The Fukushima Nuclear Accident

Report
A Summary
Dennis Quinn, CHP
DAQ, Inc.
en.wikipedia.org/wiki/Browns_Ferry_Nuclear_Power_Plant
~96 rods per assembly
~400-800 assemblies per Rx
1. The nuclear fuel contains almost all of
the radioactivity (>99%).
2. The nuclear fuel continues to generate
heat after the reactor is shut down.
a. 19 MW after 1 day
b. 12 MW after 1 week
c. 7 MW after 3 months
3. The fuel must be cooled, or there is a
risk of fuel damage and release of
radioactivity.
Fuel Temperature (oF)
Activity Available for Release (Curies)
Stainless Steel Melts
Reactor Service Floor
(Steel Construction)
Spent Fuel Pool
Concrete Reactor Building
(secondary Containment)
Fresh Steam line
Main Feedwater
Reactor Core
Reactor Pressure Vessel
Containment (Dry well)
Containment (Wet Well) /
Condensation Chamber
From Areva Presentation The Fukushima Daiichi Incident – Dr. Matthias Braun
• Earthquake causes loss of
offsite power.
•Emergency Diesel
Generators supply power
•Tsunami disables EDGs
•Steam dumps to wet well
• Water level in reactor
decreases
• Fuel heats up
• Cladding is damaged and
releases noble gases and
volatile isotopes (cesium
and iodine)
> 99.9% of
radioactivity
is in the fuel
From Areva Presentation The Fukushima Daiichi Incident – Dr. Matthias Braun
• Large volume in wet well
eventually heats to boiling
and no more pressure
suppression
• Pressure increases
•Hydrogen created by high
temperature reaction of
cladding & steam
• Operators decide to vent
primary containment gas to
secondary containment
• Gas has fission products
and hydrogen
From Areva Presentation The Fukushima Daiichi Incident – Dr. Matthias Braun
From Areva Presentation The Fukushima Daiichi Incident – Dr. Matthias Braun
Background is 0.005 – 0.01 mR/hr
Fukushima Daiichi Main Gate dose rates
dependent on wind direction & events:
3/14: 50 mR/hr
3/15: 300 mR/hr due to venting from Unit 2
3/15: 1200 mR/hr due to explosion & fire on Unit 4
3/16: 850 mR/hr explosion on Unit 2
3/17: 1100 mR/hr – releases from Units 2 and 3 of
plant
U.S. 7th Fleet ship contaminated helicopter crew.
US news crews returning after 2 wks have
contaminated equipment.
Date, Time
Evacuate
Shelter
March 11, 15:42 - Loss of power in Nuclear Power Plants
March 11, 21:23
3 km
March 12, 05:44
10 km
March 12, 18:25
20 km
March 15, 11:06
20 km
10 km
30 km
March 21 – First food restrictions: spinach, kakina, & milk
April 22 – Selected areas 20-30 km termed Planned Evacuation
Zones if estimated dose > 20 mSv (2 rem)
I-131, Cs-134, Cs-137
Milk
Produce (leafy vegetables,
spinach, etc.)
Drinking water (peak at 3x limit @
30 km, now below limits).
Seawater, fish products
Initially prevented sale of food &
seafood within 30 km radius
Recent identification of beef
with Cesium contamination.
Type of Sample
Percent above Percent above Action
Action Level for I- Level for Cs-134 and
131
Cs-137
Meat and Eggs
0%
0%
Milk
4%
0.2%
Produce
2%
5%
Seafood
0.4%
7%
Tea Products
0%
14%
Total
2%
5%
Data from April - July 2011. After this synopsis of data on the
WHO website, some samples of beef were found above the 500
Bq/kg limit for meat.
Nuclide
I-131
Water,
Milk
300*
Vegetables
2,000
Meat,
Fish
2,000
IAEA for
all food
3,000
Cs-134
200
500
500
1,000
Cs-137
200
500
500
2,000
*Infant water and milk limit is 100 Bq/kg
IAEA Limits based on 1 rem per year to most restrictive individual
(generally infant) if consuming food for 1 year at the limit
Resin Spraying for Soil Control
Rx 2 – Leak to the Sea
Chernobyl
Level 7
Fukushima Daiichi
Level 7
TMI
Level 5
As a nuclear or industrial accident, it was major
– resulted in evacuation, loss of a major
electricity source, and uncertainty in the public
for months.
It was not a major health catastrophe, and it is
not likely that there will be significant health
effects.
Why? – The emergency plan actually worked.
Despite the initial confusion, people were
evacuated, controls were placed on food, etc.

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