/d); ingestion of marine fish and shellfish (11 µg/d); and root uptake
from soils and surface waters followed by ingestion of crops and animal products (200 µg/d).
128. The PC-CREAM computer code [S8] also implements the model by Titley et al. The approach
used to estimate the collective dose is similar to that used for tritium and 14C, except that individual
intakes were estimated using transfer factors to relate the activity concentrations in food and air to theactivity concentrations in the various compartments, rather than to the intake of stable iodine. The
Committee still considers this approach to be appropriate.

D. Krypton-85
129. The Committee’s approach to estimating the global dispersion of 85Kr is described in detail in the
UNSCEAR 1988 Report [U5]. It was based on the approach presented in the UNSCEAR 1982 Report[U4], where a simple two-compartment model was used for the discharge of 85Kr [C2]. The twocompartments represent the tropospheres of the northern and southern hemispheres. A transfer
coefficient of 0.5 a−1 between the compartments was used. The time-integrated activity concentration in
air per unit discharge was 10−10 (Bq s)/m3 per Bq [U4]. The dose coefficients to convert from activity
concentration in air to absorbed dose rate in air and absorbed dose rate in skin from the emitted beta
radiation were derived from [C2].
130. The value of the collective effective dose equivalent per unit discharge used in the UNSCEAR
1982 Report [U4] was 0.17 man Sv/PBq (based on a world population in 1982 of 4 billion). This wasscaled to 0.2 man Sv/PBq for an assumed population in 1988 of 4.6 billion [U5]. It was noted that thiscollective dose commitment would be delivered during the first 50 years after discharge.
131. No changes have been made to the previous approach to modelling the dispersion of 85Kr. Around
50% of the effective dose arises from gamma irradiation of the whole body, and 50% arises from beta
irradiation of the skin [I8, Z1]. The value of dose rate for unit activity per mass of air is 8 × 10−9 Sv/aper Bq/kg (the value is given per unit mass of air because this expression is required for the global
circulation model and was obtained using a density of air of 1.225 kg/m3), based on an assumption of
immersion in a semi-infinite cloud (with no shielding) [S8]. The collective dose commitment is thenestimated as follows:

S (t )= I (t ) ⋅ F ⋅ P(17)

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 73

where S (t) is the collective dose commitment truncated at time t (man Sv); I(t) is the time-integrated
activity concentration in air of the appropriate hemisphere at time t ((Bq a)/kg); F is the dose rate perunit concentration in air (Sv/a per Bq/kg); and P is the number of people in the exposed population. As
for the other globally circulating radionuclides, the Committee has taken for its methodology values ofcollective doses derived by PC-CREAM 08, which implements the model used by the Committee anduses a world population of 10 billion.
Table 22. Collective dose commitments from globally dispersed radionuclides
Collective dose commitment truncated after a given timefrom a radionuclide discharge of 1 Bq/s over a year (man Sv)
Radionuclide3

To atmosphere

To a marine environment

100 years

500 years

10 000 years

100 years

500 years

10 000 years

H

1.0 × 10−8

1.0 × 10−8

1.0 × 10−8

1.1 × 10−9

1.1 × 10−9

1.1 × 10−9C

2.8 × 10−4

5.6 × 10−4

2.7 × 10−3

1.1 × 10−4

3.5 × 10−4

2.5 × 10−3Kr

8.0 × 10−9

8.0 × 10−9

8.0 × 10−9

—

—

—

I

2.7 × 10−3

3.1 × 10−3

7.4 × 10−3

3.3 × 10−6

6.7 × 10−6

1.4 × 10−4

14
85

129

V. LIMITATIONS OF THE MODELS AND DATA USED132. The methodology is generic and intended for use with discharges of radionuclides from nuclear
energy generating technologies, and a number of non-nuclear electrical energy production sources,
throughout the world. It builds on previous work that has provided the Committee with robust resultsthat have been suitable for its purposes. In developing the methodology further, no intentional bias has
been introduced to either under- or overestimate radiation exposures; the aim has been to be generic andas realistic as possible. It is difficult to quantify the uncertainties, because of the generic nature of themethodology. Nevertheless, this section outlines the limitations and uncertainties associated with themethodology. The Committee notes the following generic limitations:(a) The input to the models is assumed to be a continuous discharge, and annual average
parameter values are used. The models therefore do not apply for short-duration planned or
accidental releases of radionuclides to the environment;(b) Although some parameter values are used that are specific to geographical region (such as forfood consumption), most of the models are generic and are not intended for detailed site-specificdose assessments, risk assessments or demonstrating regulatory compliance;(c) The assumptions and data used for estimating individual doses are intended to apply to acharacteristic individual living local to the discharge point with typical habits and behaviour;(d) In order to be realistic rather than cautious in estimating characteristic individual doses, it isassumed that only 25% of food intake (both terrestrial and aquatic) is locally produced. The
resulting ingestion doses are sensitive to this assumption, being directly proportional to the foodintake, and the overall dose will be similarly sensitive where ingestion is a major component.
However, it should be noted that this assumption is not used in the assessment of collective doses;

74 UNSCEAR 2016 REPORT(e) The assessed collective doses are directly proportional to the assumed population densities forreleases to atmosphere or to the assumed total amount of drinking water or aquatic foods forreleases to water bodies. The methodology gives results for releases to atmosphere for four
different population distributions with values provided by geographical region for three of them.
The effect of using different distributions can be seen in the results presented in the following
section but are generally only relatively small. However, the use of a very low population density,
suitable for remote sites, leads to collective doses around two orders of magnitude lower than when
the default population densities are used. Therefore, the value for the very low population density
should be used with caution.
(f) The models and data are thought to be the most appropriate for use currently and are also
assumed to apply for representing the future. No account is taken of possible future changes, suchas to population distributions in different regions or the effects of climate change. The uncertainties
in the results of the methodology increase with time; this is particularly the case for global
circulation models of long-lived radionuclides when integrated for 10,000 years or more.
133. Specific limitations and uncertainties relating to the different areas of the methodology are notedin the following sections.

A. Discharges to atmosphere134. A standard Gaussian-plume model is used to estimate the dispersion of radionuclides following
discharges to atmosphere. As discussed in section III.A, the Gaussian model can be implemented
generically for assessing exposures from different sources of discharges throughout the world and it
produces results that agree reasonably well with measurements [C5]. However, as implemented in themethodology, the model makes no allowance for local topographical features (such as hills, buildings or
the site being on the coast) which can strongly influence dispersion, particularly close to the discharge
point. The height of the discharge, which is related to both the physical height of the discharge stack
and any buoyancy of the discharge caused, for example, by heat (referred to as plume rise), also has asignificant effect on the subsequent dispersion of the radionuclides. However, this effect reduces with
distance from the discharge point (see electronic attachment 4), and so the Committee agreed to adopt asingle value for stack height of 30 m for its generic methodology.
135. A simplified approach has also been retained to account for the deposition of radionuclides in theplume on the ground. An effective deposition velocity of 0.002 m/s is used to represent both dry andwet deposition for all radionuclides (apart from noble gases, tritium and carbon-14, for which, a valueof zero is used because noble gases do not deposit, and because deposition is not explicitly modelled fortritium and carbon-14, as they exchange quickly between the atmosphere and ground and a specificactivity approach is used instead and). If, for example, a higher deposition velocity were used, it would
clearly lead to higher deposition close to the discharge point but lower deposition at greater distances
because of depletion of radionuclides in the plume. Thus, overall, for the estimation of collective doses,
the effects tend to counteract each other (except for very short-lived radionuclides). However, theestimation of characteristic individual doses is more sensitive to the assumed deposition velocity.
Nevertheless, because this methodology is intended for comparative purposes, the Committee
considered that the simplified approach was justified.
136. The approach used to estimate the transfer of radionuclides through the terrestrial environment tofood is again a standard one. Although the model used, FARMLAND [B6], was developed in the

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 75

United Kingdom, it has been validated against measured data [S8] and is in reasonable agreement withmodels used elsewhere in the world [I6]. Also, to some extent, parameter values that are considered to
be widely applicable are used, as discussed in section III. The FARMLAND model was also used in a
modified form for the Committee’s 2013 assessment of the levels and effects of the nuclear accident
following the 2011 great east-Japan earthquake and tsunami [U12]—agricultural practices andparameter values specific to Japan were used. A comparison of the results of the use of two versions of
FARMLAND—the one using parameter values that are considered to be widely applicable and theother parameter values that are specific to Japan—are compared in electronic attachment 4. Although
there are some differences, these are not significant for the purposes of the methodology.
137. The methodology makes use of consumption rates of terrestrial foods that differ by geographicalregion (see table 7). This is a compromise between the use of a single diet for the world and morecountry-specific consumption rates. From table 7, it is clear that there are differences in the total
amount of food that is eaten annually, which will have a direct influence on both collective andcharacteristic individual doses but these are generally less than a factor of two (differences of up to afactor of 5 are seen for individual food types). There are also differences in the composition of the diet,and it is less clear what impact this will have on estimated doses. For discharges from nuclear sites, oneof the most important radionuclides in terms of both collective and individual doses is carbon-14 [U8].
A specific-activity model is included in the methodology, so that the intake of carbon-14 is related tothe intake of stable carbon in the diet. As carbon is an essential component of the diet and is found in all
foods, it is likely that the intake of carbon-14 is insensitive to changes in the dietary composition. Thiswas investigated in a sensitivity study (described in electronic attachment 4) that considered the intakesof carbon for diets typical of Japan and the United Kingdom. This study showed that the total amountof carbon ingested was similar and therefore the dose estimates would be similar even though the foodsfrom which the carbon was derived were different.
138. The estimation of doses due to external exposure from both radionuclides in the plume and those
deposited on the ground takes account of the shielding effects of buildings when people are indoors.
The methodology uses a single indoor occupancy factor and single shielding/location factors forradionuclides in the plume and those on the ground. The indoor occupancy factor is 0.8 and any
variations in this for much of the world are likely to be less than a factor of two and so the effect would
be relatively minor. The shielding factors, 0.1 and 0.2 for radionuclides deposited on the ground and in
the plume, respectively, are typical of those for standard single-storey buildings. As discussed in
section III.A, there are differences between the shielding factors for different building types (shielding
factors might be a factor of 5 or 6 higher than used here for wooden buildings and a factor of up to
10 times lower for multi-storey buildings). There is also evidence for location factors changing as afunction of time. The empirical models used are based on measurements and there can be good
agreement between the results of such models and personal dosimeter measurements where local
factors are taken into account. The factors used here are considered to be appropriate for use in theCommittee’s assessments, recognizing the variations that occur globally

B. Discharges to freshwater and marine environments
139. The methodology includes consideration of two generic freshwater environments for aquatic
discharges: (a) a small river and (b) a large river; the results for a large river are also considered toapply to a large lake. In all cases, instantaneous mixing is assumed within a single body of water, which
is obviously a significant simplification. In reality, lakes and rivers are complex environments andrivers have many tributaries and sections with different flow rates, volumes and behaviours. Similarly,

76 UNSCEAR 2016 REPORTthe methodology uses a generic approach for discharges to a marine environment with a simple
compartmental model consisting of two compartments representing local and regional marine waters.
Again in reality, there are significant differences between marine environments depending on local andregional currents, and the nature of the coastline and local environment. Although there have beenvalidation studies showing good agreement between models and predictions, these are for specific sites
and situations and are not necessarily applicable to the simplified generic approach adopted here.
However, the Committee considers that its generic approach is adequate for the purpose of assessing
worldwide exposures from radioactive discharges and for comparative studies, but notes the limitationsof the approach for other purposes.
140. Similar to terrestrial foods, the values for consumption rates of freshwater and marine fish are
based on data by geographical region and are suitable for estimating the characteristic individual dose.
There are differences in the values of consumption rates for freshwater fish and some marine fish.
Table 13 for freshwater fish shows differences of up to a factor of 6 between regions, and table 20
shows differences of a factor of 10 or more for the consumption of crustaceans and even greater
differences for consumption rates of molluscs. These differences would be directly reflected in thevalues of the calculated individual doses.
141. The methodology now considers the transfer of radionuclides from freshwater to terrestrial foodsby means of irrigation. There are many different types of irrigation systems and significant variations
across the world in their usage, the source of water (surface or groundwater), and the type of crops thatare irrigated. The estimation of the transfer of radionuclides to terrestrial foods through irrigation istherefore particularly uncertain. The simplifying assumptions in the methodology however are only
intended to be suitable for generic assessments and the Committee considers that its adopted approachis robust enough and suitable for this purpose. Nevertheless, the limitations should be recognized; theimportance of these limitations will depend on the relative importance of the irrigation exposure
pathway compared to exposures from intakes of drinking water and freshwater fish.
142. The estimation of collective dose from discharges of radionuclides to rivers, lakes and the sea is
not based on the sum of individual doses as is the case for discharges to atmosphere. Instead, thecollective dose is based on estimates of the total amount of fish caught in the part of the environment ofinterest, and the amount of water that is abstracted for drinking water and for irrigation. As such, themethodology assumes that the fish, drinking water and irrigated foods are consumed but no account istaken of who consumes them. The Committee considers that this approach is adequate for estimatingcollective doses for its purposes, but notes that it is not possible with its methodology to break down thecollective dose into individual doses or to distinguish between local and regional components ofcollective dose for any aquatic discharges.

C. Global modelling
143. The approach used to estimate collective doses from the four most important radionuclides thatcan be globally dispersed (3H, 14C, 85Kr and 129I) is one that is well accepted and has been used by theCommittee for a number of years. The globally dispersed radionuclides, particularly 14C, are the biggest
contributors to the overall collective doses due to discharges from the nuclear industry when thesedoses are integrated over 500 years or more. One of the factors that influences the estimated collective
doses is the size of the global population that is assumed, because the global collective dose is
proportional to the size of the global population. A rounded value of 10 billion people is included in themethodology; the uncertainty associated with this value increases with time. The global models areANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 77

based on movements of water, carbon and other natural elements through the environment. Suchmovements are likely to be affected by changes in the climate, sea level, ocean currents andatmospheric conditions. The model for carbon is a specific activity approach based on the global carbon
cycle and the amounts of stable carbon in different parts of the environment. Increases in stable carbon
due to the burning of fossil fuels will influence the transfers in the future. These possible future changes
are not taken into account in the methodology, which leads to increasing uncertainties in estimation ofdoses in the longer term. It is also not possible to validate this type of model whose scope covers wide
areas and time frames.

D. Comparison of the current and previous methodologies
144. The methodology described in this annex has been developed from that used previously by theCommittee [U6, U7, U10]. The main changes that have been made are discussed in electronic
attachment 1, with further information given in electronic attachment 2.
145. The main changes that have been introduced are:(a) The results of the methodology are now given in terms of the dose per unit discharge rather
than being normalized to the amount of electricity generated (dose factors normalized toelectricity generated can be calculated subsequently as required);(b) The methodology has been extended for application to the estimation of exposures fromdischarges of radionuclides from non-nuclear electrical energy production;(c) The inclusion of factors that depend on geographical region, notably for population
distributions, consumption rates and fish-catch data;(d) The inclusion of a more detailed approach for modelling the transfer of radionuclides from
fresh water to irrigated crops;(e) The results are provided for a range of integration times;(f) Some updates have been made to the various models included in the methodology.
As noted in electronic attachment 1, many parts of the methodology remain unchanged, because theCommittee considered, following review, that they were still appropriate for its purposes.
146. The results of the various workbooks implementing the methodology were compared with data
derived from the previous methodology [U6, U7]. The estimates of the annual collective effective doses
from the following pathways were compared:(a) External exposure due to deposited radionuclides from discharges to atmosphere;(b) Inhalation of radionuclides discharged to atmosphere;(c) Ingestion of radionuclides discharged to atmosphere;(d) All pathways from radionuclides discharged to both freshwater and marine environments.
In general, the results are within about an order of magnitude, despite the changes that have been
introduced to parts of the methodology (see electronic attachment 1, tables 2–6).

78 UNSCEAR 2016 REPORT

VI. APPLICATION OF THE METHODOLOGY147. The Committee decided that its calculations should be transparent and that the methodology
should be able to be relatively easily applied and updated in the future. It agreed that the methodology
be implemented in a series of Excel® workbooks. The appendix describes the end points considered, theworkbook design, the mathematical equations to implement the methodology in the workbooks, thetreatment of progeny, the quality assurance carried out to ensure that the workbooks were implemented
correctly, and details of how the workbooks could be used for assessing the exposures from different
source terms.
148. The results of the methodology, as given by the workbooks, are for specific discharges todifferent environments. The results are in the form of dose calculation factors for individual
radionuclides; for radionuclides that are in secular equilibrium with their short-lived progeny, thefactors represent the sums of the contributions from the parent and progeny (see appendix). The factors
are for characteristic individual doses (in units of sieverts) in the 100th year of a continuous dischargeof a radionuclide at a rate of 1 Bq/s, and collective doses (in units of man–sieverts) integrated to 100,
500 and 10,000 years for a continuous discharge of a radionuclide at a rate of 1 Bq/s for 1 year (seesection II.C). For most radionuclides the collective doses to 100 years only are provided because thiswas deemed to be sufficient. However collective doses integrated to other times are given for 3H, 14C,
85
Kr and 129I.
149. The resulting characteristic individual and collective dose calculation factors for unit discharge ofradionuclides to atmosphere, to the different freshwater environments (the results for a large river also
apply to a lake) and to a marine environment—derived using the methodology implemented in the
workbooks—are presented in tables 23–31. The doses can then be scaled by the actual rates ofdischarge of each radionuclide from a particular site and then summed over all relevant radionuclides togive the overall characteristic individual and collective doses. Results are given for sites located indifferent regions of the world, with additional results for coastal and inland nuclear sites and for sites
situated in areas of low population density.
150. For future assessments, where discharges are reported to the Committee for broad groups ofradionuclides (e.g. gross alpha, noble gases, radioiodines or particulates), some assumptions would
need to be made about the proportion of the different radionuclides constituting the group (seesection II.D.2).

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 79

Table 23. Estimated characteristic individual doses in the 100th year from a continuous dischargeof a radionuclide to atmosphere
The characteristic individual dose is to a person living 5 km from the discharge point obtaining 25% of their food locally. The
regions are as shown in figure II

Individual effective dose in the 100th year of a continuous discharge at a rate of 1 Bq/s (Sv)Radionuclide

AfricaAsia & Pacific

EuropeLatin
America

North
AmericaWest Asia

Ha

4.2 × 10−14

4.4 × 10−14

4.8 × 10−14

4.3 × 10−14

4.7 × 10−14

4.1 × 10−14

14

C

3.3 × 10−12

3.7 × 10−12

3.7 × 10−12

3.4 × 10−12

3.6 × 10−12

3.6 × 10−1235

S

5.1 × 10−12

7.2 × 10−12

1.4 × 10−11

1.2 × 10−11

1.8 × 10−11

7.6 × 10−1241Ar

4.2 × 10−14

4.2 × 10−14

4.2 × 10−14

4.2 × 10−14

4.2 × 10−14

4.2 × 10−1454

Mn

1.5 × 10−12

1.6 × 10−12

1.9 × 10−12

1.7 × 10−12

2.0 × 10−12

1.5 × 10−1258

Co

6.4 × 10−12

6.8 × 10−12

7.9 × 10−12

7.4 × 10−12

8.4 × 10−12

6.7 × 10−1260

Co

2.3 × 10−10

2.5 × 10−10

3.0 × 10−10

2.9 × 10−10

3.5 × 10−10

2.5 × 10−1065Zn

3.0 × 10−11

3.9 × 10−11

6.7 × 10−11

6.1 × 10−11

8.8 × 10−11

4.0 × 10−1185

Kr

8.7 × 10−17

8.7 × 10−17

8.7 × 10−17

8.7 × 10−17

8.7 × 10−17

8.7 × 10−17

90

Srb

2.4 × 10−10

2.8 × 10−10

3.8 × 10−10

2.9 × 10−10

3.7 × 10−10

2.5 × 10−10

106

Rub

1.9 × 10−11

2.1 × 10−11

2.9 × 10−11

2.7 × 10−11

3.5 × 10−11

2.1 × 10−11

129

I

4.3 × 10−10

4.9 × 10−10

5.6 × 10−10

4.6 × 10−10

5.3 × 10−10

4.5 × 10−10131I

1.3 × 10−11

1.5 × 10−11

1.8 × 10−11

1.4 × 10−11

1.7 × 10−11

1.3 × 10−11

133

Xeb

1.0 × 10−15

1.0 × 10−15

1.0 × 10−15

1.0 × 10−15

1.0 × 10−15

1.0 × 10−15

135

Xe

8.6 × 10−15

8.6 × 10−15

8.6 × 10−15

8.6 × 10−15

8.6 × 10−15

8.6 × 10−15

138

Xeb

3.2 × 10−14

3.2 × 10−14

3.2 × 10−14

3.2 × 10−14

3.2 × 10−14

3.2 × 10−14

134

Cs

1.2 × 10−10

1.4 × 10−10

1.7 × 10−10

1.5 × 10−10

1.8 × 10−10

1.4 × 10−10

137

Csb

2.1 × 10−10

2.2 × 10−10

2.4 × 10−10

2.3 × 10−10

2.6 × 10−10

2.2 × 10−10

210

Pb

1.1 × 10−9

1.2 × 10−9

1.3 × 10−9

1.1 × 10−9

1.2 × 10−9

1.0 × 10−9

210

Po

2.1 × 10−9

2.3 × 10−9

2.7 × 10−9

2.4 × 10−9

2.8 × 10−9

2.1 × 10−9

222

Rnb

2.7 × 10−12

2.7 × 10−12

2.7 × 10−12

2.7 × 10−12

2.7 × 10−12

2.7 × 10−12

226

Ra

2.2 × 10−9

2.3 × 10−9

2.4 × 10−9

2.2 × 10−9

2.3 × 10−9

2.1 × 10−9

230

Th

5.7 × 10−9

5.7 × 10−9

5.7 × 10−9

5.6 × 10−9

5.7 × 10−9

5.6 × 10−9

232

Thb

2.8 × 10−8

2.8 × 10−8

2.8 × 10−8

2.8 × 10−8

2.8 × 10−8

2.8 × 10−8234

U

1.4 × 10−9

1.5 × 10−9

1.5 × 10−9

1.5 × 10−9

1.5 × 10−9

1.4 × 10−9

238

Ub

1.2 × 10−9

1.2 × 10−9

1.2 × 10−9

1.2 × 10−9

1.2 × 10−9

1.2 × 10−9

239

Pu

2.0 × 10−8

2.0 × 10−8

2.0 × 10−8

2.0 × 10−8

2.0 × 10−8

2.0 × 10−8

240

Pu

2.0 × 10−8

2.0 × 10−8

2.0 × 10−8

2.0 × 10−8

2.0 × 10−8

2.0 × 10−8

241

Am

1.7 × 10−8

1.7 × 10−8

1.7 × 10−8

1.7 × 10−8

1.7 × 10−8

1.7 × 10−83aFor 3H the calculated doses include a contribution from HTO and OBT as discussed in section III.A.3.

b

For these radionuclides the calculated doses include a contribution from the ingrowth of progeny (see appendix for details).

Characteristic individual doses are to people living 5 km downstream of the discharge point obtaining 25% of their food locally. The regions are as shown in figure II

Individual effective dose in the 100th year of a continuous discharge at a rate of 1 Bq/s (Sv)Radionuclide

AfricaAsia & Pacific

Small

Large

Small

Large

Hb

3.0 × 10−12

3.0 × 10−14

3.0 × 10−12

14C

1.6 × 10−8

1.6 × 10−10

35

S

6.2 × 10−11

54

Mn

58

EuropeLatin America

Small

Large

Small

Large

3.0 × 10−14

3.0 × 10−12

3.0 × 10−14

3.0 × 10−12

4.5 × 10−8

4.5 × 10−10

2.0 × 10−8

2.0 × 10−10

6.5 × 10−13

1.4 × 10−10

1.3 × 10−12

7.3 × 10−11

5.2 × 10−9

3.5 × 10−12

5.3 × 10−9

3.5 × 10−12Co

4.7 × 10−9

4.0 × 10−12

4.7 × 10−960

Co

1.2 × 10−8

1.1 × 10−1165Zn

1.0 × 10−9

90

Src

106

North America
Small

Large

3.0 × 10−14

3.0 × 10−12

9.3 × 10−9

9.4 × 10−11

8.0 × 10−13

4.5 × 10−11

5.2 × 10−9

3.5 × 10−12

4.0 × 10−12

4.7 × 10−9

1.2 × 10−8

1.1 × 10−11

9.0 × 10−12

2.7 × 10−9

1.2 × 10−9

1.9 × 10−11

Ruc

1.7 × 10−9

129

I

131

West Asia
Small

Largea3.0 × 10−14

3.0 × 10−12

3.0 × 10−14

2.6 × 10−8

2.6 × 10−10

7.6 × 10−9

7.8 × 10−11

4.9 × 10−13

9.0 × 10−11

9.6 × 10−13

4.1 × 10−11

4.7 × 10−13

5.2 × 10−9

3.5 × 10−12

5.2 × 10−9

3.5 × 10−12

5.2 × 10−9

3.5 × 10−12

4.1 × 10−12

4.7 × 10−9

4.0 × 10−12

4.7 × 10−9

4.1 × 10−12

4.7 × 10−9

4.0 × 10−12

1.2 × 10−8

1.1 × 10−11

1.2 × 10−8

1.1 × 10−11

1.2 × 10−8

1.1 × 10−11

1.2 × 10−8

1.1 × 10−11

2.2 × 10−11

1.3 × 10−9

1.1 × 10−11

6.9 × 10−10

6.1 × 10−12

1.6 × 10−9

1.4 × 10−11

5.9 × 10−10

5.3 × 10−12

1.2 × 10−9

1.5 × 10−11

1.2 × 10−9

2.7 × 10−11

1.2 × 10−9

1.9 × 10−11

1.2 × 10−9

2.8 × 10−11

1.2 × 10−9

2.0 × 10−11

3.5 × 10−12

1.7 × 10−9

3.4 × 10−12

1.7 × 10−9

3.7 × 10−12

1.7 × 10−9

3.5 × 10−12

1.7 × 10−9

3.8 × 10−12

1.6 × 10−9

3.5 × 10−12

4.7 × 10−9

6.1 × 10−11

5.1 × 10−9

5.3 × 10−11

4.7 × 10−9

7.4 × 10−11

4.6 × 10−9

5.9 × 10−11

4.8 × 10−9

7.6 × 10−11

4.6 × 10−9

6.3 × 10−11I

4.0 × 10−10

1.9 × 10−12

4.0 × 10−10

1.9 × 10−12

4.0 × 10−10

2.0 × 10−12

4.0 × 10−10

1.9 × 10−12

4.0 × 10−10

2.0 × 10−12

4.0 × 10−10

1.9 × 10−12

134

Cs

8.6 × 10−9

1.8 × 10−11

1.2 × 10−8

2.1 × 10−11

9.2 × 10−9

2.0 × 10−11

7.8 × 10−9

1.7 × 10−11

1.0 × 10−8

2.1 × 10−11

7.6 × 10−9

1.7 × 10−11

137

Csc

4.1 × 10−9

1.1 × 10−11

6.7 × 10−9

1.2 × 10−11

4.5 × 10−9

1.2 × 10−11

3.5 × 10−9

9.9 × 10−12

5.0 × 10−9

1.3 × 10−11

3.4 × 10−9

1.0 × 10−11

210

Pb

2.0 × 10−8

2.2 × 10−10

2.1 × 10−8

2.0 × 10−10

2.0 × 10−8

2.5 × 10−10

1.9 × 10−8

2.1 × 10−10

2.0 × 10−8

2.6 × 10−10

1.9 × 10−8

2.2 × 10−10

210

Po

3.4 × 10−8

3.5 × 10−10

3.7 × 10−8

3.4 × 10−10

3.4 × 10−8

3.9 × 10−10

3.3 × 10−8

3.5 × 10−10

3.5 × 10−8

4.0 × 10−10

3.3 × 10−8

3.5 × 10−10

226

Ra

7.6 × 10−9

1.1 × 10−10

7.8 × 10−9

9.0 × 10−11

7.7 × 10−9

1.4 × 10−10

7.6 × 10−9

1.0 × 10−10

7.7 × 10−9

1.4 × 10−10

7.6 × 10−9

1.1 × 10−10

230

Th

3.2 × 10−9

3.7 × 10−11

3.2 × 10−9

3.4 × 10−11

3.2 × 10−9

4.4 × 10−11

3.2 × 10−9

3.7 × 10−11

3.2 × 10−9

4.6 × 10−11

3.2 × 10−9

3.7 × 10−11

232

Thc

3.3 × 10−8

2.8 × 10−10

3.3 × 10−8

2.5 × 10−10

3.3 × 10−8

3.2 × 10−10

3.3 × 10−8

2.7 × 10−10

3.3 × 10−8

3.3 × 10−10

3.3 × 10−8

2.8 × 10−10234

U

7.4 × 10−10

9.6 × 10−12

7.4 × 10−10

8.4 × 10−12

7.4 × 10−10

1.2 × 10−11

7.4 × 10−10

9.5 × 10−12

7.4 × 10−10

1.3 × 10−11

7.4 × 10−10

9.7 × 10−12

238

Uc

7.3 × 10−10

9.4 × 10−12

7.4 × 10−10

8.3 × 10−12

7.3 × 10−10

1.2 × 10−11

7.3 × 10−10

9.3 × 10−12

7.3 × 10−10

1.2 × 10−11

7.3 × 10−10

9.5 × 10−12

239

Pu

3.5 × 10−9

4.1 × 10−11

3.6 × 10−9

3.7 × 10−11

3.5 × 10−9

4.9 × 10−11

3.4 × 10−9

4.1 × 10−11

3.5 × 10−9

5.1 × 10−11

3.4 × 10−9

4.1 × 10−11

240

Pu

3.5 × 10−9

4.1 × 10−11

3.6 × 10−9

3.7 × 10−11

3.5 × 10−9

4.9 × 10−11

3.4 × 10−9

4.1 × 10−11

3.5 × 10−9

5.1 × 10−11

3.4 × 10−9

4.1 × 10−11

241

Am

3.8 × 10−9

3.4 × 10−11

5.6 × 10−9

3.1 × 10−11

4.1 × 10−9

4.1 × 10−11

3.4 × 10−9

3.3 × 10−11

4.5 × 10−9

4.3 × 10−11

3.3 × 10−9

3.3 × 10−11

3

a

a

a

a

The dose estimates for large rivers are also assumed to apply to lakes.

b

For 3H the calculated doses include a contribution from HTO and OBT as discussed in section III.A.3.

c

For these radionuclides the calculated doses include a contribution from the ingrowth of progeny (see appendix for details).

aa

80 UNSCEAR 2016 REPORT

Table 24. Estimated characteristic individual dose in the 100th year of a continuous discharge of a radionuclide to rivers

Table 25. Estimated characteristic individual dose in the 100th year of a continuous discharge of a radionuclide to a marine environment
The characteristic individual dose is for people ingesting crustaceans and molluscs from the local marine compartment plus 25% of their marine fish consumption from the local compartment and 75% from theregional compartment. The regions are as shown in figure IIRadionuclide

Asia and Pacific

EuropeLatin America

North America

West Asia

H

5.0 × 10−17

1.6 × 10−16

1.5 × 10−16

7.0 × 10−17

1.7 × 10−16

4.0 × 10−17

14C

3.2 × 10−11

1.0 × 10−10

9.4 × 10−11

4.5 × 10−11

1.1 × 10−10

2.6 × 10−1135

S

1.9 × 10−15

1.1 × 10−14

7.6 × 10−15

3.5 × 10−15

9.5 × 10−15

1.5 × 10−1554Mn

2.6 × 10−9

5.3 × 10−9

5.2 × 10−9

5.2 × 10−9

5.3 × 10−9

5.2 × 10−958

Co

4.0 × 10−10

8.6 × 10−10

8.3 × 10−10

8.1 × 10−10

8.5 × 10−10

8.0 × 10−1060

Co

1.2 × 10−9

2.6 × 10−9

2.5 × 10−9

2.4 × 10−9

2.6 × 10−9

2.3 × 10−965Zn

2.8 × 10−10

3.7 × 10−9

2.1 × 10−9

1.4 × 10−9

5.6 × 10−9

5.9 × 10−10

90

Sra

2.5 × 10−13

1.6 × 10−12

1.1 × 10−12

5.1 × 10−13

1.5 × 10−12

2.2 × 10−13

106

Rua

2.3 × 10−11

6.0 × 10−11

5.2 × 10−11

4.8 × 10−11

5.6 × 10−11

4.6 × 10−11129

I

2.7 × 10−12

7.6 × 10−12

7.3 × 10−12

3.3 × 10−12

7.0 × 10−12

1.9 × 10−12131I

3.6 × 10−14

8.8 × 10−14

8.5 × 10−14

5.7 × 10−14

8.3 × 10−14

4.7 × 10−14

134

Cs

1.5 × 10−11

3.1 × 10−11

3.2 × 10−11

2.6 × 10−11

3.2 × 10−11

2.4 × 10−11

137

Csa

7.2 × 10−12

1.5 × 10−11

1.6 × 10−11

1.2 × 10−11

1.6 × 10−11

1.0 × 10−11

210

Pba

2.3 × 10−8

4.2 × 10−7

2.2 × 10−7

1.2 × 10−7

5.1 × 10−7

4.1 × 10−8

210

Po

1.0 × 10−8

1.4 × 10−7

7.5 × 10−8

4.0 × 10−8

1.5 × 10−7

1.3 × 10−8

226

Raa

2.4 × 10−8

4.2 × 10−7

2.2 × 10−7

1.3 × 10−7

5.1 × 10−7

4.1 × 10−8

230

Th

3.7 × 10−10

1.6 × 10−9

1.3 × 10−9

6.3 × 10−10

1.8 × 10−9

3.2 × 10−10

232

Tha

6.3 × 10−9

1.6 × 10−8

1.5 × 10−8

1.3 × 10−8

1.7 × 10−8

1.2 × 10−8234

U

2.5 × 10−13

6.8 × 10−12

3.2 × 10−12

1.5 × 10−12

5.5 × 10−12

3.3 × 10−13

238

Ua

6.4 × 10−12

3.3 × 10−11

2.4 × 10−11

1.2 × 10−11

3.4 × 10−11

5.8 × 10−12

239

Pu

9.1 × 10−11

3.0 × 10−9

1.4 × 10−9

5.7 × 10−10

1.9 × 10−9

8.5 × 10−11

240

Pu

9.1 × 10−11

3.0 × 10−9

1.4 × 10−9

5.7 × 10−10

1.9 × 10−9

8.5 × 10−11

241

Am

1.5 × 10−10

1.2 × 10−9

6.8 × 10−10

4.0 × 10−10

1.0 × 10−9

2.3 × 10−10

For these radionuclides the calculated doses include a contribution from the ingrowth of progeny (see appendix for details).

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 81

Africa3

aIndividual effective dose in the 100th year of a continuous discharge at a rate of 1 Bq/s (Sv)The collective doses are out to 1,500 km based on the population distributions given in table 3 for different regions of the world as shown in figure II. They can be used for discharges from any type of source forcomparative purposes and are the only values appropriate for non-nuclear sites

Collective doses integrated to 100 years from a year’s continuous discharge at a rate of 1 Bq/s (man Sv)

Radionuclide

AfricaLocal

3

Asia and PacificRegional

Local

EuropeRegional

Local

Latin America

Regional

Local

North America

Regional

Local

West Asia

Regional

Local

Regionalb

1.4 × 10

1.2 × 10

5.6 × 10

4.7 × 10

3.0 × 10

2.5 × 10

2.6 × 10

2.2 × 10

7.3 × 10

6.0 × 10

1.8 × 10C

1.1 × 10−6

5.3 × 10−6

4.3 × 10−6

2.2 × 10−5

2.0 × 10−6

1.0 × 10−5

1.9 × 10−6

9.7 × 10−6

4.9 × 10−7

2.5 × 10−6

H

14

−8

−7

−8

−7

−8

−7

−8

−7

−9

−8

World averagea

−8

−7

Local

Regional

1.5 × 10−8

3.2 × 10

2.7 × 10−7

1.5 × 10−6

7.8 × 10−6

2.4 × 10−6

1.2 × 10−535

S

1.8 × 10−6

8.2 × 10−6

9.1 × 10−6

4.2 × 10−5

8.2 × 10−6

3.8 × 10−5

7.5 × 10−6

3.5 × 10−5

2.7 × 10−6

1.3 × 10−5

3.5 × 10−6

1.6 × 10−5

6.9 × 10−6

3.2 × 10−541Ar

6.1 × 10−10

3.2 × 10−15

2.2 × 10−9

1.1 × 10−14

9.8 × 10−10

5.2 × 10−15

1.0 × 10−9

5.5 × 10−15

2.5 × 10−10

1.3 × 10−15

7.9 × 10−10

4.2 × 10−15

1.2 × 10−9

6.5 × 10−15

54Mn

3.8 × 10−7

1.8 × 10−6

1.6 × 10−6

7.4 × 10−6

9.0 × 10−7

4.3 × 10−6

7.8 × 10−7

3.7 × 10−6

2.3 × 10−7

1.1 × 10−6

5.0 × 10−7

2.4 × 10−6

9.2 × 10−7

4.4 × 10−658

8.9 × 10−7

4.1 × 10−6

3.6 × 10−6

1.7 × 10−5

2.4 × 10−6

1.1 × 10−5

2.2 × 10−6

1.0 × 10−5

6.7 × 10−7

3.1 × 10−6

1.3 × 10−6

6.0 × 10−6

2.3 × 10−6

1.1 × 10−560

3.0 × 10−5

1.4 × 10−4

1.3 × 10−4

6.3 × 10−4

9.6 × 10−5

4.6 × 10−4

9.4 × 10−5

4.5 × 10−4

3.1 × 10−5

1.5 × 10−4

5.0 × 10−5

2.4 × 10−4

9.1 × 10−5

4.3 × 10−4

Co
Co

65

Zn

8.5 × 10−6

4.0 × 10−5

4.3 × 10−5

2.0 × 10−4

3.7 × 10−5

1.7 × 10−4

3.5 × 10−5

1.6 × 10−4

1.2 × 10−5

5.9 × 10−5

1.6 × 10−5

7.6 × 10−5

3.2 × 10−5

1.5 × 10−485

Kr

1.4 × 10−11

1.1 × 10−10

4.8 × 10−11

4.0 × 10−10

2.2 × 10−11

1.8 × 10−10

2.3 × 10−11

1.9 × 10−10

5.5 × 10−12

4.6 × 10−11

1.8 × 10−11

1.5 × 10−10

2.7 × 10−11

2.3 × 10−10

90

Src

8.7 × 10−5

4.2 × 10−4

3.6 × 10−4

1.7 × 10−3

2.3 × 10−4

1.1 × 10−3

1.8 × 10−4

8.6 × 10−4

5.5 × 10−5

2.6 × 10−4

1.2 × 10−4

5.5 × 10−4

2.2 × 10−4

1.0 × 10−3

106

Ruc

3.9 × 10−6

1.9 × 10−5

1.8 × 10−5

8.4 × 10−5

1.3 × 10−5

5.9 × 10−5

1.2 × 10−5

5.7 × 10−5

4.1 × 10−6

1.9 × 10−5

6.2 × 10−6

3.0 × 10−5

1.2 × 10−5

5.6 × 10−5129I

1.6 × 10−4

7.6 × 10−4

6.4 × 10−4

3.1 × 10−3

3.3 × 10−4

1.6 × 10−3

2.9 × 10−4

1.4 × 10−3

7.9 × 10−5

3.8 × 10−4

2.1 × 10−4

1.0 × 10−3

3.6 × 10−4

1.7 × 10−3131I

3.9 × 10−6

1.4 × 10−5

1.6 × 10−5

5.6 × 10−5

9.3 × 10−6

3.2 × 10−5

7.6 × 10−6

2.7 × 10−5

2.2 × 10−6

7.9 × 10−6

5.1 × 10−6

1.8 × 10−5

9.3 × 10−6

3.2 × 10−5

133

Xec

1.6 × 10−10

8.0 × 10−10

5.6 × 10−10

2.9 × 10−9

2.6 × 10−10

1.3 × 10−9

2.7 × 10−10

1.4 × 10−9

6.5 × 10−11

3.3 × 10−10

2.1 × 10−10

1.0 × 10−9

3.2 × 10−10

1.6 × 10−9

135

Xe

8.3 × 10−10

1.7 × 10−10

3.0 × 10−9

5.9 × 10−10

1.4 × 10−9

2.7 × 10−10

1.4 × 10−9

2.9 × 10−10

3.4 × 10−10

6.8 × 10−11

1.1 × 10−9

2.2 × 10−10

1.7 × 10−9

3.4 × 10−10

138

Xec

1.9 × 10−12

1.7 × 10−31

6.7 × 10−12

6.2 × 10−31

3.0 × 10−12

2.8 × 10−31

3.2 × 10−12

3.0 × 10−31

7.7 × 10−13

7.1 × 10−32

2.4 × 10−12

2.3 × 10−31

3.8 × 10−12

3.5 × 10−31

134

Cs

2.9 × 10−5

1.4 × 10−4

1.2 × 10−4

5.9 × 10−4

7.3 × 10−5

3.5 × 10−4

6.9 × 10−5

3.3 × 10−4

2.1 × 10−5

9.9 × 10−5

4.4 × 10−5

2.1 × 10−4

7.5 × 10−5

3.6 × 10−4

137

Csc

3.5 × 10−5

1.7 × 10−4

1.4 × 10−4

6.8 × 10−4

7.9 × 10−5

3.8 × 10−4

7.6 × 10−5

3.6 × 10−4

2.2 × 10−5

1.0 × 10−4

5.0 × 10−5

2.4 × 10−4

8.5 × 10−5

4.1 × 10−4

210

Pb

3.0 × 10−4

1.4 × 10−3

1.2 × 10−3

5.5 × 10−3

6.0 × 10−4

2.9 × 10−3

5.0 × 10−4

2.4 × 10−3

1.4 × 10−4

6.7 × 10−4

3.5 × 10−4

1.7 × 10−3

6.4 × 10−4

3.1 × 10−3

210

Po

4.4 × 10−4

2.1 × 10−3

1.7 × 10−3

8.2 × 10−3

1.1 × 10−3

5.0 × 10−3

9.0 × 10−4

4.2 × 10−3

2.8 × 10−4

1.3 × 10−3

5.5 × 10−4

2.6 × 10−3

1.0 × 10−3

4.9 × 10−3

222

Rnc

4.0 × 10−7

1.7 × 10−6

1.4 × 10−6

6.0 × 10−6

6.4 × 10−7

2.8 × 10−6

6.8 × 10−7

2.9 × 10−6

1.6 × 10−7

6.9 × 10−7

5.1 × 10−7

2.2 × 10−6

8.0 × 10−7

3.4 × 10−6

226

Ra

4.3 × 10−4

2.1 × 10−3

1.7 × 10−3

8.0 × 10−3

8.4 × 10−4

4.0 × 10−3

7.4 × 10−4

3.5 × 10−3

2.0 × 10−4

9.5 × 10−4

5.4 × 10−4

2.6 × 10−3

9.3 × 10−4

4.4 × 10−3

82 UNSCEAR 2016 REPORT

Table 26. Local and regional components of collective dose for discharges to atmosphere from sites in different regions of the world

Collective doses integrated to 100 years from a year’s continuous discharge at a rate of 1 Bq/s (man Sv)

Radionuclide

AfricaAsia and Pacific

EuropeLatin America

North America

West Asia

World averagea

Local

Regional

Local

Regional

Local

Regional

Local

Regional

Local

Regional

Local

Regional

Local

RegionalTh

5.7 × 10−4

2.7 × 10−3

2.0 × 10−3

9.8 × 10−3

9.5 × 10−4

4.5 × 10−3

9.8 × 10−4

4.7 × 10−3

2.4 × 10−4

1.1 × 10−3

7.3 × 10−4

3.5 × 10−3

1.2 × 10−3

5.5 × 10−3

232

Thc

2.9 × 10−3

1.4 × 10−2

1.0 × 10−2

5.0 × 10−2

4.9 × 10−3

2.3 × 10−2

5.0 × 10−3

2.4 × 10−2

1.2 × 10−3

5.8 × 10−3

3.7 × 10−3

1.8 × 10−2

5.9 × 10−3

2.8 × 10−2

234

U

1.5 × 10−4

7.3 × 10−4

5.6 × 10−4

2.7 × 10−3

2.7 × 10−4

1.3 × 10−3

2.7 × 10−4

1.3 × 10−3

6.9 × 10−5

3.3 × 10−4

2.0 × 10−4

9.5 × 10−4

3.2 × 10−4

1.5 × 10−3

238

Uc

1.3 × 10−4

6.2 × 10−4

4.8 × 10−4

2.3 × 10−3

2.3 × 10−4

1.1 × 10−3

2.3 × 10−4

1.1 × 10−3

5.9 × 10−5

2.8 × 10−4

1.7 × 10−4

8.1 × 10−4

2.7 × 10−4

1.3 × 10−3

239

Pu

1.9 × 10−3

9.2 × 10−3

6.8 × 10−3

3.3 × 10−2

3.1 × 10−3

1.5 × 10−2

3.3 × 10−3

1.6 × 10−2

7.9 × 10−4

3.8 × 10−3

2.5 × 10−3

1.2 × 10−2

3.9 × 10−3

1.9 × 10−2

240

Pu

1.9 × 10−3

9.2 × 10−3

6.8 × 10−3

3.3 × 10−2

3.1 × 10−3

1.5 × 10−2

3.3 × 10−3

1.6 × 10−2

7.9 × 10−4

3.8 × 10−3

2.5 × 10−3

1.2 × 10−2

3.9 × 10−3

1.9 × 10−2

241

Am

1.6 × 10−3

7.7 × 10−3

5.7 × 10−3

2.7 × 10−2

2.6 × 10−3

1.3 × 10−2

2.8 × 10−3

1.3 × 10−2

6.6 × 10−4

3.2 × 10−3

2.1 × 10−3

1.0 × 10−2

3.3 × 10−3

1.6 × 10−2a

The world-average value is based on a world-average population density given in table 3 together with a world-average consumption rate for terrestrial foods (table 7).

b

For 3H the calculated doses include a contribution from HTO and OBT as discussed in section III.A.3.

c

For these radionuclides the calculated doses include a contribution from the ingrowth of progeny (see appendix for details of the progeny included).

Table 27. Local and regional components of collective dose for discharges to atmosphere for inland nuclear sites
These collective doses are based on the population distributions out to 1,500 km for inland nuclear sites given in table 4 for the regions shown in figure II. They apply to inland nuclear sites only. Because there were
no inland operating nuclear power plants in Africa or West Asia at the time of analysis, results are not given for these regions

Radionuclide

Collective doses integrated to 100 years from a year’s continuous discharge at a rate of 1 Bq/s (manSv)
Asia and Pacific
Local

EuropeRegional

Local

1.2 × 10

3.3 × 10C

9.2 × 10−6

35

S

41

Latin America
Regional

Local

3.4 × 10

1.6 × 10

1.6 × 10−5

2.3 × 10−6

2.0 × 10−5

3.1 × 10−5Ar

4.6 × 10−9

54

Mn

58

North America

Regional

Local

2.8 × 10

2.4 × 10

6.7 × 10−6

2.1 × 10−6

9.4 × 10−6

2.5 × 10−5

1.1 × 10−14

1.1 × 10−9

3.3 × 10−6

5.4 × 10−6Co

7.8 × 10−6

60

Co

65

Zn

b

H

14

3

World averagea

Regional

Local

2.2 × 10

1.1 × 10−6

8.1 × 10−6

4.8 × 10−15

1.0 × 10−6

1.2 × 10−5

2.8 × 10−4
9.2 × 10−5

−7

Regional

6.7 × 10−8

2.9 × 10

1.1 × 10−7

1.5 × 10−6

2.8 × 10−6

2.2 × 10−6

5.2 × 10−6

4.0 × 10−6

8.1 × 10−6

1.5 × 10−5

6.3 × 10−6

1.4 × 10−5

1.1 × 10−9

8.3 × 10−16

7.4 × 10−10

2.1 × 10−15

1.1 × 10−9

3.9 × 10−15

2.9 × 10−6

8.4 × 10−7

4.3 × 10−7

7.0 × 10−7

1.3 × 10−6

8.4 × 10−7

1.9 × 10−6

2.7 × 10−6

7.3 × 10−6

2.3 × 10−6

1.2 × 10−6

2.0 × 10−6

3.6 × 10−6

2.1 × 10−6

4.7 × 10−6

4.6 × 10−4

1.1 × 10−4

3.1 × 10−4

1.0 × 10−4

5.2 × 10−5

9.2 × 10−5

1.7 × 10−4

8.4 × 10−5

1.9 × 10−4

1.5 × 10−4

4.2 × 10−5

1.2 × 10−4

3.7 × 10−5

1.9 × 10−5

3.7 × 10−5

6.8 × 10−5

2.9 × 10−5

6.5 × 10−5

−7

−8

−7

−8

−8

−8

−8

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 83

230

Collective doses integrated to 100 years from a year’s continuous discharge at a rate of 1 Bq/s (manSv)
Asia and Pacific

EuropeLatin America

North America

World averagea

Local

Regional

Local

Regional

Local

Regional

Local

Regional

Local

Regional

85Kr

1.0 × 10−10

2.8 × 10−10

2.5 × 10−11

1.2 × 10−10

2.5 × 10−11

2.2 × 10−11

1.7 × 10−11

5.1 × 10−11

2.5 × 10−11

9.4 × 10−11

90

Src

7.7 × 10−4

1.3 × 10−3

2.6 × 10−4

7.2 × 10−4

1.9 × 10−4

9.9 × 10−5

1.7 × 10−4

3.0 × 10−4

2.0 × 10−4

4.5 × 10−4

106

Ruc

3.8 × 10−5

6.1 × 10−5

1.4 × 10−5

4.0 × 10−5

1.3 × 10−5

6.6 × 10−6

1.2 × 10−5

2.2 × 10−5

1.1 × 10−5

2.4 × 10−5129I

1.4 × 10−3

2.2 × 10−3

3.8 × 10−4

1.1 × 10−3

3.1 × 10−4

1.6 × 10−4

2.4 × 10−4

4.3 × 10−4

3.3 × 10−4

7.5 × 10−4131I

3.4 × 10−5

4.3 × 10−5

1.1 × 10−5

2.3 × 10−5

8.2 × 10−6

3.2 × 10−6

6.7 × 10−6

9.6 × 10−6

8.5 × 10−6

1.5 × 10−5

133

Xe

1.2 × 10−9

2.2 × 10−9

3.0 × 10−10

9.1 × 10−10

2.9 × 10−10

1.7 × 10−10

1.9 × 10−10

4.0 × 10−10

2.9 × 10−10

7.4 × 10−10

135

Xe

6.3 × 10−9

5.5 × 10−10

1.6 × 10−9

2.5 × 10−10

1.5 × 10−9

4.3 × 10−11

1.0 × 10−9

1.1 × 10−10

1.5 × 10−9

2.0 × 10−10

138

Xec

1.4 × 10−11

5.8 × 10−31

3.5 × 10−12

2.6 × 10−31

3.5 × 10−12

4.5 × 10−32

2.3 × 10−12

1.1 × 10−31

3.5 × 10−12

2.1 × 10−31

134

Cs

2.6 × 10−4

4.3 × 10−4

8.4 × 10−5

2.3 × 10−4

7.4 × 10−5

3.8 × 10−5

6.2 × 10−5

1.1 × 10−4

6.9 × 10−5

1.6 × 10−4

137

Csc

3.0 × 10−4

4.9 × 10−4

9.1 × 10−5

2.5 × 10−4

8.2 × 10−5

4.2 × 10−5

6.5 × 10−5

1.2 × 10−4

7.8 × 10−5

1.8 × 10−4

210

Pb

2.5 × 10−3

4.0 × 10−3

6.9 × 10−4

1.9 × 10−3

5.4 × 10−4

2.8 × 10−4

4.2 × 10−4

7.7 × 10−4

5.9 × 10−4

1.3 × 10−3

210

Po

3.7 × 10−3

6.0 × 10−3

1.2 × 10−3

3.3 × 10−3

9.7 × 10−4

4.9 × 10−4

8.2 × 10−4

1.5 × 10−3

9.6 × 10−4

2.1 × 10−3

222

Rnc

3.0 × 10−6

4.7 × 10−6

7.4 × 10−7

2.0 × 10−6

7.3 × 10−7

3.6 × 10−7

4.8 × 10−7

8.7 × 10−7

7.3 × 10−7

1.6 × 10−6

226

Ra

3.6 × 10−3

5.8 × 10−3

9.7 × 10−4

2.7 × 10−3

7.9 × 10−4

4.1 × 10−4

5.9 × 10−4

1.1 × 10−3

8.5 × 10−4

1.9 × 10−3

230

Th

4.4 × 10−3

7.1 × 10−3

1.1 × 10−3

3.0 × 10−3

1.0 × 10−3

5.4 × 10−4

7.1 × 10−4

1.3 × 10−3

1.1 × 10−3

2.4 × 10−3

232

Thc

2.2 × 10−2

3.6 × 10−2

5.6 × 10−3

1.6 × 10−2

5.3 × 10−3

2.7 × 10−3

3.6 × 10−3

6.7 × 10−3

5.4 × 10−3

1.2 × 10−2234

U

1.2 × 10−3

1.9 × 10−3

3.1 × 10−4

8.6 × 10−4

2.9 × 10−4

1.5 × 10−4

2.1 × 10−4

3.8 × 10−4

3.0 × 10−4

6.7 × 10−4

238

Uc

1.0 × 10−3

1.7 × 10−3

2.7 × 10−4

7.4 × 10−4

2.5 × 10−4

1.3 × 10−4

1.8 × 10−4

3.3 × 10−4

2.5 × 10−4

5.7 × 10−4

239

Pu

1.5 × 10−2

2.4 × 10−2

3.6 × 10−3

1.0 × 10−2

3.5 × 10−3

1.8 × 10−3

2.4 × 10−3

4.3 × 10−3

3.6 × 10−3

8.0 × 10−3

240

Pu

1.5 × 10−2

2.4 × 10−2

3.6 × 10−3

1.0 × 10−2

3.5 × 10−3

1.8 × 10−3

2.4 × 10−3

4.3 × 10−3

3.6 × 10−3

8.0 × 10−3

241

Am

1.2 × 10−2

2.0 × 10−2

3.0 × 10−3

8.4 × 10−3

3.0 × 10−3

1.5 × 10−3

2.0 × 10−3

3.6 × 10−3

3.0 × 10−3

6.8 × 10−3aThe world-average value is based on a world average population density given in table 4 together with a world-average consumption rate for terrestrial foods (table 7).

b

For 3H the calculated doses include a contribution from HTO and OBT as discussed in section III.A.3.

c

For these radionuclides the calculated doses include a contribution from the ingrowth of progeny (see appendix for details).

84 UNSCEAR 2016 REPORTRadionuclideTable 28. Local and regional components of collective dose for discharges to atmosphere for coastal nuclear sites
These collective doses are based on the population distributions out to 1 500 km for coastal nuclear sites given in table 4 for the regions shown in figure II. They apply to coastal nuclear sites only. Because there
were no coastal operating nuclear power plants in West Asia at the time of analysis, results are not given for this region

Collective doses integrated to 100 years from a year’s continuous discharge at a rate of 1 Bq/s (manSv)

Radionuclide

AfricaLocal

Asia and Pacific
Local

Regional

Local

2.3 × 10

6.9 × 10

5.3 × 10

1.6 × 10C

1.7 × 10−6

2.8 × 10−7

4.1 × 10−635

S

2.8 × 10−6

4.3 × 10−741Ar

9.6 × 10−10

54

Mn

58

Latin America

Regional

Local

2.5 × 10

1.2 × 10

7.7 × 10−6

1.6 × 10−6

8.6 × 10−6

1.5 × 10−5

6.1 × 10−17

2.0 × 10−9

6.1 × 10−7

9.7 × 10−8Co

1.4 × 10−6

60

Co

65

North America

Regional

Local

2.2 × 10

6.1 × 10

4.8 × 10−6

1.6 × 10−6

6.7 × 10−6

1.8 × 10−5

4.8 × 10−15

8.1 × 10−10

1.5 × 10−6

2.6 × 10−6

2.2 × 10−7

3.4 × 10−6

4.8 × 10−5

7.7 × 10−6Zn

1.3 × 10−5

85

Kr

90

World averagea

Regional

Local

3.4 × 10

3.0 × 10−6

6.3 × 10−6

3.5 × 10−15

7.4 × 10−7

5.9 × 10−6

1.2 × 10−4

2.1 × 10−6

2.1 × 10−11

Src

106

b

H

14

Regional

6.3 × 10−8

3.6 × 10

1.1 × 10−7

2.3 × 10−6

2.7 × 10−6

2.7 × 10−6

5.0 × 10−6

1.1 × 10−5

1.3 × 10−5

1.4 × 10−5

7.7 × 10−6

1.4 × 10−5

8.7 × 10−10

3.4 × 10−15

1.2 × 10−9

2.2 × 10−15

1.4 × 10−9

3.6 × 10−15

2.1 × 10−6

6.6 × 10−7

1.2 × 10−6

1.1 × 10−6

1.2 × 10−6

1.0 × 10−6

1.8 × 10−6

1.9 × 10−6

5.3 × 10−6

1.8 × 10−6

3.2 × 10−6

3.1 × 10−6

3.4 × 10−6

2.6 × 10−6

4.5 × 10−6

2.2 × 10−4

7.9 × 10−5

2.2 × 10−4

7.9 × 10−5

1.4 × 10−4

1.4 × 10−4

1.6 × 10−4

1.0 × 10−4

1.8 × 10−4

4.0 × 10−5

7.2 × 10−5

3.0 × 10−5

8.4 × 10−5

2.9 × 10−5

5.1 × 10−5

5.8 × 10−5

6.5 × 10−5

3.6 × 10−5

6.4 × 10−5

6.5 × 10−12

4.5 × 10−11

1.4 × 10−10

1.8 × 10−11

8.5 × 10−11

2.0 × 10−11

5.5 × 10−11

2.6 × 10−11

4.8 × 10−11

3.1 × 10−11

9.3 × 10−11

1.4 × 10−4

2.2 × 10−5

3.4 × 10−4

6.1 × 10−4

1.9 × 10−4

5.2 × 10−4

1.5 × 10−4

2.7 × 10−4

2.6 × 10−4

2.9 × 10−4

2.4 × 10−4

4.4 × 10−4

Ruc

6.2 × 10−6

9.9 × 10−7

1.7 × 10−5

3.0 × 10−5

1.0 × 10−5

2.9 × 10−5

1.0 × 10−5

1.8 × 10−5

1.9 × 10−5

2.1 × 10−5

1.3 × 10−5

2.4 × 10−5129

I

2.5 × 10−4

4.0 × 10−5

6.1 × 10−4

1.1 × 10−3

2.7 × 10−4

7.7 × 10−4

2.4 × 10−4

4.3 × 10−4

3.7 × 10−4

4.2 × 10−4

4.0 × 10−4

7.3 × 10−4131I

6.2 × 10−6

6.4 × 10−7

1.5 × 10−5

2.0 × 10−5

7.6 × 10−6

1.7 × 10−5

6.4 × 10−6

9.4 × 10−6

1.1 × 10−5

9.4 × 10−6

1.0 × 10−5

1.4 × 10−5

133

Xec

2.5 × 10−10

3.8 × 10−11

5.3 × 10−10

1.0 × 10−9

2.1 × 10−10

6.6 × 10−10

2.3 × 10−10

4.7 × 10−10

3.0 × 10−10

3.8 × 10−10

3.6 × 10−10

7.1 × 10−10

135

Xe

1.3 × 10−9

3.2 × 10−12

2.8 × 10−9

2.5 × 10−10

1.1 × 10−9

1.8 × 10−10

1.2 × 10−9

1.7 × 10−10

1.6 × 10−9

1.1 × 10−10

1.9 × 10−9

1.8 × 10−10

138

Xec

3.0 × 10−12

3.3 × 10−33

6.3 × 10−12

2.6 × 10−31

2.5 × 10−12

1.9 × 10−31

2.7 × 10−12

1.8 × 10−31

3.6 × 10−12

1.2 × 10−31

4.2 × 10−12

1.9 × 10−31

134

Cs

4.6 × 10−5

7.4 × 10−6

1.2 × 10−4

2.1 × 10−4

6.0 × 10−5

1.7 × 10−4

5.8 × 10−5

1.0 × 10−4

9.7 × 10−5

1.1 × 10−4

8.4 × 10−5

1.5 × 10−4

137

Csc

5.5 × 10−5

8.9 × 10−6

1.3 × 10−4

2.4 × 10−4

6.5 × 10−5

1.8 × 10−4

6.4 × 10−5

1.1 × 10−4

1.0 × 10−4

1.2 × 10−4

9.5 × 10−5

1.7 × 10−4

210

Pb

4.7 × 10−4

7.6 × 10−5

1.1 × 10−3

2.0 × 10−3

4.9 × 10−4

1.4 × 10−3

4.2 × 10−4

7.5 × 10−4

6.6 × 10−4

7.4 × 10−4

7.2 × 10−4

1.3 × 10−3

210

Po

6.9 × 10−4

1.1 × 10−4

1.6 × 10−3

2.9 × 10−3

8.7 × 10−4

2.4 × 10−3

7.6 × 10−4

1.3 × 10−3

1.3 × 10−3

1.4 × 10−3

1.2 × 10−3

2.1 × 10−3

222

Rnc

6.2 × 10−7

7.5 × 10−8

1.3 × 10−6

2.2 × 10−6

5.3 × 10−7

1.4 × 10−6

5.7 × 10−7

1.1 × 10−6

7.6 × 10−7

8.5 × 10−7

8.9 × 10−7

1.5 × 10−6

226

Ra

6.8 × 10−4

1.1 × 10−4

1.6 × 10−3

2.8 × 10−3

6.9 × 10−4

1.9 × 10−3

6.2 × 10−4

1.1 × 10−3

9.3 × 10−4

1.0 × 10−3

1.0 × 10−3

1.9 × 10−3

3

−8

−9

−8

−7

−8

−7

−8

−8

−8

−8

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 85

Regional

EuropeAfrica

Asia and Pacific

EuropeLatin America

North America

World averagea

Local

Regional

Local

Regional

Local

Regional

Local

Regional

Local

Regional

Local

Regional

230

Th

9.0 × 10−4

1.5 × 10−4

1.9 × 10−3

3.5 × 10−3

7.8 × 10−4

2.2 × 10−3

8.2 × 10−4

1.5 × 10−3

1.1 × 10−3

1.2 × 10−3

1.3 × 10−3

2.3 × 10−3

232

Thc

4.6 × 10−3

7.3 × 10−4

9.8 × 10−3

1.8 × 10−2

4.0 × 10−3

1.1 × 10−2

4.2 × 10−3

7.4 × 10−3

5.7 × 10−3

6.4 × 10−3

6.6 × 10−3

1.2 × 10−2234

U

2.4 × 10−4

3.9 × 10−5

5.3 × 10−4

9.5 × 10−4

2.2 × 10−4

6.3 × 10−4

2.3 × 10−4

4.1 × 10−4

3.2 × 10−4

3.7 × 10−4

3.6 × 10−4

6.5 × 10−4

238

Uc

2.1 × 10−4

3.3 × 10−5

4.5 × 10−4

8.1 × 10−4

1.9 × 10−4

5.3 × 10−4

2.0 × 10−4

3.5 × 10−4

2.8 × 10−4

3.1 × 10−4

3.1 × 10−4

5.5 × 10−4

239

Pu

3.0 × 10−3

4.9 × 10−4

6.4 × 10−3

1.2 × 10−2

2.6 × 10−3

7.3 × 10−3

2.8 × 10−3

4.9 × 10−3

3.7 × 10−3

4.2 × 10−3

4.3 × 10−3

7.9 × 10−3

240

Pu

3.0 × 10−3

4.9 × 10−4

6.4 × 10−3

1.2 × 10−2

2.6 × 10−3

7.3 × 10−3

2.8 × 10−3

4.9 × 10−3

3.7 × 10−3

4.2 × 10−3

4.3 × 10−3

7.9 × 10−3

241

Am

2.5 × 10−3

4.1 × 10−4

5.4 × 10−3

9.7 × 10−3

2.2 × 10−3

6.1 × 10−3

2.3 × 10−3

4.1 × 10−3

3.1 × 10−3

3.5 × 10−3

3.6 × 10−3

6.6 × 10−3aThe world-average value is based on a world average population density given in table 3 together with a world-average consumption rate for terrestrial foods (table 7).

b

For 3H the calculated doses include a contribution from HTO and OBT as discussed in section III.A.3.

c

For these radionuclides the calculated doses include a contribution from the ingrowth of progeny (see appendix for details).

86 UNSCEAR 2016 REPORT

Collective doses integrated to 100 years from a year’s continuous discharge at a rate of 1 Bq/s (manSv)

Radionuclide

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 87

Table 29. Local and regional components of collective dose for discharges to atmosphere for low
population density sites
These collective dose estimates are for locations with a low population density out to 1,500 km and are based on a population
density of 5 km−2. They apply to the world as a whole and are intended for use for uranium mines and mill tailings sites

Radionuclide

Collective dose integrated to 100 years from a year’s continuous discharge
at a rate of 1 Bq/s (man Sv)
Local component

Regional componentHa

1.0 × 10−9

8.4 × 10−914C

7.5 × 10−8

3.8 × 10−735

S

2.2 × 10−7

1.0 × 10−6

41Ar

3.8 × 10−11

2.0 × 10−1654Mn

2.9 × 10−8

1.4 × 10−758

Co

7.3 × 10−8

3.4 × 10−760

Co

2.9 × 10−6

1.4 × 10−565Zn

1.0 × 10−6

4.7 × 10−685

Kr

8.6 × 10−13

7.2 × 10−12

90

Srb

6.8 × 10−6

3.2 × 10−5

106

Rub

3.7 × 10−7

1.8 × 10−6129I

1.1 × 10−5

5.4 × 10−5131I

2.9 × 10−7

1.0 × 10−6

133

Xeb

1.0 × 10−11

5.1 × 10−11

135

Xe

5.3 × 10−11

1.1 × 10−11

138

Xeb

1.2 × 10−13

1.1 × 10−32

134

Cs

2.4 × 10−6

1.1 × 10−5

137

Csb

2.7 × 10−6

1.3 × 10−5

210

Pb

2.0 × 10−5

9.6 × 10−5

210

Po

3.3 × 10−5

1.5 × 10−4

222

Rnb

2.5 × 10−8

1.1 × 10−7

226

Ra

2.9 × 10−5

1.4 × 10−4

230

Th

3.6 × 10−5

1.7 × 10−4

232

Thb

1.9 × 10−4

8.9 × 10−4

234

U

1.0 × 10−5

4.8 × 10−5

238

Ub

8.6 × 10−6

4.1 × 10−5

239

Pu

1.2 × 10−4

5.8 × 10−4

240

Pu

1.2 × 10−4

5.8 × 10−4

241

Am

1.0 × 10−4

4.9 × 10−43aFor 3H the calculated doses include a contribution from HTO and OBT as discussed in section III.A.3.

b

For these radionuclides the calculated doses include a contribution from the ingrowth of progeny (see appendix for details).

Values are for small and large rivers situated in the regions shown in figure II. The results for large rivers are also assumed to apply for lakes

Collective doses integrated to 100 years from a year’s continuous discharge at a rate of 1 Bq/s (man Sv)

Radionuclide

Africa
Small

Large

Small

Europe

Large

Small

Latin America
Large

Small

North America

Large

Small

West Asia

Large

Small

World averagea

Large

b

H

1.9 × 10

1.9 × 10

1.9 × 10

1.9 × 10

1.9 × 10

1.9 × 10

1.9 × 10

1.9 × 10

1.9 × 10

1.9 × 10

1.9 × 1014

C

2.3 × 10−3

1.2 × 10−3

2.3 × 10−3

1.2 × 10−3

2.3 × 10−3

1.2 × 10−3

2.3 × 10−3

1.2 × 10−3

2.3 × 10−3

1.2 × 10−335

S

7.4 × 10−6

4.5 × 10−6

7.4 × 10−6

4.8 × 10−6

7.4 × 10−6

4.6 × 10−6

7.4 × 10−6

4.3 × 10−6

7.4 × 10−654

Mn

1.5 × 10−6

9.2 × 10−7

1.5 × 10−6

9.8 × 10−7

1.5 × 10−6

9.4 × 10−7

1.5 × 10−6

8.8 × 10−758

Co

1.6 × 10−6

1.3 × 10−6

1.6 × 10−6

1.4 × 10−6

1.6 × 10−6

1.3 × 10−6

1.6 × 10−660

Co

7.2 × 10−6

6.4 × 10−6

7.2 × 10−6

6.8 × 10−6

7.2 × 10−6

6.5 × 10−665Zn

1.4 × 10−4

6.1 × 10−5

1.4 × 10−4

6.1 × 10−5

1.4 × 10−4

90

Src

7.2 × 10−5

1.0 × 10−4

7.2 × 10−5

1.2 × 10−4

106

Ruc

1.4 × 10−5

1.2 × 10−5

1.4 × 10−5129I

3.1 × 10−4

3.8 × 10−4131I

5.7 × 10−6

134

Cs

137

Small

Large

1.9 × 10−7

1.9 × 10

1.9 × 10−7

2.3 × 10−3

1.4 × 10−3

2.3 × 10−3

1.2 × 10−3

5.2 × 10−6

7.4 × 10−6

1.7 × 10−5

7.4 × 10−6

4.8 × 10−6

1.5 × 10−6

1.1 × 10−6

1.5 × 10−6

3.6 × 10−6

1.5 × 10−6

9.7 × 10−7

1.3 × 10−6

1.6 × 10−6

1.4 × 10−6

1.6 × 10−6

3.1 × 10−6

1.6 × 10−6

1.4 × 10−6

7.2 × 10−6

6.1 × 10−6

7.2 × 10−6

7.2 × 10−6

7.2 × 10−6

2.2 × 10−5

7.2 × 10−6

6.7 × 10−6

6.1 × 10−5

1.4 × 10−4

6.0 × 10−5

1.4 × 10−4

6.2 × 10−5

1.4 × 10−4

9.2 × 10−5

1.4 × 10−4

6.1 × 10−5

7.2 × 10−5

1.1 × 10−4

7.2 × 10−5

8.8 × 10−5

7.2 × 10−5

1.4 × 10−4

7.2 × 10−5

9.8 × 10−4

7.2 × 10−5

1.2 × 10−4

1.2 × 10−5

1.4 × 10−5

1.2 × 10−5

1.4 × 10−5

1.2 × 10−5

1.4 × 10−5

1.2 × 10−5

1.4 × 10−5

1.5 × 10−5

1.4 × 10−5

1.2 × 10−5

3.1 × 10−4

4.5 × 10−4

3.1 × 10−4

4.0 × 10−4

3.1 × 10−4

3.4 × 10−4

3.1 × 10−4

5.3 × 10−4

3.1 × 10−4

3.3 × 10−3

3.1 × 10−4

4.4 × 10−4

5.3 × 10−6

5.7 × 10−6

5.4 × 10−6

5.7 × 10−6

5.4 × 10−6

5.7 × 10−6

5.3 × 10−6

5.7 × 10−6

5.5 × 10−6

5.7 × 10−6

9.1 × 10−6

5.7 × 10−6

5.4 × 10−6

3.5 × 10−4

7.8 × 10−5

3.5 × 10−4

8.7 × 10−5

3.5 × 10−4

8.1 × 10−5

3.5 × 10−4

7.1 × 10−5

3.5 × 10−4

9.8 × 10−5

3.5 × 10−4

4.9 × 10−4

3.5 × 10−4

8.5 × 10−5

Csc

2.4 × 10−4

5.5 × 10−5

2.4 × 10−4

6.3 × 10−5

2.4 × 10−4

5.7 × 10−5

2.4 × 10−4

5.0 × 10−5

2.4 × 10−4

7.2 × 10−5

2.4 × 10−4

3.9 × 10−4

2.4 × 10−4

6.1 × 10−5

210

Pb

1.3 × 10−3

1.2 × 10−3

1.3 × 10−3

1.3 × 10−3

1.3 × 10−3

1.2 × 10−3

1.3 × 10−3

1.2 × 10−3

1.3 × 10−3

1.3 × 10−3

1.3 × 10−3

2.5 × 10−3

1.3 × 10−3

1.3 × 10−3

210

Po

2.3 × 10−3

2.1 × 10−3

2.3 × 10−3

2.1 × 10−3

2.3 × 10−3

2.1 × 10−3

2.3 × 10−3

2.1 × 10−3

2.3 × 10−3

2.1 × 10−3

2.3 × 10−3

2.3 × 10−3

2.3 × 10−3

2.1 × 10−3

226

Ra

4.9 × 10−4

5.9 × 10−4

4.9 × 10−4

6.6 × 10−4

4.9 × 10−4

6.1 × 10−4

4.9 × 10−4

5.4 × 10−4

4.9 × 10−4

7.5 × 10−4

4.9 × 10−4

3.8 × 10−3

4.9 × 10−4

6.5 × 10−4

230

Th

2.0 × 10−4

2.0 × 10−4

2.0 × 10−4

2.0 × 10−4

2.0 × 10−4

2.0 × 10−4

2.0 × 10−4

2.0 × 10−4

2.0 × 10−4

2.0 × 10−4

2.0 × 10−4

2.7 × 10−4

2.0 × 10−4

2.0 × 10−4

232

Thc

1.5 × 10−3

1.6 × 10−3

1.5 × 10−3

1.6 × 10−3

1.5 × 10−3

1.6 × 10−3

1.5 × 10−3

1.5 × 10−3

1.5 × 10−3

1.7 × 10−3

1.5 × 10−3

4.3 × 10−3

1.5 × 10−3

1.6 × 10−3

234

U

4.7 × 10−5

5.1 × 10−5

4.7 × 10−5

5.3 × 10−5

4.7 × 10−5

5.1 × 10−5

4.7 × 10−5

4.9 × 10−5

4.7 × 10−5

5.7 × 10−5

4.7 × 10−5

1.7 × 10−4

4.7 × 10−5

5.3 × 10−5

238

Uc

4.6 × 10−5

5.0 × 10−5

4.6 × 10−5

5.2 × 10−5

4.6 × 10−5

5.1 × 10−5

4.6 × 10−5

4.8 × 10−5

4.6 × 10−5

5.5 × 10−5

4.6 × 10−5

1.6 × 10−4

4.6 × 10−5

5.2 × 10−5

239

Pu

2.3 × 10−4

2.2 × 10−4

2.3 × 10−4

2.2 × 10−4

2.3 × 10−4

2.2 × 10−4

2.3 × 10−4

2.2 × 10−4

2.3 × 10−4

2.2 × 10−4

2.3 × 10−4

3.3 × 10−4

2.3 × 10−4

2.2 × 10−4

240

Pu

2.3 × 10−4

2.2 × 10−4

2.3 × 10−4

2.2 × 10−4

2.3 × 10−4

2.2 × 10−4

2.3 × 10−4

2.2 × 10−4

2.3 × 10−4

2.2 × 10−4

2.3 × 10−4

3.3 × 10−4

2.3 × 10−4

2.2 × 10−4

241

Am

3.1 × 10−4

1.8 × 10−4

3.1 × 10−4

1.8 × 10−4

3.1 × 10−4

1.8 × 10−4

3.1 × 10−4

1.8 × 10−4

3.1 × 10−4

1.9 × 10−4

3.1 × 10−4

3.1 × 10−4

3.1 × 10−4

1.8 × 10−43aAsia and Pacific

−7

−7

−7

−7

−7

−7

−7

−7

−7

−7

−7

−7

The world-average collective dose is calculated using world-average values for irrigation (tables 11, 12 and 17) (note that the catch data for unit river length is the same for all regions and the world-average).
For 3H the calculated doses include a contribution from HTO and OBT as discussed in section III.A.3.
c
For these radionuclides the calculated doses include a contribution from the ingrowth of progeny (see appendix for details).
b

88 UNSCEAR 2016 REPORT

Table 30. Collective dose for discharges to small and large rivers

Table 31. Local and regional components of collective dose for discharges to a marine environment
These results are for discharges to a marine environment for the regions shown in figure II

Collective dose integrated to 100 years from a year’s continuous discharge at a rate of 1 Bq/s (man Sv)

Radionuclide

AfricaLocal

3

Regional

Local

Regional

Local
−13

Regional
−14

Local
−12

Regional
−14

Local
−12

West Asia

Regional
−14

Local
−12

World averagea

Regional
−14

Local
−12

Regional

5.8 × 10

6.0 × 10

4.7 × 10

1.4 × 10

2.8 × 10

1.1 × 10

1.8 × 10

1.0 × 10

5.7 × 10

2.2 × 10

3.1 × 10−14

14

5.5 × 10−7

3.3 × 10−8

2.2 × 10−6

4.0 × 10−8

3.9 × 10−7

3.2 × 10−8

9.2 × 10−7

1.9 × 10−8

6.9 × 10−7

1.2 × 10−8

6.5 × 10−7

3.9 × 10−8

1.4 × 10−6

2.1 × 10−8S

4.9 × 10−11

5.0 × 10−13

2.7 × 10−10

6.6 × 10−13

3.9 × 10−11

4.9 × 10−13

9.7 × 10−11

3.0 × 10−13

6.3 × 10−11

2.0 × 10−13

5.4 × 10−11

5.9 × 10−13

1.8 × 10−10

3.6 × 10−1354

Mn

5.1 × 10−7

1.5 × 10−9

3.9 × 10−6

5.2 × 10−9

4.5 × 10−7

1.4 × 10−9

1.2 × 10−6

1.8 × 10−9

7.2 × 10−7

1.1 × 10−9

5.1 × 10−7

1.7 × 10−9

2.6 × 10−6

3.3 × 10−958

2.5 × 10−7

3.7 × 10−10

1.6 × 10−6

9.9 × 10−10

1.9 × 10−7

3.4 × 10−10

5.8 × 10−7

3.9 × 10−10

3.8 × 10−7

2.5 × 10−10

2.8 × 10−7

4.2 × 10−10

1.1 × 10−6

6.1 × 10−1060

1.4 × 10−6

7.6 × 10−9

8.8 × 10−6

2.0 × 10−8

1.0 × 10−6

7.0 × 10−9

3.1 × 10−6

8.0 × 10−9

2.1 × 10−6

5.2 × 10−9

1.5 × 10−6

8.7 × 10−9

5.8 × 10−6

1.3 × 10−865Zn

2.7 × 10−5

3.1 × 10−8

1.0 × 10−4

1.1 × 10−7

1.2 × 10−5

1.7 × 10−8

5.3 × 10−5

5.5 × 10−8

4.7 × 10−5

4.8 × 10−8

3.5 × 10−5

4.0 × 10−8

7.0 × 10−5

7.2 × 10−8

90

Srb

7.6 × 10−9

2.4 × 10−10

4.1 × 10−8

3.3 × 10−10

5.6 × 10−9

2.3 × 10−10

1.5 × 10−8

1.5 × 10−10

1.0 × 10−8

9.8 × 10−11

8.6 × 10−9

2.8 × 10−10

2.7 × 10−8

1.8 × 10−10

106

Rub

5.7 × 10−8

8.9 × 10−11

4.1 × 10−7

5.1 × 10−10

4.7 × 10−8

7.7 × 10−11

1.4 × 10−7

1.7 × 10−10

8.4 × 10−8

1.1 × 10−10

5.9 × 10−8

9.6 × 10−11

2.7 × 10−7

3.3 × 10−10

129I

3.4 × 10−8

2.8 × 10−9

1.6 × 10−7

3.3 × 10−9

3.0 × 10−8

2.7 × 10−9

5.6 × 10−8

1.6 × 10−9

3.6 × 10−8

1.0 × 10−9

3.8 × 10−8

3.3 × 10−9

1.0 × 10−7

1.7 × 10−9131I

2.4 × 10−10

6.1 × 10−13

1.1 × 10−9

7.2 × 10−13

2.1 × 10−10

6.0 × 10−13

3.9 × 10−10

3.4 × 10−13

2.5 × 10−10

2.2 × 10−13

2.7 × 10−10

7.1 × 10−13

7.1 × 10−10

3.8 × 10−13

134

Cs

5.9 × 10−8

3.9 × 10−9

2.1 × 10−7

4.6 × 10−9

4.6 × 10−8

3.9 × 10−9

8.7 × 10−8

2.2 × 10−9

6.3 × 10−8

1.4 × 10−9

7.0 × 10−8

4.6 × 10−9

1.4 × 10−7

2.4 × 10−9

137

Csb

4.1 × 10−8

3.6 × 10−9

1.5 × 10−7

4.1 × 10−9

3.2 × 10−8

3.5 × 10−9

6.0 × 10−8

2.0 × 10−9

4.4 × 10−8

1.3 × 10−9

4.9 × 10−8

4.2 × 10−9

9.4 × 10−8

2.2 × 10−9

210

Pbb

2.5 × 10−3

1.1 × 10−5

1.2 × 10−2

2.9 × 10−5

1.4 × 10−3

8.9 × 10−6

5.3 × 10−3

1.3 × 10−5

4.2 × 10−3

1.0 × 10−5

3.2 × 10−3

1.3 × 10−5

7.9 × 10−3

1.8 × 10−5

210

Po

7.6 × 10−4

2.6 × 10−6

3.8 × 10−3

5.0 × 10−6

4.6 × 10−4

2.4 × 10−6

1.6 × 10−3

2.2 × 10−6

1.2 × 10−3

1.6 × 10−6

9.2 × 10−4

3.1 × 10−6

2.5 × 10−3

2.9 × 10−6

226

Rab

2.6 × 10−3

1.2 × 10−5

1.2 × 10−2

3.2 × 10−5

1.4 × 10−3

9.7 × 10−6

5.3 × 10−3

1.4 × 10−5

4.3 × 10−3

1.1 × 10−5

3.2 × 10−3

1.5 × 10−5

8.0 × 10−3

2.0 × 10−5

230

Th

8.7 × 10−6

3.5 × 10−7

3.8 × 10−5

4.4 × 10−7

5.8 × 10−6

3.4 × 10−7

1.6 × 10−5

2.1 × 10−7

1.2 × 10−5

1.4 × 10−7

1.0 × 10−5

4.1 × 10−7

2.5 × 10−5

2.4 × 10−7

232

Thb

3.1 × 10−5

7.3 × 10−7

1.4 × 10−4

1.0 × 10−6

1.8 × 10−5

7.0 × 10−7

5.9 × 10−5

4.7 × 10−7

4.7 × 10−5

3.2 × 10−7

3.8 × 10−5

8.6 × 10−7

9.0 × 10−5

5.5 × 10−7234

U

2.9 × 10−8

1.9 × 10−10

1.9 × 10−7

5.3 × 10−10

2.2 × 10−8

1.8 × 10−10

6.7 × 10−8

2.1 × 10−10

4.4 × 10−8

1.3 × 10−10

3.2 × 10−8

2.2 × 10−10

1.3 × 10−7

3.3 × 10−10

238

Ub

1.7 × 10−7

6.1 × 10−9

7.9 × 10−7

7.9 × 10−9

1.2 × 10−7

5.9 × 10−9

3.2 × 10−7

3.7 × 10−9

2.4 × 10−7

2.4 × 10−9

2.0 × 10−7

7.1 × 10−9

5.2 × 10−7

4.3 × 10−9

239

Pu

1.1 × 10−5

9.0 × 10−8

8.4 × 10−5

2.4 × 10−7

9.9 × 10−6

8.8 × 10−8

2.6 × 10−5

8.9 × 10−8

1.5 × 10−5

5.3 × 10−8

1.1 × 10−5

1.0 × 10−7

5.5 × 10−5

1.5 × 10−7

240

Pu

1.1 × 10−5

9.0 × 10−8

8.4 × 10−5

2.4 × 10−7

9.9 × 10−6

8.8 × 10−8

2.6 × 10−5

8.9 × 10−8

1.5 × 10−5

5.3 × 10−8

1.1 × 10−5

1.0 × 10−7

5.5 × 10−5

1.5 × 10−7

241

Am

4.4 × 10−6

6.3 × 10−8

2.7 × 10−5

1.1 × 10−7

3.3 × 10−6

6.0 × 10−8

9.7 × 10−6

4.8 × 10−8

6.5 × 10−6

3.1 × 10−8

4.9 × 10−6

7.3 × 10−8

1.8 × 10−5

6.6 × 10−8aThe world-average value is calculated using the world-average annual catch of fish, crustacea and molluscs from table 21.

b

For these radionuclides the calculated doses include a contribution from the ingrowth of progeny (see appendix for details).

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 89

3.4 × 10

Co

−14

North America

4.8 × 10Co

−12

Latin America

8.5 × 1035

−14EuropeHC−13Asia and Pacific90 UNSCEAR 2016 REPORTVII. CONCLUSIONS
151. An important aspect of the Committee’s work is the periodic assessment of global and regionalradiation exposures to the public from discharges of radionuclides to the environment. Such studies
require a robust, generic methodology that is defensible and takes into account developments in thefield. The methodology used by the Committee for many years has proved to meet its needs forworldwide exposure assessments but, as previously, before any major evaluation of exposures, themethodology has been reviewed by the Committee to ensure its continued validity. An important factor
for the current review was the decision by the Committee to update its evaluations of human radiation
exposures from all significant types of electrical energy production. Following the review, theCommittee decided to make some changes to parts of the methodology, while retaining other parts thatit felt were still appropriate for its purposes. Previously, the results had often been expressed in terms ofdose per unit of electricity generated but, for flexibility, it was agreed that the results be presented interms of dose per unit of activity discharged.
152. The updated methodology can be used to estimate characteristic individual doses (typical of theaverage person living in the area around the source) and collective doses due to discharges toatmosphere, to freshwater bodies (small and large rivers or a lake) and to the sea. A wide range ofradionuclides are included to enable exposures to be assessed for nuclear and non-nuclear forms ofelectrical energy production. The methodology applies to routine, continuous discharges only and it
cannot be used for accidental releases; nor is it suitable for detailed site-specific assessments of doses torepresentative persons for regulatory purposes. As previously mentioned, local, regional and global
components of collective dose are estimated, as appropriate. However, it is now possible to gain
additional insight for discharges to atmosphere on collective doses within different distance bands fromthe discharge point. Global components of collective dose are now also available for integration timesof 100, 500 and 10,000 years.
153. The methodology now includes factors for population densities and for food consumption rates
that vary with geographical region. The Committee added this detail because non-nuclear power
stations are found throughout the world where population densities and patterns of food consumption
are significantly different from a generic world average. However, the geographical regions adopted arestill very large and the inclusion of such region-specific data does not mean that the methodology issuitable for site-specific assessments. Another addition to the methodology is the inclusion of doses dueto the irrigation of terrestrial foods with fresh water into which radionuclides had been discharged. The
extent and nature of irrigation is very variable throughout the world but, for the purposes of thismethodology, a simplified generic approach has been adopted for estimating exposures due toirrigation.
154. This scientific annex describes the methodology, outlines changes from previous versions anddiscusses its limitations and particular areas of uncertainty. Where possible, the results from applying
the methodology have been compared with those from other methodologies and published studies.
Although the purpose of the other studies would have influenced the developers’ choice of models andparameter values and hence the estimated doses, the comparisons still helped to give confidence that theCommittee’s methodology is fit for its purposes.

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 91

155. The methodology has been implemented in a series of Excel® workbooks to ensure that it istransparent for use by the Committee in any future studies. It should also be relatively easy to update
the methodology using such a system. The workbooks enable the user to obtain information on theimportant exposure pathways and radionuclides to gain insight for the Committee’s work. The
workbooks have been checked and verified by people not involved in their development.
156. The Committee considers that the methodology should also be transparent to the wider community andtherefore, in addition to the information presented here, further detail is provided in electronic attachments
available on the UNSCEAR website (http://www.unscear.org/unscear/en/publications/2016.html). The
Committee is satisfied that the methodology, as implemented in the workbooks, is robust, builds on thestrong position of the previous versions of the methodology and is suitable for assessing worldwide
exposures due to routine discharges of radionuclides to the environment. It can be used to assess—in aconsistent way—exposures due to releases from non-nuclear and nuclear sites of electricity generation
including the related fuel-cycle sites (e.g. uranium mining and milling, nuclear fuel reprocessing and nuclear
power stations that are being decommissioned).

VIII. ACKNOWLEDGEMENTS
The Committee wishes to acknowledge with gratitude the experts directly involved in developing themethodology and the related workbooks, and those who carried out quality control checks, and support
staff in their institutes who assisted them. In particular, the Committee would like to thank: theconsultants, C. Robinson and J. Simmonds; the expert group, who provided valuable oversight andadvice for the work; staff, T. Anderson and K. Jones, from Public Health England in the United
Kingdom, who developed the workbook system and supported development of the methodology; andH. Grogan, who reviewed and checked the workbook system. The views expressed in the scientificannex and related material remain those of the Committee and do not necessarily represent the views ofindividual experts, the United Nations or its Member States.
Expert group
Co-chairs: E. Waller (Canada)
Members: T. Anderson (United Kingdom), L. Anspaugh (United States), H. Grogan (United States),
G. Hirth (Australia), K. Jones (United Kingdom), L. Hubbard (Sweden), R. Michel (Germany),
J. Simmonds (United Kingdom)
Observer: G. Proehl (IAEA)The Committee would also like to acknowledge with gratitude: the staff of the Metadata and SocioEconomics unit of UNEP/DEWA/GRID-GENEVA who analysed the population data around nuclear
power plants; P. Verger and colleagues from WHO for their analyses of food consumption data;
S. Golikov and M. Balonov for reviewing the model for external exposure from deposited material; andM. Tzivaki for conducting some specialized quality checks of the workbooks and their results.

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 93

APPENDIX A. IMPLEMENTATION OF THE METHODOLOGY
A1. The aim of this appendix is to provide more details of how the Committee has implemented themethodology as a set of Excel® workbooks by describing the workbook design (including the end
points considered, the mathematical equations to implement the methodology in the workbooks, andinformation on how the workbooks can be used to assess exposures from different types of discharge),
details of how radioactive progeny have been treated, and quality assurance.

I. WORKBOOK DESIGN
A2. The methodology has been implemented as a series of Excel® workbooks from which dose
calculation factors (i.e. the calculated individual and collective doses from unit discharge ofradionuclides under a set of defined conditions) can be derived. The series includes a workbook foreach environment into which a discharge can be made (i.e. atmosphere, freshwater bodies, and marine
environments); a further workbook summarizes the doses due to discharges into each of the threeenvironments, and another provides dose values for globally circulating radionuclides. Table A1summarizes the various end points that are produced by the workbooks, and how the relevant
populations and pathways are treated.
A3. The workbook for each environment into which a discharge is made comprises a number ofinterlinked worksheets. An initial status worksheet describes the purpose of the workbook and provides
key information about its format and contents, version and quality control. Other worksheets containvalues of the model input parameters (radionuclide-specific ones and others such as habit data);intermediate calculations (e.g. of activity concentrations of radionuclides as a function of distance fordischarges to atmosphere); and output values for the end points (i.e. dose calculation factors).
A4. Discharges to atmosphere. The workbook first calculates activity concentrations of radionuclides
in air at a number of distances from the point of discharge. Deposition rates and activity concentrationsof radionuclides on the ground surface, in soil and in crops, meat and milk are derived for eachdistance. These activity concentrations are used to calculate characteristic individual and collective
doses due to inhalation of the plume, and due to external exposure from radionuclides in the plume anddeposited on the ground. Consumption rates of terrestrial food for different geographical regions areused to calculate characteristic individual and collective doses from consumption of foods. Table A2
lists the equations that are implemented for discharges to an atmospheric environment that give rise toexposure through terrestrial pathways.
A5. Discharges to a freshwater environment. The workbook calculates activity concentrations ofradionuclides in water for two sizes of river (the results for a large river are also applied for a lake).
Concentration factors are used to derive activity concentrations in freshwater fish, and irrigation rates
are used to calculate activity concentrations in irrigated crops. Activity concentrations of radionuclides
in riverbank sediment are assumed to be the same as those in riverbed sediment. These values are used
to derive characteristic individual and collective doses from consumption of irrigated foods and water

94 UNSCEAR 2016 REPORT

abstracted from the river, consumption of fish caught from the river and individual doses from external
exposure to radioactive material in riverbank sediments. Table A3 lists the equations implemented fordischarges to a freshwater environment.
A6. Discharges to a marine environment. The workbook is based on the assumption that radionuclides
are discharged to a relatively small, local compartment and water in the local compartment is
exchanged with that in a larger, regional compartment. Activity concentrations in water are calculated
for each compartment, and activity concentrations in fish, crustaceans, molluscs and beach sediment arederived. The workbook calculates individual doses from external exposure to beach sediment, andindividual and collective doses from consumption of shellfish harvested in the local compartment andconsumption of fish caught in both compartments. Table A4 lists the relevant equations for discharges
to a marine environment.
A7. Summary workbook. This is linked to the above workbooks for each environment into which adischarge is made and, for this reason, must be saved in the same electronic folder as them. It presentscharacteristic individual and collective doses for each geographical region from discharges toatmospheric, freshwater and marine environments. The doses from discharges of radionuclides withvery short-lived progeny (e.g. 137Cs and 137mBa) include the contributions from radioactive progeny. In
other cases (i.e. radionuclides with longer-lived progeny), the contribution from the progeny are
considered separately (see section II below). If the degree of equilibrium between different members of
the radionuclide chain is significantly different from that assumed here, then the doses from the parent
and progeny have to be summed once the activity of radionuclides in the discharge and the degree of
equilibrium are specified.
A8. Globally circulating radionuclides. The final workbook includes calculation factors for collective
doses from the global circulation of the relevant radionuclides for 100, 500 and 10,000 years following
unit discharge. These factors have been derived using the PC-CREAM 08 computer system [S8], which
implements each of the global circulation models adopted by the Committee.
A9. The results can be scaled by the actual rates of discharge of each radionuclide from a particularsite and then summed over all relevant radionuclides to give the overall characteristic individual andcollective doses. Results are produced for sites located in different regions of the world, with additional
results for coastal and inland nuclear sites and sites situated in areas of low population density.

II. TREATMENT OF RADIOACTIVE PROGENY
A10. For most radionuclides the workbooks for atmospheric, freshwater and marine environments
provide the relevant dose factors separately for the parent and any progeny. (This permits the
workbooks to be used when non-equilibrium conditions apply). Tables A5, A6 and A7 contain further
details on how dose contributions from radioactive progeny have been treated for terrestrial, freshwaterand marine pathways respectively, following the general principles outlined in section II.D.2. The
summary workbook contains summed values based on the assumptions detailed in those tables.
However, for radionuclides that are in secular equilibrium with their short-lived progeny, the doses
presented and clearly marked in the workbooks are the sums of the doses from the parent and progeny.

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 95

III. QUALITY ASSURANCE
A11. A systematic review of the completed workbooks was carried out for quality assurance purposes,
firstly by the workbook developers and then by independent reviewers. This included a comparison of
the parameter values and variables with source data, and the workbook equations with the agreed
calculation methodology, defined by the lists of equations and data presented below in tables A2-A4.
This ensured that the workbooks had implemented the methodology agreed by the Committee.
A12. As further verification, a workbook was created that compared a sample of the results of the
workbooks with those published in the UNSCEAR 2000 Report [U6]. The results are discussed indetail in electronic attachment 1.

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 97

TABLES
Table A1. Summary of end points, populations and pathways considered(a) Characteristic individual dose
End point/pathway

Key features of methodology

Integration considerations

DISCHARGE TO ATMOSPHERE
Characteristic individual dose

External irradiation (beta + gamma
radiation from plume, and gamma
radiation from deposited radionuclides)

Total dose from all exposure pathways assuming
location 5 km distant from site of discharge

Time integration: 100 years
Individual dose in 100th year following
100 years continuous discharge

Activity concentrations of radionuclides in plumederived using approach in [U6]Time-integrated activity concentrations in soil from
[S8]
Dose factors (table A3 below)

Inhalation

Activity concentrations of radionuclides in plumederived using approach in [U6]

Ingestion of terrestrial foods

Activity concentrations of radionuclides interrestrial foods per unit deposition rate from [S8]Approaches for 14C and 3H based on [I5]

DISCHARGE TO FRESHWATER ENVIRONMENT
Characteristic individual dose

Total dose from all exposure pathways assuming
complete instantaneous mixing
For two situations: discharge into large and small
rivers (for nuclear and mines/non-nuclear
discharges, respectively)

External irradiation from occupancy on
freshwater sediments

Time-integrated activity concentrations ofradionuclides in sediment from [S8] 5 km distantfrom discharge point

Drinking water

Ingestion rate from [U6]

Fish ingestion

Region-specific consumption rates from [F3]Ingestion of irrigated terrestrial foods

Deposition rate related to generic irrigation rate
and growing period appropriate for grain [W2]Time integration: 100 years
Individual dose in 100th year following
100 years continuous discharge

Approaches for 14C and 3H derived from [C1]

DISCHARGE TO MARINE ENVIRONMENT
Characteristic individual dose

Total dose from exposure pathways calculatedusing a two-compartment model
Activity concentrations of radionuclides inseawater in local marine compartment

External irradiation from occupancy on
marine sediments

Time-integrated activity concentrations ofradionuclides in sediments within the local
marine box [S8]Ingestion of marine foods (fish,
crustaceans and molluscs)

Ingestion of crustaceans and molluscs from thelocal compartment (25%) and regional
compartment (75%)

Time integration: 100 years
Individual dose in 100th year following
100 years continuous discharge

98 UNSCEAR 2016 REPORT(b) Collective dose
Component

Key features of methodology

Integration considerations

DISCHARGE TO ATMOSPHERE
Local component

Regional component

Based on individual dose at midpoint and numberof people in annuli around discharge point
derived from population density informationfrom [F1] for nuclear sites or using a population
density of 5 km−2 for sites in areas of low
population (see electronic attachment 3)

Time integration: 100 years

Based on individual dose and number of people inannuli around discharge point for nuclear sites(see electronic attachment 3) or derived fromweighted population density information from
[F1]

Time integration: 100 years, 500 years

Distance integration: using activity
concentrations of radionuclides andindividual doses at centre point of annulararea, 0–100 km

Distance integration: using activity
concentrations of radionuclides andindividual doses at centre point offollowing annular areas: 100–500,
500−1 000 and 1 000−1 500 km
For discharge continuing for 100 years andintegration times of 100 years

Global component

Based on collective dose from globally dispersedradionuclides [S8], which implements models
referred to in [U6]Time integration: 100 years, 500 years and
10 000 years

DISCHARGE TO FRESHWATER ENVIRONMENT
Local and regional components from
freshwater pathways (external
irradiation from exposure on freshwater
sediment not included)

Based on total collective intakes from abstractionof drinking water and freshwater fish-catch datafrom specified lengths of small and large rivers

Global component

Based on collective dose from globally dispersedradionuclides [S8], which implements models
referred to in [U6]Time integration: 100 years

Consumption of irrigated terrestrial foods basedon generalized yield data and areas of land
equipped for irrigation as function of region(from [F1])DISCHARGE TO MARINE ENVIRONMENT
Regional component(External exposure on marine sediment
not included)
Global component

Based on total collective intake from seafoodcatch data derived from the representative
regional marine compartment
Based on collective dose from globally dispersedradionuclides [S8], which implements models
referred to in [U6]Time integration: 100 years

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 99

Table A2. Parameter and equation list: Atmospheric discharge and terrestrial environment
Parameter

Symbol

Value

Units

Reference

ATMOSPHERIC DISPERSION
Activity concentration in air at a specified distance calculated using:Cair,i ( x ) = D1 ⋅ Q ⋅ x − n e − λi x ua

(T1)

Activity concentration of radionuclide, i, in air
at distance, x, from discharge point

Cair,i ( x )Equation (T1)

Bq/m3

—

Dilution factor at 1 km

D1

5.3 × 10−7

s/m3

[U6]

Discharge rate

Q

Unit discharge rate = 1

Bq/s

—

Downwind distance from discharge pointx

5, 50, 300, 750, 1 250

km—

Empirical indexnNoble gases,
tritium: 1.2
14
C: 1.4
All others: 1.42

—

[U6]

Radioactive decay constant of radionuclide, iliRadionuclide-specific

s−1

[I9]

Geometric mean of wind speed at the heightof release representative of one yearua

2 × 10−3

km/s

[I2]

Activity concentration in air of 135Cs (progeny of 135Xe) and 138Cs (progeny of 138Xe) calculated using:=
Cair , progeny ( x ) Cair , parent ( x )(λparent
−( λλ
−
1− e
λλ
progeny − parent
progeny

parent)( x u a )

)

(T2)

(note this equation is valid for one progeny and does not include a branching fraction)
Activity concentration of progeny in air at
distance, x, from discharge point

Cair,progeny ( x )Equation (T2)

Bq/m3

—

Activity concentration of parent in air at
distance, x, from discharge point

Cair,parent ( x )Equation (T1)

Bq/m3

—

Radioactive decay constant of
parent/progeny

λparent , λprogeny

Radionuclide-specific

s−1

[I9]

Downwind distance from discharge pointx

5, 50, 300, 750, 1 250km—

Geometric mean of wind speed at the heightof release representative of one yearua

2 × 10−3

km/s

[I2]

Deposition rate at a specified distance calculated using:di ( x ) = VT Cair,i ( x )Total daily-average deposition rate at
distance, x, of radionuclide, i, from both
wet and dry processesdi ( x )Equation (T3)

(T3)
Bq/(m2 s)—

100 UNSCEAR 2016 REPORTParameter
Total deposition velocity (wet and dry)SymbolValue

VT

Noble and non-reactive gases: 0

Units

Reference

m/s

[U6]

Bq/m3

—

Tritium: 0
14

C: 0

All others: 0.002
Activity concentration of radionuclide, i, in
air at distance, x, from discharge point

Cair,i ( x )Equations (T1), (T2)ENVIRONMENTAL TRANSFER
Activity concentration in terrestrial food calculated using:C f ,i ( x ) = C f ,unit,i di ( x )(T4)Activity concentration of radionuclide, i, in
terrestrial food, f, at distance, x, fromdischarge pointC f ,i ( x )Equation (T4)

Bq/kg or Bq/L—

Activity concentration of radionuclide, i, inyear 100 in terrestrial food, f, per unit
deposition rate for continuous depositionC f ,unit,i

PC-CREAM output [S8]Bq/kg per Bq/(m2 s)orBq/L per Bq/(m2 s)—

Total daily average deposition rate at
distance, x, of radionuclide, i, from both
wet and dry processesdi ( x )Equation (T3)

Bq/(m2 s)—

14

C activity concentration in terrestrial food (cereal, vegetables and pasture) calculated using:C=( x ) Cair,14C ( x ) ⋅f ,14 C

Sp

(T5)

Sair

Activity concentration of 14C in food, andpasture, f, at distance, x, from discharge
point

C f ,14 C ( x )Equation (T5)

Bq/kg

[I5]

Activity concentration of 14C in air at distance,x, from discharge point

Cair,14C ( x )Equation (T1)

Bq/m3

—

Concentration of stable carbon in the plant(fresh weight)

Sp

Cereal: 3.9 × 102

g C/kg[I5]

g C/m3[I5]Vegetables: 30
Pasture: 1 × 102

Concentration of stable carbon in air
14

0.2

Sair

C activity concentration in terrestrial food (animal products) calculated using:C f ,14 C ( x ) =f C ⋅ Cpasture,14C ( x ) ⋅ S a

(T6)

Sp

Activity concentration of 14C in food, f, atdistance, x, from discharge pointC f ,14 C ( x )Equation (T6)

Bq/kg

[I5]

Fraction of animal feed that is contaminated

fC

1

—

[I5]

Activity concentration of 14C in pasture at
distance, x, from discharge point

Cpasture,14C ( x )Equation (T5)

Bq/kg

—

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 101

Parameter

SymbolConcentration of stable carbon in the animal
product (fresh weight)

Sa

Concentration of stable carbon in the plant(fresh weight)

Sp

Value

Units

Milk: 65

Reference

g/kg

[I5]

g/kg

[I5]

Beef: 200
Pasture: 1 × 102

Activity concentration of HTO in soil water calculated using:

Csw,HTO ( x ) =CR s-a ⋅ Cair,HTO ( x )
Ha

(T7)

Activity concentration of HTO in soil water at
distance, x, from discharge point

Csw,HTO ( x )Equation (T7)

Bq/L

[I5]

Empirical constantCR s-a

0.3

—

[I5]

Activity concentration of HTO in air at
distance, x, from discharge point

Cair,HTO ( x )Equation (T1)

Bq/m3

—

Absolute humidityHa

6 × 10−3

L/m3

[I5]

Calculated using:



C
( x)
C f ,HTO ( x=
) WC p ⋅  RH air,HTO + (1 − RH ) Csw,HTO ( x ) γ
H
a



(T8)

Activity concentration of HTO in food, f, atdistance, x, from discharge point (fresh
weight)C f ,HTO ( x )Equation (T8)

Bq/kg

[I5]

Fractional water content of the plant (fresh
weight)WC p

Cereal: 0.12

L/kg

[I5]

Vegetables: 0.92
Pasture: 0.76

Relative humidity

RH

0.7

—

[I4]

Activity concentration of HTO in air at
distance, x, from discharge point

Cair,HTO ( x )Equation (T1)

Bq/m3

—

Absolute humidityHa

6 × 10−3

L/m3

[I2]

Activity concentration of HTO in soil water at
distance, x, from discharge point

Csw,HTO ( x )Equation (T7)

Bq/L

[I5]

Ratio of HTO vapour pressure to H2O vapour
pressure

γ

0.909

—

[I5]

Weighted concentration of HTO in drinking water and feed calculated using:

CR f ,HTO ( x ) = 0.5 ⋅ Csw,HTO ( x ) + 0.5 ⋅Weighted concentration of HTO in drinking
water and of water in feed (assumes that
50% intake is drinking water and 50% is
pasture)CR f ,HTO ( x )Equation (T9)

Cpasture,HTO ( x )

(T9)

WC p
Bq/L

—

102 UNSCEAR 2016 REPORTParameter

Symbol

Value

Units

Reference

Activity concentration of HTO in soil water at
distance, x, from discharge point

Csw,HTO ( x )Equation (T7)

Bq/L

[I5]

Activity concentration of HTO in pasture at
distance, x, from discharge point (fresh
weight)Cpasture,HTO ( x )Equation (T8)

Bq/kg

[I5]

Fractional water content of the plant

WCp

0.76

L/kg

[I5]

HTO activity concentration in terrestrial food (animal products) calculated using:C f ,HTO=( x ) CR a ,HTO ⋅ CR f ,HTO ( x )(T10)

Activity concentration of HTO in food, f, atdistance, x, from discharge pointC f ,HTO ( x )Equation (T10)

Bq/kg

[I5]

Concentration ratio: concentration of HTO in
product (fresh weight) divided byconcentration of HTO in water intake

CR a ,HTO

Milk: 0.87

L/kg

[I5]

Weighted concentration of HTO in drinking
water and of water in feed

CR f ,HTO ( x )

Bq/L

—

Beef: 0.66
Equation (T9)

OBT activity concentration in terrestrial food (cereal, vegetables and pasture) calculated using:C f ,OBT ( x ) =(1 − WC p ) ⋅WEQ p ⋅ R p ⋅ C f ,HTO ( x )

(T11)

WC p

Activity concentration of OBT in food, f, atdistance, x, from discharge pointC f ,OBT ( x )Equation (T11)

Bq/kg

[I5]

Fractional water content of the plant (fresh
weight)WC p

Cereal: 0.12

L/kg

[I5]

L/kg

[I5]

Vegetables: 0.92
Pasture: 0.76

Water equivalent factor

WEQ p

Cereal: 0.56
Vegetables: 0.51
Pasture: 0.56

Partition factor

Rp

0.54

—

[I5]

Activity concentration of HTO in food, f, atdistance, x, from discharge pointC f ,HTO ( x )Equation (T8)

Bq/kg

[I5]

OBT activity concentration in terrestrial food (animal products)

C f ,OBT=( x ) CR a ,OBT ⋅ Cpasture,OBT ( x )(T12)Activity concentration of OBT in food, f, atdistance, x, from discharge pointC f ,OBT ( x )Equation (T12)

Bq/kg

[I5]

Concentration ratio: concentration of OBT inmilk (fresh weight) divided byconcentration of OBT in intake (dry weight)

CR a ,OBT

Milk: 0.24

kg/L

[I5]

Mean concentration of OBT in feed

Cpasture,OBT ( x )

Bq/kg

—

Beef: 0.40
Equation (T11)ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 103

Parameter

Symbol

Value

Units

Reference

INDIVIDUAL DOSE CALCULATIONS
Effective dose from inhalation at a specified distance calculated using:

H E ( inh ),i ( x=) Cair,i ( x ) ⋅ Dinh,i ⋅I inh⋅ Oann86 400(T13)

Effective dose from inhalation ofradionuclide, i, at distance, x, fromdischarge point

H E (inh ),i ( x )Equation (T13)

Sv—

Activity concentration of radionuclide, i, in air
at distance, x, from discharge point

Cair,i ( x )Equation (T1)

Bq/m3

—

Dose coefficient for inhalation ofradionuclide, i, (see equation (T14) for
calculation of dose coefficient for 222Rn plus
short-lived progeny)

Dinh,i

Dependent on radionuclide

Sv/Bq

[I14]

Adult inhalation rate

I inh

20

m3/d

[U6]

86 400s/d—3.15 × 107 (rounded)s—

Conversion factor
Annual occupancy at location

Oann

Dose coefficient for inhalation of radon and its short-lived progeny calculated using:

Dinh,222Rn= 24 ⋅Dose coefficient for inhalation of 222Rn plus
short-lived progeny(

DC 222 Rn EF222 Rn,in ⋅ O222 Rn,in + EF222 Rn,out ⋅ O222 Rn,out

Dinh,222Rn

Conversion factor

)

I inh

(T14)

Equation (T14)

Sv/Bq

[U6]

24

h/d

—

Dose conversion factor for radon

DC 222 Rn

9 × 10−9

Sv per (Bq h/m3)[U6]

Indoor equilibrium factor for radon

EF222 Rn,in

0.4

—

[U6]

Indoor occupancy factor

O222 Rn,in

0.8

—

[U6]

Outdoor equilibrium factor for radon

EF222 Rn,out

0.6

—

[U6]

Outdoor occupancy factor

O222 Rn,out

0.2

—

[U6]

Adult inhalation rate

I inh

20

m3/d

[U6]

Dose from external exposure from immersion in the plume at a specified distance calculated using:

H E (ex,cloud),i=( x ) Cair,i ( x ) ⋅ Dex,cloud,i ⋅ Oann ⋅ ( Oout + (1 − Oout ) Lcloud )Effective gamma dose from external
exposure to radionuclide, i, at distance, x,from discharge point

H E (ex,cloud),i ( x )Equation (T15)

Sv

(T15)
—

104 UNSCEAR 2016 REPORTParameter

Symbol

Value

Units

Reference

Activity concentration of radionuclide, i, in air
at distance, x, from discharge point

C air,i ( x )Equation (T1)

Bq/m3

External dose coefficient for immersion in theplume

Dex,cloud,iDependent on radionuclide

Sv per (Bq s/m3)

Annual occupancy at location

Oann

3.15 × 107 (rounded)s—

Fraction of occupancy that is outdoors

Oout

0.2

—

[U4]

Building shielding factor in plume (location
factor)Lcloud0.2——[E2, P2]

Dose from external exposure from deposits calculated using:

H E ( ex,deposit ),i ( x=) di ( x ) ⋅ tdischarge ⋅ Dex,deposit,i ⋅ ( Oout + (1 − Oout ) Ldeposit )(T16)

Annual effective dose from the depositedradionuclide, i, at distance, x, fromdischarge point

H E ( ex,deposit ),i ( x )Equation (T16)

Sv—

Total daily average deposition rate at
distance, x, of radionuclide, i, from both
wet and dry processesdi ( x )Equation (T3)

Bq s/m2—

Duration of deposition

tdischarge

3.15 × 107 (rounded)s

1 year

Dose coefficient for external exposure from
deposited material, integrated to 100 years(time dependence taken into account using
equation given by [G2])Dex,deposit,iDependent on radionuclide

Sv per (Bq/m2)[E2, P2]

Fraction of occupancy that is outdoors

Oout

0.2

—

[U4]

Building shielding factor from depositedmaterial (location factor)

Ldeposit

0.1—

Effective dose from ingestion calculated using:

H E (ing ), f ,r ,i ( x=
) C f ,i ( x ) ⋅ Ding,i ⋅ Flocal ⋅ I f ,r(T17)

Annual effective dose from the ingestion offood, f, containing radionuclide, i, atdistance, x, from discharge point in region r

H E (ing ), f ,r ,i ( x )Equation (T17)

Sv—

Activity concentration of radionuclide, i, in
terrestrial food, f, at distance, x, fromdischarge pointC f ,i ( x )Equations (T4), (T5), (T6), (T8),(T10), (T11), (T12)

Bq/kg or Bq/L—

Dose coefficient for ingestion

Ding,i

Dependent on radionuclide

Sv/Bq

[I14]

Fraction of food that is locally produced

FlocalIndividual dose: 0.25—

Collective dose: 1.0
Amount of food, f, ingested per caput in ayear in region, rI f ,rDependent on region andfood

kg or L[W2]

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 105

Parameter

Symbol

Value

Units

Reference

Total effective dose from ingestion calculated using:

H E ( ing ),r ,i ( x ) = ∑ H E (ing ), f ,r ,i ( x )

(T18)

f

Total annual effective dose in region, r, fromingestion of radionuclide, i, in food at
distance, x, from discharge point

H E (ing ),r ,i ( x )Equation (T18)

Sv—

Annual effective dose from ingestion of food,f, containing radionuclide, i, at distance, x,from discharge point in region, r

H E (ing ), f ,r ,i ( x )Equation (T17)

Sv—

Total individual effective dose calculated using:

H E ( atmos ),r ,i ( x ) =H E (inh ),i ( x ) + H E (ex,cloud),i ( x ) + H E ( ex,deposit ),i ( x ) + H E (ing ),r ,i ( x )(T19)

Total effective dose in region, r, fromradionuclide, i, at distance, x, fromdischarge point

H E ( atmos ),r ,i ( x )Equation (T19)

Sv—

Effective dose from inhalation ofradionuclide, i, at distance, x, fromdischarge point

H E (inh ),i ( x )Equation (T13)

Sv—

Effective dose from external exposure toradionuclide, i, at distance, x, fromdischarge point

H E (ex,cloud),i ( x )Equation (T15)

Sv—

Effective dose from the depositedradionuclide, i, at distance, x, fromdischarge point

H E ( ex,deposit ),i ( x )Equation (T16)

Sv—

Total effective dose in region, r, fromingestion of radionuclide, i, in food at
distance, x, from discharge point

H E (ing ),r ,i ( x )Equation (T18)

Sv—

COLLECTIVE DOSE CALCULATIONS
Collective effective dose calculated using:S E ( atmos ),r=x , xk +1 ) N r ( xk , xk +1 ) ⋅ H E ( atmos ),r ,i ( x ),i ( k

(T20)

Collective effective dose in region, r, in theannulus limited by xk and xk+1

S E ( atmos ),r ,i ( xk , xk +1 ) Equation (T20)

Total population in region, r, in the annulus
limited by xk and xk+1

N r ( xk , xk +1 )Dependent on region

Annular distances (the outer distance foreach annuli)( x1 , x2 , x3 , x4 , x5 ){0,100,500,1 000,1 500}

km—

Total effective dose from radionuclide, i, atdistance, x, from discharge point where x is
the midpoint between xk and xk+1

H E ( atmos ),r ,i ( x )Equation (T19)

Sv—

man Sv—see electronic
attachment 3
and [F1]

106 UNSCEAR 2016 REPORTParameter

Symbol

Value

Units

Reference

Local collective effective dose calculated using:2

S E ( atmos ),r ,i ( local ) = ∑ S E (atmos),r ,i ( xk , xk +1 )

(T21)

k =1

Local (0 km to 100 km) collective effective
dose in region, r, from radionuclide, i

S E ( atmos ),r ,i ( local )Equation (T21)

man Sv—

Total annual collective effective dose inregion, r, from radionuclide, i, in theannulus limited by xk and xk+1

S E (atmos),r ,i ( xk , xk +1 ) Equation (T20)

man Sv—

Regional component of collective effective dose
5

S E ( atmos ),r ,i ( regional ) = ∑ S E (atmos),r ,i ( xk , xk +1 )

(T22)

k =3

Regional component (100 km to 1500 km) of
collective effective dose in region, r, fromradionuclide, i

S E ( atmos ),r ,i ( regiona Equation (T21)

man Sv—

Total annual collective effective dose inregion, r, from radionuclide, i, in theannulus limited by xk and xk+1

S E (atmos),r ,i ( xk , xk +1 ) Equation (T20)

man Sv—

GLOBAL DISPERSION
Collective doses from tritium, 14C, 85Kr and 129I were calculated by PC-CREAM (incorporates global dispersion models referenced in [U6])ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 107

Table A3. Parameter and equation list: Freshwater environment
Parameter

Symbol

Value

Units

Reference

FRESHWATER DISPERSION
Activity concentration in unfiltered water calculated using:Cuw , s =Q
Friver, s(F1)

Activity concentration in unfiltered water

Cuw ,sEquation (F1)

Bq/m3

—

Annual discharge rate of radionuclide, i

Q

1

Bq/s

—

Volumetric flow rate of river of size, sFriver,s

Large: 1 000

m3/s

—

Small: 10
Activity concentration in filtered water calculated using:Cfw , s ,i =Cuw , s1 + K d ,i ⋅ α s(F2)Activity concentration of radionuclide, i, in filtered waterfrom river of size, s

Cfw , s ,iEquation (F2)

Bq/m3

—

Activity concentration in unfiltered water

Cuw ,sEquation (F1)

Bq/m3

—

Sediment–water distribution factor

K d ,i

Dependent on elementm3/t[I2, I5]

Suspended sediment load in river of size, sαsLarge: 5 × 10−4

t/m3

[O1]

Small: 2 × 10

−5ENVIRONMENTAL TRANSFERS
Activity concentrations in freshwater fish calculated using:

Cfish, s ,i =Cfw , s ,i ⋅ Bfish,i

(F3)

1 000

Activity concentration of radionuclide, i, in freshwater fish

Cfish, s ,iEquation (F3)

Bq/kg

—

Activity concentration of radionuclide, i, in filtered waterfrom river of size, s

Cfw , s ,iEquation (F2)

Bq/m3

—

Concentration factor for freshwater fish (fresh weight)

Bfish,iDependent on food andelement

Bq/kg per
Bq/L

[I5]

1 000

L/m3

—

Conversion factor
Activity concentration of HTO in fish calculated using:

Cfish, s ,HTO =Activity concentration of HTO in freshwater fish

WC f ⋅ Cfw , s ,HTO

Cfish, s ,HTO

(F4)

1 000
Equation (F4)

Bq/kg

—

108 UNSCEAR 2016 REPORTParameter

Symbol

Value

Units

Reference

Fractional water content of fish (fresh weight)

WC f

0.78

L/kg

[I5]

Activity concentration of HTO in filtered water from river ofsize, sCfw , s ,HTO

Equation (F2)

Bq/m3

—

1 000

L/m3

—

Conversion factor
Activity concentration of OBT in fish calculated using:

Cfish, s ,OBT =(1 − WC ) ⋅ WEQ ⋅ R ⋅Cff

f

fw , s ,HTO

(F5)

1 000

Activity concentration of OBT in freshwater fish

Cfish, s ,OBT

Equation (F5)

Bq/kg

—

Fractional water content of fish (fresh weight)

WC f

0.78

L/kg

[I5]

Water equivalent factor for fish

WEQ f

0.65

—

[I5]

Partition factor for fish (geometric mean, fresh weight)

Rf

6.6 × 10−4

kg/kg

[I5]

Activity concentration of HTO in filtered water from river ofsize, sCfw , s ,HTO

Equation (F2)

Bq/m3

—

1 000

L/m3

—

Conversion factor
Activity concentrations of 14C in fish calculated using:

Cfish, s ,14 C =Cfw , s ,14 C ⋅ Bfish,14 C

(F6)

1 000

Activity concentration of 14C in freshwater fish (adaptedfrom Equation (F3))

Cfish, s ,14 C

Equation (F6)

Bq/kg

—

Activity concentration of 14C in filtered water from river ofsize, sCfw , s ,14 C

Equation (F2)

Bq/m3

—

Concentration factor for 14C in freshwater fish

Bfish,14 C

5 × 104

Bq/kg per
Bq/L

[I5]

1 000

L/m3

—

Conversion factor
Deposition rate from irrigation calculated usingdirr, s= Cuw , s ⋅ I irr ⋅ Firr

(F7)

Total daily average deposition rate of radionuclide, i, from
irrigationdirr,sEquation (F7)

Bq/m2

—

Average concentration of radionuclide, i, in river water used
for irrigation

Cuw ,sEquation (F1)

Bq/m3

—

Daily irrigation rate

I irr

0.005

m3/m2

[N2]

Fraction of the year for which irrigation occurs

Firr

150
=0.41
365

—

[N2]

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 109

Parameter

Symbol

Value

Units

Reference

Activity concentration in terrestrial food (cereals, vegetables) calculated using:C f , s ,i =C f ,unit,i ⋅ dirr, s(F8)

86 400

Activity concentration of radionuclide, i, in irrigated,terrestrial food, f

C f , s ,iEquation (F8)

Bq/kg

—

Activity concentration of radionuclide, i, in terrestrial food, f,
per unit deposition rate

C f ,unit,i

PC-CREAM output

Bq/kg perBq s/m2—

Total daily average deposition rate of radionuclide, i, from
irrigationdirr,sEquation (F7)

Bq/m2

—

86 400s/d—Conversion factor
Activity concentration of HTO in soil water calculated using:Csw , s ,HTO =I irr ⋅ Cuw , s(F9)

P + 1 000 ⋅ I irr

Activity concentration of HTO in soil water irrigated fromriver of size, s

Csw , s ,HTO

Equation (F9)

Bq/L

[I4]

Daily irrigation rate (averaged over 150-day growing
season)

I irr

0.005

m3/m2

[N2]

Average concentration of radionuclide, i, in river water used
for irrigation

Cuw ,sEquation (F1)

Bq/m3

—

Daily precipitation rate (averaged over 150-day growing
season)

P

5

L/m2

[U6]

1 000

L/m3

—

Conversion factor

HTO activity concentration in terrestrial food (cereals, vegetables) calculated using:C f , s ,HTO
= WC p ⋅  RH ⋅ Cam + (1 − RH ) ⋅ Csw , s ,HTO  γ

(F10)

Activity concentration of HTO in food, f

C f , s ,HTO

Equation (F10)

Bq/kg

[I5]

Fractional water content of the plant

WC pCereal: 0.12

L/kg

[I5]

Vegetables: 0.92
Relative humidity

RH

0.7

—

[I4]

HTO concentration in air moisture

Cam

Assumed approximately
equal to Csw , s ,HTO

Bq/L

[I4]

Activity concentration of HTO in soil water

Csw , s ,HTO

Equation (F9)

Bq/L

—

Ratio of HTO vapour pressure to H2O vapour pressure

γ

0.909

—

[I5]

Activity concentration of OBT in terrestrial food (cereals, vegetables) calculated using:C f , s ,OBT =(1 − WC p ) ⋅WEQ p ⋅ R p ⋅ C f , s ,HTO
WC p

(F11)

110 UNSCEAR 2016 REPORTParameter

Symbol

Value

Units

Reference

Activity concentration of OBT in terrestrial foodC f , s ,OBT

Equation (F11)

Bq/kg

—

Fractional water content of plant (fresh weight)

WCp

Cereal: 0.12

L/kg

[I5]

L/kg

[I5]

Vegetables: 0.92
Water equivalent factor for plant

WEQp

Cereal: 0.56
Vegetables: 0.51

Partition factor

Rp

0.54

—

[I5]

Activity concentration of HTO in food, f

C f , s ,HTO

Equation (F10)

Bq/kg

[I5]

Specific activity of 14C in plant calculated using:

I ⋅C
SA
SA
CDc ⋅ irr uw , s
=
=
p
air
Fc

(F12)

Specific activity of 14C in plant

SAp

Equation (F12)Bq/(g C)

[I4]

Specific activity of 14C in air

SAair

Equation (F12)Bq/(g C)

[I4]

Canopy dilution factor

CDc

0.15

—

[I4]

Daily irrigation rate (averaged over growing season)

Iirr

0.005

m3/m2

[N2]

Activity concentration of dissolved radionuclide i in
unfiltered water

Cuw,sEquation (F1)

Bq/m3

—

Average production rate of carbon by decomposition ofcrop residues

Fc

0.66

(g C)/m2[I4]

14

C activity concentration in terrestrial food (cereals, vegetables) calculated using:C f , s ,14 C=

Cair,14C
Sair⋅ S p= SA air ⋅ S p(F13)

C activity concentration in food, f, irrigated from river ofsize, sC f , s ,14 C

Equation (F13)

Bq/kg

[I4]

Specific activity of 14C in air

SAair

Equation (F12)Bq/(g C)

[I4]

Concentration of stable carbon in the plant

Sp

Cereal: 3.9 × 102(g C)/kg[I5]

14

Vegetables: 30

INDIVIDUAL DOSE CALCULATIONS
Individual dose from ingestion of drinking water calculated using

H E ( water ), s ,i = Cuw , s ⋅ Ding,i ⋅ I water ⋅ FWT ⋅ Priver(F14)

Annual effective dose from the ingestion of radionuclide, i,in drinking water

H E ( water ), s ,iEquation (F14)

Sv—

Average activity concentration of radionuclide, i, in water
assuming complete mixing

Cuw ,sEquation (F1)

Bq/m3

—

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 111

Parameter

Symbol

Value

Units

Reference

Dose coefficient for ingestion of radionuclide, iDing,i

Dependent on radionuclide

Sv/Bq

[I14]

Amount of water ingested in one year

I water

0.5

m3

[U6]

Drinking water treatment removal factor

FWT

Dependent on element

—

[B7]

Fraction of individual water intake from river

Priver1——

Dose from external exposure from freshwater sediments calculated using:

H E ( ex,riverbank ), s=
Csed, s ,i ⋅ rsed ⋅ tsed ⋅ Fgeom ⋅ Dex,deposit ⋅ Oriverbank
,i

(F15)

Annual effective dose from radionuclide, i, from occupancy
on river banks

H E ( ex,riverbank ), s ,iEquation (F15)

Sv—

Activity concentration of radionuclide, i, in freshwater
riverbank sediment based on discharge rate of 1 Bq/s
(assumed to be the same as bed sediment) (dry weight)

Csed, s ,i

PC-CREAM output

Bq/kg

—

Density of riverbank sediment

ρsed

1 200

kg/m3

[I2]

Thickness of riverbank sediment

tsed

0.05

m

[I2]

Geometry factor for river banks for external dosecoefficientsFgeom

0.2 (rounded)

—

[A2]

Integrated dose coefficient for irradiation from surface
deposits

Dex,deposit

Dependent on radionuclide

Sv/s per
Bq/m2

[E2]

River bank occupancy

Oriverbank

1.8 × 105 (50 hours)sAssumed value

Ingestion of freshwater fish

H E (ing,fish ), s ,r ,i = Cfish, s ,i ⋅ Ding,i ⋅ Flocal ⋅ I fish,r(F16)

Annual effective dose from radionuclide, i, from ingestionof freshwater fish in region, r

H E (ing,fish ), s ,r ,iEquation (F16)

Sv—

Average activity concentration of radionuclide, i, infreshwater fish

Cfish, s ,iEquations (F3), (F4), (F5),
(F6)

Bq/kg

—

Dose coefficient for adults for ingestion

Ding,i

Dependent on radionuclide

Sv/Bq

[I14]

Fraction of food that is locally produced

Flocal0.25—

See para.11[U12]

Amount of freshwater fish ingested in a year in region, rI fish,r

Dependent on region

kg

[F3]

Dose from ingestion of irrigated, terrestrial foods calculated using:

H E (ing,irr ), f , s ,r ,i = C f , s ,i ⋅ Ding,i ⋅ Flocal ⋅ Fspray, s ,r ⋅ I f ,rAnnual effective dose from the ingestion of irrigated,terrestrial food, f, containing radionuclide, i, in region, r

H E (ing,irr ), f , s ,r ,iEquation (F17)

(F17)
Sv

—

112 UNSCEAR 2016 REPORTParameter

Symbol

Value

Units

Reference

Activity concentration of radionuclide, i, in irrigated,terrestrial food, f

C f , s ,iEquations (F8), (F10), (F11),
(F13)

Bq/kg

—

Adult dose coefficient for ingestion

Ding,i

Dependent on radionuclide

Sv/Bq

[I14]

Fraction of food that is locally produced

Flocal0.25—

See para.11[U12]

Fraction of food that is spray irrigatedFspray, s ,rSmall rivers: 0

—

[I7]

kg

[W2]

Large rivers: dependent on
regionAmount of food, f, ingested in a year in region, rDependent on region andfood

I f ,rTotal effective dose from ingestion of irrigated, terrestrial foods calculated using:

H E (ing,irr ), s ,r ,i = ∑ H E (ing,irr ), f , s ,r ,i

(F18)

f

Total effective dose in region, r, from ingestion of irrigated,terrestrial food containing radionuclide, i

H E (ing,irr ), s ,r ,iEquation (F18)

Sv—

Annual effective dose from the ingestion of irrigated,terrestrial food, f, containing radionuclide i in region, r

H E (ing,irr ), f , s ,r ,iEquation (F17)

Sv—

Total individual dose from freshwater pathways calculated using:

H E ( fw ), s ,r ,i = H E ( water ), s ,i + H E ( ex,riverbank ), s ,i + H E ( fish ), s ,r ,i + H E (ing,irr ), s ,r ,i(F19)

Total individual dose from freshwater pathways

H E ( fw ), s ,r ,iEquation (F19)

Sv—

Annual effective dose from the ingestion of radionuclide, i,in drinking water

H E ( water ), s ,iEquation (F14)

Sv—

Annual effective dose from radionuclide, i, from occupancy
on river banks

H E ( ex,riverbank ), s ,iEquation (F15)

Sv—

Annual effective dose from radionuclide, i, from ingestion of
freshwater fish in region, r

H E ( fish ), s ,r ,iEquation (F16)

Sv—

Total effective dose in region, r, from ingestion of irrigated,terrestrial food containing radionuclide, i

H E (ing,irr ), s ,r ,iEquation (F18)

Sv—

COLLECTIVE DOSE CALCULATIONS
Volumetric abstraction rate of water calculated using:

Virr,surface,=
Friver, s ⋅ Firr,surface,r
s ,r

(F20)

Volumetric abstraction rate of surface water from river ofsize, s, in region, rVirr,surface, s ,rEquation (F20)

m3/s

—

Volumetric flow rate of river of size, sFriver,s

Large: 1 000

m3/s

—

m2 a/m3[F4]

Small: 10
Fraction of surface water withdrawn for irrigation in region, rFirr,surface,rDependent on region

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 113

Parameter

Symbol

Value

Units

Reference

Area irrigated by abstracted water calculated using:Airr,surface, s ,r = 3.15 × 107 ⋅ Airr,unit,r ⋅ Virr,surface, s ,r(F21)

Area irrigated by water abstracted from river of size, s, inregion, r

Airr,surface, s ,rEquation (F21)m2—

Area irrigated per unit volume water withdrawn in a year inregion, r

Airr,unit,rDependent on region

m2 a/m3[F4]

Volumetric abstraction rate of surface water from river ofsize, s, in region, rVirr,surface, s ,rEquation (F20)

m3/s

—

3.15 × 107 (rounded)s/aConversion factor
Irrigation rate calculated using:C ⋅Vdirr,surface, s ,r = uw , s irr,surface, s ,rAirr,surface, s ,r(F22)

Irrigation rate, assumed to be the same volume of waterwith the same activity concentration abstracted from riverof size, s, in region, rdirr,surface, s ,rEquation (F22)

Bq s/m2—

Activity concentration in unfiltered water

Cuw ,sEquation (F1)

Bq/m3

—

Volumetric abstraction rate of surface water from river ofsize, s, in region, rVirr,surface, s ,rEquation (F20)

m3/s

—

Area irrigated by water abstracted from river of size, s, inregion, r

Airr,surface, s ,rEquation (F21)m2—

Activity concentration in irrigated, terrestrial foods calculated using:C=
Ccereal,unit,i ⋅ dirr,surface, s ,rcereal, s , r ,i(F23)

Activity concentration of radionuclide, i, in terrestrial food(represented by cereal) irrigated from river of size, s, inregion, r

Ccereal, s ,r ,iEquation (F23)

Bq/kg

Activity concentration of radionuclide, i, in terrestrial food,f, per unit deposition rate

Ccereal,unit,i

PC-CREAM output

Bq/kg perBq s/m2

Irrigation ratedirr,surface, s ,rEquation (F22)

Bq s/m2——

Activity concentration of 14C in cereals calculated using:Cair,14C

Ccereal, s ,r ,14=C

Sair

SA air
⋅ S=
p
(F24)

Cuw , s
CDc ⋅
=
⋅ Sp
365 ⋅ Airr,unit,r ⋅ Fc
Activity concentration of 14C in food, f, irrigated from river ofsize, sCcereal, s ,r ,14 C

Equation (F24)

Bq/kg

Canopy dilution factor

CDc

0.15

—

Equations(F13) & (F12)[I4]

114 UNSCEAR 2016 REPORTParameter

Symbol

Value

Units

Reference

Activity concentration in unfiltered water

Cuw ,sEquation (F1)

Bq/m3

—

Area irrigated per unit volume in region, rAirr,unit,rDependent on region

m2 a/m3[F4]

Average daily production rate of carbon by decompositionof crop residues

Fc

0.66

(g C)/m2[I4]

Concentration of stable carbon in the plantSp

3.9 × 102(g C)/kg

[I5]

365

d/a

—

Conversion factor
Collective dose from ingestion of irrigated, terrestrial food calculated using:S E (ing,irr ), s ,r ,=Ccereal, s ,r ,i ⋅ Ycereal,r ⋅ Fspray, s ,r ⋅ Airr,surface, s ,r ⋅ Ding,i
i

(F25)

Collective dose from consumption of food (represented bymajor food group, cereal) in region, r

S E (ing,irr ), s ,r ,iEquation (F25)man Sv—

Activity concentration of radionuclide, i, in terrestrial food(represented by cereal) irrigated from river of size, s, inregion, r

Ccereal, s ,r ,iEquations (F23), (F10), (F11),
(F24)

Bq/kg

—

Yield per unit area of cereal in region, r

Ycereal,rDependent on region

kg/m3

[F1]

Fraction of food that is spray irrigatedFspray, s ,rSmall rivers: 0

—

[I7]

Large rivers: dependent on
regionArea irrigated by water abstracted from river of size, s, inregion, r

Airr,surface, s ,rEquation (F21)m2—

Adult dose coefficient for ingestion

Ding,i

Dependent on radionuclide

Sv/Bq

[I14]

Collective dose from drinking water calculated using:S E ( water ), s ,i = Cuw ,i ⋅ Ding,i ⋅ Friver, s ⋅ Tdw ⋅ Amun ⋅ Fdw ⋅ FWT(F26)

Collective dose from drinking water for river of size, s

S E ( water ), s ,iEquation (F26)

man Sv—

Activity concentration of dissolved radionuclide, i, in
unfiltered water

Cuw ,iEquation (F1)

Bq/m3

—

Dose coefficient for ingestion of radionuclide, iDing,i

Dependent on radionuclide

Sv/ q

[I14]

Volumetric flow rate of river of size, sFriver,s

Large: 1 000

m3/s

—

Small: 10
Duration of abstraction

Tdw

3.15 × 107 (rounded)

S—

Abstraction fraction for municipal water

Amun

0.01

—

—

Fraction of municipal water that is drunk

Fdw

0.01

—

—

Drinking water treatment removal factor

FWT

Dependent on element

—

[B7]

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 115

Parameter

Symbol

Value

Units

Reference

Collective dose from freshwater fish ingestion calculated using:S E (ing,fish ), s ,i = Cfish, s ,i ⋅ Ding,i ⋅ Yfish, s ⋅ Lriver, s(F27)Collective dose from ingestion of freshwater fish from riverof size, s

S E (ing,fish ), s ,iEquation (F27)

man Sv—

Activity concentration of radionuclide, i, in filtered waterfrom river of size, s

Cfish, s ,iEquations (F3), (F4), (F5),
(F6)

Bq/m3

—

Dose coefficient for ingestion of radionuclide, iDing,i

Dependent on radionuclide

Sv/Bq

[I14]

Representative freshwater fish catch in river of size, s

Yfish,sLarge: 104

kg/km

[F1]

km

[I2]

Small: 10

3

Length of river of size, s

Lriver,s

Large: 5 × 102
Small: 1 × 102

Total collective dose from all freshwater pathways calculated using:S E ( fw ), s ,r ,i = S E (ing,irr ), s ,r ,i + S E ( water ), s ,i + S E (ing,fish ), s ,i(F28)

Total collective dose in region, r, from discharges into riverof size, s

S E ( fw ), s ,r ,iEquation (F28)

man Sv—

Collective dose from consumption of food (represented bymajor food group, cereal) in region, r

S E (ing,irr ), s ,r ,iEquation (F25)man Sv—

Collective dose from drinking water for river of size, s

S E ( water ), s ,iEquation (F26)

man Sv—

Collective dose from ingestion of freshwater fish of size, s

S E (ing,fish ), s ,iEquation (F27)

man Sv—SE(fish),s,i

GLOBAL DISPERSION
Collective doses from tritium, 14C, 85Kr and 129I were calculated by PC-CREAM (incorporates global dispersion models referenced in [U6])116 UNSCEAR 2016 REPORT

Table A4. Parameter and equation list: Marine environment
Parameter

Symbol

Value

Units

Reference

MARINE DISPERSION
Sedimentation decay constant

λs ,c ,i =K d , c ,i ⋅ S c(M38)

hc ⋅ (1 + K d ,c ,i ⋅ α c )Sedimentation decay constant for compartment, cls,c,iEquation (M38)

a−1

[C2]

Marine sediment distribution factor for compartment
c and radionuclide, i

Kd,c,i

Dependent on radionuclide

m3 t−1[I3]

Sedimentation rate in compartment, c

Sc

Local: 1.0 × 10−4

t m−2 a−1(see section III.C of main
text)

m

(see section III.C of main
text)

t m−3

(see section III.C of maintext)

Regional: 1.0 × 10−5
Depth of compartment, chcLocal: 10
Regional: 1000

Suspended sediment load in compartment, c

αcLocal: 2.0 × 10−4
Regional: 1.0 × 10−7

Flow rate constant, local to regionalll ,r =

∆Vl ,rVl(M39)

Flow rate constant, local compartment to regional
compartment

ll,rEquation (M39)a−1(see section III.C of maintext)

Volumetric exchange between regional compartment
and global oceans∆Vl ,r2 × 1010

m3 a−1(see section III.C of maintext)

Volume of local compartment

Vl

109

m3

(see section III.C of maintext)

Flow rate constant, regional compartment to global oceans

λr , g =∆Vr , g

(M40)

Vr

Flow rate constant, regional compartment to global
oceanslr,gEquation (M40)a−1(see section III.C of maintext)

Volumetric exchange between local and regional
compartments∆Vr , g1015

m3 a−1(see section III.C of maintext)

Volume of regional compartment

Vl

1015

m3

(see section III.C of maintext)

Combined decay constant, local to regionalΛ l ,i = li + ls ,l ,i + ll ,rCombined decay constant for local compartment andradionuclide, iΛ l ,iEquation (M41)

(M41)
a−1

[C2]

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 117

Parameter

Symbol

Value

Units

ReferenceRadioactive decay constant for radionuclide, iliDependent on radionuclide

a−1

[I9]

Sedimentation decay constant for local compartment

ls,l,iEquation (M38)

a−1

[C2]

Flow rate constant, local compartment to regional
compartment

ll,rEquation (M39)a−1(see section III.C of maintext)

Combined decay constant, regional compartment to global oceansΛ r ,i = λλλi + s , r ,i + r , g(M42)

Combined decay constant for regional compartment
and radionuclide, iΛ r ,iEquation (M42)

a−1

[C2]

Radioactive decay constant for radionuclide, iliDependent on radionuclide

a−1

[I9]

Sedimentation decay constant for regional
compartment

ls,r,iEquation (M38)

a−1

[C2]

Flow rate constant, regional compartment to global
oceanslr,gEquation (M40)a−1(see section III.C of main
text)

Activity in local compartment

A=l ,i ( t )

(

Q
−Λ ⋅t
1 − e l ,rΛ l ,r)(M43)

Activity of radionuclide, i, in local compartment attime, tAl ,i ( t )Equation (M43)

Bq

[C2]

Discharge rate

Q

3.15 × 107 (rounded)

Bq a−1= 1 Bq s−1

Combined decay constant for local compartment andradionuclide, iΛ l ,rEquation (M41)

a−1

[C2]

Duration of discharge

t

100

a

—

Activity in regional compartment=
Ar ,i ( t )ll ,r ⋅ Al ,i ( t )Λ l ,r(1 − e−Λ l ,r ⋅t

)

(M44)

Activity of radionuclide, i, in regional compartment attime, t

Ar ,i ( t )Equation (M44)

Bq

[C2]

Rate constant for movement of water from local
compartment to regional compartment

ll,r

20

a−1

(see section III.C of main
text)

Activity of radionuclide, i, in local compartment attime, tAl ,i ( t )Equation (M43)

Bq

[C2]

Combined decay constant for regional compartment
and radionuclide, iΛ l ,rEquation (M41)

a−1

[C2]

Duration of discharge

t

100

a

—

118 UNSCEAR 2016 REPORTParameter

Symbol

Value

Units

Reference

Activity concentration in water

Cc ,i ( t ) =Ac ,i ( t )
Vc

(M45)

Activity concentration of radionuclide, i, in water incompartment, c, at time, t

Cc ,i ( t )Equation (M45)

Bq m−3—

Activity of radionuclide, i, in compartment, c, at time,

Ac ,i ( t )Equations (M43), (M44)

Bq

[C2]

Vc

Local: 1.0 × 109

m3(see section III.C of maintext)tVolume of compartment, cRegional: 1.0 × 10

15ENVIRONMENTAL TRANSFERS
Activity concentrations in marine foods

C f , c ,i =Cc ,i ⋅ B f ,i

(M46)

1 000

Activity concentration of radionuclide, i, in marine
food, f, in compartment, c

Cf,c,iEquation (M46)

Bq kg−1—

Activity concentration of radionuclide, i, in water attime, tCc,iEquation (M45)

Bq m−3—

Bioaccumulation factor for marine food, f,
concentration in marine food (fresh weight) divided
by concentration in seawater

Bf,iDependent on food andelement

L kg−1

[I3]

1 000

L m−3

—

Conversion factor
Activity concentration in beach sediment

Cbeach,i = 0.1⋅ tsed ⋅ ρsed ⋅ K d ,local,i ⋅ Clocal,i(M47)

Activity concentration per unit area in beachsediment

Cbeach,iEquation (M47)

Bq m−2—

Kd adjustment factor for coarser grains (i.e. sand

—

0.1

—

[S7]

Average thickness of beach sediment

tsed

0.05

m

[I2]

Average density of beach sediment

rsed

1.2

t m−3

[I2]

Marine sediment distribution factor in local
compartment for radionuclide, iKd,local,iDependent on radionuclide

m3 t−1(L kg−1)[I3]

Activity concentration of radionuclide, i, in water

Clocal,i

Equation (M45)

Bq m−3—rather than fine bed sediment)

INDIVIDUAL DOSE CALCULATIONS
External dose from beach occupancy

H E ( ex,beach ),i = Cbeach,i ⋅ Fgeom ⋅ Dex,deposit,i ⋅ Obeach(M48)

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 119

Parameter

Symbol

Value

Units

Reference

Effective dose from radionuclide, i, from beachoccupancy

H E ( ex,beach ),iEquation (M48)

Sv—

Activity concentration of radionuclide, i, in beachsediment

Cbeach,iEquation (M47)

Bq m−2—

Geometry factor for beaches for external dosecoefficients

Fgeom

0.5

—

[E2]

Dose coefficient for irradiation from surface deposits

Dex,deposit,iDependent on radionuclide

Sv s−1 Bq−1
m2

[E2]

Beach occupancy (typical rather than critical)

Obeach

3.6 × 105s

[R1]

Ingestion of marine food

H E (ing,marine ), f ,r=,i(C

f ,local,i⋅ f f ,local + C f ,regional,i ⋅ f f ,regional ) ⋅ Ding,i ⋅ I f ,rAnnual effective dose from radionuclide, i, fromingestion of freshwater fish in region, r

H E (ing,marine ), f ,r Equation (M49)

Average activity concentration of radionuclide, i, infood, f, in the local marine compartment

C f ,local,iFraction of food, f, that is caught in the local marine
compartment

f f ,local

(M49)

Sv

—

Equation (M46)

Bq kg−1—

Fish: 0.25—

Crustaceans: 1.0
Molluscs: 1.0

Fish: consistent withfreshwater andterrestrial
Crustaceans andmolluscs: [S7]Average activity concentration of radionuclide, i, infood, f, in the regional marine compartment

C f ,regional,iEquation (M46)

Bq kg−1

Fraction of food, f, that is caught in the regional
marine compartment

f f ,regional

Fish: 0.75—

Crustaceans: 0.0
Molluscs: 0.0—

Fish: consistent withfreshwater andterrestrial
environments
Crustaceans & molluscs:[S7]

Adult dose coefficient for ingestion

Ding,i

Dependent on radionuclide

Sv Bq−1[I14]

Amount of marine food, f, ingested in a year inregion, r

If,rDependent on region

kg

[W2]

Total effective dose from ingestion of marine foods

H E (ing,marine ),r ,i = ∑ H E (ing,marine), f ,r ,i

(M50)

f

Total effective dose in region, r, from ingestion ofmarine food containing radionuclide, i

H E (ing,marine ),r ,i Equation (M50)

Sv—

Effective dose from the ingestion of marine food fcontaining radionuclide, i, in region, r

H E (ing,marine ), f ,r Equation (M49)

Sv—

120 UNSCEAR 2016 REPORTParameter

Symbol

Value

Units

Reference

Total individual dose from marine pathwaysH=
H E ( ex,beach ),i + H E (ing,marine ),r ,iE ( marine ), r ,iTotal individual dose from marine pathways in region,(M51)

H E ( marine),r ,iEquation (M51)

Sv—

Effective dose from beach occupancy

H E ( ex,beach ),iEquation (M48)

Sv—

Effective dose from the ingestion of radionuclide, i, in
marine foods in region, r

H E (ing,marine ),r ,i Equation (M50)

Sv

—

r

COLLECTIVE DOSE CALCULATIONS
Collective dose from ingestion of marine fish

S E (ing,marine ),fish,c ,=Cfish,c ,i ⋅ Yfish,r ⋅ Fed,fish ⋅ Ac ⋅ Ding,i
r ,i

(M52)

Collective dose from ingestion of marine fish forradionuclide, i

S E (ing,marine ),fish, Equation (M52)

man Sv—

Activity concentration of radionuclide, i, in fish incompartment, cCfish,c ,iEquation (M46)

Bq kg−1—

Fish catch in 1 year in region, r

Yfish,rDependent on region

kg km−2[F2]

Edible fraction of catch

Fed,fish

0.5

—

[S6]

Area of compartment, cAc

Local: 1 × 102

km2(see section III.C of maintext)

Sv Bq−1[I14]

Regional: 1 × 10

6Adults dose coefficient for ingestion

Ding,i

Dependent on radionuclide

Collective dose from ingestion of shellfish

S E (ing,marine ), f ,c ,r ,=i C f ,c ,i ⋅ Y f ,r ⋅ Fed, f ⋅ Lc ⋅ Ding,iCollective dose from ingestion of marine food, f,(where f ∈ {molluscs,crustaceans} ) in

(M53)

S E (ing,marine ), f ,c ,r Equation (M53)

man Sv—

compartment, c, for radionuclide, iActivity concentration of radionuclide, i, in marine
food, f, in compartment, c

C f , c ,iEquation (M46)

Bq kg−1—

Harvest of marine food, f, in 1 year per unit length ofcoastline in region, rY f ,rDependent on region

kg km−1[F2]

Edible fraction of catch for marine food, fFed, fCrustaceans: 0.35

—

[S6]

km

(see section III.C of maintext)

Molluscs: 0.15
Length of coastline in compartment, c

Lc

Local: 10
Regional: 1 000

Adults dose coefficient for ingestion

Ding,i

Dependent on radionuclide

Sv Bq−1[I14]

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 121

Parameter

Symbol

Value

Units

Reference

Total collective dose from all marine pathways

S E ( marine ),c ,r ,i = ∑ S E (ing,marine ), f ,c ,r ,i

(M54)

f

Total collective dose in compartment, c

S E ( marine ),c ,r ,iEquation (M54)

man Sv—

Collective dose from consumption of food, f, incompartment, c

S E (ing,marine ), f ,c ,r Equations (M52) and (M53)

man Sv—

GLOBAL DISPERSION
Collective doses from tritium, 14C, 85Kr and 129I calculated by PC-CREAM (incorporates global dispersion models referenced in UNSCEAR 2000
Report [U6])122 UNSCEAR 2016 REPORT

Table A5. Treatment of progeny for atmospheric and terrestrial pathways
Half-lives are given in brackets to two significant figures [I9]Discharged
parentProgeny

Exposure pathway
Plume (external irradiationand inhalation)

Deposited material(external irradiation)

Food (ingestion)

Y (64 h)Dose coefficient for
inhalation of parent
accounts for progeny.
Activity concentration ofprogeny assumed equal toparent for estimatingexternal exposure

Deposition and dose
rates calculated forparent and progeny
separately

Dose coefficient for ingestion ofparent accounts for progeny

Sr (29 a)

90

106

Ru (370 d)

106

Rh (30 s)

Secular equilibrium
assumed. Dose rates
calculated for both parent
and progeny

Deposition and dose
rates calculated forparent and progeny
separately

Dose coefficient for ingestion ofparent accounts for progeny

135

Xe (9.1h)135

Cs (2.3 × 106 a)

Activity concentrations ofprogeny in air calculated
explicitly based on transit
time

Deposition and dose rate
calculated for progeny

Activity concentration calculated from
deposition rate for progeny138

Xe (14 m)

138

Cs (32 min)

Activity concentration ofprogeny in air calculated
explicitly based on transit
time

Deposition and dose rate
calculated for progeny

Activity concentration calculated from
deposition rate for progeny137

Cs (30 a)137m

Ba (2.6 min)Dose coefficient for
inhalation of parent
accounts for progeny.
Activity concentration ofprogeny calculated at yieldof 94.6% for estimatingexternal exposure

Deposition and dose
rates calculated forparent and progeny
separately

Dose coefficient for ingestion ofparent accounts for progeny

210

Pb (22 a)210

Bi (5.0 d)

210

Po (140 d)

Ingrowth insignificant
during plume transit;
progeny not considered

Negligible dose fromprogeny following
ingrowth after
deposition of 210Pb; notconsidered

Ingrowth following deposition of 210Pb
to soil and plant, but activity
concentration of 210Po in terrestrial
foods significantly lower than fordeposition of 210Po; subsequent
small doses compared to those from
210
Pb; ingrowth not considered218

Po (3.1 min)214

Pb (27 min)214

Bi (20 min)214

Po (164 μs)

210

Pb (22 a)

Negligible contributions
to dose from
deposition of progeny
compared with dosefrom inhalation; notconsidered

Because of time taken for ingrowth
and reduced activities of long-lived
progeny compared to 222Rn,
negligible doses from ingestion ofprogeny in terrestrial foods; notconsidered210

Bi (5.0 d)

210

Po (140 d)

Dose coefficient for
inhalation of 222Rn includes
contribution from four
immediate short-lived
progeny [U9]. Longer lived
progeny (210Pb, 210Bi and
210Po) will not grow induring plume transit andso not considered

90

222

Rn (3.8 d)

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 123

Discharged
parent226

232

Ra (1 600 a)

Th (1.4 × 1010 a)Progeny222

Rn (3.8 d)

218

Po (3.1 min)214

Pb (27 min)214

Bi (20 min)214

Po (164 μs)

210

Pb (22a)210

Bi (5.0 d)

210

Po (140 d)

228

Ra (5.8 a)

228

Ac (6.1 h)

228

Th (1.9 a)

212

Pb (11 h)

234

U (2.4 × 105 a)

230

Th (7.7 × 104 a)

238

U (4.5 × 109 a)

234

Th (24 d)
Pa (1.2 min)

234m

239

Pu (2.4 × 104 a)

235

U (7.0 × 108 a)

240

Pu (6 500 a)

236

U (2.3 × 107 a)

241

Am (430 a)

237

Np (2.1 × 106 a)

Exposure pathway
Plume (external irradiationand inhalation)

Deposited material(external irradiation)

Food (ingestion)

Ingrowth insignificant
during plume transit;
progeny not considered

Ingrowth following
deposition of 226Ra, butradon gas largely
emitted to atmosphereand further diluted.
Small doses fromprogeny comparedwith parent; notincluded

Ingrowth following deposition of226
Ra, but radon gas largely emitted toatmosphere and further diluted. Smalldoses from progeny compared withparent; not included

Secular equilibrium
assumed; activity
concentration in air
assumed equal to parent

Deposition rate
calculated for eachprogeny in secularequilibrium

Activity concentration of parent in air
used as proxy for secular equilibrium
in soil after 100 years. Only 228Ra,
228
Th and 212Pb included

Parent half-life sufficiently long that ingrowth not relevant at 100 years
Secular equilibrium
assumed; activity
concentration in air
assumed equal to parent

Deposition rate
calculated for eachprogeny

Activity concentration of parent in air
used as proxy for secular equilibrium
in soil after 100 years. Only 234Th
includedParent half-life sufficiently long that ingrowth not relevant at 100 years

124 UNSCEAR 2016 REPORT

Table A6. Treatment of progeny for freshwater pathways
Half-lives are given in brackets to two significant figures [I9]Discharged parent

Progeny

Exposure pathway
Riverbank occupancy90

Sr (29 a)90

Ru (370 d)

106

106

Y (64 h)Secular equilibrium
assumeda

Rh (30 s)

Secular equilibrium
assumeda137

Cs (30 a)

137m

210

Pb (22 a)210

Bi (5.0 d)

210

Po (140 d)

222

Rn (3.8 d)

218

Po (3.1 min)214

Pb (27 min)214

Bi (20 min)214

Po (164 μs)

210

Pb (22 a)210

Bi (5.0 d)

210

Po (140 d)

228

Ra (5.8 a)

228

Ac (6.1 h)

228

Th (1.9 a)

212

Pb (11 h)

226

232

Ra (1 600 a)

Th (1.4 × 1010 a)Ba (2.6 min)234

U (2.4 × 105 a)

230

Th (7.7 × 104 a)

238

U (4.5 × 109 a)

234

Th (24 d)
Pa (1.2 min)

234m

a

239

Pu (2.4 × 104 a)

235

U (7.0 × 108 a)

240

Pu (6 500 a)

236

U (2.3 × 107 a)

241

Am (430 a)

237

Np (2.1 × 106 a)

Freshwater fish

Drinking water

Irrigated food

Dose coefficient for ingestion of parent accounts for progeny

Ba activity
concentration in filteredwater calculated at yieldof 94.6% a137m

Negligible doses from
ingrowth compared withtotal dose for 210Pb; notconsidered
Rn gas mainly emitted toatmosphere;
contributions from
subsequent progeny
omitted222

Secular equilibrium
assumeda

Ingrowth limited during transit time in freshwater body;doses from progeny not included

Secular equilibrium
assumed in water a

Secular equilibrium
assumed in
untreated water a

Deposition rate ofparent used asproxy for secularequilibrium in soil
after 100 years.
Only 228Ra, 228Th
and 212Pb included

Parent half-life sufficiently long that ingrowth not relevant at 100 years
Secular equilibrium
assumeda

Dose rates calculated from parent and each progeny separately.

Secular equilibrium
assumed in water a

Secular equilibrium
assumed in
untreated water a

Deposition rate ofparent used asproxy for secularequilibrium in soil
after 100 years.
Only 234Th included

Parent half-life sufficiently long that ingrowth not relevant at 100 years

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 125

Table A7. Treatment of progeny for marine pathways
Half-lives are given in brackets to two significant figures [I9]Discharged
parentProgeny

Exposure pathway
Beach occupancy

Sr (29 a)

90

106

Ru (370 d)

106

137

Cs (30 a)

137m

210

Pb (22 a)210

Bi (5.0 d)

210

Po (140 d)

222

Rn (3.8 d)

218

Po (3.1 min)214

Pb (27 min)214

Bi (20 m)

214

Po (164 μs)

210

Pb (22 a)210

Bi (5.0 d)

210

Po (140 d)

228

Ra (5.8 a)

228

Ac (6.1 h)

228

Th (1.9 a)

212

Pb (11 h)

90

Marine foodY (64 h)Secular equilibrium assumeda226

Ra (1 600 a)Th(1.4 × 1010 a)

232

Dose coefficient for ingestion of parent accounts forprogeny

Rh (30 s)
Ba (2.6 min)234

U (2.4 × 105 a)

230

Th (7.7 × 104 a)

238

U (4.5 × 109 a)

234

Th (24 d)

Ba activity in local/regional compartment
and on beach calculated at yield of 94.6%a137m

Secular equilibrium assumeda

Secular equilibrium assumed in water;
bioaccumulation factors for parent and progeny
explicitly applied

Most radon is assumed not emitted toatmosphere; secular equilibrium assumed a

Secular equilibrium assumed in water;
bioaccumulation factors for parent and progeny
explicitly applied

Secular equilibrium assumed a

Secular equilibrium assumed in water;
bioaccumulation factors for parent and progeny
explicitly applied

Parent half-life sufficiently long that ingrowth not relevant at 100 years
Secular equilibrium assumed aPa (1.2 min)

234m

a

239

Pu (2.4 × 104 a)

235

U (7.0 × 108 a)

240

Pu (6 500 a)

236

U (2.3 × 107 a)

241

Am (430 a)

237

Np (2.1 × 106 a)

Secular equilibrium assumed in water;
bioaccumulation factors for parent and progeny
explicitly applied

Parent half-life sufficiently long that ingrowth not relevant at 100 years

Dose rates from external exposure calculated from parent and each progeny separately.

ANNEX A: METHODOLOGY FOR ESTIMATING PUBLIC EXPOSURES DUE TO RADIOACTIVE DISCHARGES 127

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