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LEE Durk-Hun
[email protected]
Regional Workshop of Nuclear and Radiological Emergency
Preparedness and Response
KINS, South Korea, June 8~19, 2014
Review of Fukushima Accident and
Lessons Learned
Module D2-10
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Contents
Overviews on Fukushima NPPs
Accident Progress of Fukushima NPPs
Results of Fukushima Accidents
Response to the Accident
Summary
I
II
III
IV
V
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Experience ? Experience is not what
happens to you; it's what
you do with what happened.
Aldous Huxley
Nuclear Accident Cases
Lessons learned from OEs
TMI-2 Accident (28 March, 1979)
Chernobyl-4 Accident (23 April, 1986)
Fukushima Accident (11 March, 2011)
http://www.basicquotations.com/index.php?aid=8http://www.basicquotations.com/index.php?aid=8http://www.basicquotations.com/index.php?aid=8
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Fukushima Accident (11 March, 2011)
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Overviews on Fukushima NPPs
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Operational Status of Japan before Accident
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Fukushima I Nuclear Power Plants
Unit 1
Unit 2
Unit 3
Unit 4
Units 5, 6
At the Time of the Earthquake Reactors 1, 2 and 3 operating
Reactors 4, 5 and 6 shutdown for
refueling
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Boiling Water Reactor(BWR)
Water inside the reactor pressure vessel of BWR is heated and
becomes steam of h
igh pressure and high temperature (285℃, 70 atm.) while flowing
among fuel rods. Resultant steam is used in driving the turbine to
generate electricity and , after gettin
g back to water at the condenser, return to the reactor.
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Boiling Water Reactor(BWR)
Spent Fuel Pool
Reactor Vessel
Suppression Pool (Torus)
Primary Containment
Steel Containment Vessel
Secondary Containment
Area of Explosion At Units 1 and 3
Boiling Water Reactor Design At Fukushima Daiichi
Seawater Pumped Into Reactor Vessels at
Units 1, 2 and 3
Damage to Torus at Unit 2
Significant Radioactive Release
at Units 1 ~ 4
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BWR Reactor Pressure Vessel
http://upload.wikimedia.org/wikipedia/commons/a/a1/Bwr-rpv.svg
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Accident Progress
of Fukushima NPPs
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2011 Tohoku earthquake
2011 Tohoku earthquake
Date : March 11, 2011 14:46 (JST)
Epicenter : 38.510°N, 142.792°E,
depth 24.4 km
Magnitude : 9.0
Automatic shutdown : 11units
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Design Basis Against Tsunami
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Loss of offsite power due to the earthquake
earthquake → reactor shutdown→ loss of site power production
earthquake → damaged outside transmission lines → loss of
offsite power Tsunami → flooding → inoperable EDG
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Decay Heat Produced for a Long Time
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Aerial view of Fukushima NPP Unit 1~4
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Current Status of Fukushima NPP Unit 1~4
Reactor
(No. of nuclear fuels
loaded in the reactor)
Spent Fuel Pool
(No. of spent fuel stored in
the SFP)
Pressure
Containment Vessel Reactor Building
Unit 1 Damaged(400) Most spent fuels not
damaged (292) Integrity Severely damaged
Unit 2 Damaged(548) Most spent fuels not
damaged (587) Damaged Partly opened
Unit 3 Damaged(548) Most spent fuels not
damaged (514) Integrity Severely damaged
Unit 4 No fuel loaded Most spent fuels not
damaged (1,331) No fuel loaded Severely damaged
Unit 5 Integrity(548) Integrity(946) Integrity Integrity
Unit 6 Integrity(764) Integrity(876) Integrity Integrity
Operation status of Fukushima Dai-Ichi NPPs
- Unit 1, Unit 2, Unit 3 : In service -> Shutdown
- Unit 4 : Outage
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Unit 1 Major Events
Diesel Generators initially provided AC power but failed due to
Tsunami ~1 hour after
earthquake, resulting in a Station Blackout
Unit 1 reactor cooled by Isolation Condenser (IC) for ~9 hours,
but IC lost due to lack
of makeup water into IC tank
IC tank makeup from fire pumps might have been available but
were not used
Hardened vent (as implemented for all US BWRs) into the
atmosphere apparently
was unavailable at Fukushima plant
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Hydrogen Explosion at Units 1&3
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Damage to Unit 2 Torus
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Concerns on Spent Fuel Pool Damage
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Results of Fukushima accident
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Released radioactive material
Early stage in accident : 8.0x1014Bq/hr
-> Early November in 2011 : 6.0x107Bq/hr
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Accident Fukushima Accident Chernobyl Accident
Nuclide NISA’ estimation
(TBq)
conversion to
I-131(TBq)
Estimation
(TBq)
Conversion to
I-131(TBq)
I-131 160,000 160,000 1,800,000 1,800,000
Cs-137 15,000 600,000 85,000 3,400,000
Total 760,000 5,200,000
Released radioactive material
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Evacuation Plan
Within 20km : Restricted Areas
Within 30km : Emergency evacuation preparation areas
(Removed on 2011.9.30)
Evacuation map of Fukushima and the surrounding area
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Comparison : TMI-2, Chernobyl, Fukushima
TMI-2 Chernobyl Unit 4 Fukushima Dai-ichi
Location U.S.(Pennsylvania) Ukraine Japan(Fukushima)
Model ? Process PWR RBMK 1000 BWR
Vendor Babcock & Wilcox(B&W) USSR GE
Capacity 906MWe 925MWe 460MWe
Commercial Date 1978. 12. 30 1984.3.26 1971.3.26
Accident Date 1979. 3. 28 04:00 1986. 4.26 2011. 03. 11
14:45
Cause Human error
Human error
- Design error, vulnerable
containment
Natural Disaster
-Earthquake, Tsunami
INES level
Level 5
(accident with wider consequences)
Level 7
(major accident)
Level 7
(잠정 등급)
Radioactive material
release to the environment
Noble gas : 250,000 Ci
Iodine : 15 Ci
Cs: 2.3x106 Ci or more
Iodine : 4.6x 107Ci or more
Cs: 4.0x105 Ci or more
Iodine : 4.3x 106Ci or more
Significant to report
Core melt
Hydrogen explosion
Containment maintained integrity
Explosion graphite combustion
Core melt
Hydrogen explosion
Damaged containment Released Radio-Quantity of Fukushima is
around 10~15% of Chernobyl case
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Current Figure of
Fukushima Daiichi Site
Feb.21, 2014
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Tomioka, Japan
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Responses to the accident
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Status of the Nuclear power plants in Japan (as of Jan.27,
2012)
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Current Status of Fukushima NPPs
“Roadmap towards Restoration from the Accident
at Fukushima 1 NPP, TEPCO” (Revised edition)
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Decommissioning plan
Work Steps Involved in Fuel Debris Removal
Mid and long-term plans for decommissioning of Fukushima NPP
Phase 1 : Remove fuels in spent fuel pool(within 2 years)
Phase 2 : Remove melted fuel in reactor(within 10 years)
Phase 3 : Complete decommissioning plan(within 30~40 years)
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Actions of Japan
Step 1. Inspection/supplementation measures of
emergency response facilities in respect of flooding(‘11.5.6,
complete)
Step 2. Inspection/supplementation measures of
severe accident response(‘11.6.22, complete)
Step 3. Conduct “Stress test*” in all NPPs(’11.7.6, in
progress)
*Conduct EU’s measure
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TEPCO Lessons Learned at Fukushima
• Common Understanding of Plant Conditions
- Leaders must lead; align on what is known and unknown
• Ensure adequate Onsite Licensee Staffing
- Maintenance and Engineering
• Onsite Prevention/Mitigation Equipment
- Infrastructure damage may prevent site access
• Handling Emotional Needs of Personnel
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EU Actions
European Council declared [3/24 and 3/25/11]
“The safety of all EU nuclear plants should be reviewed, on
the
basis of a comprehensive & transparent risk assessment”
EU Approach – “Stress Tests” based on WENRA Guideline
Identify potential weak points and cliff-edge effects for
each
extreme situation considered
Initiating events(Earthquake, Tsunami, Flooding,
Earthquake…)
Consequences of Loss of Safety Functions from any initiating
event conceivable at the plant site(Loss of electrical
power,
Loss of the ultimate heat sink,…)
Severe Accident Management Issues(Loss of core cooling
function,…)
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Stress Tests
Definition of “Stress Tests” (WENRA Specification, April 2011) A
targeted reassessment of the safety margins of NPPs in the
light
of the events which occurred at Fukushima: extreme natural
events
challenging the plant safety functions and leading to a
severe
accident
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Stress Tests
Definition of “Cliff-edge Effect” (WENRA Specification, April
2011)
Step change in the event sequence
A cliff-edge effect could be, for instance, exceeding a point
where
significant flooding of plant space start or exhaustion of the
capacity
of the batteries in the event of a station blackout.
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Reaction of French
2010 ASEAN Nuclear Training
FARN "Nuclear rapid response force"
Proposed by EDF, a national response system comprising
specialist
crews and equipment, able to take over from the personnel of a
site
affected by an accident and deploy additional emergency
response
resources in less than 24 hours
Hard Core
Following the complementary safety assessments (CSA), ASN
considers that the safety of nuclear facilities must be made
more
robust to improbable risks which are not currently included in
the
initial design of the facilities or following their periodic
safety review.
These facilities must be given the means to enable them to deal
with:
A combination of natural phenomena of an exceptional scale and
which
exceed the phenomena used in the design or during the Periodic
Safety
Review
Very long duration loss of electrical source or heat sink
situations capable
of affecting all the installations on a given site
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NRC Actions
Forming Task Force [NRC News. 4/1/11] for Review of Agency’s
Response to Japan Nuclear Event Identification of potential
near-term actions that affect U.S. power reactors,
including their spent fuel pools
Development of recommendations for Commission consideration on
whether
it should require immediate enhancements at U.S. reactors and
any changes
to NRC regulations, inspection procedures, and licensing
processes
Temporary Instruction TI 2515/184 “Availability and
Readiness
Inspection of Severe Accident Management Guidelines (SAMGs)”
[4/29/11 Issued; 5/27/11 Inspections Completed] Availability and
maintenance of SAMGs
Licensee implementation of SAMG training and exercises
NRC Bulletin 2011-01 “Mitigating Strategies” [5/11/11
Issued]
Written response to the NRC with regard to a comprehensive
verification of compliance with 10 CFR 50.54 (hh)(2)
requirements
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2010 ASEAN Nuclear Training
Reaction of USA
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IAEA Actions
The mission was divided into four areas: Regulatory Review and
Assessment Process
External Hazards and Evaluation of Safety Margins
Plant Vulnerabilities against Station Blackout and Loss of
Ultimate Heat Sink;
Severe Accident Management
Good Practice Based on NISA instructions and commitments of the
licensees, emergency
safety measures were promptly addressed in NPPs in Japan
following the
accident on 11 March, 2011;
NISA conducted an independent plant walkdown of emergency
measures
implemented by the licensee. This walkdown was appropriate and
enhanced
confidence that postulated actions could be performed;
NISA demonstrated a notable level of transparency and interested
party
consultation related to the Comprehensive Safety Assessment and
its review
process; and
By observing the European stress tests, NISA is demonstrating
its commitment
to further enhance nuclear safety by gaining experience from
other countries.
