impact and radiation effects resulting from the nuclear events in japan
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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. - PowerPoint PPT PresentationTRANSCRIPT
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Impact and Radiation Effects Resulting from the Nuclear Events in Japan
The Foundation for Nuclear StudiesRayburn 2325April 1, 2011 10:00 AM
Mark PiersonAssociate Professor
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Fukushima Dai-ichi
Source: Nuclear Energy Institute
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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 TEPCOBackup power sources were located 10
to 13 meters above sea levelPlant withstood the earthquake,
but the tsunami caused the extended loss of site power
Earthquake and Tsunami
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Japanese Nuclear Event Was Caused by Nature Not
Man
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Fukushima Dai-ichi nuclear power plants were designed to withstand a ground acceleration of about 0.46gMaximum 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
Ground Acceleration
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To prevent escape of radioactivity, multiple barriers are used to block passage to the surrounding population:
Principle of Multiple Barriers
• Fuel• Cladding• Reactor Vessel/Closed
coolant system• Containment building• Site location• Evacuation
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On-Site Barriers
http://www.nrc.gov/about-nrc/emerg-preparedness/images/barriers.jpg
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Mark 1 BWR Containment
Source: NEI Mark 1 Containment Report
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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
Evacuation Zones
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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 miJapan is already overburdened with
refugeesSimilarly, U.S. Navy has
evacuated all dependents and unnecessary people from its Tokyo base and sent its ships to sea
Evacuation Zones
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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.
Evacuation Zones
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Need redundant and reliable power sources to handle a prolonged station blackoutBackup generators (many U.S. plants
have these)Underground off-site power cablesSustainable fuel sources for diesel
generatorsNeed redundant sources of
backup water cooling for the reactorJapanese 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
Lessons Learned
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Need redundant sources of water for spent fuel poolAfter 9/11, U.S. took a hard look at large
site disastersSignificant upgrading of firefighting
capability including for spent fuel poolExample: North Anna Power Station has
a diesel-driven fire pump with a fire main that can discharge directly into the spent fuel pool
Lessons Learned
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Need hardened hydrogen ventsAfter Three Mile Island, U.S.
incorporated hardened vents into plantsConsider other methods of
burning/removing hydrogenNote that a hydrogen explosion did
occur inside the Three Mile Island Unit 2 containment building, but caused no damage
Lessons Learned
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Need better communications with the publicU.S. learned that lesson from Three Mile
Island accidentPublic lost confidence in the nuclear
utilities as a resultWe now see the same effect in Japan
Lessons Learned
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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
U.S. Nuclear Plants Remain Very Safe
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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
Two-Pronged Review by U.S. NRC
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Units of effective radiation doseU.S. unit is the rem or millirem (1 mrem
= 0.001 rem)International unit is the Sievert,
milliSievert, or microSievert 1 mSv = 0.001 Sv1 μSv = 0.001 mSv = 0.000001 Sv
Multiply Sieverts by 100 to obtain remDivide mSv by 10 to obtain rem
Let’s Talk About Radiation
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Annual Radiation Limits
U.S. Units International Units
Member of Population
100 mrem 1 mSv
Occupational Worker
5 rem 50 mSv
In Emergency Only
25 rem 250 mSv
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Linear No Threshold Model
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Average Dose in U.S. is 620 mREM/year
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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-ray1000 mrem = 1 rem from torso
CT scan30 mrem from food and water
consumed throughout the year100 mrem from a mammogram
Radiation Perspective
We are showered in radiation daily
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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
Radioactivity
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Do not buy potassium iodide pillsDo NOT take potassium iodide in
the U.S. due to radioactivity released by the Japanese nuclear plantsKI is a drug and may have side effectsThere is no benefit
Potassium Iodide (KI)
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Questions
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