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

Peter F Caracappa Ph D CHP

Radionuclide Release at Fukushima

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

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Accident Review

6/14/2012

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Fukushima Radioactive Releases

Reactor Status at time of Earthquake

 Units 1, 2, and 3 were operating normally  Unit 4 was shut down and empty, core fully

• ffloaded 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

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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

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p “exceeded design basis earthquake ground motion” (DBEGM)

 Disabled offsite power systems  No serious damage to onsite safety

systems

Earthquake resulted in Loss of Offsite Power Tsunami disabled diesel

Progression of the Accident

generator backup power Battery power operable for only a limited time (<6 hr to ~3 days)

Fission product release from damaged fuel

Some discharge through valves to wet well

Progression of the Accident

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

Gas is released into the reactor service floor Pressure reduced (~ 4 bar) Hydrogen and some fission

Progression of the Accident

Hydrogen and some fission products (iodine, cesium and noble gases)

12 March 2011 (Day 2)

H2 explosion in Unit 1 service area

Steel frame roof destroyed Concrete building intact Seawater injected

Progression of the Accident

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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

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Expected Radioactive Material Release

 Noble Gasses (Xe-Kr)  I  Cs, Rb

T Sb Decreasing

 Te, Sb  Ba, Sr  Ru, Mo, Rh, Tc, Co  Nd, Y, Ce, Pr, La, Nb,

Am, Cm, Pu, Np, Zr

Radiation and Fukushima

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Likelihood

• f Release

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

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Radioactive Material Transportation and Deposition

6/14/2012

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Fukushima Radioactive Releases

Transport and Deposition of Radioactive Releases

 Iodine-131 detected worldwide  Cesium-137 & -134 detected over relatively

broad areas, including western US

Fukushima Radioactive Releases

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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

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Early Radionuclide Analysis

Fukushima Radioactive Releases

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Transport and Deposition of Radioactive Releases

 I-131 Transport

Fukushima Radioactive Releases

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Transport and Deposition of Radioactive Releases

 Cs-137 Deposition

 Nuclear weapons testing responsible for ~2000 Bq/m2 of Cs-137 (in

undisturbed soil @ 40˚ N)

63095

Fukushima Radioactive Releases

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10000 1585 251 40 6.3 1 .16

Transport and Deposition of Radioactive Releases

 Cs-137 Deposition

398k 63095

Fukushima Radioactive Releases

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10000 1585 251 40 6.3 1 .16

Transport and Deposition of Radioactive Releases

 Deposition of Cs-134 and Cs-137 in the area

immediately surrounding the plant

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Radiation Monitoring Results in CA

 Air monitoring

Radiation and Fukushima

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UC Berkeley, Nuclear Engineering Dept.

Radiation Monitoring Results in CA

 Rainwater monitoring

Radiation and Fukushima

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UC Berkeley, Nuclear Engineering Dept. UC Berkeley, Nuclear Engineering Dep

Radiation Monitoring Results in CA

 Milk samples

Radiation and Fukushima

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UC Berkeley, Nuclear Engineering Dept.

Dose Impacts

6/14/2012

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Fukushima Radioactive Releases

Dose Due to Radioactive Releases

 Air Submersion

 Instantaneous/transient

 Inhalation

 Dose commitment

 Ground Irradiation

 Persistent

 Ingestion

 Dose commitment

Fukushima Radioactive Releases

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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

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Radioactive Material in Air

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Radioactive Material in Air

Fukushima Radioactive Releases

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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 m3/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

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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/m2

 Accounts for time spent inside/outside

ccou ts o t e spe t s de/outs de

Fukushima Radioactive Releases

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Radioactive Material on Ground

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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

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Radioactive Material on Ground

 Material deposited on the ground may enter

the food chain and be ingested

Fukushima Radioactive Releases

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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

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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

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Impacts of Radioactive Releases

 Measured external integrated dose (MEXT monitoring

stations – most begun ~1 week after accident)

Fukushima Radioactive Releases

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Impacts of Radioactive Releases

 Projected external dose for year following accident (not

including potential consumption or inhalation)

Fukushima Radioactive Releases

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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

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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 h ff d l i d h l to the most affected population, and perhaps several 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

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Reported Doses to Plant Workers

 As of 9/15

Dose Category (mSv) External Internal Total >250 5 6 200-250 1 2 150 200 9 1 14

Fukushima Radioactive Releases

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150-200 9 1 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

Conclusions

 Deaths due to earthquake/tsunami: ~25,000  Deaths or serious injuries due to direct

radiation exposures: 0

 Cancer deaths due to accumulated radiation

’t b l d t ti exposures: can’t be ruled out – conservative 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

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