Radionuclide Release at Fukushima Peter F Caracappa Ph D CHP Peter - PowerPoint PPT Presentation

Radionuclide Release at Fukushima Peter F Caracappa Ph D CHP Peter F. Caracappa, Ph.D., CHP American Nuclear Society – Connecticut Section November 16, 2011

Overview  Accident Review  Radioactive Material Releases  Transport and Deposition  Dose Impacts  Dose Impacts  On-site impacts  Comparisons with Chernobyl are problematic, but inevitable Fukushima Radioactive Releases 2

Accident Review Fukushima Radioactive Releases 3 6/14/2012

Reactor Status at time of Earthquake  Units 1, 2, and 3 were operating normally  Unit 4 was shut down and empty, core fully offloaded in spent fuel pool  Units 5 and 6 were shut down but remained  Units 5 and 6 were shut down, but remained fully loaded Fukushima Radioactive Releases 4

Progression of the Accident 14:46 , 11 March 2011 (Day 1) Magnitude 9.0 Earthquake  Units 1 to 3 shutdown automatically (SCRAM), per design  Power generators “tripped”, per design Movement of plant foundation p “exceeded design basis earthquake ground motion” (DBEGM)  Disabled offsite power systems  No serious damage to onsite safety systems 5

Progression of the Accident Earthquake resulted in Loss of Offsite Power Tsunami disabled diesel generator backup power Battery power operable for only a limited time (<6 hr to ~3 days)

Progression of the Accident Fission product release from damaged fuel Some discharge through valves to wet well to wet well Some stay in wet well water Some enter dry well Some deposit on dry well surfaces Build up of hydrogen, nitrogen and water vapor pressure

Progression of the Accident Gas is released into the reactor service floor Pressure reduced (~ 4 bar) Hydrogen and some fission Hydrogen and some fission products (iodine, cesium and noble gases)

Progression of the Accident 12 March 2011 (Day 2) H 2 explosion in Unit 1 service area  Steel frame roof destroyed  Concrete building intact  Seawater injected j

Expected Radioactive Material Releases  WASH 1400 identified four stages of core material release  Gap Release  Meltdown Release  Vaporization Release  Oxidation Release  Time since shutdown has significant effect  Spent fuel pools will not contain short-lived products Fukushima Radioactive Releases 10

Expected Radioactive Material Release  Noble Gasses (Xe-Kr)  I  Cs, Rb Decreasing  Te, Sb T Sb Likelihood  Ba, Sr of Release  Ru, Mo, Rh, Tc, Co  Nd, Y, Ce, Pr, La, Nb, Am, Cm, Pu, Np, Zr Radiation and Fukushima 11

Observed Radioactive Material Releases  I-131 – 130-160 PBq (3.5-4.3 MCi)  Cs-137 – 6.1-15 PBq (165-405 kCi)  Chernobyl: 1760 PBq I-131 & 81 PBq Cs-137  Reports indicate small quantities of Sr and Pu p q detected outside of plant (3.4-4400 Bq/kg combined Sr-89 & Sr-90 on site)  Isotopes detected in stagnant water in plant:  Cl-38, As-74, Y-91, I-131, Cs-134, Cs-136, Cs-137, La-140 Fukushima Radioactive Releases 12

Radioactive Material Transportation and Deposition Fukushima Radioactive Releases 13 6/14/2012

Transport and Deposition of Radioactive Releases  Iodine-131 detected worldwide  Cesium-137 & -134 detected over relatively broad areas, including western US Fukushima Radioactive Releases 14

Early Radionuclide Analysis  Kyoto University personnel performed gamma spec on soil samples in Iiate prefecture (25-45 km NW of plant) ~17-18 days after the accident Fukushima Radioactive Releases 15

Early Radionuclide Analysis Fukushima Radioactive Releases 16

Transport and Deposition of Radioactive Releases  I-131 Transport Fukushima Radioactive Releases 17

Transport and Deposition of Radioactive Releases  Cs-137 Deposition  Nuclear weapons testing responsible for ~2000 Bq/m 2 of Cs-137 (in undisturbed soil @ 40 ˚ N) 63095 10000 1585 251 40 6.3 1 .16 Fukushima Radioactive Releases 18

Transport and Deposition of Radioactive Releases  Cs-137 Deposition 398k 63095 10000 1585 251 40 6.3 1 .16 Fukushima Radioactive Releases 19

Transport and Deposition of Radioactive Releases  Deposition of Cs-134 and Cs-137 in the area immediately surrounding the plant 20

Radiation Monitoring Results in CA  Air monitoring Radiation and Fukushima 21 UC Berkeley, Nuclear Engineering Dept.

Radiation Monitoring Results in CA  Rainwater monitoring Radiation and Fukushima 22 UC Berkeley, Nuclear Engineering Dept. UC Berkeley, Nuclear Engineering Dep

Radiation Monitoring Results in CA  Milk samples Radiation and Fukushima 23 UC Berkeley, Nuclear Engineering Dept.

Dose Impacts Fukushima Radioactive Releases 24 6/14/2012

Dose Due to Radioactive Releases  Air Submersion  Instantaneous/transient  Inhalation  Dose commitment  Ground Irradiation  Persistent  Ingestion  Dose commitment Fukushima Radioactive Releases 25

Radioactive Material in Air  Early dose measurements dominated by atmospheric submersion  Radiation monitoring posts registered “spikes” that quickly returned to elevated sp es a qu c y e u ed o e eva ed steady state Fukushima Radioactive Releases 26

Radioactive Material in Air 27

Radioactive Material in Air Fukushima Radioactive Releases 28

Radioactive Material in Air  Dose commitment from breathing contaminated air:  Dose commitment per hour is up to 240  Dose commitment per hour is up to 240 times external exposure rate  1.2 m 3 /hr breathing rate  Cs-137:Cs-134:I-131 at 1:1:16  Absent I-131, dose commitment is ~74x (time dependent value) Fukushima Radioactive Releases 29

Radioactive Material on Ground  After plume passes, radiation dose will be dominated by material deposited on ground  Estimated dose rate is 16.6 mSv / MBq/m 2  Accounts for time spent inside/outside ccou ts o t e spe t s de/outs de Fukushima Radioactive Releases 30

Radioactive Material on Ground 31

Radioactive Material on Ground  Inhalation hazard may be generated by resuspension of deposited material  Assuming resuspension factor ~ 10 -6 m -1  Assuming resuspension factor 10 m , inhalation dose commitment rate ~0.4% of external dose rate (combined Cesium) Fukushima Radioactive Releases 32

Radioactive Material on Ground  Material deposited on the ground may enter the food chain and be ingested Fukushima Radioactive Releases 33

Radioactive Material on Ground  Some radioactive material, primarily I-131, detected in water supplies and foodstuffs  Most measurements returned to background by early April by ea y p Fukushima Radioactive Releases 34

Radioactive Material on Ground  I-131 contamination of varying levels was detected in milk, spinach, and other produce following the accident  Export and consumption restrictions remain in effect for much of the area Fukushima Radioactive Releases 35

Impacts of Radioactive Releases  Measured external integrated dose (MEXT monitoring stations – most begun ~1 week after accident) Fukushima Radioactive Releases 36

Impacts of Radioactive Releases  Projected external dose for year following accident (not including potential consumption or inhalation) Fukushima Radioactive Releases 37

Impacts of Radioactive Releases  Population (outside 20 km zone) affected by radioactive deposition (pre-earthquake census information)  Government has set 20 mSv/a limit for occupation Fukushima Radioactive Releases 38

Impacts of Radioactive Releases  All cumulative dose estimates outside 80 km (50 miles), and much of the area inside that distance, are less than 1 mSv/a  Collective dose estimates can vary widely based upon assumptions and future evacuation plans, but reasonable current estimates are in the range of 800-1800 person-Sv to the most affected population, and perhaps several h ff d l i d h l times that to the greater surrounding population  Chernobyl ~255,000 person-Sv  TMI ~20 person-Sv (total)  At this level, projected increase in cancer mortality would be ~0.001% above the natural rate Fukushima Radioactive Releases 39

Reported Doses to Plant Workers  As of 9/15 Dose Category (mSv) External Internal Total >250 0 5 6 200-250 0 1 2 150 200 150-200 9 9 1 1 14 14 100-150 28 5 77 50-100 165 78 309 20-50 515 259 985 10-20 1451 684 1652 <10 12673 12552 11340 Total 14841 13585 14385 Fukushima Radioactive Releases 40

Conclusions  Deaths due to earthquake/tsunami: ~25,000  Deaths or serious injuries due to direct radiation exposures: 0  Cancer deaths due to accumulated radiation exposures: can’t be ruled out – conservative ’t b l d t ti risk estimates ~100s cases, against an expected ~10 million cases  Remediation efforts or further evacuation may be necessary to avoid a sub-population with a significantly higher risk Fukushima Radioactive Releases 41