Estimated Atmospheric Release of Radioactive Materials Due to Fukushima Daiichi NPS Accident

Estimated Atmospheric Release of
Radioactive Materials Due to
Fukushima Daiichi NPS Accident
U.S. NRC Regulatory Information Conference
Technical Session T-5
North Bethesda, Maryland
March 10th, 2015
Kenji Tateiwa
Manager, Nuclear Power Programs
Tokyo Electric Power Company, Washington Office
[email protected]
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Great East Japan Earthquake (March 11, 2011)
Houses Swept Away
Epicenter
http://archive.shinsai.yahoo.co.jp/
http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=77331
http://archive.shinsai.yahoo.co.jp/
 Largest earthquake (M9.0)
and tsunami (M9.1) in
recorded history of Japan
 20+ m tsunami run-up in
coast line spanning 200 km
 560 km2 flooded
(10x Manhattan)
 19,000 dead/missing
Cruise Ship Stranded
http://archive.shinsai.yahoo.co.jp/
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Overview of the 10-Unit Simultaneous Accidents
Date
(2011)
Fukushima Daiichi (1F)
2
3
4
5
1
Fukushima Daini (2F)
1
2
3
4
6
OPERATING
15:22~ Tsunamis
OPERATING
OUTAGE
15:27 1st Tsunami, 15:35 2nd Tsunami
3/11
3/12
Station Blackout
3/12 8:13
D/G-6B
Water Injection: NO
Heat Removal: NO
Water Injection: YES
Heat Removal: NO
3/12 12:15
15:36 Unit 1 Explosion
Loss of Ultimate Heat Sink
3/13
3/14 1:24
RHR
3/14
3/14 7:13
RHR
3/14 15:42
RHR
11:01 Unit 3 Explosion
3/14 17:00
3/14 18:00
6:00-6:10 Unit 4 Explosion
3/15 7:15
3/15
3/16
-19
3/20
3/19 5:00
RHR
3/20 15:46
P/C-2C
3/20 15:46
P/C-2C
3/22 10:36
P/C-4D
3/22 10:35
P/C-4D
3/20 14:30
3/19 22:14
RHR
3/20 14:30
Water Injection: YES
Heat Removal: YES
Cold Shutdown
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My Post-Accident Activities
IAEA Preliminary Mission
(4/6/2011@Fukushima Daiichi NPS)
IAEA: International Atomic Energy Agency
4
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How Much Radioactivity Was Released?
Estimation of Radioactive
Estimation
of Radioactive
Material
Released
to the
Material Released to the
Atmosphere
Atmosphere
During the Fukushima
during the Fukushima
Daiichi
DaiichiNPS
NPS Accident
Accident
May 2012
May 2012
Tokyo Electric Power Company
“DIANA” code used to estimate radioactivity release
http://www.tepco.co.jp/en/press/corp-com/release/2012/1204659_1870.html
Dose Information Analysis for Nuclear Accident
(3-D Atmospheric Diffusion Model)
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Estimation of Release Rate
Release rate
assumption
Dose rate
calculation by
DIANA
Calibration
with observed
data
Updated
release rate
( Iteration)
Back-calculated release rate based on
observed air dose rate
(stack monitor was lost due to SBO)
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Air Dose Rate (µSv/h)
Available Dose Rate Data
Site Map
Unit 1
Unit 2
Unit 3
Unit 4
Main Gate
Monitoring posts unavailable due to SBO
Relied on on-site monitoring car
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7
Estimation of Nuclide Composition and Deposition
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Estimating Nuclide Composition from Dose Rate Curve
Decay curve dependent
on iodine composition
Background level
increase due to Cs
deposition
Breaking down single source estimate into
multiple radionuclides based on observed data
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Air Dose Rate (µSv/h)
Estimating Susceptibility of Release of Radionuclides
Best matches observed data assuming following ratio
(compared to core inventory)
noble gas : iodine : cesium = 100 : 10 : 1
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Noble Gas (
I-131 (
Cs-137 (
): 500 PBq
): 500 PBq
): 10 PBq
PBq (Cs-137)
PBq (noble gas/I-131)
Estimated Cumulative Release
date
Cumulative release of radioactivity in March 2011
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11
Land Contamination in Northwest Area
Steam from Unit 2
Reactor Building
[Morning of March 15, 2011]
Max. dose rate at main gate: 10 mSv/h
Significant drop in Unit 2 drywell pressure
Steam observed near Unit 2 reactor building
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Land Contamination in Northwest Area (cont’d)
1F site
1F site
Trajectory of plume from Unit 2
on March 15
Radar image on March 15 at 11 pm
http://agora.ex.nii.ac.jp/earthquake/201103-eastjapan/weather/data/radar-20110311/
Rainfall caused deposition of radionuclides in
plume from Unit 2, resulting in land contamination
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Summary Results
Release
Mode
Noble
Gas
INES
I-131
Cs-134
Cs-137
(PBq)
(PBq)
(PBq)
(PBq)
(I-equivalent)
5
1
0.02
0.01
-
10
3
0.07
0.05
-
500
500
10
10
-
Total
500
500
10
10
900
Cf.
6,500
1,800
-
85
5,200
Containment
Venting
Reactor
Building
Explosion
Uncontrolled
Release from
R/B
Chernobyl
(PBq)
Dominant release path assumed to be
uncontrolled release from reactor buildings
(not venting or explosion)
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Current Status of Fukushima Daiichi (1F)
View 1
Unit 1
Unit 2
Unit 3
View 2
Unit 4
Unit 1
Unit 2
Live Camera View
(as of 2/20/2015)
http://www.tepco.co.jp/en/nu/f1-np/camera/index2-e.html
http://www.tepco.co.jp/en/nu/f1-np/camera/index-e.html
Unit 3
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Investigation Insights of 1F Units 1, 2, and 3
Unit 1
 Two locations of leakage found in
torus room
 Indication of leakage in drywell
shell
Unit 2
 No leakage confirmed in torus
room
 Likely leakage near bottom of
suppression chamber
Unit 3
 Leakage from drywell to reactor
building found at main steam line
penetration
 No indication of leakage from
suppression chamber
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Decommissioning Roadmap for 1F
Cold Shutdown
Condition Achieved
(Dec., 2011)
Within
2 years
Within
10 years
Phase-1
Phase-2
Phase-3
Begin retrieval of
fuel debris
Begin removal of fuels
from spent fuel pools
30 to
40 years
Complete
decommissioning
Unit 4: Nov. 2013
Fuel
Handling
Machine
Crane
Today
Common pool
Stop Leakage
Flood PCV and
Remove Fuel Debris
Global collaboration vitally important to tackle
this unprecedented undertaking
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TEPCO’s Post-Accident Activities in the U.S.
Nuclear Industry
Global
Organizations
Academia
Gov’t Agencies
Professional Organizations,
Think Tanks, NPOs, Media
Committed to sharing lessons learned; making nuclear
power plants safer; carrying out decommissioning safely
 Hosting Weekly Update Teleconferences
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