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
The report of the Committee without its annexes appears as Official Records of the General
Assembly, Seventy-first Session, Supplement No. 46 and corrigendum (A/71/46 and Corr.1). The
report ­reproduced here includes the corrections of the corrigendum.
The designations employed and the presentation of material in this publication do not imply
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The country names used in this document are, in most cases, those that were in use at the time thedata were collected or the text prepared. In other cases, however, the names have been updated,
where this was possible and appropriate, to reflect political changes.

UNITED NATIONS PUBLICATION
Sales No. E.17.IX.1
ISBN: 978-92-1-142316-7
eISBN: 978-92-1-060002-6© United Nations, January 2017. All rights reserved, worldwide.
This publication has not been formally edited.
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ANNEX B
RADIATION EXPOSURES FROMELECTRICITY GENERATION

135

Corrigendum to Sales No. E.17.IX.1

1 August 2017

Sources, Effects and Risks of Ionizing Radiation: United
Nations Scientific Committee on the Effects of Atomic
Radiation 2016 Report to the General Assembly, with
Scientific Annexes — Scientific Annexes A, B, C and D
Corrigendum
1. Annex B (Radiation exposures from electricity generation), page 142, table 1,
footnote a
The footnote should read
The value for the nuclear fuel cycle was 5.7 man Sv/(GW a); for globally-circulating
radionuclides after 100 years the value was 12 man Sv/(GW a); for uranium mine andmill tailings after 100 years of radon releases, the value was 0.25 man Sv/(GW a).
2. Annex B (Radiation exposures from electricity generation), page 142, table 1,
footnote e
The footnote should read
The value for the nuclear fuel cycle was 3.0 man Sv/(GW a); for globally-circulating
radionuclides after 10,000 years the value was 50 man Sv/(GW a); for uranium mineand mill tailings after 10,000 years of radon releases, the value was 150 man Sv/(GW a).

V.17-05540 (E)*1705540*

Corrigendum to Sales No. E.17.IX.1

15 December 2020

Sources, Effects and Risks of Ionizing Radiation: United
Nations Scientific Committee on the Effects of Atomic
Radiation 2016 Report to the General Assembly, with
Scientific Annexes
Corrigendum
Annex B (Radiation exposures from electricity generation), page 164, table 14
Column headed “Asia and Pacific”, subsection entitled “Aquatic discharges”
In the entry for Power plants, for 1.5 × 10−4 read 8.4 × 10−5
Column headed “Europe”, subsection entitled “Aquatic discharges”
In the entry for Power plants, for 1.2 × 10−3 read 6.6 × 10−4
In the entry for Reprocessing, for 6.9 × 10−4 read 6.0 × 10−4
Column headed “Latin America”, subsection entitled “Aquatic discharges”
In the entry for Power plants, for 1.5 × 10−4 read 1.0 × 10−4
Column headed “North America”, subsection entitled “Aquatic discharges”
In the entry for Power plants, for 5.0 × 10−5 read 4.1 × 10−5
Column headed “Asia and Pacific”, subsection entitled “Total for all discharges”
In the entry for Power plants, for 2.0 × 10−4 read 1.3 × 10−4
Column headed “Europe”, subsection entitled “Total for all discharges”
In the entry for Power plants, for 1.3 × 10−3 read 7.3 × 10−4
In the entry for Reprocessing, for 7.5 × 10−4 read 6.6 × 10−4
Column headed “Latin America”, subsection entitled “Total for all discharges”
In the entry for Power plants, for 2.6 × 10−4 read 2.1 × 10−4
Column headed “North America”, subsection entitled “Total for all discharges”
In the entry for Power plants, for 1.1 × 10−4 read 9.9 × 10−5

V.20-07527 (E)*2007527*

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 137

CONTENTSI.

INTRODUCTION ................................................................................................................................. 139
A. Scope............................................................................................................................................. 140

II. BACKGROUND ................................................................................................................................... 141
A. Global trends in electricity generation technology ..................................................... 142
B. Electricity generation worldwide in 2010 ........................................................................ 144
III. ASSESSMENT APPROACH AND END POINTS .......................................................................... 145
A. Recapitulation of key features of the methodology for estimating
public exposures due to radioactive discharges ........................................................... 147
IV. RADIATION EXPOSURES ARISING FROM ELECTRICITY GENERATION BY NUCLEAR
POWER ......................................................................................................................................................... 151
A. Introduction................................................................................................................................ 151
B. Public exposure ......................................................................................................................... 152
C. Occupational exposure for the nuclear fuel cycle ........................................................ 174
D. Decommissioning..................................................................................................................... 178
V. RADIATION EXPOSURES ARISING FROM ELECTRICITY GENERATION BY COMBUSTION
OF FOSSIL FUELS ...................................................................................................................................... 182
A. Coal ................................................................................................................................................ 182
B. Natural gas .................................................................................................................................. 194
C. Oil ................................................................................................................................................... 197
D. Comparisons of exposures from fossil-fuel electricity generation ......................... 199
VI. RADIATION EXPOSURES ARISING FROM ELECTRICITY GENERATION FROMGEOTHERMAL ENERGY........................................................................................................................... 199
VII. ASSESSING DOSES FROM THE CONSTRUCTION PHASE OF ELECTRICITY-GENERATINGTECHNOLOGIES ........................................................................................................................................ 201
VIII. COMPARISON OF RADIATION EXPOSURES FROM ELECTRICITY-GENERATINGTECHNOLOGIES ........................................................................................................................................ 211
A. Comparison of public exposures due to radioactive discharges fromthe electricity-generating technologies based on the nuclear fuelcycle, coal cycle, combustion of natural gas and oil, and use ofgeothermal energy .................................................................................................................. 211
B. Comparison of public and occupational exposures .................................................... 220
C. Commentary on significance of accidents ...................................................................... 224

138 UNSCEAR 2016 REPORTIX. RESEARCH NEEDS ............................................................................................................................. 225
X. CONCLUSIONS................................................................................................................................... 227
XI. ACKNOWLEDGEMENTS .................................................................................................................. 229
REFERENCES ............................................................................................................................................... 231

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 139

I. INTRODUCTION
1.
A reliable and affordable supply of electricity is important to improve human health and welfare
worldwide, an objective recognized by both the United Nations Millennium Development Goals [U2,U3] and Sustainable Development Goals. 1 However, policy makers and the general public also haveinterest in the impacts of electricity generation on humankind and the environment.
2.
Interest in exposure of the public and workers to radiation due to nuclear power dates back to theearliest use of the technology. The first UNSCEAR Report to the General Assembly in 1958 included
data on exposures of contract employees of the United States Atomic Energy Commission and arecognition of the need to keep track of the exposure of workers in view of the anticipated growth in theuse of nuclear technology and the associated worker population [U4]. Since then, the Committee has
periodically reviewed exposures of both the public and of workers, related to nuclear power [U5, U6,
U7, U8, U9, U11]. As a result, the Committee’s records of exposures of workers and the public from
nuclear power provide one of the most complete and accurate global pictures of radiation exposuresfrom any source of ionizing radiation.
3.
The Committee has conducted evaluations of radiation exposures of the public arising from formsof electricity generation other than nuclear power to a much more limited extent. Radiation exposuresfrom industrial activities outside of the nuclear sector are generally not monitored or reported in asystematic manner; consequently, the assessment of these exposures has often relied on incomplete datafrom isolated surveys or ad hoc collection of data from various reports and publications.
4.
The Committee’s thematic priorities identified in its strategic plan 2 for 2009–2013 included
radiation levels of energy production and in its plan 3 for 2014–2019 the global impact of energy
production. The Committee decided to update its assessments of the exposures from electricity
generation, considering the principal relevant commercial technologies, both nuclear and non-nuclear.
5.
The world’s mix of electricity-generating technologies changes over time in response to thelandscape of climatic, environmental, resource, political and economic challenges. Governments andresearchers may conduct various comparative studies that among other things take into account thevarious implications for the public and the environment of the different technologies. Exposure toionizing radiation is only one of the many factors that such assessments may take into account.
However, the Committee considers that an update and extension of its past assessments of radiation
exposures of the public and workers from electricity generation could be a useful source of information
for such studies.
6.
This scientific annex thus presents an analysis of the total population exposure, public andoccupational, to ionizing radiation from the different life cycle stages of electricity-generating
technologies, normalized to the electricity generated during one year for that technology. The annex isalso an update and extension of the Committee’s earlier evaluations of radiation exposures resulting
from discharges associated with different electricity-generating technologies. The Committee
1

Transforming our world: the 2030 Agenda for Sustainable Development. Resolution adopted by the General Assembly on
25 September 2015. General Assembly, Seventieth session, Agenda items 15 and 116 (A/RES/70/1).
2
Official Records of the General Assembly, Sixty-third session, Supplement No. 46 (A/63/46).
3
Official Records of the General Assembly, Sixty-eighth session, Supplement No. 46 (A/68/46).

140 UNSCEAR 2016 REPORT

emphasizes that the objective of this study was comparative in nature. Common approaches, available
data and balanced assumptions for assessing the main exposures and identifying the dominantcomponents of those exposures for different electricity-generating technologies have been used to theextent possible.
7.

Specifically, the following core questions have been addressed:− How do the individual and population exposures of humans to ionizing radiation that
result from different phases of the life cycle of each electricity-generating technology
compare with each other across the world and by region?
− What are the main factors, in terms of principal sources, radionuclides, time periods andexposed populations, contributing to the exposure for each technology?
− What would be needed to improve such assessments in the future in terms of data andresearch?

8.
To conduct the assessment, the Committee has in parallel reviewed and revised its methodology
for estimating exposures of the public due to radioactive discharges (annex A). Other exposures, suchas occupational exposures, are assessed using other methods described here.

A. Scope
9.
This annex describes an assessment of the exposures to ionizing radiation in the life cycle ofelectricity-generating technologies that are currently deployed commercially, and fuelled by nuclear
energy, combustion of coal, oil or gas, geothermal energy, solar energy, wind or biomass. The
assessment includes exposures from activities in the life cycle of each technology that are relevant to theradiological impact, from construction to decommissioning. For electricity-generating technologies
using solar energy, wind and biomass, the only activity that has been assessed in this context is themining of metals needed for construction. Exposures from electrical energy storage, transmission anddistribution are not considered. Moreover, the evaluation does not address energy generation other thanelectricity generation, such as process heat generation or other means of distributing energy, such as
district heating.
10. The assessment considers normal operations only. Exposures from incidents and accidents are notconsidered in detail here; the Committee has earlier reviewed radiation exposures in accidents (annex C[U12]), and considered in detail the radiation exposures from the 1986 accident at the Chernobyl nuclear
power plant (annex D [U12]) and the 2011 accident at the Fukushima-Daiichi nuclear power station(annex A [U13]) and continues to monitor developments after these accidents. The annex discusses theirsignificance only in drawing conclusions from this assessment for the General Assembly.
11. The assessment is limited to considering individual and population exposure of humans.
Exposures of non-human biota in the environment are not considered. Assessing impacts other thanradiation exposure from electricity generation, such as social benefits, economic issues, or nonproliferation or security matters, is outside of the Committee’s remit and competence.
12. This work aims to compare exposures to ionizing radiation for different electricity-generating
technologies where individual and collective doses may be used for performing a comparative exposure
assessment. However, calculated doses are recommended only for comparative purposes and not forANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 141

estimations related to health effects. It is important to state that collective doses, as used here, are solely
an instrument to compare radiation exposures for different technologies used for electricity generation.
Collective dose is not intended as a tool for epidemiological risk assessment. Moreover, the aggregationof very low individual doses over extended time periods is inappropriate for use in risk projections and,in particular, the calculation of numbers of cancer deaths from collective doses based on individual
doses that are well within the variation in background exposure should be avoided. Collective doses
estimated in this annex only provide information for decision makers and researchers on radiation
exposures from different electricity generation technologies. Dose estimations for the evaluation of
implications for health should be more specific to each exposure situation.
13. The annex begins with a chapter providing background information to support the study, followed
by a chapter discussing the assessment approach and the end points for the study. That chapter also
includes a description of terminology relevant to applying the methodology for estimating public
exposures due to radioactive discharges (see annex A). The following chapters cover the radiation
exposures arising from electricity generation from each of the electricity-generating technologies: nuclear
fuel cycle, fossil fuel energy (coal, oil and gas) and geothermal energy. Next comes a chapter on assessing
occupational doses from the mining of metals for the construction phase of the electricity-generating
technologies: nuclear, coal, natural gas and the renewable technologies (biomass, solar and wind). Finally,
there are chapters that include comparisons of exposures from the principal electricity-generating
technologies, discussions of uncertainties, suggestions for future work that could improve understanding,and concluding remarks. Note that all supporting values and calculations were manipulated with full
precision and any discrepancies in the numbers presented in tables and figures are due to rounding.

II. BACKGROUND
14. The Committee’s past assessments in this field have covered each stage of the nuclear fuel cycle:
resource extraction (uranium mining and milling); fuel manufacture (uranium enrichment and fuelfabrication); power generation (nuclear power reactors); reprocessing of spent nuclear fuel to recoveruranium and plutonium for subsequent use in nuclear fuels; and the management of solid wastes
generated at the various stages. They have also included exposures from transportation activities within
and between the fuel-cycle stages [U5, U6, U7, U8, U9, U11].
15. The Committee’s most recent and comprehensive review of public exposures due to non-nuclear
electricity generation (coal, oil, natural gas, peat and geothermal technologies) was published in 1993
[U8], based principally on the parameters and assessments presented in the UNSCEAR 1988 Report[U7] and the assessment methodology adopted in the UNSCEAR 1982 Report [U6]. Public exposures
were expressed in terms of the collective effective dose normalized to electricity generated, in units ofman–sieverts per gigawatt–year. The results from those earlier UNSCEAR assessments of normalized
collective effective doses to the public from discharges for various electricity-generating technologies
are summarized in table 1.
16. According to the UNSCEAR 1993 Report, public exposures in terms of collective effective dose per
year of practice and per unit of electricity generated due to the burning of coal and peat, and due togeothermal sources exceeded that due to operational discharges from nuclear power generation. However,with continued improvements in efficiency of electricity generation from fossil-fuel plants and in emission
control technology, those earlier estimates of the Committee were deemed very likely to be outdated andpotentially misleading. Reductions in exposures were expected from newer and retrofitted power plants.

142 UNSCEAR 2016 REPORT

Since its 1993 evaluation, the Committee had only updated its estimates of exposures from the generationof nuclear power, where the most recent estimates showed a decrease for the normalized collective
effective dose to the public from power plant operation from 0.45 man Sv/(GW a) for the period 1990–
1994 to 0.27 man Sv/(GW a) for the period 1998–2002 [U11].
Table 1. Collective effective dose to the public normalized to electricity generated due todischarges from different electricity-generating technologies from previous UNSCEAR assessments

UNSCEAR ReportaNormalized collective effective dose to public(man Sv/(GW a))
Nuclear power
plant operation

Coal

Peat

Gas

Oil

Geothermal

1982 [U6]

4.2a

2

—

—

—

6

1988 [U7]

2.5

c

4

2

0.03

0.5

2

1993 [U8]d

1.34e

20f

—

(0.03)(0.5)(2)

2000 (for 1990-1994) [U9]

0.45g

—

—

—

—

—

2008 (for 1998-2002) [U11]

0.27

—

—

—

—

—

b

h

The value for the nuclear fuel cycle was 5.7 man Sv/(GW a); for globally-circulating radionuclides after 100 years the value was

12 man Sv/(GW a); for uranium mine and mill tailings after 100 years of radon releases, the value was 0.25 man Sv/(GW a).
b

The value for the nuclear fuel cycle was 4.0 man Sv/(GW a); for mine and mill tailings and globally-circulating radionuclides
the total was 200 man Sv/(GW a).
c

The value was 6 man Sv/(GW a) for older coal-fired power plants, which were considered to constitute two thirds of the world
total and 0.3 man Sv/(GW a) for modern coal-fired power plants, which were considered to constitute one third of the world total.

d

The values reported in the UNSCEAR 1993 Report [U8] for gas, oil and geothermal technologies were not from newassessments but taken from the UNSCEAR 1988 Report [U7].

eThe value for the nuclear fuel cycle was 3.0 man Sv/(GW a); for globally-circulating radionuclides after 10,000 years the value

was 50 man Sv/(GW a); for uranium mine and mill tailings after 10,000 years of radon releases, the value was 150 man Sv/(GW a).
f

From coal-fired power plants (assumed one third modern-style, one third old-style and one third Chinese-style [U8]).

g

The reported dose value is for power plant operation only.

h

The value for the nuclear fuel cycle was 0.72 man Sv/(GW a).

A. Global trends in electricity generation technology
17. Figure I shows the global trends in electricity generation and contributions made by the various
electricity-generating technologies between 1980 and 2014. Combustion of coal for electricity
generation has dominated during this period with nearly 40% of total electricity generated; at the sametime, total global electricity generation has grown by about a factor of three. The use of both natural gas
and nuclear fuels to generate electricity has grown as a percentage of the total and also in total amountof electricity generated over the same period. The use of oil has fallen as a percentage of the total, but
only slightly in total electricity generated. The use of hydropower has increased in the total amount ofelectricity generation, although it has fallen as a percentage of the total. The contribution of the “others”
category, which includes renewable energies (geothermal, wind, solar and biomass), has increased from
1% to 7% during the 34 years, with a faster increase in their use since about 2008.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 143

Figure I. Trends in worldwide electricity generation (GW a) from 1980 to 2014
The “others” category comprises geothermal, solar, wind, biomass and waste [W13]. Supporting values were expressed as full
precision and any discrepancies in the numbers presented are due to rounding

144 UNSCEAR 2016 REPORTB. Electricity generation worldwide in 2010
18. The reference year for assessments presented in this annex is 2010. Table 2 and figure II
summarize worldwide electricity generation in 2010 [I15]. Total electricity generation worldwide in2010 is reported as 2,452 GW a (table 2), which also shows the contribution by type for the six
geographical regions of the world as adopted by the United Nations Environment Programme (UNEP).
These regions are the same as those used in annex A. Marginally different values for electricity
generated by nuclear power in 2010 were obtained from IAEA [I6] and used in the application of therevised methodology for estimating public exposures due to radioactive discharges (annex A). The
IAEA database [I6] provided detailed data on electricity generated in 2010 both by region and as afunction of reactor type; these data were not used to generate table 2, but were used in the more detailed
assessments discussed in chapter IV.B.2.
19. Total annual average worldwide electricity generated from nuclear power plants 1998–2002 wasreported as 278 GW a in table 16 and table A-5 from [U11], which can be compared to 314 GW a for 2010.
Table 2. Summary of worldwide electricity generated in 2010
Supporting values were manipulated with full precision and any discrepancies in the numbers presented are due to rounding

Electricity generated in 2010 (GW a) [I15, I16]

Type
AfricaAsia and
Pacific

EuropeLatin America
and Caribbean

North
America

West
Asiaa

Total

Nuclearb

1.38

66.4

137.4

3.14

106.0

—

314.3

Coal

29.6

567.7

150.6

6.26

237.4

0.00

991.6

Gas

22.7

146.9

177.0

35.8

122.0

39.4

543.8

Oil

9.26

36.9

12.8

20.2

6.33

27.1

112.6

Geothermal

0.17

3.19

1.28

1.13

2.00

—

7.77

Solar

0.06

0.68

2.62

0.03

0.47

0.00

3.86

Wind

0.23

8.80

17.4

0.14

11.9

0.00

38.5

Biomass

0.09

5.95

17.3

4.85

9.59

0.00

37.8

Hydro

12.4

128.6

105.3

80.9

72.7

0.94

400.8

Tide

—

—

0.11

0.02

0.00

—

0.13

Other

—

0.00

0.55

—

0.10

—

0.65

Total

76

965

622

153

569

67

2 452

a

The numerical entry 0.00 corresponds to no electricity generated and the entry — corresponds to no data available. West Asia isomitted in all tables generated from the assessments reported in this annex, except for the assessments on gas and oil.

b

Marginally different values, obtained from IAEA [I6], were used in the application of the revised methodology for estimating
public exposures due to radioactive discharges (annex A) for the electricity generated by nuclear power in 2010.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 145

Figure II. Breakdown of the electricity generated worldwide in 2010 by generation technology
Derived from data in table 2 (excluding contributions from “Tide” and “Other”. Supporting calculations were made to full
precision and any discrepancies in the final numbers are due to rounding

III. ASSESSMENT APPROACH AND END POINTS
20. The main end point in this annex is an assessment and comparison of collective doses, andcollective doses normalized to the electricity produced, for one year of different electricity-generating
technologies, using consistent assessment approaches. To this end, the dominant exposure pathways foreach of the electricity-generating technologies considered in this study have been assessed.
21. The Committee conducted this study by investigating sources of exposure from electricitygenerating technologies based on (a) nuclear power, (b) the combustion of coal, natural gas, oil andbiofuels, and (c) geothermal, wind and solar power. Two electricity-generating technologies (nuclear
power and combustion of coal) were investigated in detail, because a more robust database existed forthese technologies. The Committee evaluated the main sources of radioactive discharges from the life
cycle of these electricity-generating technologies. For nuclear power, these sources included uranium
mining and milling, mill tailings, power plant operation and reprocessing activities. For combustion ofcoal, they were the mining for coal, power plant operation for a prototype of both a modern coal plant
and an older-style coal plant, and deposits of coal ash. These sets of sources will hereafter be called the“nuclear fuel cycle” and “coal cycle”, respectively, for simplicity.

146 UNSCEAR 2016 REPORT

22. The Committee pursued two paths for the assessments presented in this annex. First,
UNSCEAR’s revised methodology for estimating public exposures due to radioactive discharges(annex A) was used to assess components of exposure due to electricity generation from the nuclear
fuel cycle and from the coal cycle in a consistent manner. These two technologies were chosen for
substantive treatment, because reasonably reliable input data existed and, from previous assessments,
they were known to be important. The use of a common methodology for these assessments allowed
consistent comparison of estimated exposures from the two technologies. A significant end point tothese assessments was to identify and discuss dominant sources of exposure from these two electricitygenerating technologies, and the dominant radionuclides contributing to those exposures.
23. The second path was to derive reasonable estimates of public exposures arising from the otherelectricity-generating technologies, and occupational exposures from all the electricity-generating
technologies considered. This permits a rough comparison of the total human exposure from each of theelectricity-generating technologies normalized to the energy generated by each technology.
24. For those electricity-generating technologies relying on power plants that burn natural gas or oil
as fuel, and power plants driven by geothermal energy, an important exposure pathway is radon gas
discharged to atmosphere. The Committee’s revised methodology for estimating public exposures due
to radioactive discharges (annex A) has been used for assessing atmospheric discharges from thesetechnologies.
25. The revised methodology (annex A) was designed for assessing public exposures from routine
releases of radionuclides to the environment during normal operations, and not for assessing occupational
exposures. Thus, occupational exposures due to electricity generation from the nuclear fuel cycle and fromthe coal cycle have been assessed here primarily from data on occupational exposure from the UNSCEAR
2008 Report [U11], adjusted for electricity generated in 2010. In some cases, particularly occupational
exposures from mining for coal and uranium and other metals, relevant new data have been obtained andestimates of dose commitments have been updated for 2010. Occupational exposures from the mining of
metal ores needed for the construction of power plants or power-generating equipment have been assessedand compared for the various electricity-generating technologies.
26. Assessments have also been made of collective effective doses for the entire decommissioning
phase of nuclear power plants based on available data on occupational exposures from existing
decommissioned plants.
27. Exposures of the public and workers due to radioactive materials from conventionalhydroelectricity generation were not included in this annex. This is because no radioactive materials aredischarged during normal operations, and the magnitude of discharges of radioactive materials andresulting exposures when constructing dams were deemed negligible when compared to otherexposures (for example, the mining of metals or mining for other fuels, such as coal or uranium). The
main exposure situation associated with hydroelectricity generation was considered to be occupational
exposure during the mining of metals needed for construction of the power plants. However, thisexposure was not evaluated because hydroelectric plants have considerable variation in their size,
leading to large uncertainties when adopting a standard plant design for assessment.
28. Finally, the total exposures during one year, including both public and occupational, for eachelectricity-generating technology (nuclear fuel cycle, coal cycle, oil, natural gas, geothermal, solar andwind), have been compared. Three main phases that contribute to the total exposure of the public andworkers for each technology have been considered: preparation, operation and decommissioning. For
all discharges, the same methodology has been used to estimate public exposures—a significant
improvement over the Committee’s earlier assessments.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 147

A. Recapitulation of key features of the methodology for estimating
public exposures due to radioactive discharges
29. The following paragraphs recapitulate some of the key features of the methodology described inannex A that are relevant for the assessment here.
30. World-average. This term is used to qualify data that are intended to represent a value averaged
across the whole world. For example, for the default population distributions (shown in table 3 ofannex A), the world-average population for a distance band is derived from the average of the values
for the distance band within each UNEP region, weighted by the population in each region. Similarly,
world-average consumption rates for terrestrial and aquatic foods are derived from the values for each
UNEP region weighted by the populations in each region.
31. Dose. In all cases and unless otherwise stated, dose refers to the protection quantity, effective
dose. The annual effective dose is the sum of the dose from external exposure in that year plus thecommitted dose from intakes by inhalation and ingestion in that year. For doses integrated over a
period, it is the sum of integrated doses from external exposure over the period and committed doses
from the integrated intakes by inhalation and ingestion over the period. Doses to the public are only
estimated for adults and the period considered for the committed dose is 50 years, i.e. adult ages from
20 to 70 years.
32. Characteristic individual dose. The individuals considered are those living in the area local to thepoint of discharge with behaviour indicative of the majority of people living in that area. The dose tothese characteristic individuals is referred to here as the “characteristic individual dose”.
33. For discharges to atmosphere, the characteristic individuals were assumed to live 5 km from thedischarge point and to obtain 25% of their food from this distance. For discharges to rivers, thecharacteristic individual was assumed to be exposed to riverbank sediment 5 km downstream from thedischarge point, to drink all of their water from the river, and to eat 25% of the freshwater fish in theirdiet from the river plus 25% of their dietary grain and leafy vegetables irrigated with water from theriver. For discharges to marine environments, the characteristic individual was assumed to be exposed
to external irradiation from radionuclides in sediments from the local marine compartment using afactor to represent average occupancy of beaches. The characteristic individual is also assumed toconsume marine foods with 25% of their dietary fish from the local marine compartment and 75% fromthe regional compartment, while 100% of the dietary consumption of crustacea and molluscs wereassumed to be from the local compartment. In all cases the consumption rates used were the average fora population. These assumptions are discussed in detail in annex A.
34. Collective doses. The standard collective dose calculated here is the integrated dose to 100 years
from one year’s discharge. (For the modelling of the globally-circulating radionuclides, collective doses
integrated to 500 and 10,000 years are also calculated, see paragraph 39.) The end point for all
radionuclides calculated in annex A was the collective dose per unit discharge integrated to 100 years.
For releases to atmosphere, the local and regional components of the collective doses derive from doses
to populations within a distance of 1,500 km from the discharge point and are based on four different
types of population distributions:(a) A default population distribution based on population densities for 2010. Values of population
density are given for six different regions (as adopted by UNEP) and also a world-average value (apopulation-weighted average of the population density for the UNEP regions). These are used toassess collective doses due to discharges from the coal cycle, combustion of gas and oil, andgeothermal energy.

148 UNSCEAR 2016 REPORT(b) The population distribution around nuclear power stations situated on the coast. Values of theaverage population within distance bands around coastal nuclear power stations are given forfive regions as adopted by UNEP (but not West Asia because there was no operating nuclear power
station in this region at the time of the assessment) and also an average value for the world. The
population densities were based on data for coastal sites of actual nuclear power stations
throughout the world and the distributions are arithmetic means of the data for distance bands
around each coastal site located in the region of interest.
(c) The population distribution around nuclear power stations situated inland. Values of theaverage population within distance bands around inland nuclear power stations are given for
four regions as adopted by UNEP (but not Africa or West Asia because there were no operating
nuclear power stations located inland in these regions at the time of the assessment) and also anaverage value for the world. The population densities were based on data for inland sites of actual
nuclear power stations throughout the world and the distributions are arithmetic means of the datafor distance bands around each inland site located in the region of interest.
(d) A single value of population density for remote sites of 5 km-2. This is used to assess collective
doses due to discharges from uranium mines and mill tailings, which are located in areas of very low
population density. This value is also used in an alternate calculation to assess collective doses due todischarges from geothermal sites. Values for regions of the world are not provided for these cases.
35. For releases to atmosphere, a distinction could be made between the local component of collective
dose (to populations within a distance of 100 km) and a regional component of the collective doses (topopulations between 100 and 1,500 km). For aquatic releases to rivers and lakes, it was not possible todistinguish between local and regional components of the collective dose because of the method used to
calculate collective dose. However, for discharges to marine environments, local and regional
compartments were used to model the dispersion of the released radionuclide, and therefore local andregional components of the collective doses could be provided. Note that the use of the word “regional”
here is distinct from its potential use as a qualifier meaning “related to the geographical regions adopted
by UNEP”.
36. Globally-circulating radionuclides. Four radionuclides (3H, 14C, 85Kr and 129I) were assumed to
become globally circulated and to continue to expose the world population for decades and, withregards to 14C, centuries, and 129I, millions of years. These radionuclides contribute to the local andregional component of collective dose when they are initially discharged (due to the so-called “firstpass”) and this component was modelled as for all other radionuclides. However, a global component
needs to be added separately for these radionuclides. Thus, an additional collective dose due to global
circulation was also modelled and results calculated. Results of the global model are provided fordischarges to atmosphere and to marine environments; for aquatic discharges to freshwater systems, theresults were assumed identical to those for a marine environment for the purposes of calculating the
global component of collective dose.
37. Integration times. The methodology applies to discharges that can be assumed to be continuous.
Account is taken of the build-up of long-lived radionuclides in the environment and the associatedcontinued exposure after the discharges have stopped. This is done by considering a year’s discharge ofa radionuclide, its dispersion in the environment and the subsequent exposure of people over many
years; the resulting dose rates are then integrated. A value of 100 years is used for the integration period
for the standard case (see further details in annex A).
38. Using the integrals it is also possible to consider that the discharges continue for many years fromthe same site. This is because the integrated dose to 100 years from one year’s discharge is numerically

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 149

equal to the dose in the 100th year from a continuous discharge at a constant rate over a 100-year
period. The characteristic individual doses are calculated by integrating dose rates to 100 years, which
also represent the annual dose that would be received in the 100th year of discharge.
39. Collective doses can be integrated to various times, but for most radionuclides it was sufficient tointegrate to 100 years because most of the collective dose commitment (i.e. the collective dosetheoretically integrated to infinity) is delivered during this period. However, for globally-circulating
radionuclides (i.e. 3H, 14C, 85Kr and 129I), the integrated collective dose continues to increase for many
years beyond 100 years (see annex A, paragraph 14). Therefore, for globally-circulating radionuclides,
collective doses integrated to 500 and 10,000 years were also calculated.
40. The main results of the revised methodology (annex A) are for a unit discharge for one year
integrated to 100 years and can be used to estimate the impact of one-year’s practice by, for example,
scaling the results by the discharge of radionuclides per unit of electricity generated, or the total
discharges from a particular type of electricity generation.
41. Waste residues from uranium mining and from coal-fired power stations. These wastes, uranium
mill tailings and coal ash, are often disposed of on the surface of the ground and they contain enhanced
levels of naturally occurring radionuclides, notably 226Ra which decays into the gas 222Rn, which can beemitted into the air for many years after the disposal occurs. The radon and its decay products give riseto human exposure (see figure III).
42. In this case one-year’s practice gives rise to a continuing discharge to atmosphere for many years.
Current best practice would rehabilitate mill tailings such that emissions were reduced to backgroundlevels (i.e. the levels that would occur from that area if the mine had not been present). Informationfrom Australia and elsewhere indicates that this process might take some 50 years and that monitoringis expected to continue for some 20 to 30 years to ensure that the rehabilitation has been successful andto monitor for any deterioration [S2, W1]. The question remains whether the site could deteriorate once
institutional control has finished, and radon emissions increase again. A base case integration time of
100 years seems reasonable with 10,000 years a cautious upper estimate.
43. Therefore, for radon discharges from land disposal of mill tailings or coal ash, allowance has to bemade for this continued discharge and this was done by multiplying the results for one year’s discharge
by 100 to allow for the discharge continuing for 100 years (see annex A, paragraph 17). This 100-year
multiplication is chosen for both individual and collective doses because 100 years is not muchdifferent from a human lifetime. The Committee has also considered the effect on the integrated
collective dose of a continuing discharge for 500 and 10,000 years.

150 UNSCEAR 2016 REPORT

Figure III. The 238U and 232Th decay series
Half-life is expressed in a = year; d = day; h = hours; m = minutes; s = seconds

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 151

44. Representative radionuclides for nuclear power plants. Discharges of radionuclides from nuclear
power plants are commonly reported by operators and regulatory bodies aggregated in groups. For
example in UNSCEAR 2008 discharges were reported as “noble gases” and “particulates” foratmospheric discharges, or “other nuclides” for liquid discharges. Accurate assessments of doses canonly be carried out on a radionuclide-specific basis and so where groups of radionuclides had beenreported, it was necessary either to apportion the discharge for the groups of nuclides among theradionuclides, or to use a “representative” radionuclide. The European Commission [E1] gives thepercentage of radionuclides discharged for different reactor types sited in Europe for different
groupings. For AGRs, FBRs and GCRs, 4 the discharges were split between the radionuclides
considered in the workbooks for the appropriate groupings (atmospheric noble gases, atmosphericparticulates and other liquids). The breakdown for GCRs was based on United Kingdom sites because
these were the only ones operational in 2010. For atmospheric particulate discharges from BWRs and
PWRs, 54Mn was selected as the representative radionuclide for any radionuclides not considered
explicitly in the workbooks. The grouping of “other liquids” did not previously include 14C and, formany countries and most reactor types, liquid discharges of 14C are not reported. However, examinationof EC RADD [E2] shows that for European PWRs liquid discharges of 14C are significant and therefore
30% of discharges from “other liquids” were assumed to be 14C for PWRs. For BWRs and PWRs any
liquid discharges for radionuclides not included in the workbooks were allocated equally between 54Mn
and 58Co. For HWRs, 41Ar, 60Co and 137Cs were assumed to represent discharges for noble gases,
atmospheric particulates and other liquids respectively, based on information in [B3, B5, C2]. For
LWGRs information was taken from the EC RADD database [E2].

IV. RADIATION EXPOSURES ARISING FROM ELECTRICITY
GENERATION BY NUCLEAR POWER
A. Introduction
45. The Committee has studied radiation exposures arising from electricity generation by nuclear
power repeatedly over the years since its first publication on this subject in 1958 (see especially [U6,U7, U8, U9, U11]). These studies have consistently shown that the major contribution to public
exposures has been through the discharges of natural radionuclides, primarily from: radon and its
progeny released during uranium mining and milling, and from mill tailings, associated with the nuclear
fuel cycle; and from carbon-14, primarily associated with reactor operation and fuel reprocessing.
46. The revised methodology for estimating public exposures due to radioactive discharges (annex A)
has been used here to assess public exposures from the following processes: uranium mining andmilling; electricity generation from nuclear power reactors; and fuel reprocessing. The assessments andresults for these processes are presented in the following section. The processes—uranium enrichment,
fuel fabrication and solid waste disposal—and their exposure characteristics are discussed in sections
4

The following abbreviations are used for the different nuclear power reactor types, categorized according to their coolant
systems and moderators: light-water-moderated and cooled pressurized or boiling-water reactors (PWRs and BWRs); heavywater-cooled and moderated reactors (HWRs); gas-cooled, graphite-moderated reactors (GCRs and AGRs); light-water cooled,graphite-moderated reactors (LWGRs); and the liquid metal cooled fast-breeder reactors (FBRs).

152 UNSCEAR 2016 REPORT

IV.B.4 and IV.B.5, and dose estimates for these processes that were published in the UNSCEAR 2008
Report [U11] have been used here. This chapter begins with the assessment of public exposures,
followed by that of occupational exposures, and ends with considering the occupational exposuresassociated specifically with the decommissioning process.

B. Public exposure
1.

Mining and milling

47. Uranium ore can be extracted from the earth by physically removing it through conventionalsurface or underground mining methods or by chemically dissolving the uranium out of the rock ore
through either heap leaching or in-situ leaching (ISL) (sometimes referred to as in situ recovery or ISR)
[U18]. Surface mining (also referred to as opencast, open pit or strip mining) techniques are applied toore bodies that are close to the surface, and are also a generally cost-effective method for extracting
large volumes of lower-grade ore, that may then be combined with other bulk extraction techniques(such as conventional milling, leaching and extraction, or alternative techniques such as heap leaching)which would be uneconomical for underground operations. Underground mining involves extractingrock through a tunnel or opening in the side of a hill or mountain and is generally applied for the
extraction of higher-grade ores. In-situ leaching is generally applied to shallow deposits that exist in
non-porous shale or mudstone, or in situations where uranium can be recovered from otherwise
inaccessible or uneconomical formations [U18].
48. Uranium ores typically contain from about 0.05 to 0.3% uranium oxide (U3O8) [U18]. After
extraction from the ground, the mined uranium ore is sent to a mill, which is usually located close to themine. This next step in the nuclear fuel cycle, called “milling”, involves the extraction and purificationof uranium from the uranium ore. After a first purification process, the uranium is precipitated in apartially refined form, known as “yellowcake”. The uranium concentrate, typically containing 75 to
95% uranium, is shipped to a chemical plant for further purification and chemical conversion [B4].
49. In-situ leaching is an alternative method for extracting uranium from low-grade ores or shallow
deposits that exist in non-porous shale or mudstone. An ISL plant chemically alters the uranium ore
underground before it is pumped out for processing. In the ISL process, wells are drilled into rockcontaining uranium ore. An alkaline or acidic solution (known as lixiviant) is injected down the wells todissolve the uranium in the rock. In the case of alkaline solutions, the lixiviant is usually (a) water
mixed with oxygen and/or (b) hydrogen peroxide mixed with sodium carbonate or carbon dioxide. In
the acid leach processes (used in Kazakhstan and Australia), sulphuric acid usage can result in lixiviant
solutions with pH as low as 1 being circulated into the ore body (the process in Kazakhstan is typicallystrongly acidic, while in Australia only mildly acidic). In some cases, an oxidant is added to increase
the efficiency of leaching. The lixiviant is then collected in a series of recovery wells, through which itis pumped to a processing plant. At the processing plant, the uranium is extracted from the solution
through an ion-exchange process, and the uranium oxide concentrate (yellowcake) is then precipitated,
dried and packed.
50. After recovery of the uranium, the barren solution is re-fortified with oxidant (if required) before
being returned to the well field via the injection wells. However, a small flow (about 0.5%) is bled off tomaintain a pressure gradient in the well field and this, with some solutions from surface processing, istreated as waste. This waste water contains various dissolved ions such as chloride, sulphate, sodium,radium, arsenic and iron from the ore body and is re-injected into approved disposal wells in a depleted

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 153

portion of the ore body. Wells must be monitored to ensure that extraction fluids do not leave the facility
or contaminate groundwater. Waste from this process, usually filters and piping, can be disposed in a
tailings pile at a mill site or a licensed disposal facility. In-situ leaching facilities have no radon dischargeduring the “mining” phase, and no surface tailings and little radon emission after closure [U11]. There canhowever be discharge of radon during the “leaching” phase of the ISL mining process, which here has
been assumed to be the same as the radon discharge occurring during the milling phase [B6, B7].
Chapter IX discusses the need for further study regarding the ISL mining process.
51. In 2014, 51% of the world’s uranium was mined using ISL operations, a share that has risen
steadily mainly because of mining operations in Kazakhstan [W8]. Table 3 shows the percentage
contribution from ISL-mining to total uranium production during the period from 2008 to 2012 in eachof the UNEP regions. For the reference year of 2010 used in this annex, the total uranium production
for 15 countries is given in table 4.
Table 3. Contribution of ISL-mining to total uranium production between 2008 and 2012
Information on percentage ISL compared with other types of mining is taken from [W10]RegionContribution to world production (%)
Total

ISL

OthersAsia and Pacific

51.6%

38%

13.6%

North America

21.1%

2%

19.1%

Africa

18.4%

0%

18.4%

Europe

8.6%

1%

7.6%

Latin America

0.3%

0%

0.3%

World

100%

41%

59%

Table 4. Uranium production in 2010 [O8]The production numbers come from OECD/NEA (table 1.21, page 60, Historical uranium production [O8]). Countries that hada label “Secretariat estimate” are not included here (Pakistan, Romania and India). Also excluded are a few countries that hadvery small production which came from mine rehabilitation efforts only

Country (UNEP region)

Uranium production (t U)

Kazakhstan (Asia and Pacific)

17 803

Canada (North America)

9 775

Australia (Asia and Pacific)

5 900

Namibia (Africa)

4 503

Niger (Africa)

4 197

Russian Federation (Europe)

3 563

Uzbekistan (Asia and Pacific)

2 874

United States (North America)

1 630

China (Asia and Pacific)

1 350

154 UNSCEAR 2016 REPORTCountry (UNEP region)

Uranium production (t U)

Ukraine (Europe)

837

Malawi (Africa)

681

South Africa (Africa)

582

Czech Republic (Europe)

254

Brazil (Latin America)

148

Iran, Islamic Rep. of (Asia and Pacific)

7

Total

54 104(a) Input to assessments for mining and milling
52. The Committee’s revised methodology for estimating public exposures due to radioactive
discharges (annex A) has been used to assess the collective doses and characteristic individual doses
from four categories of sources for radon discharges:(a) Mining (underground uranium mining)(b) Milling (natural radionuclides other than radon are also discharged)(c) Operational mill tailings(d) Mill tailings
53. The third category, operational mill tailings, refers to the mill tailings produced during the milling
process, and the fourth category, mill tailings, represents the tailings that are positioned in some otherplace for more permanent holding. They can be eventually treated or mitigated to reduce the dischargeof radionuclides. Assessments were conducted using the methodology described in annex A for the four
categories of sources above. They were performed using the discharges normalized to energy generated
shown in table 5 and table 6, and the values for electricity generation for each region given in table 7 toestimate characteristic individual doses to the public. As noted in the tables, many of the values for thenormalized discharges were taken from previous UNSCEAR reports. However, the estimate for thedischarge of radon from mill tailings has been updated. A value for the discharge of radon per energy
produced of 0.3 TBq/(GW a), based on a tailings area of 1 hectare and a radon emanation rate of
1 Bq s−1 m−2, was used in [U9]. This was lower than the previous value of 1 TBq/(GW a). Information
on emissions from Australian mine tailings [L2] is that the value of 1 Bq s−1 m−2 is high compared to
the range of levels that are measured. Measurements taken over a number of years at the El Sharena
mines were in the range 9–36 mBq s−1 m−2 with an average baseline value of 17 mBq which isequivalent to 0.005 TBq/(GW a) based on a tailings area per electricity generated of 1 ha/(GW a). In
other cases where the tailings have been rehabilitated, the emissions rates are at background levels. A
study at the Ranger uranium mine found that the emission rates ranged from 0.2 to about 0.9 Bq s−1 m−2.
The studies related to trial landforms intended to develop their rehabilitation strategies with the aim of
reducing the long-term radon emission rates. For Olympic Dam, an emission rate of 0.5 Bq s−1 m−2 waspublished, a value equivalent to 0.15 TBq/(GW a) while other information gives emission rates of 0.3,
0.14 and 0.04 Bq s−1 m−2 for the inner mine, outer mine and region. These are equivalent to 0.1, 0.04
and 0.01 TBq/(GW a) based on 1 ha/(GW a). These Australian values indicate that the UNSCEAR
2000 value (0.3 TBq/(GW a)) may be too high based on mines operating with best practice for which avalue of 0.1 or lower may be more appropriate. In the light of this, the Committee agreed that a roundedemission rate of 0.1 TBq/(GW a) should be used in this study.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 155

Table 5. Discharges of radon from the uranium mining and milling process normalized toelectricity generated
SourceNormalized discharges(TBq/(GW a))

Mining (world average, all mines except ISL, only radon discharges)

66aMining (world average, all ISL mines, only radon discharges from leaching phase of
ISL mining process)3

Milling (world average, all mines, radon discharges plus nuclides in table 6)

3bOperational mill tailings (world average, all mines except ISL, only radon discharges)

3cMill tailings (world average, all mines except ISL, only radon discharges)

0.1d

a

A value of 75 TBq/(GW a) was used in earlier UNSCEAR assessments [U8], and was based on the assumption that there wereon average 300 GBq of radon released per tonne of uranium oxide [U8].

b

From UNSCEAR 1993 Report [U8].

c

From UNSCEAR 2000 Report [U9].

dFrom annex A.

Table 6. Airborne discharges during the milling process (all mines including ISL) ([U8] tables 19 and 22)
Radionuclide

Activity discharged per unit of electricity generated(TBq/(GW a))

210

Po

2 × 10−5

210

Pb

2 × 10−5Ra

2 × 10−5

234

U

4 × 10−4

238

U

4 × 10−4

Th

2 × 10−5

226

230

54. The estimate for the discharge of radon from uranium mining (non-ISL mines) has also been
updated. Total uranium production in 2010, shown in table 4 [O8], was assumed to be the amount thatwas mined in that year. Values were summed for all countries to give a rounded total of 54,100 tonnesof uranium. Similarly, total uranium production in 2010 from table 4 is assumed to equal the total
amount of uranium milled. The value for the mass of uranium required per unit of electricity generated
given in the UNSCEAR 2008 Report was 220 t/(GW a) ([U11] table 18A), which is lower than thevalue of 250 t/(GW a) used earlier by the Committee [U7, U8, U9]. The trend in uranium required perunit of electricity generated (the uranium requirement) is generally downwards, because of increasing
efficiencies in power plant operation and lower enrichment tails assays. For example, the 2014 Red
Book [O8] reported that the generic reactor uranium consumption had reduced from 175 t/GW(e) per
year at 0.30% tails assay [O6] to 163 t/GW(e) per year at 0.25% tails assay. The corresponding figures
for U3O8 are 206 and 192 tonnes, respectively.
55. The value of 220 t/(GW a) used in the UNSCEAR 2008 Report is the value used in this assessment.
Given the information in the previous paragraph, this is possibly a slight overestimate; however, it was
retained for continuity with the previous UNSCEAR assessments. This gives a value for the discharge ofradon from the mining process normalized to electricity generated of 66 TBq/(GW a), which is lower thanthe value of 75 TBq/(GW a) used in earlier UNSCEAR studies [U7, U8, U9].

156 UNSCEAR 2016 REPORT

56. In modern ISL facilities, the circulating lixiviant goes directly from the well field to the header
houses and the dissolved uranium is extracted from the lixiviant through the ion exchange process. The
lixiviant is then reconstituted and returned directly to the well field in an essentially closed(pressurized) system. In older non-pressurized systems (such as at Crow Butte, United States), the resin
column is not pressurized, so the lixiviant is exposed to normal atmospheric conditions, which results insuper-saturated radon being discharged. The discharged radon gas is vented through an exhaust stack to
the atmosphere. This discharge is most similar to that from the milling phase, not from the mining
phase. The assessments in this annex have assumed radon discharges during ISL uranium mining are
the same as those from the milling phase.
57. In order to perform assessments of the characteristic individual doses to the public for eachregion, electricity generation in 2010—broken down into ISL and non-ISL mining sources—wasneeded for the different regions. Total uranium production for 15 countries in 2010 is given in table 4.
Table 3 shows the contribution from ISL-mining to the total uranium production in each UNEP region
between 2008 and 2012. Using the value for uranium requirement of 220 t/(GW a), the electricity
generated from the total uranium production for each region could be estimated as shown in table 7.
Assessments for mining and milling using the revised methodology for estimating public exposures due
to radioactive discharges (annex A) used the values for total electricity generated with the normalizeddischarges for milling, the total electricity generation from ISL mining with the normalized discharges
for ISL mining processes, and the total electricity generation excluding ISL mining sources with thenormalized discharges for the processes mining (non-ISL), operational mill tailings and mill tailings, tocalculate characteristic individual doses. Collective doses resulting from mining and milling wereassessed assuming a low population density (defined in annex A), and no aquatic discharges were
included in the assessment.

Table 7. Inferred electricity generation from the uranium production in each region and from ISL and non-ISL contributions
The assessment assumes 220 tonnes of uranium per gigawatt-year. Note that the total inferred electricity generation is 246 GW a, which is somewhat less than the world total nuclear electricity generation in 2010at 314 GW a (table 2). However, this difference is not unreasonable because current reactor fuel requirements were met from primary supply (direct mine output: 78% in 2009) and secondary sources: commercial
stockpiles, nuclear weapons stockpiles, recycled plutonium and uranium from reprocessing used fuel, and some from re-enrichment of depleted uranium tailings (left over from original enrichment) [O6, W11]
Region% from ISL% from otherproduction methods

Mass of uranium
from ISL (tonnes)

Mass of uranium fromother production
methods (tonnes)

Inferred electricity
generated from ISL(GW a)

Inferred electricity
generated from otherproduction methods(GW a)

Total inferred
electricity generated(GW a)

Africa

18.4

0

18.4

0

9 954

0

45

45

Asia and Pacific

51.6

38

13.6

20 558

7 358

93

33

126

Europe

8.6

1

7.6

541

4 112

3

19

22

Latin America

0.3

0

0.3

0

162

0

1

1

North America

21.1

2

19.1

1 082

10 333

5

47

52

Total

100

41

59.0

22 18131 919

101

145

246

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 157% of world
production

158 UNSCEAR 2016 REPORT

2.

Electricity generation from nuclear power reactors

58. The nuclear power reactors used for electricity generation that are treated here can be categorizedaccording to their coolant systems and moderators: light-water-moderated and cooled pressurized orboiling-water reactors (PWRs and BWRs); heavy-water-cooled and moderated reactors (HWRs); gascooled, graphite-moderated reactors (GCRs and AGRs); and light-water cooled, graphite-moderated
reactors (LWGRs). These reactor types are all thermal reactors that use the moderator material to slow
down the fast fission neutrons to thermal energies. In fast-breeder reactors (FBRs), the coolant is aliquid metal, there is no moderator and fast neutrons induce fission.

(a) Assessments for nuclear reactor operation
59. The distribution of electricity generated by geographic region and type of location of the nuclear
power plants in the world are presented in table 8. The electricity generated in 2010 by nuclear power
was about 300 GW a according to the IAEA PRIS database [I6] (table 9). PWRs contributed most to
the total electricity generated worldwide from nuclear reactors (about 68%), followed by BWRs (about21%) [I6]. The distribution of electricity generated by geographic region from nuclear power plants in2010 by reactor type is shown in table 9. (The ordering of the individual reactor types in all relevant
tables and figures in this annex is according to their world share of electricity generated in 2010, as
shown in table 9.)60. Radionuclide discharges and electricity generation data used with the revised methodology for
estimating public exposures due to radioactive discharges (annex A), for assessing discharges from
nuclear power plants in 2010 normalized to the electricity generated, are described in table 10. The
main basis for deriving the normalized discharge values was the IAEA PRIS database [I6], the EC
RADD database [E2] and the discharge data for the year 2002 in the UNSCEAR 2008 Report [U11].
Using these data the normalized discharges for 2002 were recalculated and adjusted to electricity
generation in 2010, for use with the revised methodology for estimating public exposures due toradioactive discharges (annex A) to assess the exposures for the reference year 2010.
61. A summary of the activities of radionuclides, or radionuclide groups, discharged in airborne andliquid effluents from nuclear reactors during routine operation in 2010, normalized to the electricity
generated in 2010, are reported in table 11. The method for determining how the aggregated nuclides
were characterized, i.e. the noble gases and particulates in the atmospheric discharges, and the “otherliquids” listed in the liquid discharges, has been addressed in earlier studies by UNSCEAR (e.g. [U7,U8, U9]). The aggregated nuclides were called “representative radionuclides for nuclear power plantdischarges” in those studies, and the term “representative radionuclides” is used in this annex also.
Chapter III.A, paragraph 44 in this annex explains how the representative radionuclides, were chosen
for use in the current study with the revised methodology for estimating public exposures due toradioactive discharges (annex A) applied to nuclear power plants.
62. The revised methodology for estimating public exposures due to radioactive discharges (annex A)
was used to assess doses due to discharges from nuclear power plants. The assessments considered
atmospheric and aquatic discharges. Collective dose estimates for discharges to atmosphere were basedon the population distributions around coastal or inland nuclear power plants, using the population
distributions generated for the different regions adopted by UNEP (see annex A). Where appropriate,
contributions from globally-circulating radionuclides were included in the assessment of collective

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 159

doses. The characteristic individual doses and collective doses were calculated separately for each of
the reactor types (PWR, BWR, HWR, LWGR, AGR, GCR and FBR).
Table 8. Number of reactors by type, location and UNEP region (2010 data)
Data from the IAEA PRIS database [I6]Reactor type

AfricaAsia and
Pacific

EuropeLatin America
and Caribbean

North
America

Grand
total

PWR total

2

55

141

2

69

269

Coastal

2

54

34

2

16

108

Inland

0

1

107

0

53

161

BWR total

0

36

19

2

35

92

Coastal

0

36

9

2

2

49

Inland

0

0

10

0

33

43

HWR total

0

24

2

2

18

46

Coastal

0

11

0

0

1

12

Inland

0

13

2

2

17

34

LWGR total

0

0

15

0

0

15

Coastal

0

0

4

0

0

4

Inland

0

0

11

0

0

11

AGR (all coastal)

0

0

14

0

0

14

GCR total

0

0

4

0

0

4

Coastal

0

0

2

0

0

2

Inland

0

0

2

0

0

2

FBR (all inland)

0

0

2

0

0

2

Grand total

2

115

197

6

122

442

160 UNSCEAR 2016 REPORT

Table 9. Electricity generation from nuclear power plants in 2010 by reactor type and UNEP region(from [I6])
The values for the total electricity generation from nuclear power plants for each UNEP region [I9] are marginally different
from those shown in table 2 [I15]. The IAEA database [I6] provided detailed data on electricity generation in 2010 both byregion and as a function of reactor type, which was not available from the database used to generate table 2, and the moredetailed data were therefore chosen for use in the assessments discussed in this chapter

Reactortype

Electricity generation (GW a)
AfricaAsia and
Pacific

EuropeLatin America
and Caribbean

North
America

West
Asia

Total

% totalperreactor
type

PWR

1.47

38.47

102.47

1.57

60.89

0.00

204.88

68

BWR

0.00

19.66

12.18

0.64

31.25

0.00

63.72

21

HWR

0.00

5.34

1.22

0.76

9.76

0.00

17.09

6

LWGR

0.00

0.00

8.15

0.00

0.00

0.00

8.15

3

AGR

0.00

0.00

5.01

0.00

0.00

0.00

5.01

2

GCR

0.00

0.00

0.93

0.00

0.00

0.00

0.93

0

FBR

0.00

0.00

0.42

0.00

0.00

0.00

0.42

0

Total

1.47

63.47

130.392.97

101.890.00

300.21100

Table 10. Key data sources and assumptions used to assess public exposures due to radioactive
discharges from nuclear power plants
Data sources

Commentary

Discharges, 2002

Taken from tables A6-A12 in UNSCEAR 2008 Report [U11]. Note that WWER was
regrouped under PWR. Data for discharges from FBR are from 2001. Discharges ofparticulates to air and other liquids for United Kingdom AGRs/GCRs were takenfrom the EC RADD database [E2]Electricity generation,
2002

Taken from [I6]. Note that HWLWR was regrouped under HWR and PHWR under
HWR. Generation data for FBR are from 2001

Electricity generation,
2010

Taken from [I6]. Note that HWLWR was regrouped under HWR and PHWR under
HWR. Includes a calculation of generation from reprocessing countries as a fractionof all generation

Countries

Countries and regions as adopted by UNEP (see annex A)

Location dataInland/coastal location of reactors, taken from [I6]

Normalized discharge data

For each reactor type:a,b the normalized discharges were scaled to the electricity
generation ratio using the 2002 to 2010 electricity generation data; information
summarized in paragraph 44 was used to apportion discharge between specificradionuclides; and location data were used to apportion between inland/coastal
locationsa

For FBRs, values of normalized discharges of 3H, 131I, 14C, liquid tritium and other liquids were taken from table 17, annex B,
UNSCEAR 2008 Report [U11] because no discharge data were available. Data for the radionuclide mix were taken from [E1].

bFor LWGRs, normalized discharge data were taken from table 17, annex B, UNSCEAR 2008 Report [U11]. EC RADD [E2]data for European LWGR reactors were used to infer mix of noble gases, particulates and other liquids.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 161

Table 11. Estimated normalized discharges from nuclear power plants 2010
Estimated normalized discharges per unit of electricity generated (TBq per GW a)
Reactortype

Discharges to atmosphere
Noble
gases

Tritium131

PWR

5.8 × 100

1.5 × 100BWR

1.8 × 101

HWR

CParticulates

S

LiquidtritiumOtherliquid

8.0 × 10−5

8.3 × 10−2

3.6 × 10−50

1.8 × 101

3.8 × 10−3

1.3 × 100

4.2 × 10−4

1.3 × 10−1

1.8 × 10−30

8.2 × 10−1

2.1 × 10−3

3.5 × 101

2.0 × 102

2.3 × 10−5

6.0 × 10−1

1.7 × 10−50

1.7 × 102

3.1 × 10−2

LWGR

4.6 × 102

2.6 × 101

9.9 × 10−3

1.3 × 100

2.7 × 10−30

7.8 × 10−1

2.0 × 10−3AGR

1.9 × 101

4.0 × 100

3.2 × 10−5

1.4 × 100

2.2 × 10−5

6.6 × 10−2

4.1 × 102

8.1 × 10−1

GCR

1.7 × 103

5.0 × 1000

5.5 × 100

3.0 × 10−4

3.7 × 10−1

4.7 × 100

1.2 × 100

FBR

4.4 × 101

4.9 × 101

2.0 × 10−4

1.2 × 10−1

1.4 × 10−40

1.7 × 100

2.3 × 10−2

3.

I

Aquatic discharges
35

14

Fuel reprocessing

63. Reprocessing of used nuclear fuel has been practised for several decades in a number of countries,
mainly for extracting and recycling fissile materials. Current recycling practices are primarily focusedon the conversion of fertile 5 238U to fissile plutonium, for which a significant amount of the plutonium
recovered from used fuel has been recycled into mixed oxide (MOX) fuel. Table 12 shows the current
location of reprocessing facilities in the world, with operations in France, the Russian Federation andthe United Kingdom dominating. Not shown in the table is the Rokkasho facility in Japan, which is
expected to start operations in 2018 and to have a commercial reprocessing capacity of 800 tonnes per
year. As of 2015, about 31% (90,000 tonnes of 290,000 tonnes) of used fuel from commercial powerreactors has been reprocessed [W12].
64. Characteristic individual doses and collective doses were calculated for Sellafield in the United
Kingdom, La Hague in France and Ozersk (Mayak) in the Russian Federation, which are also the threemain reprocessing facilities (table 12), using available data on discharges. The doses due to discharges
from fuel reprocessing facilities were assessed using the revised methodology for estimating public
exposures due to radioactive discharges (annex A).
65. Data for both atmospheric and aquatic discharges were obtained for the reprocessing facilities at
Sellafield, United Kingdom and La Hague in France for the year 2010 [E2] and for atmosphericdischarges only at Ozersk (Mayak), Russian Federation [F2]. These data include discharges from otheractivities on site but it could be assumed that most discharges are related to reprocessing activities.
Discharges normalized to electricity generation were calculated for La Hague based on the assumptionthat discharges from the reprocessing facility were related to the reprocessing of fuel equivalent to that
required to power French PWRs in 2010, 47 GW a [I6, W9]. However, for Sellafield and Mayak it was
not possible to relate the discharges to electricity generated.
5

Fertile material is a material that is not fissionable by thermal neutrons, but can be converted into a fissile material by neutron
absorption and subsequent nuclei conversions.

162 UNSCEAR 2016 REPORT

66. The discharges for reprocessing facilities are shown in table 13. Consequently, characteristic
individual doses and collective doses (as defined in section III) could be assessed for all three of thesefacilities, all located in the region named Europe (as adopted by UNEP). However, because discharges
normalized to electricity generation were only available for La Hague in France, the characteristic dosenormalized to electricity generated could be assessed only for this facility. Collective doses normalized
to electricity generation for Europe and the whole world were also based on La Hague, but took into
account the fraction of electricity generated by all French PWRs in 2010 compared to Europe and thewhole world, 0.55 and 0.24 respectively, for the calculation of the doses due to the first pass.
Table 12. World commercial reprocessing capacity [N1, O2, W12]
Fuel type
LWR fuel

Facility

Commercial reprocessing capacity(tonnes per year)

France, La Hague

1 700

United Kingdom, Sellafield (THORP)

600

Russian Federation, Ozersk (Mayak)

400

Total LWR
Other nuclear fuelsapproximately 2 700

United Kingdom, Sellafield (Magnox)

1 500

India (PHWR, 4 plants)

330

Japan, Tokai (MOX)

40

Total otherapproximately 1 870

Total civil capacity

approximately 4 570

Table 13. Discharges from reprocessing facilities [E2]Discharged
radionuclide

Discharges to atmosphere
Sellafield

La HagueAquatic discharges
Mayak

Sellafield

La Hague

Mayak

DISCHARGES PER UNIT OF ELECTRICITY GENERATED (TBq/(GW a))H—

3.8 × 104——

6.7 × 106

—

14

C

—

1.1 × 104——

5.0 × 103

—

41

Ar

—

—

—

—

—

—

54

Mn

—

—

—

—

58

Co

—

—

—

60

Co

—

4.9 × 10−3

85

Kr

—

90

3

0

1.4 × 10——−2

7.0 × 10———

4.4 × 101—

1.5 × 108

—

—

—

—

Sr

—

—

106

—

—

9.1 × 10——−2

4.8 × 10

—

—

3

Ru

1.4 × 10

—

129

I

—

3.1 × 100——

9.3 × 102

—

131

I

—

1.6 × 10−1——

7.9 × 100

—

135

Xe

—

—

—

—

—

—

1

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 163

Discharged
radionuclide

Discharges to atmosphere

Aquatic discharges

Sellafield

La Hague

Mayak

Sellafield

La Hague

Mayak

134

Cs

—

3.6 × 10−3——

5.1 × 101

—

137

Cs

—

3.0 × 10——2

7.3 × 10

—

239

Pu

—

1.3 × 10——0

6.3 × 10

—

241

Am

—

—

—

—

1.3 × 101

—

−3
−3

AVERAGE DISCHARGE RATE OVER A YEAR (Bq/s)
H

6

3.1 × 10

1.8 × 106—

4.4 × 107

3.2 × 108

—

14

C

8.7 × 103

5.1 × 105—

1.4 × 105

2.3 × 105

—

41

Ar

—

—

1.2 × 106

—

—

—

54

Mn

—

—

—

58

Co

—

—

60

Co

—

85

Kr

90

3

—

1

6.4 × 10

—

—

—

0

3.3 × 10—

2.3 × 10−1

3.4 × 10−1

3.1 × 103

2.0 × 103—

1.4 × 109

7.1 × 109

—

—

—

—

Sr

1.3 × 10

—

106

Ru

1

2.4 × 10

2.2 × 10

5.7 × 10

3.7 × 10

6.5 × 10

—

129

I

3.1 × 102

1.4 × 102—

8.7 × 103

4.3 × 104

—

131

I

1.2 × 101

7.7 × 100

2.5 × 101—

3.7 × 102

—

135

Xe

—

—

1.8 × 10

—

—

—

134

Cs

—

1.7 × 10137

Cs

3.0 × 100

239

Pu

241

Am

0

0

1

4.2 × 104

3.2 × 103

4.2 × 10

—

4

4

0

5

—

3

3.5 × 103

2.4 × 10—

1.4 × 10−1

2.1 × 101

1.5 × 105

3.4 × 104—

6.2 × 10−1

5.9 × 10−2

1.3 × 101

4.2 × 103

2.9 × 102—

1.2 × 10——

1.1 × 10

6.2 × 10

—

−1

0

4

2

(a) Results—public exposures from mining and milling, electricity generation from
nuclear power reactors and fuel reprocessing
67. Characteristic individual doses to the public—for the nuclear fuel cycle processes: mining andmilling; electricity generation from nuclear power reactors; and fuel reprocessing—normalized to theelectricity each process generated in 2010 are summarized in table 14. Doses for the characteristic
individual from mining and milling are shown for both non-ISL and ISL mines. The characteristic
individual was assumed to be located 5 km from the source. The doses represent the radiation exposure
from all discharges in a year and, in the case of mill tailings, the doses are associated with thoseemissions for a period of 100 years (see chapter III).
68. The largest estimated characteristic individual doses normalized to electricity generation in 2010
for all discharges come from mining and milling activities in non-ISL mines in all regions, followed byoperational discharges from nuclear power plants. Estimated characteristic individual doses from ISL
mines are about an order of magnitude smaller than those from non-ISL mines, owing to the differencesin radon discharges from the two processes. Estimated characteristic individual doses from mining andmilling are primarily associated with radon exposures, while those from nuclear power plant operations
reflect differences in the type and relative proportion of the different reactor types and thus different

164

UNSCEAR 2016 REPORT

radionuclide discharge mixes within a region, and to a lesser extent, variations in food consumption
patterns across regions. Estimated characteristic individual doses for a region normalized to electricity
generated that are associated with reprocessing are only reported for the region Europe, where theFrench, British and Russian reprocessing facilities are located. All of the estimated characteristic
individual doses are very low.
Table 14. Summary of characteristic individual doses to the public normalized to electricity
generated in 2010 for mining and milling, electricity generation from nuclear power reactors, andfuel reprocessing (mSv/(GW a))
Characteristic individual doses a,b to the public (mSv/(GW a))

Discharge type and source

Asia and
Pacific

AfricaEuropeLatin
America

North
America

ATMOSPHERIC DISCHARGESc

6.9 × 10−3

6.9 × 10−3

6.9 × 10−3

6.9 × 10−3

6.9 × 10−3—

5.5 × 10−4

5.5 × 10−4—

5.5 × 10−4

Power plants

1.3 × 10−5

5.1 × 10−5

7.2 × 10−5

1.1 × 10−4

5.8 × 10−5

Reprocessing——

5.7 × 10−5

—

—

—

—

—

Mining and milling - non-ISL mines
Mining and milling - ISL mines

AQUATIC DISCHARGES
Mining and milling - non-ISL mines—

Mining and milling - ISL mines—

Power plants

7.0 × 10

Reprocessing

—

—
—
−5

—
−5

—
−4

—
−4

8.4 × 10

6.6 × 10

1.0 × 10

4.1 × 10−5—

6.0 × 10−4——

TOTAL FOR ALL DISCHARGESc

6.9 × 10−3

6.9 × 10−3

6.9 × 10−3

6.9 × 10−3

6.9 × 10−3—

5.5 × 10−4

5.5 × 10−4—

5.5 × 10−4

Power plants

8.2 × 10−5

1.3 × 10−4

7.3 × 10−4

2.1 × 10−4

9.9 × 10−5

Reprocessing——

6.6 × 10−4——

Mining and milling - non-ISL mines
Mining and milling - ISL minesa

The characteristic individuals are those living 5 km from the points of discharge with behaviour indicative of the majority ofpeople living the area.
b

It is only appropriate to present the characteristic individual doses for discharges normalized to electricity generated and notsummations of the various individual dose values, because the same individuals cannot be exposed to all discharges from thevarious sources in each region. Because collective doses are the sum of all individual doses, they can be presented both as totalcollective dose and as collective dose normalized to electricity generated.
c

The radon emissions from mill tailings produced per unit of electricity generated are assumed to continue for 100 years.

69. Collective doses to the public for discharges from mining and milling, power plant operation andreprocessing in 2010 are summarized in table 15, and in table 16 normalized to the electricity generated
by each process for that year. The local component (for the region-averaged or world-averaged
population within 100 km) and the regional component (for the region-averaged or world-averaged
population between 100 km and 1,500 km) of the collective doses due to the atmospheric releases arepresented separately, integrated to 100 years (first pass). Radon emissions from mill tailings produced
per unit of electricity generated are assumed to continue for 100 years. The global components ofcollective doses resulting from the globally-circulating radionuclides (3H, 14C, 85Kr and 129I) are also
shown, integrated to 100, 500 and 10,000 years. For ease of comparison, table 17 shows the final

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 165

aggregated values for the total collective dose to the world public and for the collective dosenormalized to electricity generated for each of the processes mining and milling, power plant operation
and reprocessing.
70. The results in tables 15 and 16 indicate that for discharges from both power plant operation andreprocessing facilities, the global component of the collective doses due to globally-circulating
radionuclides integrated to 100 years and longer exceed the local and regional components of thecollective doses due to the initial discharge (first pass) integrated out to 1,500 km. It is important torecognize that global components are summed over the population of the entire world, which is taken as1010 people to account for growth over the next 100 years (called “whole world population” in thetables 15 and 16). This component thus is the sum of a large number of very small doses with per caput
values of the order of 10−8 Sv, and per caput values normalized to electricity generated of the order of
10−10 Sv/(GW a). Values for the collective doses in both tables 15 and 16 for the first-pass calculation
are the doses integrated to 100 years and to a distance of 1,500 km for the local and regional
components due to atmospheric discharges. Based on the results of the assessment, doses beyond thisdistance were assumed to be negligible.
71. For the nuclear industry, a significant fraction of the collective dose is due to radon discharges
from mining and disposal of mill tailings. The importance of carbon-14 discharges from nuclear power
plants and reprocessing is also evident. Table 18 shows the contribution from individual radionuclides
to the collective doses to the public, and collective doses per unit of electricity generated, from
reprocessing integrated to 100 years, not including contributions from globally-circulating
radionuclides. Figure IV is derived from the data in table 18, showing collective doses per unit ofelectricity generated for individual radionuclides discharged from reprocessing. The importance of the
carbon-14 contribution to dose is evident.
72. Figure V shows collective doses per unit of electricity generated due to the globally-circulating
radionuclides (tritium, 14C and 85Kr) integrated to 100, 500 and 10,000 years, for each reactor typeconsidered. Besides indicating the variation in the dose contribution from globally-circulating
radionuclides for the different reactor types, the graphs also illustrate the importance of 14C, whose
contribution to collective dose increases with integration time. The global circulation for 129I is notincluded in figure V because it is only discharged during the reprocessing phase.
73. Figure VI compares the collective doses to the public from all discharges, atmospheric andaquatic, from all nuclear power plants by region and by reactor type, not including contributions fromglobally-circulating radionuclides. The data indicate that HWRs and PWRs are the reactor types that
contribute most to the collective doses. Table 19 shows the total collective dose for all nuclear reactor
types summed and by region, with North America and Europe showing the highest values.

Discharge type and source

Collective dosea, b (man Sv)
AfricaAsia and Pacific

EuropeLatin America

North America

World

LOCAL COMPONENT – ATMOSPHERIC RELEASESMining and milling

No data by region

1.0 × 101

Power plants
Inland0

1.2 × 100

2.0 × 100

1.7 × 10−1

2.2 × 100

5.3 × 100

Coastal

8.2 × 10−3

2.7 × 100

1.2 × 100

1.5 × 10−2

1.2 × 10−1

3.8 × 100——

1.3 × 100——

2.1 × 100

Reprocessing

REGIONAL COMPONENT – ATMOSPHERIC DISCHARGES
Mining and milling

No data by region

4.3 × 101

Power plants
Inland0

3.0 × 100

6.7 × 100

1.3 × 10−1

5.8 × 100

1.6 × 101

Coastal

1.6 × 10−3

6.8 × 100

3.5 × 100

2.9 × 10−2

1.5 × 10−1

8.4 × 100——

4.3 × 100——

4.4 × 100

Reprocessing

LOCAL AND REGIONAL COMPONENT – AQUATIC DISCHARGES
Mining and milling

No data by region—

Power plants
Inland0

1.4 × 100

1.4 × 101

8.1 × 10−1

1.8 × 101

3.4 × 101

Coastal

9.3 × 10−5

2.5 × 10−2

6.8 × 10−2

3.5 × 10−4

1.3 × 10−3

3.9 × 10−1——

2.6 × 10-1——

1.1 × 100

Reprocessing

LOCAL AND REGIONAL COMPONENTS (ATMOSPHERIC AND AQUATIC DISCHARGES)Mining and milling

No data by region

5.3 × 101

Power plants

9.9 × 10−3

1.5 × 101

2.8 × 101

1.2 × 100

2.6 × 101

6.8 × 101

Reprocessing——

5.8 × 100——

7.6 × 100

9.9 × 10−3

1.5 × 101

3.3 × 101

1.2 × 100

2.6 × 101

1.3 × 102TOTAL LOCAL AND REGIONAL COMPONENTSc

166 UNSCEAR 2016 REPORT

Table 15. Summary of collective doses to the public due to mining and milling, electricity generation from nuclear power reactors, and fuel reprocessing (in 2010)

GLOBAL COMPONENT – GLOBALLY-DISPERSED RADIONUCLIDES

Source and integration time

Collective dose (man Sv)
Whole world population

Mining and milling integrated to
100 years—

500 years—

10 000 years—

Power plants integrated to
100 years

5.3 × 102500 years

1.0 × 103

10 000 years

5.0 × 103

Reprocessing integrated to
100 years

2.6 × 102500 years

4.9 × 102

10 000 years

2.4 × 103

Local and regional components of the collective doses (due to the first pass) are integrated to 100 years. The local and regional components are explained in chapter III. Per caput values are not given in the table, but are
discussed in the text.

bc

For all tables in the annex, the calculations resulting from assessments are made to full precision and any discrepancies in the final sum of numbers in the tables are due to rounding.

Total of the local and regional components due to mining and milling, power plants and reprocessing from the first-pass. The totals for each region include only discharges from power plants, except for Europe, which
also has a value for reprocessing.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 167aDischarge type and source

Collective dosea per unit of electricity generated (man Sv/(GW a))
AfricaAsia and Pacific

EuropeLatin America

North America

World-averageb

LOCAL COMPONENT – ATMOSPHERIC DISCHARGES
Mining and milling

No data by region

4.1 × 10−2

Power plants
Inland0

8.0 × 10−1

2.2 × 10−2

2.2 × 10−1

2.5 × 10−2

2.9 × 10−2

Coastal

5.6 × 10−3

4.3 × 10−2

3.2 × 10−2

6.8 × 10−3

8.5 × 10−3

3.3 × 10−2——

1.2 × 10−2——

8.6 × 10−3

Reprocessing

REGIONAL COMPONENT – ATMOSPHERIC RELEASESMining and milling

No data by region

1.7 × 10−1

Power plants
Inland0

2.0 × 100

7.2 × 10−2

1.7 × 10−1

6.5 × 10−2

8.9 × 10−2

Coastal

1.1 × 10−3

1.1 × 10−1

9.4 × 10−2

1.3 × 10−2

1.1 × 10−2

7.2 × 10−2——

4.0 × 10−2——

1.8 × 10−2

Reprocessing

LOCAL AND REGIONAL COMPONENTS (AQUATIC DISCHARGES)Mining and milling

No data by region—

Power plants
Inland0

9.3 × 10−1

1.5 × 10−1

1.1 × 100

2.0 × 10−1

1.9 × 10−1

Coastal

6.3 × 10−5

4.1 × 10−4

1.8 × 10−3

1.6 × 10−4

9.6 × 10−5

3.3 × 10−3——

3.0 × 10−3——

2.1 × 10−3

Reprocessing

LOCAL AND REGIONAL COMPONENTS (ATMOSPHERIC AND AQUATIC DISCHARGES)Mining and milling

No data by region

2.2 × 10−1

Power plants

6.7 × 10−3

2.4 × 10−1

2.1 × 10−1

3.9 × 10−1

2.6 × 10−1

2.3 × 10−1

Reprocessing——

5.5 × 10−2——

2.9 × 10−2

6.7 × 10−3

2.4 × 10−1

2.6 × 10−1

3.9 × 10−1

2.6 × 10−1

4.3 × 10−1

TOTAL LOCAL AND REGIONAL COMPONENTSc

168 UNSCEAR 2016 REPORT

Table 16. Summary of collective doses to the public due to mining and milling, electricity generation from nuclear power reactors, and fuel reprocessing (in 2010)
normalized to electricity generated

GLOBAL COMPONENT – GLOBALLY-DISPERSED RADIONUCLIDES

Source and integration time

Collective dose per unit of electricity generated (man Sv/(GW a))
Whole world population

Mining and milling integrated to
100 years—

500 years—

10 000 years—

Power plants integrated to
100 years

1.8 × 100

500 years

3.4 × 100

10 000 years

1.7 × 101

Reprocessing integrated tod
100 years

1.2 × 100

500 years

2.1 × 100

10 000 years

1.0 × 101

Local and regional components of the collective doses (due to the first pass) are integrated to 100 years. The local and regional components are explained in chapter III. Per caput values are not given in the table, but are
discussed in the text.
bWorld-average is used to qualify the calculations and data that are intended to represent a value averaged across the whole world. In this case the world average is the average of the population in each annulus for all
nuclear sites for which data are available (annex A). Similarly, consumption rates for terrestrial and aquatic foods are average values for the world population. The world-average values can be used for comparative
purposes including for comparison with the previous versions of the methodology for estimating public exposures due to radioactive discharges (annex A).
c

Total of the local and regional components due to mining and milling, power plants and reprocessing from the first-pass. The totals for each region include only discharges from power plants, except for Europe, which
also has a value for reprocessing.

d

The normalized values were calculated as described in paragraphs 65 and 66.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 169a170 UNSCEAR 2016 REPORT

Table 17. Comparison of the worldwide collective dose, and associated collective dose normalized
to electricity generated, from mining and milling, power plant operation and reprocessing
Nuclear fuel cycle

Collective dose(man Sv)

Normalized collective dosea(man Sv/(GW a))

Local and regional component from mining andmilling, power plants and reprocessing (first pass)b

130

0.43

100 years

910

3.0

500 years

1 700

5.5

10 000 years

7 600

25

Local and regional component (integrated to
100 years) plus global component integrated toaThese values are averages for the whole world. The world average is the average of the population in each annulus for all
nuclear sites for which data are available (annex A). Similarly, consumption rates for terrestrial and aquatic foods were averagevalues for the world population. The results can be used for comparative purposes including for comparison with the previous
versions of the methodology for estimating public exposures due to radioactive discharges (annex A).
b

Local and regional components of the collective doses (due to the first pass) are integrated to 100 years. The local and regional
components are explained in chapter III.

Table 18. Radionuclide contributions to the local and regional components of collective doses tothe public from reprocessing integrated to 100 years

Radionuclide

Collective dose per unit of electricity
generated (man Sv/(GW a))

Collective dose(man Sv)

Atmosphere

Aquatic

Total

Atmosphere

Aquatic

Total

H

1.3 × 10−3

3.6 × 10−6

1.3 × 10−3

7.1 × 10−1

8.0 × 10−4

7.1 × 10−1

14C

2.0 × 10−2

1.7 × 10−3

2.2 × 10−2

4.0 × 100

5.4 × 10−1

4.5 × 100

41

Ar

0

0

0

1.7 × 10−30

1.7 × 10−3

54

Mn

0

8.4 × 10−7

8.4 × 10−70

1.7 × 10−4

1.7 × 10−4

58

Co

0

1.8 × 10−8

1.8 × 10−80

3.6 × 10−6

3.6 × 10−660

Co

3.4 × 10−7

6.1 × 10−5

6.1 × 10−5

1.6 × 10−4

3.0 × 10−2

3.0 × 10−285

Kr

4.5 × 10−30

4.5 × 10−3

1.1 × 1000

1.1 × 100

90

Sr

0

5.8 × 10−7

5.8 × 10−7

3.0 × 10−2

9.8 × 10−4

3.1 × 10−2

106

Ru

4.2 × 10−7

9.0 × 10−5

9.0 × 10−5

1.2 × 10−3

2.8 × 10−2

2.9 × 10−2

129I

8.3 × 10−4

2.3 × 10−5

8.5 × 10−4

5.1 × 10−1

5.3 × 10−3

5.2 × 10−1

131I

9.6 × 10−7

1.3 × 10−9

9.6 × 10−7

1.1 × 10−3

2.6 × 10−7

1.1 × 10−3

135

Xe

0

0

0

3.6 × 10−40

3.6 × 10−4

134

Cs

2.0 × 10−7

1.7 × 10−6

1.9 × 10−6

3.9 × 10−5

8.1 × 10−4

8.5 × 10−4

137

Cs

1.9 × 10−7

1.7 × 10−5

1.7 × 10−5

6.5 × 10−3

1.8 × 10−2

2.5 × 10−2

239

Pu

3.7 × 10−6

8.3 × 10−5

8.7 × 10−5

1.6 × 10−1

2.5 × 10−1

4.2 × 10−1

241

Am

0

5.7 × 10−5

5.7 × 10−5

1.2 × 10−2

2.0 × 10−1

2.2 × 10−1

Total

2.7 × 10−2

2.1 × 10−3

2.9 × 10−2

6.5 × 100

1.1 × 100

7.6 × 100

3

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 171

Table 19. Local and regional components of collective dose integrated to 100 years summed over
all reactor types

Collective dose (man Sv)

AfricaAsia and
Pacific

EuropeLatin
America

North
AmericaWorld

9.9 × 10−3

1.5 × 101

2.8 × 101

1.2 × 100

2.6 × 101

6.8 × 101

Figure IV. Contribution of radionuclides to the local and regional components of collective dose to
the public from reprocessing integrated to 100 years and normalized to electricity generation
See data in table 18

172 UNSCEAR 2016 REPORT

Figure V.

Collective doses from globally-circulating radionuclides per unit of electricity generated

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 173

Figure VI. Local and regional components of the collective doses to the public due to total estimateddischarges from nuclear power plants (2010) integrated to 100 years, by UNEP region and by reactor type4.

Uranium enrichment and fuel fabrication

74. The discharges from the processes of conversion, uranium enrichment and subsequent fuelfabrication needed for different reactor types have generally been determined in earlier studies to berelatively small, consisting mainly of radionuclides within the decay chains of uranium isotopes. The
collective dose to the public estimated on the basis of the electricity generated, derived in the
UNSCEAR 2000 Report [U9] and re-used in the UNSCEAR 2008 Report [U11], were used here toobtain an updated value based on the 2010 electricity generation from nuclear power. This value for
uranium enrichment and fuel fabrication facilities is 0.003 man Sv/(GW a). The Committee earlier
estimated the average annual collective dose to the public from all plants for the period 1998–2002 to
be 0.8 man Sv [U11]. Updating this value to the electricity generated from nuclear power in 2010 fromtable 2, the average annual collective dose to the public due to uranium enrichment and fuel fabricationin the year 2010 is about 0.9 man Sv.

174 UNSCEAR 2016 REPORT

5.

Solid waste disposal

75. Solid wastes arise at various stages in the nuclear fuel cycle. These include low- and intermediatelevel wastes, mainly from reactor operations, high-level wastes from fuel reprocessing, and spent fuelfor direct disposal. The activity concentrations of these wastes can range from just above natural
background levels, as in mill tailings, to much higher levels, such as in spent reactor fuel.
76. Low- and intermediate-level wastes are generally disposed of by shallow burial in trenches orconcrete-lined structures, but more advanced disposal sites also exist. Before disposal, all such material
is manipulated and transported, which gives rise to both occupational and public exposures. For the
nuclear fuel cycle, doses to members of the public from the transport of radioactive material have been
earlier estimated using the factor of 0.1 man Sv/(GW a) for the collective dose per unit of electricity
generated [U11]. Wastes from the nuclear fuel cycle also include large quantities of depleted uranium
from uranium enrichment operations [U18]. High-level wastes and spent fuel are presently retained ininterim storage facilities until adequate methods for disposal have been devised and disposal sites
selected [U11].
77. Estimates of the doses due to solid waste disposal have been based on the projected eventual
migration of radionuclides from the burial site into groundwater. The collective dose due to low- andintermediate-level waste disposal normalized to electricity generated is estimated to be approximately
0.5 man Sv/(GW a), due almost entirely to 14C. The average worldwide per caput annual effective dosewould be about 1 nSv per year of practice [U11].

C. Occupational exposure for the nuclear fuel cycle
78. The assessment of occupational exposures for the nuclear fuel cycle considers the practices ofmining, milling, uranium enrichment and conversion, fuel fabrication, reactor operation, fuelreprocessing and research.
79. Collective doses due to occupational exposure for each practice in the nuclear fuel cycle that werereported in the UNSCEAR 2008 Report [U11] for the years 2000–2002 were used as the starting point
to estimate the 2010 occupational exposures. This approach was taken since data were not readily
available on the total number of, or the average annual effective dose to, monitored workers worldwide
in 2010. As reported in the UNSCEAR 2008 Report, the Committee used the amount of electricity thatcan be generated from each practice (i.e. how much electricity can be generated from the uranium thatis mined, milled, converted, and so on) to normalize collective doses to the electricity generated.
80. Table 20 summarizes the data on occupational exposure for the nuclear fuel cycle in the period
2000−2002 that are relevant for estimating occupational exposure for the nuclear fuel cycle in 2010.
81. The ratio from the 2000–2002 data for the average annual collective dose per unit of electricity
generated was combined with the electricity generation for 2010 to estimate the annual collective dosefor 2010. Similarly, the ratio obtained from 2002 for the average annual collective dose per unit mass ofuranium mined, which can be further transformed to the collective dose per unit of electricity generated
is assumed appropriate for the mining process. Actual data from the Canada, the United Kingdom andthe United States for 2010 were obtained on the number of monitored workers and their average annual
effective dose, and were compared with the respective country values for 2000−2002 in the UNSCEAR
2008 Report [U11]. These comparisons showed reasonable agreement with the scaled average annual
effective dose, giving some confidence in the assumptions used.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 175

Table 20. Worldwide average annual individual and collective doses to workers due to the commercial
nuclear fuel cycle
From table 72 in the UNSCEAR 2008 Report [U11]; for the years 2000–2002a

Practice

Monitored
workers(thousands)

Average annualb
collective dose(man Sv)

Average annualb collective
dose per unit of electricity
generated(man Sv/(GW a))

Average annualb
effective dose tomonitored workers(mSv)

Mining

12

22

0.1

1.8

Milling

3

3

0.02

1.0

Enrichment

18

2

0.02

0.1

Fuel fabrication

20

31

0.1

1.6

Reactor operation

437

617

2.5

1.4

Reprocessing

76

68

Research

90

36

0.1

0.4

Total

656

779

2.8

1.2

c,d

0.9

a

Some values in the table have been corrected since table 72 was published in the UNSCEAR 2008 Report [U11]; for the years
2000–2002.
b

The words “average annual” used in the table denote the annual dose averaged over the 2000-2002 year span.

c

Also includes the reprocessing of some fuel associated with military application.

d

The average annual collective dose per unit of electricity generated was not possible to obtain, because there were no datareadily available on the amount of electricity generated from the reprocessed fuel.

82. Table 21 shows the current results for 2010 for the worldwide average annual collective dosecompared to the 2000–2002 results. The procedure for estimating the values for each practice for 2010is explained below.
−

Uranium mining. The amount of uranium ore mined was assumed equal to the amountproduced [U11]. Total uranium production in 2010 for 16 countries is shown in table 4 [O8].
Values were summed for all countries to give 54,100 t of uranium. Of this amount, 31,900 t
was produced from open pit and underground uranium mines and 22,200 t was produced fromin-situ leaching (ISL) processes. Assuming the same collective dose per unit mass of uranium
extracted of 0.623 man Sv/kt as for 2000–2002 [U11], then the collective dose (rounded) is
20 man Sv. This value excludes uranium produced from ISL.

−

Uranium milling. As for uranium mining, the total uranium production in 2010 was taken fromtable 4 [O8] and assumed to equal the total amount of uranium milled, 54,104 t. Applying thesame simplifying assumptions used in the UNSCEAR 2008 Report [U11] (i.e. that all milled
uranium is used in LWRs and that the uranium requirement is 220 t/(GW a) ([U11]; table 18-A)),the equivalent amount of electricity for 2010 is 246 GW a. The collective dose (rounded) for2010 is then 5 man Sv. While ISL extract is not milled, it does go through some treatment toproduce yellowcake. Thus the full amount of uranium mined, 54,100 t, is used here.

−

Uranium conversion and enrichment, and fuel fabrication. UNSCEAR 2008 Report (table 15)
shows the worldwide installed capacity for fuel cycle installations taken from the IAEA
Nuclear Fuel Cycle Information System, NFCIS. Compiling the data from NFCIS for 2010
and comparing with table 15 from the UNSCEAR 2008 Report shows little has changed in the176 UNSCEAR 2016 REPORT

capacity of these processes. All three processes show decreased capacities of between 8% and
9%. Using the assumption that these practices give the same collective dose per unit ofelectricity generated in 2010 as in 2002, the average annual collective dose for 2010 intable 21 has been adjusted to a lower value by 8%.
−

Reactor operation. The normalized average annual collective dose for 2000–2002 was
2.5 man Sv/(GW a). Instead of using this value directly, as explained above, data from theOECD/NEA [O4] indicated a general decrease in the average annual collective doses. The
reported average annual collective dose for operating nuclear power plants fell by 20%
between 2002 and 2010, attributed to additional operating experience and the global exchangeof best radiation protection practices. Using this, the normalized average annual collective
dose for 2010 can be taken as 2.0 man Sv/(GW a). Assuming the total worldwide electricity
generation in 2010 is 314 GW a, an average annual collective dose of 628 man Sv wascalculated, about the same as that reported for 2002, as shown in table 21.

−

Reprocessing. In the absence of updated data on occupational exposures during fuelreprocessing in 2010, it was assumed that reprocessing activities have remained more or lessconstant and the same collective dose was assigned as previously, i.e. no change. Data fromUNSCEAR [U11] were not presented in terms of dose per unit of electricity generated.

−

Research. In the absence of updated data on occupational exposures obtained during researchfor 2010, it was assumed that research activities have remained more or less constant and thesame collective dose was assigned as previously. However, it should be noted that a slightdownward trend in collective dose was observed over the previous two time periods in
UNSCEAR [U11]. Data from UNSCEAR [U11] were not presented in terms of dose per unitof electricity generated.

Table 21. Worldwide levels of exposure of workers due to the commercial nuclear fuel cycle for 2010 and 2000–2002
Practice

Average annual collective dose2010 (man Sv)(Estimates from this study)

Average annual collective dose per unit ofelectricity generated (man Sv/(GW a))(From [U11] for years 2000–2002)

Remarks

Mining

22

20

0.1

U production 2010=54.1 kt; of this 31.9 kt was the amount of
U produced excluding ISL production (35 ktU average in
1998–2003)

Milling

3

5

0.02

246 GW a calculated using same simplifying assumption
from UNSCEAR 2008 Report, table 18-A, that all milled
uranium was used in LWRs, and that uranium requirement
was 220 t/(GW a). Doses resulting from subsequent
remediation activities were not accounted for

Enrichment

2

2

0.02

8% lower capacity than in 2000–2002 (not noticeable
because numbers are rounded)

Fuel fabrication

31

29

0.1

8% lower throughput than in 2000–2002

Reactor operation

617

628

2.5

314 GW a total electricity generated by nuclear power plants
in 2010 [I15, I16]

Reprocessing

68

68

Research

36

36

0.1

Total

779

788

2.8

Assumed constant collective dose–i.e. no change. Data were
not presented [U11] in terms of dose per unit of electricity
generated
Assume constant collective dose–i.e. no change

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 177

Average annual collective effective
dose 2000–2002 (man Sv)(From [U11] for years 2000–2002)

178 UNSCEAR 2016 REPORT

D. Decommissioning
83. When a power company decides to close a nuclear power plant permanently, the facility must be
decommissioned by safely removing it from service and reducing residual radioactivity to a level that
permits release of the property and termination of the operating licence. As more commercial nuclear
power reactors reach the end of their operating licence, there is a commensurate increase indecontamination and decommissioning activities that involve radiation exposure. These activities
include decontamination of structures and components, dismantling of components and demolition ofbuildings, remediation of any contaminated ground, and removal of the resulting waste. As of 2015,
156 commercial and prototype reactors located in 19 countries with a total of 60.9 GW(e) capacity werepermanently shut down [I8]. Most of these reactors were PWRs, GCRs and BWRs. The current
assessment concentrated on occupational exposures during the decommissioning process.
84. The decommissioning process begins when a power company decides to permanently cease
operations. The operator of a nuclear facility may choose between three decommissioning strategies:(a) immediate dismantling, (b) deferred dismantling after a safe storage period, and (c) entombment of
the facility. Under immediate dismantling, decommissioning activities begin shortly after thepermanent cessation of operations. This strategy implies prompt completion of the decommissioning
project (approximately 10 to 20 years) and involves the removal of all radioactive material from thefacility to another new or existing licenced facility.
85. Under deferred dismantling (sometimes called safe storage, safe store or safe enclosure), a nuclear
facility is maintained and monitored in a condition that allows the radioactivity to decay and thus
reduce occupational exposure. Parts of a facility containing radioactive contaminants are safely stored
and maintained for upwards of 40 to 60 years until they can subsequently be decontaminated to levels
that permit parts of the facility to be dismantled and released for unrestricted use.
86. Under entombment, radioactive contaminants are encased in a structurally long-lived material
such as concrete until radioactivity decays to a level permitting the unrestricted release of the facility,
or release with restrictions imposed by the regulatory body.
87. As of December 2015, the International Atomic Energy Agency/Nuclear Energy Agency
Information System on Occupational Exposure (ISOE) database (http://www.isoe-network.net/)contained data on doses to workers from 84 reactors that were shut down, in some stage ofdecommissioning or fully decommissioned. These reactor units were generally of different types andsizes, and at different phases of their decommissioning programmes. At least 15 reactors had been fully
dismantled, over 50 reactors were being dismantled, over 50 reactors were in deferred dismantlement,
three had been entombed, and for others the decommissioning strategy was not specified yet.
88. Table 22 provides the average annual collective dose for occupational exposure per unit for up to
71 permanently shut down reactors by country and reactor type for 2008−2013, based on data recordedin the ISOE database and supplemented by individual country reports. Different decontamination anddecommissioning strategies were being employed and each facility shown in the database was in adifferent stage of decommissioning, making definitive trends difficult to deduce from this information.
Depending on the phase of decommissioning, there may be little or no worker exposure one year andthe next year collective dose to workers may rise as much as 100-fold (adapted from [O5]). Considering
the average collective doses for each of the reactor types, however, and the total average for all theunits, the average values demonstrate some stability over these six years, with the total average for allunits being about 0.06 man Sv per year and reactor.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 179

89. Table 23 shows data from the whole decommissioning period for nuclear power plants thathave been immediately decontaminated and decommissioned. The dose values given are theintegrated doses for the whole decommissioning process. There may be some additional dose due tospent fuel storage until a permanent repository is opened, but these occupational exposures can beconsidered negligible compared to active decommissioning. For example, for five of thedecommissioned units that reported to the REIRS database (Radiation Exposure and Information
Reporting Systems) ([U24]; table 3.1), collective doses from occupational exposure due to spent fuelstorage ranged from 0 to 1.86 × 10−3 man Sv annually. The values for electricity supplied were thetotal integrated electricity generation from the time the unit went on the grid until it ceased operation.
90. The relative quantity needed for the comparative study conducted here was an estimate of thecollective doses from occupational exposure for decommissioning, integrated over the period of
decommissioning. The fact that the annual collective dose varies from year to year is not relevant if areasonable average can be obtained. Although limited, the Committee considered that the data on
integrated doses for nuclear reactors shown in table 23 were sufficient for its use here.
91. The average total collective dose associated with the strategy of immediate decontamination anddecommissioning of the commercial nuclear power plants shown in table 23 was less than 10 man Sv
per reactor. While the alternative decommissioning strategies, deferred dismantling and entombment,
may result in some reduction in the total collective dose per reactor from decommissioning, it may be
another 10 to 20 years before any definitive conclusions can be documented.
92. Table 23 also shows the collective dose from occupational exposure normalized to the total
integrated electricity supplied for each of the reactors, with an average for these 8 reactors of
1.80 man Sv/(GW a).

The columns headed dose give the average annual collective dose from occupational exposure in man-millisieverts per reactor (man mSv)

2008

PWR

VVER

BWR

2009

2010

2011

2012

2013

No.

Dose

No.

Dose

No.

Dose

No.

Dose

No.

Dose

No.

Dose

France

1

23.2

1

62.1

1

117.2

1

264.1

1

275.6

1

189.3

Germany

5

160.0

5

128.0

3

278.6

3

126.3

3

114.4

4

77.7

Italy

1

1.1

1

1.7

1

3.2

1

1.8

1

3

1

5.2

Spain

1

134.7

1

244.0

1

53.0

1

190.0

1

307.9

1

468.9

United States

10

7.1

8

1.5

8

2.4

6

49.4

6

127.1

12

47.3

Average

18

57.2

16

60.0

14

73.5

12

94.4

12

141

19

81.1

Bulgaria

4

31.0

4

29.4

4

11.3

4

9.2

4

10.1

4

3.3

Germany

5

27.0

5

20.0

—

—

—

—

—

—

—

—

Russian Federation

2

78.0

2

84.0

2

77.6

2

66.3

2

79.2

2

49.6

Slovak Republic

1

48.2

2

106.0

2

12.4

2

10.0

2

4.3

—

—

Average

12

38.6

13

46.0

8

28.2

8

23.7

8

25.9

6

18.7

Germany

3

179.0

3

138.0

1

427.1

1

289.5

1

88.2

1

72.0

Italy

2

29.1

2

61.8

2

60.3

2

15.1

2

18.4

2

34.2

Japan

—

—

—

—

2

123.8

2

48.4

2

41.2

2

64.2

The Netherlands

1

0.3

1

0.6

n/a

n/a

1

10

—

—

—

—

Sweden

2

39.1

2

27.0

2

6.2

2

27.2

2

20

2

3.45

United States

3

13.4

4

5.1

5

21.8

4

30.7

4

59.4

5

55.7

Average

11

64.9

12

51.1

12

76.3

12

50.3

11

44.1

12

46.2

180 UNSCEAR 2016 REPORT

Table 22. Number of units and average annual collective dose from occupational exposure per reactor by country and reactor type for definitely shutdown reactors, 2008–2013

2008

2009

2010

2011

2012

2013

Dose

No.

Dose

No.

Dose

No.

Dose

No.

Dose

No.

Dose

France

6

2.8

6

8.8

6

1.3

6

2.4

6

7.4

6

8.2

Germany

2

13.0

2

17.0

—

—

—

—

—

—

—

—

Italy

1

2.9

1

0

1

1.7

1

10.4

1

0.2

1

2.2

Japan

1

20.0

1

20.0

1

50

1

50

1

70

1

10

Spain

—

—

—

—

—

—

1

0

1

0

1

0

United Kingdom

16

48.0

16

42.0

16

55

16

49

19

56

19

57.3

United States

—

—

—

—

—

—

—

—

1

0

1

0

Total number,average dose

26

32.1

26

30.0

24

39.1

25

34.4

28

42.1

28

41.1

HTGR

Germany

1

0

1

0

1

0

1

0

—

—

1

0

FBR

United States

—

—

1

80.14

1

77.9

1

294.9

1

2

1

0.1

LWGR

Lithuania

1

188.4

1

144.7

2

236.2

2

304.8

2

264.9

2

304.8

LWCHWR

Japan

1

431.3

1

114.6

1

111.6

1

126.6

1

148.8

1

134.1

All Units

Average

70

52.3

71

47.7

63

59.9

62

61.5

64

66.3

71

57.8

GCR

This table is adapted from table 4 in the 2012 ISOE annual report [O5]and table 5 from the 2010 ISOE annual report [O4]. Additional information was obtained from the individual country reports and the ISOE database,and the United States Nuclear Regulatory Commission Radiation Exposure and Information Reporting System (REIRS) [U24] database for United States definitely shut reactors. Data for 2013 were obtained from the2013 ISOE country reports [O7] and the ISOE database [I20].
Dashes (—) represent missing or partial data in the data source. The acronyms for the reactor type used in tables 22 and 23 differ somewhat from those in the other tables in this annex (see paragraph 58). The acronyms inthis table and table 23 are the designations used by the Nuclear Energy Agency.
The following explains the meaning of the acronyms that differ from previous tables:
LWCHWR (Light Water Cooled Heavy Water Reactor) also known as a CANDU reactor is the Canadian designed system. IAEA would refer to this as a PHWR.
VVER (water, water, energetic reactor) is a Soviet designed PWR.
HTGR, (also called HTGC, high temperature gas cooled) reactor. More of a prototype reactor but nuclear power plants include Peach Bottom and Fort Saint Vrain in the United States; Dragon reactor in the United
Kingdom, and THTR-300 and AVR in Germany.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 181

No.

182 UNSCEAR 2016 REPORT

Table 23. Collective dose, and collective dose normalized to electricity supplied, due to the complete
decommissioning process of immediately decontaminated and decommissioned commercial nuclear
power plants
Reactor gross electrical capacity and total electricity supplied were obtained from the IAEA PRIS database [I7]. Collective
doses were obtained from the ISOE database [I20] and REIRS reports [U24]Reactortype
PWR

Country

Plant

Gross
Capacity(MW(e))

Collective
dose(man Sv)

Electricity
supplied(GW a)

Normalized
collective dose(man Sv/ GW a)

United States

Haddem Neck

603

8.457

12.1

0.70

Maine Yankee

900

6.195

13.6

0.46

Rancho Seco

917

2.345

5.1

0.46

San Onofre 1

456

3.002

5.8

0.52

Trojan

1 155

2.973

9.6

0.31

Yankee Rowe

180

6.467

3.9

1.66

4.907

8.34

0.69

AVERAGE
BWR

United States

Big Rock Point

71

5.703

1.45

3.93

HTGR

United States

Fort St. Vrain

342

3.961

0.62

6.39

All units

Average

4.900

1.80

V. RADIATION EXPOSURES ARISING FROM ELECTRICITY
GENERATION BY COMBUSTION OF FOSSIL FUELS

A. Coal1.

Introduction

93. Coal is a family name for a variety of solid organic fuels and refers to a whole range of
combustible sedimentary rock materials spanning a continuous quality scale. For convenience, thiscontinuous series is often divided into two main categories: hard coal (which includes anthracite andbituminous coal) and brown coal (which includes sub-bituminous coal and lignite). The International
Energy Agency [I15] makes use of two broad categories of coal; hard coal as having a gross calorificvalue not less than 23.9 GJ/t (5,700 kcal/kg) and brown coal with a gross calorific value less than
23.9 GJ/t (5,700 kcal/kg). Often coal data are presented in tonnes of coal equivalent (TCE) where one
tonne of coal is equivalent to 7 million kilocalories. This description standardizes the carbon content
and heat value of a particular type of coal. The International Energy Agency estimates that there are
equal recoverable global reserves of both hard coal and brown coal [I14].

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 183

94. Combustion of coal for electricity generation is the largest contributor to worldwide electricity
generation (figure I). Coal has maintained a share of about 40% of the total electricity generated forsome decades, while the total electricity generation from coal and other sources has increased steadily
as shown in figure I [I15]. The UNEP geographic region—Asia and the Pacific—accounted for 57% of
the total electricity generation from coal in 2010, with China accounting for about 70% of this [U17]. In
contrast, the geographic region—West Asia—used no coal for electricity generation in 2010 (table 2).
95. Electricity generation is not the only end-product of coal combustion, others being for example
steel production and cement manufacturing. The largest 10 coal-producing countries are shown for theyears 2008–2012 in table 24. China was the largest producer with a 30% increase in production overthis five-year period. The total world primary coal production for this period had a 16% increased
production in 2012 compared with 2008, and about a 60% increased production during the 10-year
period since 2002 [U17].
96. Coal contains naturally occurring radionuclides from the uranium and thorium series (figure III)and potassium-40. The concentration of naturally occurring radioactive material in coal depends on thecharacteristics of the geological formation of the coal seams where it originated. Table 25 provides arepresentative overview of the range in concentrations, where large variations in the activity
concentrations can be noted.
Table 24. Total primary coal production 2008–2012 (million metric tonnes, Mt)
Source: United States Energy Information Administration, International Energy Statistics 2008–2012, open source data [U17]Country

2008

2009

2010

2011

2012

China

2 811

2 995

3 230

3 518

3 645

United States

1 063

975

984

994

922

India

517

558

562

575

589

Australia

392

408

424

402

421

Russian Federation

305

276

322

322

354

South Africa

252

249

255

253

259

Indonesia

249

291

325

360

443

Poland

143

135

133

139

144

Kazakhstan

111

101

111

116

126

Colombia

74

73

74

86

89

World

6 778

6 896

7 257

7 660

7 881

184 UNSCEAR 2016 REPORT

Table 25. Example ranges and/or averages of radionuclide activity concentrations in coal (Bq/kg)(table VII from IAEA [I2])Country

U

238

Th

230

226

21–68

Ra

Pb

Po

Th

Ra

210

210

232

228

19–24

20–33

16–28

11–69

11–64

72

62

62
8

K

40

Australia

8.5–47

Brazila

72

72

Egypt

59

26

8

10–145

10–63

10–700

32a

21a

225a

Lignite

<1–58

<1–58

<4–220(Former
Democratic
Republic of
Germany)

10a

8a

22a

Germany

Greeceb

117–390

Hungary

20–480

12–97

30–384Italyc23±3

18±4

218±15

Poland

<159
18d

<123
11d

<785

Romania<415
80a

UnitedKingdom

7–19

United States

6.3–73aAverage.

b

Lignite.

cLignite, average.

d

Average for all coal seams.

44–206<557
126a
8.5–25.5

59–205

23–140

<510
210a

9–41

<580
262a

7.8–21.8
8.9–59.2

<170
62a
7–19

12.2–77.7

3.3–51.8

55–314

3.7–21.1

97. When coal is combusted the majority of the non-combustible matter remains in the bottom and flyash. Because radionuclides are present in the mineral constituents, they also tend to remain in the ash,where the concentration of the radionuclides becomes enhanced [I2, S4, Z1]. However, radon is a noble
gas and all the radon present in the coal is emitted through the flue-gas stack. As coal-fired power
plants have modernized, the cleaning and filtering systems have become increasingly efficient andlarger fractions of the particulate matter in the fly ash have been captured and removed from thedischarge to atmosphere. The coal ash that is collected is either recycled for beneficial use or it isdisposed of in landfills or impoundments. 6
98. The components of the coal cycle that can lead to radiation exposures of the public are(a) discharges to atmosphere of radon from coal-mining activities and other wastes produced during
mining, (b) radioactive discharges from the operation of coal-fired power plants, and (c) radiation
exposures from the recycling and use of, or disposal of, coal ash. Occupational radiation exposures
6

Coal ash can be disposed as a coal slurry in impoundments, a dammed reservoir that contains the coal slurry.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 185

occur during (a) the mining for coal, and (b) work performed associated with power plant operation anddisposal operations. In earlier studies, occupational exposures from work performed at the power plant
were determined to be small [C5, G4, G5] in relation to the occupational radiation exposures incurred
during coal mining. For this reason, combined with the relatively small number of workers involved
compared to coal mining, this exposure source was not considered further in the current study. The
following sections consider the other exposure sources and pathways.

2.

Public exposure(a) Coal mining
99. Radon emissions from coal mining contribute to exposure of the public from the coal cycle.
Radon gas is emitted from the mines as a result of the coal mining activities, primarily through ventingof the mines. Although data that could enable the assessment of this impact have earlier been scarce,
new measurements on radon emissions from coal mining in China have become available. Radonemissions from 23 large-, medium- and small-sized coal mines in eight different provinces in China
have been assessed, based on the monitoring results of radon activity in the mines. The large- andmedium-sized coal mines are equipped with ventilation systems that are described as “good” or“relatively good.” The smaller, privately owned coal mines generally are poorly ventilated, with radon
concentrations 15 to 30 times higher than in the larger mines [L1]. The radon emissions have beennormalized to the unit of coal output and per unit of electricity generated for each coal mine and foreach size-class of coal mine. Typical values were obtained as shown in table 26 [W2].
Table 26. Radon emissions during one year from large-, medium- and small-sized coal mines in
China [W2]Type of coal mine

Coal output(t/a)

Number ofcoal mines

Radon emissions
per unit of coal
output (Bq/t)

Radon emissions per unit ofelectricity generated(TBq/(GW a))a

Large-sized

1.6 × 1097

1.9 × 105

0.57

Medium-sized

8

5.7 × 104

6

1.3 × 10

3.6

Small-sized

3.9 × 10812

3.5 × 10611

9.3 × 105

2.8

Typical valuea

From the data in table 26, obtained from the Chinese delegation to the Committee, the coal production per unit of electricity
generation could be calculated as between 2.8 and 3.1 × 106 t/(GW a).

100. The radioactive content of coal-mine tailings do not differ significantly from backgroundconcentrations of natural radionuclides in soil; this situation is different from uranium mining and milltailings, which have higher concentrations of the natural radionuclides [U9]. This exposure pathway isthus not considered further in this analysis.
101. The typical value for the radon emission (based on discharges of radon during one year)
normalized to electricity generated obtained from the Chinese data, 2.8 TBq/(GW a), has been usedwith the electricity generation data from table 2 and the Committee’s revised methodology for
estimating public exposures due to radioactive discharges (annex A) to assess the radiological impact
from this source. The default population distribution (see section III.A) was used and the radon was
assumed to be released on its own with account taken of its short-lived progeny (218Po, 214Pb, 214Bi, and
214Po) in estimating the doses from inhalation.

186 UNSCEAR 2016 REPORT(b) Electricity generation from combustion of coal
102. Coal combustion in power plants results in the direct release of gaseous radionuclides, and the
production of ash with enhanced concentrations of natural radionuclides relative to those of coal [S4].
A fraction of the ash produced is released to atmosphere, dependent on the particulate collection
devices used in the power plant. Modern coal-fired power plants have more efficient particulate
collection devices than older coal-fired power plants.
103. To assess the doses due to atmospheric releases from coal-fired power plants, a representative
case was considered. The coal (e.g. hard coal) was assumed to have an energy equivalent of 24 GJ/t
with a power generation efficiency of 38% [I13]. Although the values of 238U concentrations shown intable 25 show wide variations, an average 238U concentration of 20 Bq/kg was chosen, based on typicalvalues for Chinese coal reported as 10–25 Bq/kg [I10]. China is the largest producer of coal worldwide,
so the value of 20 Bq/kg for the 238U concentration in coal was considered reasonable as a typical
average global value. Other studies have also found a normal range of 20–25 Bq/kg observed globallyfor good quality coal [S4, T1, U6]. A value of 20 Bq/kg for the 238U concentration in coal had also beenused in the UNSCEAR 1988 Report [U7]. It should also be noted that the resulting individual andcollective doses calculated by the revised methodology for estimating public exposures due toradioactive discharges (annex A) are directly proportional to the 238U concentration in coal.
104. Two different release rates were evaluated to represent the discharge characteristics of older coalfired power plants and modern coal-fired power plants (table 27). The relative distribution among thedifferent radionuclides in table 27 for the older plants were taken from Hedvall and Erlandsson [H2]while the same for the modern plants were based on Zeevaert et al. [Z1]. The key difference between
the two data sets is that 222Rn concentrations in the discharges are 100 times larger than 226Ra in older
plants and 1,500 larger than 226Ra in modern plants that have more efficient filtering systems. However,in both cases the value for the discharge of lead and polonium particles has been chosen as twice that ofuranium and radium [C4, T1]. Because radon is a noble gas, it is unaffected by filters. As seen fromtable 27, these releases are not in secular equilibrium. The distribution of older versus modern coalfired power plants in the various regions of the world is not well-characterized so the results from bothcases are included to illustrate the difference in the resulting doses.
105. The assessments presented in this annex using the Committee’s revised methodology for
estimating public exposures due to radioactive discharges (annex A) do not include dose contributions
from 40K or the 232Th decay chain. The absorption of 40K in humans is homeostatically controlled andtherefore any doses from 40K discharges have been neglected. The contribution of the 232Th decay chain
to exposures due to electricity generation from coal combustion has been studied by Zeevaert et al.
[Z1]. They found that the concentrations of the radionuclides in the 238U and 232Th decay chains in fluegases discharged were similar. The largest contribution to individual doses came from deposition, with
consumption of food crops dominating. In this category, the contribution from the 238U decay series was
one order of magnitude larger than the contribution from the 232Th decay series. Although inclusion of
the 232Th decay series may lead to somewhat higher doses from electricity generation due to coal
combustion, it was excluded from the analysis in this annex.
106. Aquatic discharges from coal-fired power plants may lead to additional exposure of local
population groups, but this contribution has been found to be small and site-specific [L2, Z1], and were
therefore not considered here.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 187

Table 27. Releases to atmosphere (during one year) normalized to electricity generated from coalfired power plants, based on a representative coal containing 20 Bq/kg of 238U
Radionuclide

Normalized release (TBq/(GW a))
Older coal-fired power plantsa

Modern coal-fired power plantsb

222

Rn

0.07

0.07

210

Po

1.4 × 10−3

9.3 × 10−5

210

Pb

1.4 × 10−3

9.3 × 10−5Ra

0. 7 × 10−3

4.7 × 10−5

234

U

0. 7 × 10−3

4.7 × 10−5

238

U

0. 7 × 10−3

4.7 × 10−5Th

0. 7 × 10−3

4.7 × 10−5

226

230

a

Relative radionuclide distribution source: [H2].

b

Relative radionuclide distribution source: [Z1].

(c) Radon discharges from coal ash disposed in landfills
107. Coal ash is also referred to as coal combustion residuals (CCR) and coal combustion products(CCP) depending on the industry and the country, and is one of the larger streams of industrial waste
generated in the United States [U21]. Coal ash includes a number of by-products from combustion ofcoal including: fly ash; (furnace) bottom ash; fluidized bed combustion ash; boiler slag; semi-dry
absorption product; and flue gas desulphurization gypsum.
108. The coal ash collected from a power plant is either recycled for beneficial use or it is disposed ofin landfills or impoundments. Figure VII shows a time history of fly ash production and the fractionused for construction in the period 1966–2010 in the United States [A1]. Approximately 40% was usedcommercially, leaving the remaining 60% for disposal. This does not include bottom ash, but the
proportion sent for disposal was similar [A2].
109. Conventional back-filling or earthmoving operations are used to dispose of the coal combustion
residues (CCR) in dry or slightly moist conditions. Impoundments represent a wet disposal method
where the CCR is mixed with water at the power station and conveyed hydraulically through pipelines
to artificial lagoons where the slurry is discharged. According to the Electric Power Research Institute[E3], about 60% of the disposed fly ash in the United States is managed dry in landfills, and 40% ismanaged wet in impoundments, and it noted that there was a long-term trend toward increased use of
dry management practices [E3].
110. Earlier studies concluded that the individual doses to the public due to radioactive discharges
from deposited coal ash were below values relevant from an individual radiation protection viewpoint(e.g. [U23]). The main reason was that the fraction of radon emanating from coal ash is small. This
pathway was however considered relevant in the current assessment for collective doses given that theamount of coal ash produced is large and could be significant to the comparisons of collective doses.
Also, a similar pathway was considered from the uranium mill tailings in the nuclear fuel cycle
motivating a comparison between these two pathways.

188 UNSCEAR 2016 REPORT

Figure VII.

Fly ash production and use in the United States (1966–2010) [A1](Blue = production, Red = used as a construction material in a variety of applications)111. Method for treating the radon discharge from coal ash deposits. The amount of radon released toatmosphere from coal ash depends on the activity concentration of radon in the ash, which is related tothe activity concentration of 226Ra, and the extent to which the radon produced in the ash is emitted toatmosphere. A recent comprehensive review of radon emanation measurements for mineral, rock, soil,
mill tailings and fly ash found the radon emanation fraction (the ratio of the radon emitted to thatgenerated in the mill tailings (or ash deposits) per unit volume) for mill tailings (mostly uranium milltailings) was 0.17 and for fly ash was 0.03 [S1]. In another study [S6] the radon emanation fraction forcoal ash was found to be between 0.08 and 0.13 [S6]. In summary, the first cited study estimated aradon emanation from coal fly-ash of about 20% of the radon emanation from uranium mill tailings,
and the second study estimated a value of about 50%. A representative average concentration of 226Ra
in coal ashes (fly- and bottom-ash) was taken as 100 Bq/kg [M2].
112. The 222Rn flux (Bq/(m2 s)) was studied using data from a repository for uranium residues in India[I5] and a linear relationship was found between the radon flux and the activity concentration of 226Ra
in the source:
222

Rn flux (Bq/(m2 s)) = 8.3 × 10-4 kg/(m2 s) × 226Ra concentration (Bq/kg)(1)113. Because the relationship between the radon flux and the radon emanation factor is linear, theconstant in the above equation can be assumed to be proportional to the ratio of the radon emanation
factors for different sources. Therefore, for fly ash the constant above could be reduced to between

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 189

20 and 50% of its value (comparable with the values from the studies cited above for the radon
emanation from coal ash as compared to uranium mine tailings) to obtain an estimate of the 222Rn flux
from coal ash based on the 226Ra concentration in coal ash. A value of 20% was used in this analysis,
giving a linear constant in the above relationship of 1.7 × 10−4 kg/(m2 s).
114. According to a survey in the United States regarding the disposal of solid waste from coal-fired
power plants, a value for the area needed for disposing of solid wastes normalized to electricity
generated was reported as 2–11 m2/(GW h) [A9, F3]. A central value of 6 m2/(GW h) was used for thisanalysis. Multiplying the radon flux during one year, obtained by using equation (1), with the linear
constant adjusted for coal ash and a 226Ra concentration of 100 Bq/kg, with the area needed for
disposing of solid wastes normalized to electricity generated, gave the source term for the annual
discharge of 222Rn from deposited coal ashes of about 0.03 TBq/(GW a).
115. A similar value was reached by an independent method. This assessment used an annual dischargeof 0.1 TBq/(GW a) as the source term for radon discharges from uranium mill tailings, one part of thenuclear fuel cycle. Using the source term 0.1 TBq/(GW a) for radon discharge from uranium milltailings and reducing it to 20 to 50% gives an estimate for the annual discharge of radon from coal ash
of 0.02–0.05 TBq/(GW a), agreeing well with the value 0.03 TBq/(GW a) obtained from the alternate
assessment above.
116. The amount of ash placed in disposal was assumed to be 60% of the total ash produced in coal
power plants, based on data cited earlier from the United States and the United Kingdom. The larger six
coal-producing countries in table 24 are also countries with large land mass and therefore the value of
60% from the United States was assumed appropriate for use in this assessment. The remaining 40% of
the ashes were assumed to be used in a variety of building-related activities and the resulting radiation
exposures are discussed in subsection (e).
117. It was explained in paragraph 43 that radon discharges from one gigawatt-year of coal ash
deposits were assumed to continue for 100 years and that allowance had to be made in the methodology
for this continued discharge. This was done by multiplying the results for one year’s discharge by 100
to allow for the discharge continuing for 100 years (see annex A, paragraph 17). Taking into account
this multiplication by 100 years and that 60% of the total ash produced in coal-fired power plants was
assumed placed in disposals, gave a value for the radon discharge from coal ash deposit normalized toelectricity generation of 1.8 TBq/(GW a).

(d) Results—public exposures due to discharges from coal mining, coal-fired
power plants and ash deposits118. The annual discharges to atmosphere obtained as described above were used to derive individualand collective doses using the revised methodology for estimating public exposures due to radioactive
discharges (annex A). The results of the calculation of the characteristic individual doses per unit ofelectricity generated integrated to 100 years due to atmospheric discharges from the three sources ofpublic exposures from the coal cycle are shown in table 28. These three sources are (a) discharges fromcoal-fired power plants, (b) discharges from coal ash disposed in landfills and (c) discharges from coalmining. The radon discharges from one gigawatt-year of coal ash deposits were assumed to continue for
100 years. The results are presented for both older coal-fired and for modern coal-fired power plants. If
the coal-fired power plants are older, then the individual doses from all three routes are similar, withthose from the discharges from power plants being the highest. For newer power plants, the doses due
to discharges from the plants are about 10% of those from the other two sources.

190 UNSCEAR 2016 REPORT119. The values for each region that are shown in table 28 for the characteristic individual doses perunit of electricity generation due to radon discharges from coal mining and from coal ash deposits
remain constant across the regions. This is because the discharges from mining and from ash deposits
are from radon gas and therefore only result in inhalation doses. However, the discharges from coalfired power plants include the other radionuclides from the 238U series, as shown in table 27, and resultin doses due to deposition and food consumption, which do have variations with geographical region.
As described above, the 232Th series was not considered in these calculations, and earlier assessments
by [Z1], imply that this contribution is less than 10% of the contribution from 238U.
120. The results also show a difference in the characteristic individual doses per unit of electricity
generated due to coal-fired power plant discharges between the older and the modern coal-fired plants
with the values for the modern plants being about 10% of those for the older plants. It could be
expected that the values resulting from discharges from ash would differ between the older and themodern coal-fired power plants, but this is not reflected in table 28. This is because the actual
difference in the amount that remains in the ash for an older versus a modern coal-fired power plant isvery small, of the order of about 1%, and for both cases most of the radionuclides stay in the ash. Thisdifference therefore does not show up in the results.
121. The collective doses to the public integrated to 100 years due to electricity generation from thecoal cycle for each region and for the world as a whole are shown for the total electricity generated
from coal in the year 2010 in table 29. Both cases, assuming (a) that all coal-fired plants are older and(b) that all coal-fired plants are modern, are compared. Considering the three discharge sources (frommining, power plants and ash deposits), the contribution to the collective dose from the discharges fromcoal-fired plants dominates for the older coal-fired plants, but is the smallest term for the modern plants
where the contribution from mining is largest. To facilitate comparison, table 30 compares only theterms from the older versus modern coal-fired power plants.
Table 28. Summary of characteristic individual doses per unit of electricity generated integrated to
100 years due to atmospheric discharges from coal-fired power plant sources (mSv/(GW a))
SourceaAfricaAsia and
Pacific

EuropeLatin
America

North
America

From mining

2.4 × 10−4

2.4 × 10−4

2.4 × 10−4

2.4 × 10−4

2.4 × 10−4

From older coal plants

3.8 × 10−4

4.0 × 10−4

4.2 × 10−4

3.9 × 10−4

4.2 × 10−4

From modern coal plants

3.1 × 10−5

3.2 × 10−5

3.4 × 10−5

3.2 × 10−5

3.4 × 10−5

From asha

1.5 × 10−4

1.5 × 10−4

1.5 × 10−4

1.5 × 10−4

1.5 × 10−4

The annual discharges of radon from coal ash produced per unit of electricity generated are assumed to continue for 100 years.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 191

Table 29. Summary of collective doses to the public integrated to 100 years for the total electricity
generated from combustion of coal (in 2010) (man Sv)
Discharge type and source

AfricaAsia and
Pacific

EuropeLatin
America

North
AmericaWorld

LOCAL COMPONENTa – ATMOSPHERIC DISCHARGES
Mining1.0 × 100

7.1 × 101

8.6 × 100

3.8 × 10−1

3.4 × 100

7.0 × 101

Older coal plants

1.8 × 100

1.3 × 102

1.9 × 101

7.1 × 10−1

7.4 × 100

1.4 × 102

Modern coal plants

1.5 × 10−1

1.1 × 101

1.5 × 100

5.6 × 10−2

5.8 × 10−1

1.1 × 101

Ashb

6.7 × 10−1

4.6 × 101

5.5 × 100

2.4 × 10−1

2.2 × 100

4.5 × 101

Total (assuming all older coal plants)

3.5 × 100

2.5 × 102

3.3 × 101

1.3 × 100

1.3 × 101

2.5 × 102

Total (assuming all modern plants)

1.9 × 100

1.3 × 102

1.6 × 101

6.8 × 10−1

6.2 × 100

1.3 × 102REGIONAL COMPONENTc – ATMOSPHERIC DISCHARGES
Mining

4.5 × 100

3.0 × 102

3.7 × 101

1.6 × 100

1.5 × 101

3.0 × 102

Older coal plants

8.7 × 100

6.4 × 102

9.0 × 101

3.4 × 100

3.5 × 101

6.4 × 102

Modern coal plants

6.9 × 10−1

5.0 × 101

6.9 × 100

2.6 × 10−1

2.7 × 100

5.0 × 101Ashb

2.9 × 100

2.0 × 102

2.4 × 101

1.0 × 100

9.4 × 100

1.9 × 102

Total (assuming all older coal plants)

1.6 × 101

1.1 × 103

1.5 × 102

6.0 × 100

5.9 × 101

1.1 × 103

Total (assuming all modern plants)

8.0 × 100

5.5 × 102

6.7 × 101

2.9 × 100

2.7 × 101

5.5 × 102TOTAL LOCAL AND REGIONAL COMPONENTS – ATMOSPHERIC DISCHARGES
Mining

5.5 × 100

3.7 × 102

4.5 × 101

2.0 × 100

1.8 × 101

3.7 × 102

Older coal plants

1.1 × 101

7.7 × 102

1.1 × 102

4.1 × 100

4.3 × 101

7.8 × 102

Modern coal plants

8.3 × 10−1

6.0 × 101

8.3 × 100

3.2 × 10-1

3.3 × 100

6.0 × 101Ashb

3.5 × 100

2.4 × 102

2.9 × 101

1.3 × 100

1.2 × 101

2.4 × 102

Total (assuming all older coal plants)

2.0 × 101

1.4 × 103

1.8 × 102

7.4 × 100

7.2 × 101

1.4 × 103

Total (assuming all modern plants)

9.9 × 100

6.8 × 102

8.3 × 101

3.6 × 100

3.3 × 101

6.7 × 102a

The local component of collective dose is calculated for people living between 0 and 100 km from the discharge point.

b

The discharges of radon from coal ash produced in 2010 from electricity generation are assumed to continue for 100 years.

c

The regional component of collective dose is calculated for people living between 100 and 1,500 km from the discharge point.

192 UNSCEAR 2016 REPORT

Table 30. Comparison of collective doses to the public integrated to 100 years from coal-fired
power plants given alternative plant design (man Sv)
Collective doses to the public integrated to 100 years (man Sv)
Doses from coal-fired power
plantsAfricaAsia and
Pacific

EuropeLatin
America

North
AmericaWorld

LOCAL COMPONENTa – ATMOSPHERIC DISCHARGES
Older coal plants

1.8 × 100

1.3 × 102

1.9 × 101

7.1 × 10−1

7.4 × 100

1.4 × 102

Modern coal plants

1.5 × 10−1

1.1 × 101

1.5 × 100

5.6 × 10−2

5.8 × 10−1

1.1 × 101

REGIONAL COMPONENTb – ATMOSPHERIC DISCHARGES
Older coal plants

8.7 × 100

6.4 × 102

9.0 × 101

3.4 × 100

3.5 × 101

6.4 × 102

Modern coal plants

6.9 × 10−1

5.0 × 101

6.9 × 100

2.6 × 10−1

2.7 × 100

5.0 × 101

TOTAL LOCAL AND REGIONAL COMPONENTS – ATMOSPHERIC DISCHARGES
Older coal plants

1.1 × 101

7.7 × 102

1.1 × 102

4.1 × 100

4.3 × 101

7.8 × 102

Modern coal plants

8.3 × 10−1

6.0 × 101

8.3 × 100

3.2 × 10−1

3.3 × 100

6.0 × 101a

The local component of collective dose is calculated for people living between 0 and 100 km from the discharge point.

b

The regional component of collective dose is calculated for people living between 100 and 1,500 km from the discharge point.

(e) Coal ash in building materials
122. Coal combustion products (CCPs) are used as ingredients in a variety of construction materials
including concrete, grouting, fill material, lightweight aggregate, road construction or maintenancematerials, and in soil stabilization [U1].
123. Fly ash and furnace bottom ash are the main CCPs and the extent to which they are utilized varies
by country. Approximately 40% of CCPs produced in the United States are utilized in construction
materials [A2], and the percentage utilization was around 45% in the European Union [E2] for fly ash
and bottom ash CCPs produced in 2010. China is the largest producer of electricity from combustion ofcoal and consequently the largest producer of coal ash. According to Tang et al. [T2], China produces
proportionately more coal ash because it has a very low coal washing rate (51%). In 2010, the fly ash
utilization rate in China was over 65% [T2]. In contrast, in 2009 less than 20% of CCPs produced inAustralia were utilized [H3].
124. As noted previously, the activity concentration of natural radionuclides in coal ash is increased
relative to coal by a factor of 5–10. However, the concentration is again diluted when the fly ash ismixed with other materials to form construction material. The presence of fly ash in building materials
may increase indoor exposures to gamma radiation from 226Ra, 232Th and 40K contained in the coal ash,and exposures due to inhalation of radon emanating from the building construction material such asconcrete [D3, F1, T4].
125. The relationship between coal ash in construction material and exposure is not straightforward.
The use of coal ash has been shown to either increase, decrease or have essentially no effect on
exposures relative to traditional construction materials [T4]. This reflects differences in the source ofthe coal, the natural radionuclide content of the traditional construction materials, and to the changes instructural properties of the construction material. For example, the use of fly ash and furnace slag inconcrete has been shown to reduce radon exhalation rates because it alters the porosity and chemistry of

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 193

the construction material [D3, D4]. As of the year 2016 there are no consistent or internationallyaccepted limits for radionuclides in building materials.
126. A population-weighted average annual effective dose of 0.41 mSv from indoor exposure to
gamma rays mainly determined by construction materials was reported by UNSCEAR [U9]. The resultsfor individual countries generally ranged between 0.3 and 0.6 mSv. A more recent analysis by de Jonget al. [D3] calculated an annual effective dose of 0.32 mSv for the Netherlands, which is at the lower
end of the range given by UNSCEAR [U9]. In both evaluations, the results included dwellings where
fly ash was used in the construction material.
127. Collective doses either for geographical region or for the world as a whole due to the use of coal
ash in building materials have not been analysed further in this study. Although the individual dosesthat have been assessed are very low, some contribution to the total collective dose can be expectedfrom the use of coal ash in construction materials. However, the various factors causing variability inthe exposure characteristics cause major uncertainty in the assessments.

3.

Occupational exposures from coal mining

128. Previous UNSCEAR studies have estimated the collective doses due to occupational exposure
from coal mining. In the UNSCEAR 1988 Report [U7], based on exposure data from British coalmining and the worldwide coal production rate, the worldwide collective dose was estimated as
2,000 man Sv. The UNSCEAR 2000 Report [U9] updated this value to an estimated 2,600 man Sv. The
UNSCEAR 2008 Report estimated the worldwide collective dose to workers from coal mining in
2002-2004 at 16,560 man Sv in a year [U11]. Most of the data on occupational exposure from coalmining that were used in the UNSCEAR 2008 Report came from China. A study on radiation levels in
China reported the annual average collective dose to underground coal miners in 2003–2004 as
16,500 man Sv [L1]. In addition, occupational exposures from coal mining in the United Kingdom in
2002 were reported in the UNSCEAR 2008 Report [U11] as 3 man Sv for 5,000 coal miners and an
average individual dose of 0.6 mSv.
129. The worldwide collective dose to coal miners in 2010 could be estimated from the 2002 collective
dose value assuming that the increase in electricity generation from coal in the period 2002–2010 was
proportional to the increase in occupational exposure due to coal mining for the same time span. This
assumed that the same collective dose normalized to electricity generation that was assessed for
2002-2004 [U11] was applicable for 2010 and that the efficiency of coal mining remained the same, i.e.
the same number of coal miners was needed to obtain the same amount of coal. The electricity
generated from coal-fired power plants in the reference year of 2010 was 992 GW a (table 2). The
corresponding number for the period of 2002–2004 considered in the UNSCEAR 2008 Report was
720 GW a [I12]. This gave a rounded worldwide estimate of the collective dose to coal miners of
23,000 man Sv, as a first approximation.
130. Table 31 shows results from a Chinese study [L1], together with data on the number of coalminers in three categories of mines in China for 2010 [W2]. No new values of the average annual
effective dose to coal miners have been published since the 2010 values in table 31.
131. Chinese coal production between 2004 and 2010 increased by approximately 50%. During thisperiod, there was an increase in the number of underground miners working at medium- and large-sizedcoal mines and a significant decrease in the number working in small-sized township and privatelyowned coal mines [W2]. The last column in table 31 uses the average annual effective dose from 2004
and the number of coal miners in 2010 to estimate the collective dose in 2010 in China for the three194 UNSCEAR 2016 REPORT

coal-mine categories: small, medium and large. This can be compared to the collective dose in
2002-2004, also shown in the table. (The number of bone-coal miners in China in 2010 was notavailable, although this group represented a small fraction of the total in the 2004 data.) This approachgave an estimated collective dose in 2010 for coal miners in China of about 10,000 man Sv.
132. During the period 2002–2004, China accounted for almost 90% of the underground coal miners in
the world. Assuming that the proportion of underground coal miners from countries worldwide was about
the same in 2010 as in 2002–2004, the total world collective dose to coal miners was estimated to be about
11,000 man Sv (compared to 23,000 man Sv obtained using the simpler approach above). This can also becompared to the value 16,560 man Sv that was reported in the UNSCEAR 2008 Report [U11]. The
implied decrease would be due to more efficient coal-mining technology for underground coal extraction
and to the closing of many of the smaller, less efficient coal mines with poor ventilation [W2].
133. The dose contribution for thorium and its decay products and aerosols containing long-lived
alpha-emitting radionuclides were not assessed in this study [L1]. In the past, the effective dose fromaerosols containing long-lived alpha-emitting radionuclides was roughly estimated by using thecontents of radioactive material in the coal and the concentrations of dust in underground coal mines.
The estimation indicated that the annual individual dose ranges from several to ten microsieverts, which
has been assumed to be of little significance in this comparative study.
Table 31. Annual doses to underground coal miners in China [L1]
The information in the table for number of miners for the year 2010 was obtained from an official communication from the
Chinese delegation to the Committee

Type of coalmine

Average annual
effective dose
(2004)(mSv)

Number ofminers in2004(millions)

Number ofminers in2010(millions)Collective
dose
2002–2004(man Sv)

Collective dose in 2010,
using average annual
effective dose from2004 and number ofminers in 2010 (man Sv)

Large-sized

0.32

1

1.26

315

403

Medium-sized

0.63

1

1.31

630

825

Small-sized

3.78

4

2.27

15 1008 581

Bone-coal

11.3

0.05

Not available

567

Not available

2.75 (weighted
average)

6.05

4.84

16 612

9 809

Total

B. Natural gas
134. According to table 2 the global combustion of natural gas produced 544 GW a of electrical energy
in 2010. This amount of electrical energy was second only to that due to the combustion of coal at
992 GW a and was 1.7 times the amount of electricity generated by nuclear power plants. The
generation of 1 kW h of electrical energy has been estimated to require the combustion of 0.286 m3 ofnatural gas [U20].
135. Natural gas is essentially methane (CH4) with trace amounts of other materials. The mostimportant radionuclide released during the combustion of natural gas is 222Rn. Several authors have

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 195

reported on the concentration of 222Rn in natural gas as measured at the wellhead or at various otherlocations in the gas-delivery system. In developed countries, natural gas is typically not used directlyfrom the wellhead, but is processed to remove moisture and refrigerated to condense and remove higher
chain gases, including ethane (C2H6), propane (C3H8) and butane (C4H10). The condensation process isimportant, because radon tends to condense with ethane and propane [D6, G2]. Gesell [G2] studied nine
gas-processing plants and found that, on average, the 222Rn content of gas ready to be sold for
combustion (the sales gas) was 34% of that at the wellhead (the input gas) with a range of 4 to 90%.
Further, natural gas may be transported by pipeline over long distances and is also typically stored at
locations near its end use. Because the half-life of 222Rn is 3.8 days, appreciable decay can occur
between the production and combustion of natural gas.
136. Measured values of 222Rn in natural gas are summarized in table 32. The range of individual
values was large; the weighted average of 879 samples was 625 Bq/m3. Most of the values in table 32
were for samples taken at the wellhead. Considering the processes that reduce the concentration ofradon from the gas at the wellhead to the gas sold for combustion [V2], a value of 300 Bq/m3 wasconsidered to be a reasonable estimate.
Table 32. Summary of reported concentrations of 222Rn in samples of natural gas
Unless noted otherwise, the samples were taken at or near the wellhead. Concentration values are in units of Bq/m3

SourceArea

Number ofsamples

Minimumvalue

Maximum
value

Mean

[B9]

NW New Mexico
SW Colorado

307

7.4

5 880

910

[M4]

NW New Mexico
SW Colorado

42

11.8

2 130

610

[G2]

Texas, Oklahoma, Louisiana

15

37

4 400

1 330

[V1]

Netherlands, Germany, North Sea,
Borneo, Nigeria

~200

33

1 650

74a

[K2]

N. Germany

196

—

4 000

580

[V2]

British Columbia

~32

7

921

272

[O9]

Ireland

8b

116

918

638

[A4] cSyrian Arab Republic

36

15

1 142

400

[R4]

Pennsylvania

21

37

2 920

1 370

[P2]

Pennsylvania

22

110

5 476

1 770

Weighted average879

aAverage results for the Netherlands only.

bSame field sampled at various times.

c

Taken at many locations, including those in gas-processing plants.

625

196 UNSCEAR 2016 REPORT137. The calculation of the activity of 222Rn released normalized to electricity generated is thus given as

0.2860

m3
Bq
h
kW
TBq
TBq
× 300 3 × 8760 × 10 6
× 10 −12= 0.75kW ⋅ h
a
GW
Bq
GW
⋅a
m

(2)

This value for the release of 222Rn normalized to electricity generated was used with UNSCEAR’s
revised methodology for estimating public exposures due to radioactive discharges (annex A). The
2010 data on electricity generation from natural gas for each region, shown in table 2, were used, andthe default population distribution based on population densities for 2010 was used for the collective
doses (see paragraph 34). The resulting characteristic individual and collective doses are compared withthose for other electricity-generating technologies in table 33 (for characteristic individual doses) at theend of this chapter and in table 46 (for collective doses) in chapter VIII.
138. Other radionuclides can appear in natural gas. One of them is 220Rn, but its half-life (55.6 s) is too
short for it to appear at the point of end use of the gas for combustion. If water is co-produced withnatural gas, the water may contain soluble amounts of radium. Radium-226 is the parent of 222Rn and isa decay product of 238U; 224Ra is the parent of 220Rn and is a decay product of 228Ra and ultimately of232
Th (see figure III). The progeny of the three radium isotopes and 222Rn can also be present in naturalgas, but typically in small amounts. Lead-210 is a longer-lived (half-life of 22.2 years) decay product of226
Ra and 222Rn, and van der Heijde et al. noted that the activities of 210Pb and its decay product 210Po innatural gas are more than can be accounted for by the decay of 226Ra and 222Rn [V1]. These authors
concluded that the additional 210Pb and 210Po had been produced from the natural gas reservoir. In
general, these radionuclides other than radon do not reach the end point of combustion of natural gas,
but they typically plate out within the gas-distribution system fairly close to the point of withdrawal
and/or treatment. Because the radionuclides are contained within equipment, workers can incur external
exposure to radiation. Organo and Fenton [O9] concluded after investigations in Ireland that workers at
offshore locations would be exposed “at most” to around 100 μSv in a year. The Pennsylvania
Department of Environmental Protection [P2] measured the external ambient dose rate at several
locations within gas production and processing sites and estimated a maximum annual average dose of
270 μSv. The Committee has assumed a reasonably realistic estimate of 100 μSv in a year.
139. A problem in estimating the collective effective dose to workers is determining the number ofworkers in the industry apportioned to the amount of natural gas used to generate electricity. An
indirect method was used to make this determination. According to the United States Bureau of Labor
Statistics [U16], there were 89,000 production and non-supervisory workers in the oil- and gasextraction subsector. Most of these workers were not working directly in support of natural gas
production for electricity generation, but there was no further breakdown in the data. In order toestimate the fraction of workers supporting the generation of electrical energy by combustion of naturalgas, data from [I17] for the OECD countries for 2010 were used. In terms of energy produced, thesedata indicated that 12% of the energy produced from oil and natural gas together was used forelectricity generation due to combustion of natural gas. Thus, it was estimated that 10,700 workers were
employed in the United States to produce natural gas for the generation of electricity.
140. According to [U19] 209.2 billion cubic metres of natural gas were used in 2010 to produce
electricity in the United States. With the use of previously mentioned conversion factors this was
equivalent to 83.5 GW a of electrical energy. Thus, the normalized collective dose for workers based on
the data originating in the United States was 0.013 man Sv/(GW a).

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 197

C. Oil141. The combustion of oil for electricity generation accounted for less than 5% of the world’s
electricity generation in 2010, but accounted for more than 30% of electrical energy generated in West
Asia. The generation of 1 kW h of electrical energy is estimated to require the combustion of 0.278 L of
petroleum [U20]. Most of the “petroleum” combusted to generate electricity in 2010 in the OECD
countries consisted of fuel oil [I17], which has an approximate density of 0.95 kg/L.
142. Petroleum is produced from underground reservoirs in the presence of geological formations that
contain the primordial radionuclides 40K, 238U and 232Th; the latter two are parents of chains that
produce a series of radionuclides usually present in secular equilibrium (see figure III). A process thatcan perturb the secular equilibrium is the dissolution of some members of the chain in water, which at
depth can be at high temperature. Water containing dissolved radium is typically co-produced with oil.
Radium-226 is a member of the chain headed by 238U; 226Ra is the parent of 222Rn and an additional
series of decay products including 210Pb and 210Po. Radium-228 is a member of the chain headed by232
Th; 228Ra is the parent of 224Ra and 220Rn. Both 226Ra and 224Ra are parents of additional short-lived
beta or gamma-emitting radionuclides.
143. Apparently some power plants can burn crude (or heavy) oil with its associated natural gas [A5], but
it is more typical that associated natural gas and water produced in the process must be removed frompetroleum before delivery to a pipeline or refinery [S5]. Radon is more typically associated with natural
gas and the soluble isotopes of radium are typically associated with the produced water. As produced
water is withdrawn from depth, it cools and dissolved minerals, including radium, can form precipitatesand deposit on the production tubing and on various other production equipment. These deposits are
known as scale or sludge. With time the radium contained within scale and sludge will come into
equilibrium with gamma-emitting decay products and give rise to external exposure of workers.
144. There are many studies of the presence of radionuclides in scale, sludge, (e.g. [I1, R3]) andproduced water [S5], and of radon in natural gas (see section V.B above), but there are few
measurements of radium or radon in crude oil or its subsequent products. Crude oil generally contains
some remaining water within a water-in-oil emulsion and this water contains dissolved radium [S5].
Radon is also quite soluble in oil [B2].
145. The report by Bell et al. [B2] appears to be the only one that reports measurements of both 222Rn
and 226Ra in the same samples of crude oil. Because the half-life of 222Rn is 3.82 days, the samples had
to be delivered quickly and correction made for decay in transit. Seven samples of crude oil from wells
in Texas and Oklahoma were measured. The results for 222Rn varied from a minimum of 3.2 Bq/kg to a
maximum of 17 Bq/kg and had an average of 7 Bq/kg. The results for 226Ra had a minimum of
0.2 Bq/kg, a maximum of 13 Bq/kg and an average of 0.7 Bq/kg. The ratio of 222Rn to 226Ra had aminimum of 4, a maximum of 38, and an average of 15. Thus, most of the 222Rn in fresh samples ofcrude oil was unsupported, that is, it was far in excess of the activity that was in equilibrium with 226Ra.
Except for those power plants that burn crude oil directly, this excess 222Rn would decay or be removed
in the refining and/or transportation processes.
146. Hamlat et al. [H1] reported concentrations of 226Ra in an unspecified number of samples of crude
oil collected in Algeria. The range of values was from 6 Bq/kg to 20 Bq/kg; these values are reasonably
consistent with those reported by Bell et al. [B2]. Al-Saleh and Al-Harshan [A7] measured
radionuclides in 14 petroleum-product samples, including crude oil drawn from the Riyadh City
Refinery. The detection limit for 226Ra was 0.014 Bq/kg; the only products with detectable amounts of226
Ra were “sweet naphtha” (0.65±0.40 Bq/kg) and “flushing oil” (0.45±0.20 Bq/kg).

198 UNSCEAR 2016 REPORT147. The limited amount of data indicated above suggests a cautious approach in estimating the releaseof radionuclides from the combustion of oil products. For this procedure the Committee estimated that
there was a concentration of 226Ra in all oil products of 1 Bq/kg. Further, it assumed that unsupported
amounts of 222Rn decayed or otherwise were eliminated in the process, so that the concentration of
222
Rn in all oil products was also 1 Bq/kg.
148. Then, the normalized release of 222Rn was calculated as

0.278

L
kg Bq
h
kW
TBq
TBq
× 0.95 × 1
× 8760 × 10 6
× 10 −12= 0.002kW ⋅ hL
kga
GW
Bq
GW ⋅ a(3)This value for the release of 222Rn normalized to electricity generated was used with the revised
methodology for estimating public exposures due to radioactive discharges (annex A). The 2010 dataon electricity generation from oil for each region, shown in table 2, were used, and the default
population distribution based on population densities for 2010 was used for the collective doses (seeparagraph 34). The resulting characteristic individual and collective doses are compared with those forother electricity-generating technologies in table 33 (for characteristic individual doses) at the end of
this chapter and in table 46 (for collective doses) in chapter VIII.
149. There may be other radionuclides emitted by the combustion of oil products; Al-Masri and
Haddad [A5] reported values of about 60 Bq/kg of 210Po in heavy oil fuel used in three power plants in
the Syrian Arab Republic. The same authors [A6] also reported that soil in the vicinity of the three
power plants contained enhanced levels of 210Pb and 210Po. Other authors have not reported
measurements of 210Pb and 210Po associated with oil-fired power plants.
150. As mentioned above, 226Ra and 228Ra and their decay products accumulate in scale and sludge
around wellheads and processing equipment. This gives rise to occupational exposure, when workers
are in the vicinity of these elements. Kvasnicka [K4] estimated that the maximum effective dose on
offshore platforms could be managed to be below 1 mSv in a year. It is expected that the doses toworkers on offshore platforms would be higher than on onshore platforms, because of more substantial
problems with scale formation and the limited space in the working environment on the platforms.
Hamlat et al. [H1] measured ambient dose rates in the vicinity of onshore oil and natural gas production
equipment. They estimated that annual effective doses around oil extraction equipment might range
from 40 to 600 μSv for normal activities. A value of 300 μSv was adopted for this analysis.
151. There were no direct data on the number of workers in the oil industry apportioned to the
combustion of oil for the generation of electricity, so an indirect method was used. According to theUnited States Bureau of Labor Statistics [U16], there were 89,000 production and non-supervisory
workers in the oil- and gas-extraction subsector in the United States in 2010. In order to estimate thefraction of workers who were supporting the generation of electrical energy by the combustion of oil,data from [I17] were used. In terms of energy produced these data indicated that only 1.7% of energy
produced from oil and natural gas was used for the generation of electricity by the combustion of oil in
2010. Thus, it was estimated that 1,520 workers in the United States could be apportioned to generationof electrical energy by the combustion of oil.
152. According to [U19] 7.02 × 109 kg of oil were used in 2010 to generate electricity in the UnitedStates. Using the conversion factors given above, this is equivalent to 3.03 GW a of electricity. Thus,
the collective dose to workers normalized to the electricity generated, based on data from the UnitedStates, was estimated to be 0.15 man Sv/(GW a).

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 199

D. Comparisons of exposures from fossil-fuel electricity generation
153. Table 33 shows characteristic individual doses integrated to 100 years per unit of electricity
generated for the UNEP regions. These doses are due to atmospheric discharges from the coal cycle andthe combustion of gas or oil in power plants generating electricity. Although the doses resulting fromthe modern coal plants are about 10% of the doses from the older plants, in total the characteristic
individual doses per unit of electricity generated from both the older and the modern coal plants arelarger than from the gas or the oil combustion technologies. See chapter VIII for further comparisons
between these and other electricity-generation technologies.
Table 33. Summary of characteristic individual doses per unit of electricity generated integrated to
100 years due to atmospheric discharges from the coal cycle and the combustion of gas and oil(mSv/(GW a))Showing results from both older and modern coal plants

Electricity
generation
technology

ReleaseAfricaAsia and
Pacific

EuropeLatin
America

North
AmericaWest Asia- From mining

Radon

2.4 × 10−4

2.4 × 10−4

2.4 × 10−4

2.4 × 10−4

2.4 × 10−40

- From older
coal plants

Naturalradionuclides
includingradon

3.8 × 10−4

4.0 × 10−4

4.2 × 10−4

3.9 × 10−4

4.2 × 10−40

3.1 × 10−5

3.2 × 10−5

3.4 × 10−5

3.2 × 10−5

3.4 × 10−50

- From ash

Radon

1.5 × 10−4

1.5 × 10−4

1.5 × 10−4

1.5 × 10−4

1.5 × 10−4

0

Gas

Radon

6.3 × 10−5

6.3 × 10−5

6.3 × 10−5

6.3 × 10−5

6.3 × 10−5

6.3 × 10−5

Oil

Radon

1.7 × 10−7

1.7 × 10−7

1.7 × 10−7

1.7 × 10−7

1.7 × 10−7

1.7 × 10−7

Coal

- Frommoderncoal plants

VI. RADIATION EXPOSURES ARISING FROM ELECTRICITY
GENERATION FROM GEOTHERMAL ENERGY
154. Geothermal energy is derived from the heat of the earth at locations where magma is closer thannormal to the earth’s surface. The generation of electricity from geothermal sources presently depends
upon the use of steam or hot water from wells drilled into underground reservoirs. As shown in table 2[I17], geothermal energy in the reference year 2010 generated 7.77 GW a of electricity and accounted
for 0.3% of the total world’s electricity generation in 2010.
155. Electricity generation from geothermal sources first began in 1904 at Larderello, Italy, with anexperimental 10 kW generator. At the present time the installed capacity is in excess of 9,000 MW in
25 countries [L3]. The larger power plants are at The Geysers, California; Larderello, Italy; Cerro
Prieto, Mexico; Leyte, Philippines; Salton Sea, California; Hellisheidi, Iceland; Tiwi and Malitbog,
Philippines; and Wayang Windu and Darajat, Indonesia [K1].

200 UNSCEAR 2016 REPORT156. Different approaches can be taken to generate electricity from geothermal sources. If dry steam isavailable, the simplest is to run the steam through a turbine and exhaust to the atmosphere. Efficiency isimproved if the dry steam is condensed, with heat dissipated through cooling towers. Most reservoirs,
however, do not produce dry steam, but some combination of steam and hot water or hot water alone.
In this situation, it is necessary to separate steam from water, or, if hot water alone is produced, to flash
the water to steam through single, double, or even triple passes. A binary process is in use at some sitesthat use water of lower temperature; hot water is run through a primary loop and a fluid with a lower
boiling point through a secondary loop. As of the year 2016, most electrical energy generation isthrough the flash process with single or double flash; the other major technology is the use of dry steamwith condensation [M3].
157. During the 1970s there was substantial interest in evaluating the potential impact of the release of222
Rn from gases vented during the operation of geothermal electricity-generating plants. The more
complete evaluations were reported for The Geysers and the Larderello Plants. Anspaugh [A10]reported that 19.3 TBq/a were being released from The Geysers during the operation of 11 dry steam
condensing units with 502 MW of electrical power; the daily rate was noted to be equivalent to theaverage daily background emission of 222Rn from about 40 km2 of soil. For the Larderello geothermal
complex, the emission rate per unit energy was 38.5 TBq/(GW a) according to George et al. [G1]. Thiswas based on measurements performed by D’Amore [D1], who calculated that 300 GBq/d were being
released from the Larderello geothermal complex, which had an installed capacity of about 420 MW[P1]. Thus, the emission rate per unit energy at Larderello was 260 TBq/(GW a).
158. The above represent the two situations where data were complete enough to estimate emissions
per unit of electricity generated. Based on this limited set of data, the Committee assumed an averagevalue of 150 TBq/(GW a). There are measurements of radon in steam or hot water from other locations,and samples of such data are given in table 34; at the time of the assessment no data were available forthe amount of 222Rn that might be released from geothermal sites using binary circle systems. A reason
that data are scarce on radon related to geothermal energy is that, following the measurements in the
1970s, it was generally concluded that this source of radon was not significant compared to the natural
exhalation of radon from soil. Measurements of 222Rn and 220Rn in geothermal fluids do continue, but
are mainly related to understanding of the dynamics of resources [W6].
Table 34. Reported concentrations of 222Rn in fluids produced from geothermal wells
Location

Activity of 222Rn per unit ofproduced fluid (Bq/kg)

Reference

The Geysers, weighted average

520

[A10]

The Geysers

620

[K3]

Larderello

1 280

[K3]

Larderello, weighted average

3 100

[G1]

Salton Sea, California

110

[K3]

East Mesa, Imperial Valley, CA

1.1

[K3]

Wairakei, New Zealand

630

[W6]

159. The value of 150 TBq/(GW a) for the release of 222Rn normalized to electricity generation fromgeothermal energy was used with the electricity generation data by region from table 2 and withestimates of population density to give an estimate of the characteristic individual and collective doses.
There is substantial uncertainty regarding the population density around geothermal power plants, as itis necessary to locate the plants within the narrow confines of the resource. The Geysers and the Cerro

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 201

Prieto plants are in isolated locations, but large metropolitan areas are within 1,500 km. The otherextremes are geothermal power plants located on islands. Because of these discrepancies and the lack of
specific population data on each power plant, the Committee made two calculations for geothermal: one
with the assumption of low-density population, as in the assessments for uranium mining and milling,
and one with the default population density.
160. Table 46 in chapter VIII compares the collective doses to the public for the discharges from thenuclear fuel cycle, coal cycle, gas, oil and geothermal electricity-generating technologies. As explainedin the previous paragraph, two values are given for geothermal energy. The normalized discharge ofradon for geothermal electricity generation is the largest of the electricity-generating technologies
shown in table 46. However, the impact of geothermal electricity generation remains small because of
the limited use of this technology. Further, there is substantial uncertainty regarding the discharge ofradon from geothermal power plants; data are available for only two plants, and the estimateddischarges from these two plants vary substantially.
161. There are even fewer data on occupational exposure in the geothermal industry. Anspaugh [A10]reported no evidence of increased external gamma exposure, but did note increased levels of radon andshort-lived progeny at several locations normally inaccessible except during maintenance. In general,
moderate to severe disequilibria were found, and an average excess amount of exposure was
0.05 Working Levels 7 (WL) (1 µJ m−3). Razzano and Cei [R1] indicated that 36 persons work overthree shifts to operate the Larderello complex. From data in the same paper, the electricity generated in2013 at Larderello was 5,659 GW h with 767 MW of “efficient” installed capacity. The combination ofthese data leads to an annual occupational exposure of 5 man WLM/(GW a). According to [I11]
1 WLM is equivalent to an effective dose of 10–20 mSv, but the higher values are associated withmines and homes. A more reasonable value for outdoor exposure is 10 mSv, which would also be
consistent with [U10]. Thus, the normalized collective dose to workers in geothermal electricity
generation would be 0.05 man Sv/(GW a).

VII. ASSESSING DOSES FROM THE CONSTRUCTION PHASE OF
ELECTRICITY-GENERATING TECHNOLOGIES
162. All electricity-generating technologies considered by the Committee have a construction phaseduring which the facilities and infrastructure are established. Although in general there are no
significant radiation exposures associated with the construction, there may be radiation exposuresassociated with obtaining the materials for construction such as in mining activities.
163. Industries not directly linked to electricity generation, such as mining, milling and processing of
metal ores, contribute to occupational and public exposure because of the presence of naturalradionuclides [U11, U22]. While public exposures from the mining industry may be negligible on an
individual basis, typical occupational doses in the mining industry may be up to a few millisieverts in ayear. The collective dose from occupational exposures during the mining of metals was evaluated forthis study on the basis of the dose per unit mass of metal ore mined for each electricity-generating
technology, as discussed in the UNSCEAR 2008 Report [U11], and on recent data from 2012 onradiation exposure of miners of rare earth metals in China [W3].
7
A working level (WL) is a unit of potential alpha energy per unit of air. In the SI system of units, one WL is equal to 2.08 × 10−5 J m−3.
A working level month is a unit of exposure to 1 WL for a month. For occupational personnel one month is considered to be 170 hours.

202 UNSCEAR 2016 REPORT164. Aggregate is also used extensively in the construction of electricity-generating plants. Aggregate
in building and construction refers to the material used for mixing with cement, bitumen, lime, gypsum
and other additives to form concrete or mortar. Commonly used aggregates include sand, crushed or
broken stone, gravel, and blast-furnace slag. In some cases, the amount of aggregate used is similar to
the total mass of all other materials.
165. The relative volumes of concrete required to construct various nuclear and coal-fired power plants
are tabulated in tables 35 and 36. Typical radionuclide concentrations in raw and processed materials
and in wastes of the mineral processing industry, including the cement industry, were reviewed in the
UNSCEAR 2000 Report (see table 27 in [U9]). Typical radionuclide concentrations in metal ores werereported to be about three orders of magnitude higher than of materials in the cement industry. For thisassessment, only the occupational exposures from the mining of metal ores needed for metals used inconstruction of electricity-generating technologies were evaluated.
Table 35. Estimates of the amounts of construction materials used in nuclear power plants
Plant

a

Mass of metals (t)Volume of concrete (m3)

PWR, 1 000 MW(e) [D5]61 000169 000

BWR, 1 000 MW(e) [D5]66 000200 000

PWR, 1 000 MW(e) [B8]a38 000 (estimated)

75 000 (estimated)

Nuclear power plant [W5]36 00075 000

The amount presented for specific metals: Al, Cr, Cu, Ag, Fe, Pb, Mg, Mn, Mo, Ni, Sn, Zn.

Table 36. Estimates of the amounts of construction materials used in coal-fired power plantsaPlantaMass ofmetals (t)Comments

Volume ofconcrete (m3)Coal-fired power plant [S7]50 000 steel

Amount presented in generic terms as "steel"and expressed in kg/MW(e)380 000

Coal-fired power plant [W5]41 000 metals

Amount presented for specific metals: Al, Cr,
Cu, Mn, Mo, Ni, steel (low alloy and stainless)and V and expressed in t/GW(e)31 0001,000 MW(e) plant assumed.

166. The mass of metal ore required to produce the metals in the building materials has been estimatedfrom information on the total metal inventory required and from the metal ore grade used. It was
assumed that steel was the primary metal used. Iron is alloyed with carbon to produce plain carbon
steel. Alloy steels also contain various alloying metals. The category of steel used in the different
electricity-generating technologies and the contents of alloying metals were considered. Plain carbon
steels were assumed to contain iron and 0.16–0.59% carbon. Low-alloy steels were assumed to containless than 0.25% carbon, as well as small amounts of nickel, chromium, molybdenum, manganese andsilicon. High-alloy stainless steels were assumed to contain molybdenum, chromium and/or nickel andother elements. These assumptions are based on the information in [C1, G3].
167. For high-alloy stainless steel, type S316 was used as the basis for this assessment, because it is
widely used in industrial applications. Type S316 contains around 2% by mass of molybdenum [A3,S3]. Other steel types may contain different levels of molybdenum, or none at all, which could
influence the results. This is because molybdenum is a low-grade metal ore and therefore extraction ofmolybdenum may make a larger contribution to occupational exposures [A3, S3].

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 203

168. Based on the above, the composition of typical steels for each category (plain, low-alloyed andhigh-alloyed stainless) was assumed as shown in table 37. If the type of steel was not known, theproportions given in table 38 were assumed.
Table 37. Composition of different types of steel (based on [C1, G3])
Material

Composition (% by weight)
PLAIN STEEL

Iron

99.62

Carbon0.38

LOW-ALLOY STEEL
Iron

99.63

Molybdenum

0.33

Carbon0.05

HIGH-ALLOY STAINLESS STEEL
Iron

65.35

Chromium

17.00

Nickel

12.00

Molybdenum

2.50

Manganese

2.00

Other non-metallic elements

1.07

Carbon0.08

Table 38. Assumed mix of steel types used in construction where details were not specified(based on [C1, G3])
Steel type

Proportion of total (%)

High-alloy stainless steel

10

Low-alloy steel

30

Plain steel

60

169. Assumptions on ores. The amount of ore required for the construction of an electricity-generating
facility also depends on the ore grade. The assumptions made regarding ore grades are shown intable 39 [A8, C3, M1].

204 UNSCEAR 2016 REPORT

Table 39. Metals and their assumed ore grades
The data presented here are typical values taken from [A8, C3, M1], and the numbers have been rounded

Resource

Ore grade at mine (%)

Tin

79

Manganese

47

Zirconium

47

Iron

46

Magnesium

41

Tantalum

31

Chromium26

Aluminium

11

Zinc

7

Lead

6

Nickel2

Copper

1.4

Vanadium

0.3

Molybdenum

0.18

Silver0.01

Gold0.0005170. Recycling of metals. Recycling is an important part of the metal industry from both an economicand energy-saving point of view. In the United States, approximately two thirds of the steel produced in2008 was made from recycled material [U15]. Around 43% of the total crude steel production
worldwide is made from recycled steel, with the main sources for steel recycling typically being
discarded cars, household appliances and steel cans, as well as old buildings and structures [W4].
Typical building construction uses approximately 60–65% recycled metal [B1], while in the United
Kingdom about 94% of construction steel is recovered [T3].
171. Special rules apply to the re-use of scrap steel and other metals from nuclear power plants;
authorities establish limits on the activity concentrations of radionuclides in materials that can bereleased for recycling. There is, however, no indication that there are significant differences in the
degree of recycling between the various electricity-generating technologies.
172. The effect of recycling metals has not been included in the present study, because of insufficient
data for large portions of the world. By not explicitly considering recycling, the collective dose per unitof electricity generated due to the extraction and processing of the metals used in the construction of a
facility is likely to be overestimated by around a factor of two on average, and possibly a factor of fiveor more for some regions of the world with developed recycling processes. This should not affect therelative comparisons of occupational exposures from mining metals between technologies, but would
affect comparisons of the total exposures (public and occupational) among the electricity-generating
technologies.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 205

173. Dose assessment. To estimate the radiation exposure of workers in the mining industry(occupational exposure) from ore extraction and processing, the following assumptions were made:(a) The ores are extracted only through underground mining. The use of above-ground mining
would give rise to smaller radiation doses than underground mining [U11]. Consequently, thisassumption leads to an overestimation of collective dose.
(b) The presence of several metals in an ore was not considered. Each ore was assumed to contain
only one metal type, and thus the contribution to occupational doses from the extraction andprocessing of the various minerals was evaluated independently and summed. In reality somemetals will be extracted together and consequently the resulting collective doses may have been
overestimated.
(c) Occupational exposures from mining and processing of raw materials were inferred from dataon uranium mining and processing, and on mining other minerals. Mining data for undergroundcopper mines in Australia (Mount Isa), Canada (Kidd Creek), South Africa (Palabora), andPortugal (Neves Corvo) show annual production rates of 1–5 kilotonnes of ore per employee [I19].
The denoted employees included all workers at the mines. Based on these data, the Committee
selected a mid-range value of 3 kt of metal ore per employee for use in this assessment (table 40).
(d) The average annual effective dose to non-uranium miners, including those involved in mineralprocessing, given in the UNSCEAR 2008 Report [U11] was 3.0 mSv, with a range of 1.3 to
5.0 mSv. Using an annual average value of 3.0 mSv for all workers associated with the mining
industry, and the value of 3 kt of metal ore per employee given in (c), the collective dose per unit
mass of ore extracted was estimated at 1 × 10−9 man Sv/kg (table 40). The data for (c) and (d) wereobtained from different worker populations and this introduces some uncertainty in the estimationof the collective dose per unit mass of ore extracted.
(e) In a recent study in China [W3] data were collected on radiation levels, and dose assessments
were performed for workers of the rare earth industry in the Baotou area and Sichuan Province,
two large mining districts in China. These regions account for about 77% of the total annual outputof rare earth mines in China; the reported annual production rates were 0.01 and 0.02 kt of rareearth metal per mining employee, respectively.
(f) The Chinese study has estimated the collective dose per unit mass of rare earth metal
extracted. The typical value for the whole rare earth industry that was obtained in the Chinese
study on radiation exposure of Chinese workers in mining, crushing, beneficiation and refining isabout 150 × 10−9 man Sv/kg. This value relates to the mass of metal extracted, which differs fromthe value 1 × 10−9 man Sv/kg given in (d) which relates to mass of metal ore. The Committee used
the latter value in the analysis in order to account for the different metal requirements withassociated metal ore grades of each electricity-generating technology.
(g) As a check, an alternative estimate was obtained by comparing with the data on uranium
mining. The collective dose per unit mass of uranium extracted given in the UNSCEAR 2008
Report [U11] was 1 man Sv/kt (based on 2000–2002 data). Assuming (from information in [I4,O8]) an average grade for uranium ore of 0.3%, the collective dose per unit mass of uranium ore
extracted is 3 × 10-9 man Sv/kg.
174. Although the assumptions in paragraph 173 affect the absolute values of the assessed collective
dose, the relative importance of the different electricity-generating technologies with regards to theconstruction phase remains.

206 UNSCEAR 2016 REPORT

Table 40. Collective effective dose per unit mass of ore mined used in this study
Estimatebased onAnnual production rateof ore per person (kt)

Average annual
occupational dose (mSv)

Collective dose per unit mass ofmetal ore extracted (man Sv/kg)

[U11]

3

3

1 × 10−9175. Nuclear power plants. For the current assessment, the assumed design lifetime of a nuclear power
plant was 40 years and the capacity factor 8 was 90% (table 41).
176. Three different studies of the use of materials in nuclear power plants have been published. Doneset al. [D5] studied the material used in two Swiss nuclear power plants—the pressurized-water reactor(PWR) at Gösgen and the boiling-water reactor (BWR) at Leibstadt. Both were of the 1,000 MW(e)type, but the capacity of the Leibstadt plant was increased to 1,190 MW(e) following construction. For
the latter, the total amount of metals used was 66,000 tonnes, of which two thirds were unalloyedsteel/iron. In addition, 200,000 m3 of concrete were used. Bryan and Dudley [B8] considered thequantities of different materials used in a typical 1,000 MW(e) PWR with river water cooling. The total
mass of metals used was estimated at 38,000 tonnes but the proportions of each metal were notspecified. The total amount of concrete used was estimated as 210,000 tonnes (~87,260 m3). White andKulcinski [W5] gave the amount of material needed for four power plants, including a nuclear power
plant, where values of 36,000 tonnes of metals and 180,000 tonnes (~75,000 m3) concrete were given.
The study focused on the energy payback ratio 9 and CO2 emissions, and it was not in that sense a fulllife cycle assessment. Furthermore, the study did not consider potential radiation exposure. The datafrom the three studies are presented in table 35.
Table 41. Assumed plant sizes, life times and capacity factors for the different electricitygenerating technologies*

Assumed to be the same as coal

Electricity-generating
technology

Typical plant gross capacity(MW(e))

Lifetime(years)Capacity factor(%)

Nuclear [I3]

1 000

40

90

Coal [F3, I18]

1 000

40

80

Natural gas [O1, S8]

505

25

80

Solar PV [F3, N3]

—

30

9.4

Wind turbine [D2, N4, O10]

25

20

24

1 000*

20

75

NA

30

NA

Biomass [W5]Geothermal [R5, S9]8
Capacity factor (net) is the ratio of the net electricity generated, for the time considered, to the energy that could have been
generated at continuous full-power operation during the same period [U25].
9Energy payback ratio is the ratio of total electrical energy produced during a system’s normal lifespan, divided by the electricalenergy required to build, maintain and fuel it.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 207

177. Example of a dose calculation for a nuclear power plant. Specifications of the typical plant grosscapacity, lifetimes and capacity factors (can also be called load factor) used in the calculations areshown in table 41. Table 42 shows an example of the details of a dose calculation for a nuclear power
plant. The collective dose was estimated based on occupational exposures related to metal ore mining
and processing of the metal ore for metals needed to construct the power plants.
Table 42. Example calculation of collective dose from occupational exposure during construction
phase of a nuclear power plant
Type: PWR Gösgen, 970 MW(e), capacity factor 90% [D5]Resource/Elements

Metal needed forconstruction (kg/kWh)

Ore grade atmine (%)

Amount of ore neededat mine (kg/kWh)

Collective dose
(manSv/(GW a))

Iron

4.7 × 10−546

1.0 × 10−4

8.9 × 10−4

Manganese

1.4 × 10−647

3.1 × 10−6

2.7 × 10−5

Chromium

1.2 × 10−526

4.8 × 10−5

4.2 × 10−4

Molybdenum

1.8 × 10−6

0.18

9.9 × 10−4

8.7 × 10−3

Nickel8.6 × 10−62

4.3 × 10−4

3.8 × 10−3

Iron

1.8 × 10−546

3.9 × 10−5

3.5 × 10−4

Molybdenum

5.9 × 10−8

0.18

3.3 × 10−5

2.9 × 10−4

Iron

1.1 × 10−446

2.4 × 10−4

2.1 × 10−3

Copper

4.7 × 10−6

1.4

3.3 × 10−4

2.9 × 10−3

Aluminium

6.3 × 10−7

11

5.6 × 10-6

4.9 × 10−5

Stainless steel

Low-alloyed

Unalloyed steel

Other

Total

1.9 × 10−2

178. Coal-fired power plants. There are a number of different designs of coal-fired power plants.
However, the amounts of material used in their construction do not differ significantly. Spath et al. [S7]conducted a full life cycle assessment of a coal-fired power plant covering the construction anddecommissioning of the plant. The amount of steel used in the construction of a 1,000 MW(e) plant was
50,000 tonnes, but no data were given on the other metals. Also, the proportions of plain carbon steel,low-alloy steel and stainless steel were not specified. White and Kulcinski [W5] described a total
amount of 41,000 tonnes of metals in their study. In both studies [S7, W5], the analysed units had anassumed capacity factor of 80% and a lifetime of 40 years. The information from these studies issummarized in table 36.
179. Natural gas power plant. The designs of natural gas power plants also vary. Spath and Mann [S8]presented a full life cycle assessment for a 505 MW(e) natural gas power plant covering its construction
and decommissioning. The study is similar in approach to the one they used for coal-fired power plants[S7]. Again, potential radiation exposure was not considered and no specific data were provided on theparticular metals used to construct the plant. The amount of steel used was 31 t/MW(e) and the amountof concrete used was 98 t/MW(e). The Committee assumed that the average capacity of a natural gas

208 UNSCEAR 2016 REPORT

power plant was 505 MW(e) to estimate the amount of each metal using the assumptions shown intable 37 and table 38.
180. Solar energy power plant. Solar energy is by far the largest energy resource available on earth.
Two different technologies contribute to solar electricity generation: solar photovoltaics (PV) andconcentrating solar power (CSP).
181. Solar PV systems convert direct and diffused solar radiation into electricity through a
photovoltaic process using semiconductor devices. Solar PV systems can be used anywhere in theworld on suitable land and on buildings. Solar PV technology is also very adaptable to being used in amodular fashion, which means that systems can be installed close to centres of demand.
182. Silicon-based PV solar cells contain small amounts of rare earth elements. Crystalline-silicon PV
cells are the most common PV cells in use today [U14].
183. Concentrating solar power (CSP) systems are designed to produce high-temperature heat forelectricity generation or for co-generation of electricity and heat. CSP systems are capable only of
exploiting direct normal irradiation, which is the energy received directly from the sun (i.e. notscattered by the atmosphere) on a surface tracked perpendicular to the sun’s rays. Areas suitable for
CSP development are those with strong sunshine and clear skies, usually arid or semi-arid areas.
Parabolic mirrors or troughs are used in CSP 10 technology. The parabolic mirrors are designed toconcentrate solar radiation onto linear heat collection elements [N2].
184. A solar energy power plant does not have a fuel cycle in the same way that most other energy
technologies do, consequently any potential human exposure to ionizing radiation is related to the useof natural resources for manufacturing the centralized CSP plants or the PV solar cells. The largest
contribution to the collective dose is from the acquisition of raw materials, especially minerals used for
manufacturing the CSP plants or PV solar cells.
185. Silicon-based PV solar cells contain small amounts of rare earth elements, which are of particularinterest because the ores from which they are obtained have relatively high contents of uranium andthorium. Thus, the mining of the ores and their subsequent processing lead to occupational radiation
exposures.
186. Because relevant data on the use of metals and other natural resources were only readily available
for the PV solar systems, the assessment was only carried out for this type of solar energy production.
187. The metals required to construct a solar PV system and amount of ore required are shown intable 43. The results are based on data for a life cycle assessment of a 3 kWp 11 multicrystalline–silicon
PV solar panel mounted on a slanted roof in Switzerland [J1]. The solar panel efficiency was 9.4%. The
solar PV system lifetime was assumed to be 30 years, with the exception of the power inverter thatchanges direct current to alternating current. In this case a lifetime of 15 years was assumed. The parts
included were mainly PV panels, mounting structures, inverter and electric installations. Metals used
for the solar panels included small amounts of rare earth elements, which are derived from ores withhigh contents of thorium or uranium.
188. The amount of ore required per unit of electricity generated depends on the ore grade. In table 43,
the values were based on published ore grades [A8, C3, J1].
10

Also called concentrated solar power and concentrated solar thermal (CST).
The symbol, kWp, stands for the peak power (kW) of the solar PV system—the basic unit for the characterization of thecapacity of PV plants measured in a standardized test at a temperature of 25 °C and an irradiation of 1,000 W/m2.
11

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 209

Table 43. Ore usage at mine for the production of energy by a PV solar system mounted on aslanted roof in Switzerland
Figures are for production of 1 kWh by a 3 kWpa PV solar system; ore grade values provided in table 38

Resource

Amount of metals required per unit
electricity producedb(kg/kW h)

Amount of ore required per unit
electricity produced(kg/kW h)

Aluminium

1.7 × 10−3

1.5 × 10−2

Chromium

2.6 × 10−6

1.0 × 10−5

Copper

4.2 × 10−4

3.0 × 10−2

Iron

1.3 × 10−3

2.7 × 10−3

Lead

1.3 × 10−6

2.2 × 10−5

Magnesium

5.4 × 10−5—

Manganese

4.4 × 10−6

9.3 × 10−6

Molybdenum

4.2 × 10−6

8.3 × 10−3

Nickel

5.0 × 10−8

2.5 × 10−6

Silver

2.9 × 10−6

2.9 × 10−2

Tantalum7.8 × 10−7

2.5 × 10−6Tin

1.6 × 10−6

2.1 × 10−6

Zinc

3.1 × 10−6

4.4 × 10−5aThe symbol, kWp, stands for the peak power (kW) of the solar PV system—the basic unit for the characterization of thecapacity of PV plants measured in a standardized test at a temperature of 25 °C and an irradiation of 1,000 W/m2.

bCalculated based on data in Jungbluth et al. [J1].

189. Wind power plant. The kinetic energy of wind is exploited in wind turbines for electricity
generation. Wind speeds suitable for electricity generation range from 4 to 25 metres per second. These
are attainable practically all over the world, with the exception of some equatorial regions. Wind poweris exploited not only onshore but also offshore, where wind speeds are higher and the wind is typicallyavailable more regularly and for longer periods of time. The depth of water and distance from centres ofdemand onshore are major factors influencing the siting of offshore developments [O3].
190. An assessment of materials used to build an onshore wind power unit was conducted by Whiteand Kulcinski [W5]. The assessment was for a three-blade wind turbine and assumed a 25 MW(e) unit,
with a capacity factor of 24% and a lifetime of 20 years. The data on construction materials issummarized in table 44.
Table 44. Estimates of the amounts of construction materials used in wind power plants
Data in White and Kulcinski [W5] and references therein. Amount presented is for low-alloy and stainless steel and expressedin t/GW(e)PlantaWind power plant [S7]a25 MW(e) plant assumed.

Mass of metals (t)Volume of concrete (m3)85 000 steel

130 000

210 UNSCEAR 2016 REPORT191. Biomass power plant. Biomass fuel includes straw, wood or wood residues from forests, andwood waste from wood-processing plants, such as sawmills or pulp and paper mills. Biomass fuel cancontain varying amounts of radionuclides associated with past emissions or accidents. One example ofthis is fuel containing varying amounts of 137Cs in wood that has been obtained from forested regions
affected by fallout from past nuclear power plant accidents. The 137Cs can be emitted in the flue gases
or concentrated in the ash from the combustion of biomass containing 137Cs and possibly lead to
exposures. In some areas filters are currently in use to decrease the 137Cs in the flue gases, andtreatment or proper burial of the ashes can reduce or prevent exposures. Exposures via these pathways
are not treated further here since the 137Cs originates from nuclear power plant accidents and areconcentrated in the forested areas that have received significant fallout from past accidents.
192. In general terms, biomass fuel has a lower energy density than coal and is more challenging tohandle. As a consequence, the fuel handling equipment is heavier than that for a coal-fired power plant ofequivalent capacity. Technically, biomass power plants can be as large as coal-fired power plants in termsof installed capacity, but, in general, biomass units are not built as large as coal units, mostly because of
the significant difficulties with supply and storage associated with materials of lower energy density [R2].
193. The design of a biomass power plant is not very different from that of a coal-fired power plant.
The main difference is that the ash handling equipment is generally smaller in a biomass plant,
depending on the type of fuel used (biomass typically generates less ash than coal). However, thisdifference may be neglected to a first approximation, and therefore the Committee assumed that thematerials required per kilowatt to build a biomass power plant were the same as those given by Whiteand Kulcinski for a coal-fired power plant [W5]. For the biomass power plant, the capacity factor was
assumed to be 75% and plant lifetime 20 years.
194. Summary. Table 45 shows occupational collective effective doses normalized to energy
production due to mining for ores and the processing needed for construction of the electricitygenerating plants or devices, as estimated in this study. Electricity-generating technologies using coal,natural gas and biomass have the lowest collective doses normalized to electricity generated, followed
by slightly higher values for nuclear power. Wind power shows a larger collective dose by about afactor of 10 compared to the lowest values, and solar power shows the largest value by about a factorof 80. The differences between the various electricity-generating technologies are connected to various
plant facilities using different types and amounts of steel and metals. Another reason is the differencesin the capacity factors and lifetime of the plants, with a higher capacity factor and longer lifetime
implying a lower collective dose per unit of electricity generation.
Table 45. Collective effective dose normalized to unit of electricity generation for construction ofelectricity-generating plants or devices
Electricity-generating technology

Normalized occupational collective dose due to mining
and processing of ores needed for construction(manSv/(GW a))

Nuclear

0.02

Coal

0.01

Natural gas

0.01

Solar PV

0.8

Wind

0.1

Biomass

0.01

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 211

VIII. COMPARISON OF RADIATION EXPOSURES FROMELECTRICITY-GENERATING TECHNOLOGIES
195. Sources of radiation exposure from electricity-generating technologies based on the (a) nuclear
fuel cycle, (b) coal cycle, the combustion of natural gas, oil and biofuels, (c) geothermal energy,(d) wind power and (e) solar energy have been investigated in this annex. Two electricity-generating
technologies, the nuclear fuel cycle and the coal cycle have been substantially investigated using thesame methodology, the Committee’s revised methodology for estimating public exposures due toradioactive discharges (annex A). This same methodology was also used to investigate public exposuresderived with more rudimentary assessments based on less available data for the electricity-generating
technologies that employ combustion of oil and natural gas, and geothermal energy.
196. Occupational exposures for all of these technologies were also estimated, relying mainly on datafrom dosimetric records of worker exposures. In addition, new assessments on occupational exposuresfrom (a) decommissioning of nuclear power reactors and (b) the mining of rare earth metals needed forthe construction phase in different electricity-generating technologies have been presented, adding forthe first time solar energy, wind power and combustion of biomass to the electricity-generating
technologies assessed by the Committee.
197. This chapter compares the results for the different electricity-generating technologies investigatedby applying the revised methodology for estimating public exposures due to radioactive discharges(annex A). This is followed by a comparison of all results for both occupational and public exposures.

A. Comparison of public exposures due to radioactive discharges
from the electricity-generating technologies based on the nuclear
fuel cycle, coal cycle, combustion of natural gas and oil, and use ofgeothermal energy
198. Table 46 shows results from applying the revised methodology for estimating public exposuresdue to radioactive discharges (annex A). The results represent the sum of all discharges assessed in thisannex for the electricity-generating technologies based on the (a) nuclear fuel cycle, (b) coal cycle andcombustion of natural gas and oil, and (c) use of geothermal energy.
199. The table provides estimates of collective doses to the worldwide public, and associated collective
doses normalized to electricity generation in 2010, integrated to 100 years. Collective doses normalized
to electricity generation are the sum of the collective doses for each process in the nuclear fuel cycle, orthe coal cycle, divided by the total electricity generated in 2010 for that cycle. For the coal cycle, thedoses were estimated assuming all discharges were either from older coal plants or from modern ones.
Both results are shown and represent a range of values for the coal cycle. Although the assessments of
the nuclear fuel cycle and coal cycle were more substantive than those for the combustion of oil andnatural gas, and geothermal energy, the Committee considered that comparing the magnitudes of thetotal and normalized collective doses was still valid.

212 UNSCEAR 2016 REPORT

Table 46. Collective dose to the worldwide public, and associated normalized collective dose for 2010,
integrated to 100 years a, b
Except where otherwise specified, the collective doses given are for the local and regional components. Shown also is thepercentage of total world electricity generation in 2010 for each electricity-generating technology and the discharges for222

Rn normalized to the electricity generation in 2010

Electricity-generating
technology

Collective
dose(man Sv)

Normalized
collective dose(man Sv/(GW a))% of total world
electricity
generation in2010

Normalized 222Rn
discharges(TBq/(GW a))

13

Uranium mining – 66

NUCLEAR FUEL CYCLE
Nuclear, total from mining andmilling, power plants andreprocessing, excluding global
component

130

0.43

Milling – 3
Operational milltailings – 3Mill tailingsc – 10

Adding global component
integrated to
100 years

910

3.0

500 years

1 700

5.5

10,000 years

7 600

25

COAL CYCLE
Coal, older coal plants
Coal, modern coal plants

1 400
670

1.4

40

Coal mining – 2.8
Power plants – 0.07

0.7

Ashc – 1.8

OTHERSNatural gas

55

0.10

22

0.75

Oil

0.03

0.000 3

4.6

0.002

Geothermal (low-density
population – default
population)

5–160

1–20

0.3

150

a

Projections of any health effects using collective doses in the table are not recommended.

b

All estimates are calculated based on best estimates; site- and location-specific collective doses are not presented.

c

The values of the normalized 222Rn discharges (TBq/(GW a)) shown in table 46 for uranium mine mill tailings (Mill tailings)
and for coal ash deposits (Ash) were multiplied by 100 to account for radon emanating for 100 years from these surfaces. The
value for coal ash deposits was also multiplied by a factor of 0.6 since only 60% of the ashes produced are deposited.

200. Excluding the global component from the globally-circulating nuclides, electricity generationfrom the coal cycle gave the highest collective dose to the public integrated to 100 years—both for the
total generation in 2010 and when normalized to unit of electricity generated—for both older andmodern coal plants. When the global component resulting from the globally-circulating radionuclides
originating from the nuclear fuel cycle was taken into account, integrated to 100 years, the totalcollective dose from the nuclear fuel cycle was of the same order as from the coal cycle, about in the
middle range of the values for modern versus older coal plants. Because of ongoing global exposuresfrom the globally-circulating radionuclide 14C discharged from nuclear power plants and from

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 213

reprocessing facilities, the collective dose from the nuclear fuel cycle slowly increases over centuries asshown in figure V, in section IV. This is also evident in the doses shown in table 46 for the global
circulation integrated to 100, 500 and 10,000 years. The total collective dose normalized to electricity
generated for the nuclear fuel cycle, including the globally-circulating nuclides and integrated to
10,000 years, is 25 man Sv/(GW a) as shown in table 46. Comparing with earlier UNSCEAR
assessments, the UNSCEAR 2000 Report [U9] estimated the same quantity as 40 man Sv/(GW a). As
described earlier, the collective dose from globally-circulating radionuclides is the sum of very small
doses to the entire world’s population. The local and regional components of collective dose assessed
for the nuclear fuel cycle excluding globally-circulating radionuclides, and for the coal cycle, are forthe local and regional populations exposed to the respective discharges of the source (seeparagraph 34).
201. The magnitude of collective doses resulting from the coal cycle, for both the older and themodern coal plants, is due in large part to (a) the amount of electricity generated from coal (40% of
the world’s electricity generation in 2010), (b) the greater number of coal mines compared touranium mines and (c) the contribution to the collective dose from the discharge of radon and otherradionuclides from the 238U series arising from the combustion of coal at the power plants. Anotherimportant factor is that a larger population base lives near coal plants and coal mines compared tonuclear plants and uranium mines.
202. Natural gas accounted for 22% of the world’s electricity generation in 2010, which led to a larger
contribution to the collective dose than oil, but was still small in relation to coal. Combustion of oil forelectricity generation contributed only marginally to collective doses. These relatively small doses fromnatural gas and oil combustion were however the dominant contribution to collective dose for West
Asia where, as shown in table 2, natural gas and oil accounted for most of the electricity generation inthat region in 2010.
203. Discharges of 222Rn normalized to the electricity generated are also shown in table 46; the largest
value is estimated for geothermal energy. This finding is based on few existing data. However, becauseof the process for generating electricity from geothermal energy discussed in section VI, it is reasonable
that the impact of 222Rn discharges from gases vented during the operation of geothermal electricityproducing plants is relatively significant. The resulting doses from geothermal energy shown in table 46
are assessed using two different population densities, low-density and the default population density(see chapter III), where the available population data discussed in chapter VI suggest the low-density
population distribution may be more realistic. The range in results for the collective dose demonstrates
the strong dependence on the population data. However, the impact of geothermal electricity generation
remains small because of the limited use of this technology.
204. The next largest value for the normalized 222Rn discharge is for uranium mining, which is a factor
of about 20 larger than the value for coal mining. This is also reasonable because uranium mining
occurs where there are high levels of uranium and therefore of its progeny products such as 222Rn.
Shown in table 47 is a comparison of estimated doses to the public from the mining of coal and themining of uranium. The assessments resulted in a larger estimate for the characteristic individual dose
per unit of electricity generated for uranium mining (non-ISL) than for coal mining, consistent with thelarger normalized 222Rn discharge. However, values for both the worldwide collective dose (essentiallycomprising local and regional components alone) and of the associated values normalized to unit ofelectricity generated in 2010 are larger for coal mining than uranium mining. This is because of thelarger number of coal mines in the world and because the population density is higher around coalmines compared to uranium mines.

214 UNSCEAR 2016 REPORT

Table 47. Comparison of doses to the public from mining of coal and mining of uranium
Coal mining

Uranium mining
non-ISLISL−6Characteristic individual dose per unit of electricity generated(Sv/(GW a))

2.4 × 10

5.5 × 10

2.5 × 10−7

Worldwide collective dose (man Sv)

3.7 × 102

4.0 × 101

1.3 × 100

World-average collective dose per unit of electricity generated(man Sv/(GW a))

3.8 × 10−1

2.8 × 10−1

1.3 × 10−2

−7205. Figure VIII shows graphically the contribution each electricity-generating technology consideredmakes to the worldwide collective dose to the public. Two distinct values are presented for the nuclear
fuel cycle: the first is the local and regional component for the population exposed directly to thedischarges, and the second includes the global component for the population of the world as a whole
due to globally circulating radionuclides. The values for both the coal cycle and geothermal energy are
deemed to represent boundary values, assuming either all modern or all older coal plants for the coal
cycle, and for geothermal energy assuming two different population distributions. Figure IX shows thesame sources as figure VIII but for the total collective dose normalized to electricity generated. The
values for the nuclear fuel cycle without global circulation are slightly less than for the coal cycle,
which lies somewhere between the two values given for the modern and older coal plants. Including the
global circulation to the nuclear fuel cycle results in the larger value for these two technologies.
Comparing these data with figure VIII shows how the magnitude of electricity generated for eachtechnology results in the collective dose to the public. Figure IX also shows the magnitude of the upperbound for the collective dose normalized to electricity generation for geothermal energy.
206. Table 48 breaks down the comparison of collective doses—and collective doses normalized toelectricity generated in 2010—for each of the source components of the nuclear fuel cycle and coal
cycle technologies that have been assessed. These components are coal mining, discharges from coal
combustion during power plant operation and from coal ash deposits associated with the coal cycle forelectricity generation. For the nuclear fuel cycle, these components are uranium mining and milling
including mill tailings, discharges during electricity generation from the nuclear power plant anddischarges from reprocessing. Collective doses normalized to electricity generated in 2010 for each of
the source components for the nuclear fuel cycle shown in table 48 use the electricity produced as aresult of each process in the normalizations.
207. Although the differences in collective doses normalized to electricity generation for the various
sources are not very large, (with the exception of old-style coal plants, which have the largest value),
the total collective doses in 2010 show significant differences. For both sets of results, the largest
values are from old-style coal combustion power plants. Collective doses for the different components
associated with the coal cycle are all larger than collective doses for the components associated with thenuclear fuel cycle, except for modern coal plants compared to nuclear power plants. The categories
shown in table 48 make clear the importance of radon discharges from coal mining and from coal ash
deposits, which—with the assumptions made in this study—make significant contributions to the totalcollective doses even when the coal combustion power plant is modern. The differences in the dosevalues for the old-style compared with the modern coal combustion power plant are due to the nuclides
in the 238U decay chain other than radon, because the radon discharge from the flue-gas stack is thesame in both cases. Table 49 shows this difference between modern versus old-style coal combustion
power plants regarding dose contribution per radionuclide from the 238U decay chain.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 215

208. Table 49 shows local and regional components of collective doses assessed from discharges ofradionuclides in the 238U decay chain from the flue-gas stack of a coal plant during the combustion ofcoal for electricity generation in a modern compared to an old-style coal plant. The 222Rn discharges are
the same for both types of coal plant; consequently the doses from 222Rn are also the same in table 49. It
is clear from the breakdown of the radionuclides shown in table 49 that the large differences in thedoses assessed for the old-style versus modern coal plants are due to the other radionuclides shown,with 210Pb and 210Po giving the largest contribution.
Figure VIII. Local and regional components of the collective doses to the public integrated to
100 years, for the electricity-generating technologies based on the nuclear fuel cycle, coal cycle,
combustion of gas and use of geothermal energy
Data from table 46

216 UNSCEAR 2016 REPORT

Figure IX. Local and regional collective doses to the public integrated to 100 years, normalized toelectricity generated for the technologies based on the nuclear fuel cycle, coal cycle, combustion ofgas and use of geothermal energy

Table 48. Comparison of collective doses to the public, and collective doses normalized toelectricity generation in 2010, integrated to 100 years, to the world-average population within a
1,500 km radius of each source for the electricity-generating technologies based on the coal cycle
and the nuclear fuel cycle
Coal
Sourcea

NuclearCollective
dose(man Sv)

Normalized
collective dose(man Sv/(Gw a))

SourceCollective
dose(man Sv)

Normalized
collective dose(man Sv/(Gw a))

Coal mining

370

0.4

Uranium mininga
and milling

53

0.2

Older coal plants

780

0.8

NPP generation

68

0.2

Modern coal plants

60

0.1

From coal ash deposits

240

0.2

Reprocessing

7.6

0.03

Of the 53 man Sv for uranium mining and milling, 40 man Sv is from mining only.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 217

Table 49. Local and regional components of collective dose, integrated to 100 years, due todischarges from modern and old-style coal combustion power plants

Radionuclide

Collective dose from modern coal plants(man Sv)

Collective dose from old-style coal plants(man Sv)

Local

Regional

Local

Regional

Pb

2

9

28

135

Po

3

14

46

216

222

Rn

2

8

2

8

226

Ra

1

7

20

98

230

Th

2

8

26

122

234

U

0.5

2

7

34

238

U

0.4

2

6

29

Totala

11

50

135

641

210
210

a
Slight differences between the totals shown here and those in table 48 are due to rounding performed on the values in table 48.
The values in table 49 are left as generated in the assessment to avoid inconsistent rounding of individual radionuclides for the
purpose of attaining the same total rounded value as shown in table 48. It should also be recalled that in this table, as in all tablesin the annex resulting from assessments, the calculations are done to full precision and any discrepancies in the final sum of
numbers in the tables are due to rounding.

209. Doses assessed from the radon emanation from coal ash versus uranium mill tailings, using 222Rn
discharges normalized to electricity generated given in table 46, are compared in table 50. As describedin chapter IV and more extensively in annex A, a low population density was used in the assessments
on uranium mill tailings whereas a default population density was used in the assessment on coal ash.
The characteristic individual dose per unit of electricity generated is larger for uranium mill tailings
compared to coal ash, reflecting the greater activity concentrations of naturally occurring radionuclides,
including radon, in mill tailings. However, when the total electricity generation is taken into account,collective doses assessed from coal ash are greater than those from mill tailings. The results show theeffect of the continued emanation of radon centuries into the future.
Table 50. Collective dose per unit of electricity generated to world-average population within
1,500 km and integrated to 100 years, also integrated for two different times since disposal, andcharacteristic individual dose per unit of electricity generated from emanation of radon from coalash and mill tailings
Time sincedisposal

Collective dose per unit of electricity
generated (man Sv/(GW a))

Characteristic individual dose per unit ofelectricity generated (Sv/(GW a))

Coal ash

Mill tailings

Coal ash

Mill tailings

100 years

0.2

0.04

1.5 × 10

8.4 × 10−7

500 years

1.2

0.2

−7

210. Significant radionuclides from nuclear power plant discharges. The importance of 14C and theglobally circulating radionuclides, and 222Rn and the 238U series, is discussed in other sections. The
following concentrates on comparing other significant radionuclides discharged from different nuclear
power plant types.

218 UNSCEAR 2016 REPORT211. Table 51 shows the world-average collective dose per unit of electricity generated for the nuclear
power plant types assessed in this annex. The table illustrates the relative importance to the worldaverage collective dose per unit of electricity generated of 90Sr, 137Cs and 35S from the GCR-type
reactor, and tritium from the HWR reactor.
Table 51. Local and regional components of collective doses, integrated to 100 years, normalized
to electricity generation in 2010, shown for all nuclear power plant types considered
See chapter IV for details on the power plant types

Discharged
radionuclide

World-average collective dose per unit of electricity generated for each nuclear power plant type(man Sv/(GW a))
PWR

BWR

HWR

LWGR

AGR

GCR

FBR

H

7.2 × 10

8.6 × 10

1.7 × 10

1.2 × 10

1.9 × 10

3.3 × 10

2.3 × 10−1

14C

4.6 × 10−2

3.2 × 10−2

1.4 × 10−1

3.1 × 10−1

3.5 × 10−1

1.3 × 100

2.8 × 10−2

35

S

0

0

0

0

4.5 × 10−2

2.4 × 10−1

0

41

Ar

4.5 × 10

4.6 × 10

1.3 × 10

3.4 × 10

8.4 × 10

7.0 × 10

0

54

Mn

2.3 × 10−4

1.0 × 100

−5

4.0 × 1000

1.8 × 10−458

Co

3.7 × 10−5

4.0 × 10−50

5.9 × 10−600

1.7 × 10−460

Co

2.0 × 10−4

5.6 × 10−3

1.5 × 10−4

8.8 × 10−3

7.0 × 10−2

3.5 × 10−3

2.3 × 10−3

65

Zn

0

5.0 × 10−40

1.6 × 10−4

7.0 × 10−5

0

0

85

Kr

2.2 × 10−5

1.4 × 10

0

0

0

0

1.7 × 10−490Sr

7.0 × 10−5

1.2 × 10−30

1.2 × 10−2

3.4 × 10−5

4.7 × 10−1

0

106

Ru

3.7 × 10−5

1.0 × 10−6

0

0

0

0

0

131

I

6.0 × 10

3.2 × 10

1.7 × 10

7.5 × 10

2.5 × 100

1.5 × 10−4

133

Xe

1.2 × 10−4

1.5 × 10−40

1.1 × 10−2

0

0

0

135

Xe

3.4 × 10−5

3.4 × 10−40

2.4 × 10−3

0

0

0

138

Xe

1.5 × 10−9

3.1 × 10−70

1.1 × 10−6

0

134

Cs

3.2 × 10

2.6 × 100

3.4 × 10137

Cs

4.2 × 10−4

1.0 × 10−3

4.6 × 10−2

Total

1.2 × 10−1

5.0 × 10−2

1.9 × 100

3

−2

−5
−5

−6

−5

−4

−3

−5

−4

−4

0

−3

−5

−1

−3

−3

−2

−4

−5

−2

−2

0

0

7.4 × 10−2

3.8 × 10

1.1 × 10−2

6.6 × 10−3

6.6 × 10−4

6.2 × 10−1

7.7 × 10−3

4.8 × 10−1

4.9 × 10−1

2.8 × 100

2.8 × 10−1−4−4212. Figure X shows estimated collective doses by world region and totalled for the world by nuclear
reactor type, with the values taken from table 51. Both collective doses, and collective doses
normalized to electricity generated in 2010 are shown. The collective doses show a different profile
than that shown in the figure displaying the collective doses normalized to electricity generated. Twonuclear power plant types, GCRs and HWRs, dominate the collective doses normalized to electricity
generated. However it is the power plant types PWRs and HWRs that dominate the contribution to thecollective doses; this is because of a combination of the number of reactors that exist in each region
coupled with the discharged amounts of significant radionuclides for each reactor type.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 219

Figure X. Local and regional collective doses to the public integrated to 100 years, and associatedvalues normalized to electricity generation, by world region and nuclear reactor type
Results shown for collective doses from all discharges (man Sv) and for collective dose from all discharges normalized toelectricity generation (man Sv/(GW a)) in 2010. Note that the order of the individual reactor types is according to their world
share of electricity generated in 2010, as shown in table 9220 UNSCEAR 2016 REPORT

B. Comparison of public and occupational exposures
213. Table 52 summarizes the results from all occupational and public exposures that have beenpresented in this annex. The table shows collective doses normalized to electricity generated in 2010,
followed by collective doses for the same year. The local and regional components of doses to the
public are for world-average populations out to 100 km and between 100 km and 1,500 km from afacility respectively, integrated over 100 years. Other conditions are as stated earlier in this chapter.
This section considers the total exposure from each electricity-generating technology, i.e. public plus
occupational exposures.
214. The occupational exposures from coal mining dominate collective doses, so that the total
exposure of the public and occupational exposures combined is largest from the coal cycle. This is true
even considering the public exposures from the nuclear fuel cycle including the global circulation
integrated out to 10,000 years. The next largest is the total exposure from the nuclear fuel cycle, where
public exposure including global circulation gives the highest dose followed by occupational exposures.
The same trend is observed for the associated collective doses normalized to electricity generated, withthe exception of the public exposures from the nuclear fuel cycle normalized to electricity generated
integrated out to 10,000 years, which gave the largest value.
215. The comparisons of public doses shown in table 52 that have been assessed using the revised
methodology for estimating public exposures due to radioactive discharges (annex A) have been describedin section A of this chapter. They are provided in this table to facilitate comparison with occupational
exposures and view the entire exposure, public and occupational, from each electricity-generating
technology. One comparison of interest noticeable in table 52 is that collective doses to the public
resulting from radon discharges from natural gas power plants are about the same as collective doses tothe public resulting from the discharges from operation of nuclear power plants (55 versus 68 man Sv,
respectively). However, the collective dose to the public normalized to electricity generated in 2010 isabout a factor of four larger for the nuclear fuel cycle than for the combustion of natural gas (not including
global circulation). The relatively large actual collective dose assessed for combustion of natural gas
results from the larger amount of electricity produced by natural gas than nuclear power in 2010.
216. The assessments on collective dose provided in the annex can be put in perspective byconsidering natural exposure to background radiation from 222Rn. All doses to the public from naturalgas, oil, and geothermal energy are calculated from the release of 222Rn. A significant fraction of thedoses from the coal and nuclear cycles are also due to the release of 222Rn. Radon-222 occurs
naturally in nature and is a major fraction of the dose to man from all naturally occurring sources ofradiation. Wilkening et al. [W7] have estimated that the average exhalation rate of 222Rn from soil is
1.6 × 10−2 Bq (m2 s)−1. As a result of this exhalation from soil and the additional exhalation of 222Rn
from building materials, the Committee [U9] has previously estimated that the average effective dosefrom 222Rn is 1.15 mSv a−1. For the world population considered here, the collective dose due toexposure to naturally occurring radon is 11,500,000 man Sv a−1, a value much larger than any given
in table 46.
217. Total occupational collective doses are significantly greater than public collective doses for thecoal cycle and combustion of oil, from a factor of about ten for coal plants to about five hundred for
combustion of oil, although the values for combustion of oil are in comparison small. For natural gas
and geothermal energy, total public collective doses were assessed to be larger than total occupational
collective doses. Total occupational collective doses for the nuclear fuel cycle are of about the sameorder as the total collective dose to the public when including the global circulation to 100 years.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 221

218. The largest occupational collective dose normalized to energy generated in 2010 resulting fromthe mining for metals for construction materials was from solar photovoltaic (PV) technology, which
was a factor of forty and eighty larger than for the nuclear fuel cycle and coal cycle, respectively. Thiswas followed by the occupational collective dose for wind power, which was also larger than the values
for the nuclear fuel cycle and coal cycle. These differences come from the different metal requirements
for solar PV and wind power technologies, discussed in chapter VII.

Nuclear fuel cycle

Coal

Moderncoal plant

Older coalplant

Natural gas

Oil

Geothermal

Solar PVWind

Biomass

0.8

0.1

0.01

COLLECTIVE DOSES NORMALIZED TO ELECTRICITY GENERATION (man Sv/(GW a))
PublicU mining andmilling

0.2

Coal mining(Rn discharge)

0.4

0.4

Nuclear power
plant operation

0.2

Coal plant
operation

0.1

0.8

Reprocessing

0.03

Ash, radon
emanation

0.2

0.2

0.7

1.4

0.1

0.000 3

1–20

11

11

0.01

0.15

0.05

0.01

0.01

0.01

Total public (not including globally
circulating radionuclides)

0.43

Total public (including
globally circulating
radionuclides)

100 years

3.0

500 years

5.5

10 000 years

25

Occupational

2.7c

Occupational - decommissioning, nuclear

1.8

Occupational - mining for construction

0.02

COLLECTIVE DOSES (man Sv)
PublicU mining andmilling

53

Coal mining(Rn discharge)

370

370

Nuclear power
plant operation

68

Coal plant
operation

60

780

Reprocessing

8Ash, radon
emanation

240

240

670

1 400

Total public (not including globally
circulating radionuclides)

130

55

0.03

5–160

222 UNSCEAR 2016 REPORT

Table 52. Comparison of the public and occupational exposures assessed in this annexa,b

Nuclear fuel cycle
Total public (including
globally circulating
radionuclides)

Coal

100 years

910

500 years

1 700

10 000 years

7 600

Occupational

788

Decommissioning (occupational) per nuclear
reactor5

Occupational - mining for construction

6

Moderncoal plant

Older coalplant

Natural gas

Oil

Geothermal

11 000

11 0007

17

0.4–0.8

7

7

3

a

Projections of any health effects using collective doses in the table are not recommended.

b

All estimates are calculated based on best estimates; site- and location-specific collective doses are not presented.

c

From UNSCEAR 2008 Report.

Solar PVWind

Biomass

34

0.4

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 223

224 UNSCEAR 2016 REPORTC. Commentary on significance of accidents
219. While this annex has focused on comparing the exposures from normal operations of the various
electricity-generating technologies, a commentary is needed regarding the risk of serious accidents thatgive rise to radiation exposure. This is clearly only significant for nuclear power. While it is beyond thecompetence of the Committee to assess the probability of any future accident, the Committee has
assessed information on past accidents that have exposed the public and workers, notably the 1986
accident at the Chernobyl nuclear power plant in the former Soviet Union (UNSCEAR 2008 Report,annexes C and D [U12]). Moreover since that report, the Committee has conducted an assessment of
the levels and effects of radiation exposure due to the 2011 nuclear accident at the Fukushima Daiichi
nuclear power station (FDNPS). The UNSCEAR 2013 Report [U13] gave estimates of the collective
doses to the population of Japan due to the FDNPS accident. These estimates were compared with theprevious estimates by the Committee for populations of European countries exposed to radiation
following the 1986 Chernobyl accident in the former Soviet Union. This comparison is shown intable 53.
Table 53. Estimates of the collective effective doses from the FDNPS and Chernobyl accidents [U13]
Accident

Fukushima Daiichi nuclear power station
Chernobyl Unit 4aCollective effective dose (thousand man Sv)
Over first year

Over ten years

Up to age 80 yearsa

18

36

48
400

Summing the dose to all exposed individuals integrated from their age at the time of the accident until they reach age 80 years.

220. Comparing radiation doses alone, it is clear that serious accidents give rise to collective doses thatare very many times greater than collective doses due to normal operations. For example, the collective
dose from the single accident at Chernobyl Unit 4 is more than 400 times the annual global collective
dose to the public from all nuclear power. Such a comparison of collective doses can be made only inorder to gain perspective on the magnitude of the radiological impact. However, great care must be
taken when assimilating these comparisons, because there are obviously many major non-radiologicaldifferences between accidents and normal operations for electricity generation. While collective doses
from such accidents have been much larger than those from annual normal operations, the distributionof doses is more localized geographically, whereas the collective doses from normal operations forelectricity generation are population-averaged over geographical regions or the world as a whole.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 225

IX. RESEARCH NEEDS
221. The use of electricity is ubiquitous throughout the world and the demand for electricity continues
to grow. Because of the prevalence of different types of electricity-generating technologies coupledwith the diversity inherent in the countries of the world, standard data on exposures to radioactive
discharges or materials is non-uniform or non-existent. Thus, any study comparing different electricitygenerating technologies will suffer from inconsistent or incomplete databases. This annex has usedconsistent methodologies together with sound judgement on the use and interpretation of available datato assess public and occupational exposures from electricity-generating technologies. Some specificareas of interest that would improve understanding or that would increase the certainty of this work areincluded in this section.
222. Data. Consistent data on radioactive discharges across all electricity-generating technologies,
including how they change with time and changing practices across all electricity-generating
technologies, would improve the ability to assess and compare these technologies. Data on occupational
exposures and their change with time and practice for each technology would also help. The following
lists some specific needs that have been identified:(a) Decommissioning of coal power plants generates NORM wastes, the magnitude of whichshould be quantified (NORM wastes are naturally occurring radionuclides such as lead andpolonium which in this case become plated out in pipes and the boiler, and other mechanical partsof the plant [M5]). Occupational exposures received during decommissioning of coal power plants
need to be monitored in a representative manner in order to allow assessment of this exposure routefor workers. This is also true regarding occupational exposures of workers decommissioning
nuclear power plants.
(b) The combustion of natural gas and oil for electricity generation causes naturally occurring
radionuclides to accumulate in the pipes. Assessment of any occupational or public exposures fromthis source is dependent on representative data on the activity concentrations that occur. There aresome data available on this, however the measured external gamma exposure rates are of moresignificance.
(c) In order to assess the occupational doses resulting from the management of radioactive waste
generated in nuclear power plants, representative data on doses received by workers needs to becollected or compiled [M5].
(d) Information on the proportion of nuclear fuel reprocessed for peaceful (i.e. electricity
generation) versus non-peaceful (i.e. military applications) has only been available for the La
Hague, France reprocessing facility and therefore the assessment of the doses due to discharges
from reprocessing activities was compromised by the lack of open information. Also, some of theoccupational doses at reprocessing facilities, such as Sellafield in the United Kingdom, are fromthe reprocessing of historical wastes so it is very hard to relate occupational doses to just nuclear
fuel that has been reprocessed, or to electricity generation. Actual data on reprocessing activities
related to electricity generation are needed to improve the exposure assessments.
(e) Storage, transmission and distribution of electricity are not included in the assessments of dosefrom electricity generation presented in this annex. These infrastructures are used regardless of thetype of electricity generation (although there are differences between centralized and distributed
grid systems that are optimal for different technologies), and these kinds of dose assessments could
be included in any future update of the evaluations presented in the annex.

226 UNSCEAR 2016 REPORT223. Databases could be consistent and standardized; these types of efforts are currently conducted byvarious international organizations. The success of these efforts, however, depends on the volunteer
compliance of member countries submitting annual reports to these organizations, such as UNSCEAR,
IAEA and NEA, and on funding and interest to keep the programmes current. These programmes
would benefit from extending the data-collection schemes to include all relevant technologies, andinvesting in research to identify significant parameters to help design streamlined data-collection
schemes that would further decrease the burden on member countries and data-collecting organizations.
224. Uranium mining using the ISL process. Explanations were given in chapter IV of the assumptions
made about radon releases during uranium mining using the ISL process. Existing data areinconclusive, and radon could be released in varying quantities from the lixiviant used to dissolve theuranium in the underground ore body, depending on the specifics of the process. Determining more
precisely the amount of radon releases from ISL uranium recovery, and how to better generalize them,requires additional research and a more complete understanding of the variation in the global processes
and procedures currently in use for mining of uranium using the ISL process.
225. Recycling of metals. In chapter VII on assessing doses from the mining of metals needed in theconstruction phase, several assumptions were made in the assessments. Although the assumptions affectthe absolute value of the assessed collective doses, the relative importance when comparing thedifferent electricity-generating technologies with regards to the construction phase should remain
relevant. However, these assumptions make a difference when comparing to the other components inthe full cycle of electricity generation, such as in table 52. One area of importance that could be studied
further is the effect of recycling metals, which has not been included in the present study because of
insufficient data for large portions of the world. By not explicitly considering recycling, the collective
dose per unit of electricity generated due to the extraction and processing of the metals used in theconstruction of a facility is likely to be overestimated by around a factor of two on average, andpossibly a factor of five or more for some regions of the world with developed recycling processes(assuming the recycled metal is not contaminated with radioactive material). Also, recycling may affectthe different technologies somewhat differently because it is more difficult and costly to recycle
electronics and components (such as in solar panels) than larger bulk metal objects (such as in moreconventional power plant components).
226. Reference year. This annex concentrates on the reference year 2010 for the assessments. Lifetime
commitments would be relevant for comparing the full impact of the different electricity-generating
technologies. Confounders in this type of extrapolation are associated with the changes in the respective
electricity-generating technologies over time, caused by, for example, improving effectiveness of eachtechnology in both economic and environmental terms and in radiation protection practices.
227. Suess effect. The displacement of 14C in atmospheric CO2 discharges during the coal cycle andother fossil fuel releases of CO2 (which are depleted in 14C) is known as the Suess effect. Research into
this effect would improve knowledge of the global carbon cycle and could help clarify the role of 14C inhuman exposures in the modern world.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 227

X. CONCLUSIONS
228. This annex provides estimates of exposures from the various electricity-generating technologies
that (a) may be used by researchers and policy-makers in their own more comprehensive assessments
for developing energy policy; (b) can be used to help inform the media and the public on these mattersin a balanced perspective; and (c) can highlight possible emerging issues or opportunities for
improvement that may warrant more attention and scrutiny, or future research. The following
summarizes the findings.
229. The Committee has updated its methodology for estimating public exposures due to radioactive
discharges, which is now more flexible for use in evaluating radiation exposures to the public fromdiverse electricity-generating technologies. This methodology along with extensive data collection andanalyses has provided the Committee with a sounder basis for comparative studies than was possible
earlier. The Committee has also re-evaluated occupational exposures arising from different electricitygenerating technologies relying on data mainly from dosimetry records of worker exposures. Theseevaluations comprised the basis for the current comparative study on radiation exposures of both the
public and of workers from electricity generation. To compare exposures, the Committee has focusedon two metrics. These were (a) the collective doses to defined population groups integrated over
specific time periods resulting from one year’s electricity generation by each technology in eachgeographical region and for the world as a whole, and (b) the relevant collective doses divided by theamount of electricity generated by each technology. The year 2010 was used as the reference year forthe comparisons.
230. The Committee has conducted this comparative study by investigating sources of radiation
exposure from electricity-generating technologies based on the (a) nuclear fuel cycle, (b) coal cycle, thecombustion of natural gas, oil and biofuels, and (c) geothermal, wind and solar power. Two electricitygenerating technologies (nuclear fuel cycle and coal cycle) were investigated in detail because a morerobust database existed for these technologies. The Committee evaluated the main sources ofradioactive discharges from the life cycle of these electricity-generating technologies. For the nuclear
fuel cycle, these were uranium mining, milling and mill tailings, power plant operation, spent fuelreprocessing, and decommissioning activities. For the coal cycle, they were the mining for coal, power
plant operation for both a modern coal plant and an older-style coal plant, and coal ash deposits.
231. The Committee estimated that, excluding long-lived globally circulating radionuclides, thecontribution from the coal cycle, assuming discharges from a modern coal plant, was more than half of thetotal collective dose to the global public from the discharges due to a single year’s global electricity
generation, while the nuclear fuel cycle contributed less than a fifth. The contribution from the coal cycle
comes from discharges of natural radionuclides (primarily radon and its radioactive progeny) during coalmining, combustion of coal at the power plant and from coal ash deposits. Similarly, almost half of thecontribution to public exposures from the nuclear fuel cycle also comes from discharges of naturalradionuclides during uranium mining and milling activities. These values depend on the amount ofelectricity generated by each technology; in 2010, the coal cycle produced the largest amount of total
electricity generated, about 40%. Although radon and its progeny are relatively important contributors tocollective doses to the public for both the nuclear fuel cycle and the coal cycle, the associated individual
doses are small compared with doses due to inhalation of naturally occurring radon [U9, W7].

228 UNSCEAR 2016 REPORT232. The Committee found, however, that the contribution to the collective dose to the public fromeach electricity-generating technology was not only because of how much electricity each technology
generated. There were differences due to the collective doses per unit of electricity generated. In normal
operations, the coal cycle gives a higher collective dose per unit of electricity generated than electricity
generation from nuclear power plants, and significantly higher than the other technologies evaluated—with the exception of geothermal energy. Based on the limited information on radon discharges fromgeothermal power plants, the collective dose per unit of electricity generated by geothermal energy
could be significant. However, because the use of geothermal technology is not widespread, its
contribution to radiation exposures of the global public is smaller than that of the coal cycle.
233. Previous investigations on electricity generation from the nuclear fuel cycle have examined thecontribution to human exposures made by long-lived radionuclides, such as carbon-14, which aredischarged, circulate globally and continue to contribute to radiation exposures of the public centuries
into the future, albeit as extremely small individual doses. The Committee found that public exposuresfrom these globally-circulating radionuclides, for one year of discharge and integrated to 100 years,
result in a contribution to exposures from the nuclear fuel cycle that are about the same as the coal
cycle. Over long integration times such as hundreds of years, the contribution from these radionuclides
results in larger collective doses to the global public from the nuclear fuel cycle than the coal cycle.
234. The Committee also assessed the occupational exposures for these technologies. The largest
collective dose to workers per unit of electricity generated resulted from coal mining, because of
exposures to naturally occurring radionuclides. Of all the collective doses evaluated, to both the public
and workers, the exposure of workers from coal mining gave the largest contribution, although it has
fallen over time because of better mining conditions. Regarding the mining of rare earth metals needed
for construction, by far the largest collective dose to workers per unit of electricity generated assessedin this study came from solar power, followed by wind power. This is because the workers are exposed
to natural radionuclides during mining, and the amount of low-grade ore required to be mined for thesetechnologies is high.
235. The total collective dose (i.e. to the global public and all exposed workers combined) per unit ofelectricity generated by the coal cycle was larger than that generated by the nuclear fuel cycle, evenwhen considering the long-lived globally-circulating radionuclides integrated out to 500 years. Whenconsidering the amount of electricity generated in the year 2010 by each technology, the coal cycle
resulted in the largest collective dose to the global public and workers combined, followed by the
nuclear fuel cycle. Of the remaining technologies, geothermal energy and combustion of natural gas
were the next largest contributors.
236. Great care should be taken when interpreting and using these results, because this analysis only
gives a perspective on the magnitude and differences of radiation exposures, and cannot be used todetermine whether one form of energy generation is preferable to another. As stated earlier, a numberof factors determine why a certain mix of energy generation technologies may be selected by countries.
Radiation exposure is only one of them.
237. Moreover, when comparing collective doses for the various electricity-generating technologies, it
is important to note that the collective dose from serious accidents, such as those that occurred at the
Chernobyl and Fukushima-Daiichi nuclear power stations, were orders of magnitude larger than thecollective doses to the world population from one year’s normal operation of all the technologies ofelectricity generation that were assessed in the annex. More significantly, the distribution of doses afteran accident is more localized geographically (local populations receive higher doses than the average),whereas the collective doses from normal operations for electricity generation are often averaged over
populations within each geographical region or the world as a whole.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 229

XI. ACKNOWLEDGEMENTS
The Committee wishes to acknowledge with gratitude the experts directly involved in compiling data,
conducting analyses and quality control checks, and drafting text and conclusions, and the support staff
in their institutes who assisted them. In particular, the Committee would like to thank: the consultant,
L. Hubbard; the expert group, who provided valuable oversight and advice for the work; staff,
T. Anderson and K. Jones, from Public Health England in the United Kingdom, who conducted manyof the analyses; L. Anspaugh, H. Grogan, V. Holahan and J. Simmonds, who provided helpful advice,drafted text, and reviewed and checked the results. The views expressed in this scientific annex andrelated material remain those of the Committee and do not necessarily represent the views of individual
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), V. Holahan (United States), 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: E. Rochedo, who conducted some ofthe preparatory work to compile data; B. Lauritzen, who compiled some of the data and conducted
some of the analyses on occupational exposures due to mining of metals for construction purposes; andM. Tzivaki for conducting some specialized quality checks of the calculations.

ANNEX B: RADIATION EXPOSURES FROM ELECTRICITY GENERATION 231

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