Nuclear Fuel Cycle Royal Commission Topic 10 Nuclear Accident: - - PowerPoint PPT Presentation

Nuclear Fuel Cycle Royal Commission Topic 10 Nuclear Accident: Fukushima Daiichi ARPANSA Submission 22 Oct 2015

Dr Stephen Solomon Chief Radiation Health Scientist ARPANSA

The 2011 Great East-Japan Earthquake and Tsunami

Fukushima Daiichi accident

Accident progression, 11 March 2011 onwards

Explosion (1, 3, 4)

Earthquake

Tsunami

Loss of off- site power

Shutdown

Loss of on- site power

Station black-out

Loss of core cooling Loss of spent fuel cooling

Venting H2 gen. Core melt

PV Breach

Damage to SFP4.

Ultimate heat sink lost

DISCHARGES

Source: ARPANSA Source: ARPANSA, based on UNSCEAR 2013

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Fukushima Daiichi after the hydrogen explosions

UNSCEAR 2013 Annex A Figure 2

UNSCEAR Report

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UNSCEAR estimates of releases to the environment

Radionuclide Inventory in Units 1 to 3 at reactor shutdown (PBq) Release to the atmosphere (PBq) Release to the ocean (PBq) Direct Indirect

131I

6,000 100 to 500 10 to 20 60 to 100

137Cs

700 6 to 20 3 to 6 5 to 8

• The exact amount of radioactive material released

to the atmosphere and to the ocean is uncertain.

• More than half of the atmospheric release was to

sea

• UNSCEAR estimated release was ~ 2% to 10% of 131I

inventory, ~1% to 4% of 137Cs inventory

UNSCEAR 2013 ANNEX A Table 3 UNSCEAR 2013 ANNEX A Figure B-8

Time sequence of releases

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• UNSCEAR used published estimates of releases to the

atmosphere over the period 11 – 30 March 2011

UNSCEAR 2013 ANNEX A Figure B-16a UNSCEAR 2013 ANNEX A Figure B-16b

Exposure pathways for releases of radioactivity

UNSCEAR 2013 ANNEX A Figure 5

UNSCEAR assessment of doses to public

External Exposure Inhalation Exposure Ingestion Exposure Ground Deposition Plume Modelling Behaviour data Representative groups 1y old infants (ages 0 – 5 years), 10y old children (ages 6 – 15 years) 20-year-olds adults (16 years and above). Effective dose Absorbed dose to; Thyroid Red bone marrow Female breast Collective dose Ground Deposition Plume Modelling Behaviour data Radioactivity in Food Radioactivity in Water Behaviour data District or Prefecture average doses for non-evacuees Settlement average doses for evacuees Doses in first year after accident Doses to year 10 after accident Doses to year 80 after accident

Pathway Input data Exposure Models Radiation Doses

Source: ARPANSA Source: ARPANSA, based on UNSCEAR 2013

Radiation measurements

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Fixed radiation monitoring station Airborne radiation survey Ground deposition survey

Atmospheric transport and dispersion modelling

UNSCEAR 2013 ANNEX A Figure C-4

Areas with protective measures 3 Aug 2011

UNSCEAR 2013 ANNEX A Figure 3

Age group EFFECTIVE DOSE (mSv) Precautionary evacuated settlements Deliberately evacuated settlements Before and during evacuation At the evacuation destination First year total Before and during evacuation At the evacuation destination First year total Adults

0 – 2.2 0.2 – 4.3

1.1 – 5.7

2.7 – 8.5 0.8 – 3.3

4.8 – 9.3

Child, 10-year-old

0 – 1.8 0.3 – 5.9

1.3 – 7.3

3.4 – 9.1 1.1 – 4.5

5.4 – 10

Infant, 1-year-old

0 – 3.3 0.3 – 7.5

1.6 – 9.3

4.2 – 12 1.1 – 5.6

7.1 – 13

Age group ABSORBED DOSE TO THE THYROID (mGy) Precautionary evacuated settlements Deliberately evacuated settlements Before and during evacuation At the evacuation destination First year total Before and during evacuation At the evacuation destination First year total Adults

0 – 23 0.8 – 16

7.2 – 34

15 – 28 1 – 8

16 – 35

Child, 10-year-old

0 – 37 1.5 – 29

12 – 58

25 – 45 1.1 – 14

27– 58

Infant, 1-year-old

0 – 46 3 – 49

15 – 82

45– 63 2 – 27

47 – 83

Effective doses and absorbed doses to thyroid for evacuees in first year

UNSCEAR 2013 Annex A Table 6

UNSCEAR estimates of effective doses & absorbed dose to thyroid for non-evacuees in first year

Residential area Average effective dose (mSv) Average absorbed dose to the thyroid (mGy) Adults 10-year old 1-year old Adults 10-year old 1-year old Group 2 - Fukushima Prefecture 1.0 – 4.3 1.2 – 5.9 2.0 – 7.5 7.8 – 17 15 – 31 33 – 52 Group 3 prefectures 0.2 – 1.4 0.2 – 2.0 0.3 – 2.5 0.6 – 5.1 1.3 – 9.1 2.7 – 15 Group 4 -Rest of Japan 0.1 – 0.3 0.1 – 0.4 0.2 – 0.5 0.5 – 0.9 1.2 – 1.8 2.6 – 3.3

• District- or prefecture- average effective doses and absorbed doses to

the thyroid for the first year for typical residents that were not evacuated

UNSCEAR 2013 Annex A Table 5

Average effective doses for non-evacuated areas, in first year, to year 10 and to age 80y

Age group as of 2011

District- or prefecture-average effective dose (mSv)

Geographical area of Japan Group 2 Fukushima Prefecture Group 3 prefectures Group 4 Rest of Japan FIRST YEAR EXPOSURE Adult

1.0 – 4.3 0.1 – 1.4 0.1 – 0.3

Infant, 1-year-old

2.0 – 7.5 0.3 – 2.5 0.2 – 0.5

10 YEAR EXPOSURE Adult

1.1 – 8.3 0.2 – 2.8 0.1 – 0.5

Infant, 1-year-old

2.1 – 14 0.3 – 6.4 0.2 – 0.9

EXPOSURE UP TO AGE 80 YEARS Adult

1.1 – 11 0.2 – 4.0 0.1 – 0.6

Infant, 1-year-old

2.1 – 18 0.4 – 6.4 0.2 – 0.9

• Detailed information about remediation was not available to UNSCEAR

and there is no allowance for these measures in assessment of doses

• For context, 80-year cumulative doses from background exposure to

natural sources of radiation in Japan are on the average about 170 mSv.

UNSCEAR 2013 Annex A Table 7

“…. when risks are small or may only be inferred on the basis of existing knowledge and risk models, and/or the number of people exposed is small, the Committee has used the phrase “no discernible increase” to express the idea that currently available methods would most likely not be able to demonstrate an increase incidence in health statistics….” “….does not rule out the possibility of future excess cancer….”

(UNSCEAR 2013 Annex A Paragraph 219)

UNSCEAR assessment of health effects and inferred risks

Implications for solid tumours

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Exposed population Baseline risk (lifetime) Dose Attributable risk (lifetime) Impact on health statistics Main determinant

• f impact level

Relative risk Absolute No cases General population 35% 1-10 mSv (First year) 0.01-0.1% Not discernible Low Children 35% 1-20 mSv (First year) 0.02-0.5% Not discernible Low Source: ARPANSA, based on UNSCEAR 2013

Implications for thyroid cancer in children

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Exposed population Baseline risk (lifetime) Dose Attributable risk Impact on health statistics Main determinant of impact level Relative risk Notional cases ~ 35 000 children 0-5y

0.5% 45-55 mGy ~0.15%

Indeterminate Medium Several tens

“Information on dose distribution and uncertainties was not sufficient for the Committee to draw firm conclusions as to whether any potential increased incidence of thyroid cancer would be discernible among those exposed to higher thyroid doses during infancy and childhood.” UNSCEAR 2013 ANNEX A Paragraph 175

Source: ARPANSA, based on UNSCEAR 2013

Health implications for emergency workers

Exposed group (percentage of workforce) Exposure estimates Risk estimation Disease incidence Nearly 25 000 (99.3%) Effective dose less than 100 mSv. Average about 10 mSv Infer a small increased risk to individuals exposed No discernible excess incidence of cancer at these levels 173 (0.7%) Effective doses 100 mSv or more. Average about 140 mSv Increased risk of cancer expected Unlikely that any increased incidence in cancer from irradiation would be discernible 2 000 (8.1%) Absorbed dose to thyroid more than 100 mGy . Average about 400 mGy Infer small increased risk of thyroid cancer Risk likely too small for any increase to be discernible among this size of population 12 (0.05%) Absorbed dose to thyroid of 2-12 Gy. Average about 5 Gy Low risk of hypothyroidism. Risk of thyroid cancer enhanced Numbers likely too small to discern an increased incidence in thyroid cancer

Source: ARPANSA, based on UNSCEAR 2013

Summary of health outcomes due to radiation from accident

• Deterministic effects: Not observed, unlikely in future
• Cancer rates: Discernible increases not expected generally,

models imply risks may have increased

• Thyroid cancer: Uncertainties in dose distribution, warrants

follow-up

• Heritable effects: Not discernible
• Birth defects: No impact
• Workers: No discernible increase expected, though risks

increased, warrants follow-up among most exposed Conclusions apply to radiation effects only, but

• Large indirect impact on social and mental well-being

Source: ARPANSA, based on UNSCEAR 2013

Affected areas into the future

Source: ARPANSA, based on UNSCEAR 2013

Implications for Australia

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Source: ARPANSA

Dr Stephen Solomon Chief Radiation Health Scientist Radiation Health Services Branch Australian Radiation Protection and Nuclear Safety Agency 613 Lower Plenty Road, Yallambie, Victoria, 3085 AUSTRALIA email stephen.solomon@arpansa.gov.au web: http://www.arpansa.gov.au

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