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 Damage to SFP4. DISCHARGES Ultimate Explosion (1, 3, 4) heat sink Shutdown lost Station black-out H 2 gen. Loss of off- Earthquake site power Loss of core Venting cooling Loss of on- Core melt Tsunami site power Loss of spent fuel PV Breach cooling Source: ARPANSA Source: ARPANSA, based on UNSCEAR 2013

Fukushima Daiichi after the hydrogen explosions 4 UNSCEAR 2013 Annex A Figure 2

UNSCEAR Report 5

UNSCEAR estimates of releases to the environment • 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 131 I inventory, ~1% to 4% of 137 Cs inventory Inventory in Release to the ocean Units 1 to 3 Release to (PBq) at the Radionuclide atmosphere reactor shutdown (PBq) Direct Indirect (PBq) 131 I 6,000 100 to 500 10 to 20 60 to 100 137 Cs 700 6 to 20 3 to 6 5 to 8 UNSCEAR 2013 ANNEX A Table 3 UNSCEAR 2013 ANNEX A Figure B-8

Time sequence of releases • 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 7

Exposure pathways for releases of radioactivity UNSCEAR 2013 ANNEX A Figure 5

UNSCEAR assessment of doses to public Pathway Input data Exposure Models Radiation Doses Ground Deposition Representative groups District or Prefecture External Plume Modelling 1y old infants average doses for Exposure Behaviour data (ages 0 – 5 years), non-evacuees 10y old children (ages 6 – 15 years) Settlement average 20-year-olds adults doses for evacuees Ground Deposition Inhalation (16 years and above). Plume Modelling Exposure Doses in first year Behaviour data Effective dose after accident Absorbed dose to ; Doses to year 10 Thyroid after accident Red bone marrow Doses to year 80 Radioactivity in Food Ingestion Female breast after accident Radioactivity in Water Exposure Collective dose Behaviour data Source: ARPANSA Source: ARPANSA, based on UNSCEAR 2013

Radiation measurements Airborne radiation survey Fixed radiation monitoring station Ground deposition survey 10

Atmospheric transport and dispersion modellin g UNSCEAR 2013 ANNEX A Figure C-4

Areas with protective measures 3 Aug 2011 UNSCEAR 2013 ANNEX A Figure 3

Effective doses and absorbed doses to thyroid for evacuees in first year EFFECTIVE DOSE (mSv) Precautionary evacuated settlements Deliberately evacuated settlements Age group Before and At the Before and At the during evacuation First year total during evacuation First year total evacuation destination evacuation destination 1.1 – 5.7 4.8 – 9.3 0 – 2.2 0.2 – 4.3 2.7 – 8.5 0.8 – 3.3 Adults 1.3 – 7.3 5.4 – 10 0 – 1.8 0.3 – 5.9 3.4 – 9.1 1.1 – 4.5 Child, 10-year-old 1.6 – 9.3 7.1 – 13 0 – 3.3 0.3 – 7.5 4.2 – 12 1.1 – 5.6 Infant, 1-year-old ABSORBED DOSE TO THE THYROID (mGy) Precautionary evacuated settlements Deliberately evacuated settlements Age group Before and At the Before and At the during evacuation during evacuation First year total First year total evacuation destination evacuation destination 7.2 – 34 16 – 35 0 – 23 0.8 – 16 15 – 28 1 – 8 Adults 12 – 58 27– 58 0 – 37 1.5 – 29 25 – 45 1.1 – 14 Child, 10-year-old 15 – 82 47 – 83 0 – 46 3 – 49 45– 63 2 – 27 Infant, 1-year-old UNSCEAR 2013 Annex A Table 6

UNSCEAR estimates of effective doses & absorbed dose to thyroid for non-evacuees in first year Average effective dose Average absorbed dose to the thyroid (mSv) (mGy) Residential area Adults 10-year old 1-year old Adults 10-year old 1-year old Group 2 - Fukushima 1.0 – 4.3 1.2 – 5.9 2.0 – 7.5 7.8 – 17 15 – 31 33 – 52 Prefecture 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 District- or prefecture-average effective dose (mSv) Age group Geographical area of Japan as of 2011 Group 2 Group 3 Group 4 Fukushima Prefecture prefectures 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

UNSCEAR assessment of health effects and inferred risks “…. 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 )

Implications for solid tumours Main determinant Baseline Attributable Impact on of impact level Exposed risk Dose risk health population Relative Absolute (lifetime) (lifetime) statistics N o cases risk General 1-10 mSv Not 35% 0.01-0.1% Low population (First year) discernible 1-20 mSv Not Children 35% 0.02-0.5% Low (First year) discernible 17 Source: ARPANSA, based on UNSCEAR 2013

Implications for thyroid cancer in children Main determinant of Baseline Impact on impact level Exposed Attributable risk Dose health population risk Relative Notional (lifetime) statistics risk cases ~ 35 000 45-55 0.5% ~0.15% children Indeterminate Medium Several tens mGy 0-5y “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 18 Source: ARPANSA, based on UNSCEAR 2013

Health implications for emergency workers Exposed group (percentage of Exposure estimates Risk estimation Disease incidence workforce) Effective dose less Infer a small increased No discernible excess Nearly 25 000 (99.3%) than 100 mSv. risk to individuals incidence of cancer at Average about 10 mSv exposed these levels Effective doses Unlikely that any 100 mSv or more. Increased risk of increased incidence in 173 (0.7%) Average about cancer expected cancer from irradiation 140 mSv would be discernible Absorbed dose to Risk likely too small for thyroid more than Infer small increased any increase to be 2 000 (8.1%) 100 mGy . risk of thyroid cancer discernible among this Average about size of population 400 mGy Absorbed dose to Low risk of Numbers likely too thyroid of 2-12 Gy. hypothyroidism. small to discern an 12 (0.05%) increased incidence in Risk of thyroid cancer thyroid cancer Average about 5 Gy enhanced 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 22 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 23