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Impact and Radiation Effects Resulting from the Nuclear Events in Japan

Impact and Radiation Effects Resulting from the Nuclear Events in Japan. Mark Pierson Associate Professor. The Foundation for Nuclear Studies Rayburn 2325 April 1, 2011 10:00 AM. Fukushima Dai- ichi. Source: Nuclear Energy Institute. Earthquake and Tsunami.

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Impact and Radiation Effects Resulting from the Nuclear Events in Japan

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  1. Impact and Radiation Effects Resulting from the Nuclear Events in Japan Mark Pierson Associate Professor The Foundation for Nuclear Studies Rayburn 2325April 1, 2011 10:00 AM

  2. Fukushima Dai-ichi Source: Nuclear Energy Institute

  3. Earthquake and Tsunami • Fukushima Dai-ichi nuclear power plants were designed to withstand an 8.0 earthquake and 5.7 meter (18.7 feet) tsunami • Actual earthquake on March 11 was 9.0 and tsunami height estimated at 8 meters (26.2 feet) by NOAA and at 14 meters ( 46 feet) by TEPCO • Backup power sources were located 10 to 13 meters above sea level • Plant withstood the earthquake, but the tsunami caused the extended loss of site power

  4. Japanese Nuclear Event Was Caused by Nature Not Man

  5. Ground Acceleration • Fukushima Dai-ichi nuclear power plants were designed to withstand a ground acceleration of about 0.46g • Maximum ground acceleration at the site from the Tohoku earthquake was estimated at 0.52g by TEPCO • U.S. Geologic Survey provisional estimate of ground acceleration was 0.25g • Diablo Canyon is designed for 0.75g peak ground acceleration and San Onofre for 0.67g

  6. Principle of Multiple Barriers • To prevent escape of radioactivity, multiple barriers are used to block passage to the surrounding population: • Fuel • Cladding • Reactor Vessel/Closed coolant system • Containment building • Site location • Evacuation

  7. On-Site Barriers http://www.nrc.gov/about-nrc/emerg-preparedness/images/barriers.jpg

  8. Mark 1 BWR Containment Source: NEI Mark 1 Containment Report

  9. Evacuation Zones • Japanese settled on a 20 km (12.5 mi) evacuation zone and for those within 30 km (19 mi) to stay indoors • U.S. has a 10 mi Emergency Planning Zone (EPZ) around its nuclear power plants that would be evacuated with a 50 mi monitoring zone around the plant • Japanese have since recommended those within 30 km to leave as it was hard to get needed services to them

  10. Evacuation Zones • NRC is being prudent to have all U.S. citizens evacuate a 50 mi zone around Fukushima as they do not need to be there • This was not a recommendation that the Japanese should evacuate all of their population within 50 mi • Japan is already overburdened with refugees • Similarly, U.S. Navy has evacuated all dependents and unnecessary people from its Tokyo base and sent its ships to sea

  11. Evacuation Zones • Most of the fission products released are particulates • Hence, most will “fallout” to the ground within a 30 mile radius • Need a large explosion and fire to carry particles high into the atmosphere to be carried around the globe (a.k.a. Chernobyl) • Concentration of the particles is significantly diluted by the time they would reach the U.S.

  12. Lessons Learned • Need redundant and reliable power sources to handle a prolonged station blackout • Backup generators (many U.S. plants have these) • Underground off-site power cables • Sustainable fuel sources for diesel generators • Need redundant sources of backup water cooling for the reactor • Japanese resorted to sea water; this should be a last resort, but better than nothing if that is all that is left • More steam-driven and diesel-driven pumps

  13. Lessons Learned • Need redundant sources of water for spent fuel pool • After 9/11, U.S. took a hard look at large site disasters • Significant upgrading of firefighting capability including for spent fuel pool • Example: North Anna Power Station has a diesel-driven fire pump with a fire main that can discharge directly into the spent fuel pool

  14. Lessons Learned • Need hardened hydrogen vents • After Three Mile Island, U.S. incorporated hardened vents into plants • Consider other methods of burning/removing hydrogen • Note that a hydrogen explosion did occur inside the Three Mile Island Unit 2 containment building, but caused no damage

  15. Lessons Learned • Need better communications with the public • U.S. learned that lesson from Three Mile Island accident • Public lost confidence in the nuclear utilities as a result • We now see the same effect in Japan

  16. U.S. Nuclear Plants Remain Very Safe • About 180 improvements were implemented in U.S. after Three Mile Island Accident • A significant review of all nuclear plants was conducted following 9/11 for security aspects and large site-wide disasters • Expect only a handful of changes as a result of the Japanese nuclear accident

  17. Two-Pronged Review by U.S. NRC • Short-term effort at 30, 60, and 90 days • Longer-term review to start within 90 days and to report out within 6 months of starting • Absolutely no reason to place a moratorium on new construction plants • Newer plants are already safer and better designed • NRC will still have time to look at incorporating any lessons learned into these plants

  18. Let’s Talk About Radiation • Units of effective radiation dose • U.S. unit is the rem or millirem (1 mrem = 0.001 rem) • International unit is the Sievert, milliSievert, or microSievert • 1 mSv = 0.001 Sv • 1 μSv = 0.001 mSv = 0.000001 Sv • Multiply Sieverts by 100 to obtain rem • Divide mSv by 10 to obtain rem

  19. Annual Radiation Limits

  20. Linear No Threshold Model

  21. Average Dose in U.S. is 620 mREM/year

  22. Radiation Perspective • 200 mrem/yr from Radon in your home • 4 mrem from round trip airline flight from NYC to LA • 200 to 400 mrem/yr for flight crews • 10 mrem typical chest x-ray • 1000 mrem = 1 rem from torso CT scan • 30 mrem from food and water consumed throughout the year • 100 mrem from a mammogram We are showered in radiation daily

  23. Radioactivity • Radioactivity limit for I-131 is 1 pCi/ml in water • A typical banana has 540 pCi, eating one-a-day could yield about 3 mrem/yr • Traces of I-131 detected in rain water and milk in U.S. have been well below limits • Impact to the U.S. population from the radioactivity released in Japan is essentially nonexistent • No known effects from radioactivity released during Three Mile Island accident to those within 50 mi

  24. Potassium Iodide (KI) • Do not buy potassium iodide pills • Do NOT take potassium iodide in the U.S. due to radioactivity released by the Japanese nuclear plants • KI is a drug and may have side effects • There is no benefit

  25. Questions?

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