Fukushima Accident : An overview

Icapp2011, 3 May 2011 Akira OMOTO, University of Tokyo, JAPAN1

[Note]1.
2.

The information contained here is preliminary andneeds to be confirmed by the Accident Investigation
Commission to be set up soon by the Government.
The views expressed here does not represent theofficial view by AEC nor U of Tokyo nor TEPCO.

2

3.11 Earthquake and aftershocks
Statement by the Headquarter for
Earthquake Research, 11March2011
The Earthquake Research Committee
evaluated earthquake motion andtsunami for the individual region off‐
shore of Miyagi prefecture, to theeast off‐shore south of Sanriku along
the trench, and to the south off‐
shore of Ibaraki prefecture, but
occurrence of the earthquake that is
linked to all of these regions is “outof hypothesis”.
[SOURCE]
http://www.jishin.go.jp/main/index‐
e.html The 2011 off the Pacific Coastof Tohoku Earthquake
http://outreach.eri.u‐tokyo.ac.jp/eqvolc/201103_tohoku/eng/#mesonet“Earthquake Research Institute, University of Tokyo, Prof. Takashi Furumura and Project
Researcher Takuto Maeda”

3

3.11 Earthquake
Design basis earthquake and observed acceleration (Basement of Reactor/B)
Nr.

1Fuku1
1Fuku2
1Fuku3
1Fuku4
1Fuku5
1Fuku6

MWe

460
784
784
784
784
1100

3.11 Observed (max. gal)

Design (Ss) (max. gal)

N‐S

E‐W

Vertical

N‐S

E‐W

Vertical

460
346
322
281
311
298

447
550
507
319
548
444

258
302
231
200
256
244

487
441
449
447
452
445

489
438
441
445
452
448

412
420
429
422
427
415

Note 1: Damage by the earthquake: Not fully inspected but maybe not significant
considering the KK earthquake (2007) where no damage to safety functions eventhough the observed acceleration exceeded design basis by factor 2‐3(Acceleration will not necessarily be damages indicators)
Note 2: Scram set points by acceleration (Basement of Reactor Building)
Horizontal=135‐150 gal, Vertical=100 gal
4

3.11 Tsunami
1F1‐3 Plant response immediately after the earthquake
14.46
Earthquake followed by Reactor SCRAM,
LOOP, EDGs start, IC/RCIC in operation
15.38‐41 Tsunami followed by complete (AC/DC) blackoutand (mostly) isolation from the Ultimate Heat Sink

http://outreach.eri.u‐tokyo.ac.jp/eqvolc/201103_tohoku/eng/#mesonet“Earthquake Research Institute, University of Tokyo, Prof. Takashi Furumura and Project
Researcher Takuto Maeda”

5

14 NPPs along the coastal line affected by Tsunami

6

Fukushima Dai‐ichi Unit 1‐47

3.11 Tsunami
GroundLevel
R/B, Intak
Tb/B e str.
[m] [m]Tsunami height Location of Electric
Equipment Room
[m]
DB
Mod
3.11 (M/C, P/C, Battery)

1Fuku1,2,3,&4

10.2 4

3.1

1Fuku5
1Fuku613.2 4

3.1

Unit

2Fuku1,2,3&4
Ogagawa1,2&3(2002)

1F1.3: 2 SC‐EDGs
1F2,4: 1 SC‐EDG + 1 AC‐EDG
2 SC‐ EDGs
2 SC‐EDGs

5.7
12
14.8

7

Type & location of
Emergency Diesel Generator
SC: Seawater‐cooled
AC: Air‐cooler

3.7

5.2

14‐
15

9.1

‐

13

1 AC‐EDG
3 SC‐EDGs
3 SC‐EDGs

Location information not listed here
Tsunami flow path @2F

1. One of the offsite power lines for 2F stayed
alive during & after the Earthquake/Tsunami
2. What mattered was the elevation of air
intake/exhaust of EDG room & location ofElectric Equipment rooms

Fuel damage or not ‐‐‐‐ What made the difference?
(1) Elevation vs. Tsunami height Site ground level saved Onagawa units Elevation of air intake/exhaust of EDG
 Location of EDG/EE room/battery(2) Availability of power Offsite power  saved 2F site Air‐cooled EDG coupled with the above 1) location/height saved 1F6‐ Air‐cooled EDG was added for 1F2,4,6 respectively in the 1990’s
as a part of SAM modifications.
 1F3/5/6 battery located at a higher elevation, escaped flooding(3) Implementation of AMG by using then‐available resources saved 1F5, SFPs (makeup water)
NOTE: Availability of UHS commensurate to decay heat level supports quick recovery
but does not seem to be a decisive factor.
‐ 1F5/6 : Use of temporary seawater pump for RHR (units were in refueling outage)‐ 2F4 : continued Rx water makeup under isolation from UHS until March 14th

9

Tsunami: NPP Design guidelines and probabilistic study Safety Design Guide (NSC) Nr. 2 [footnote] “….Anticipated natural hazard includes flood, Tsunami ….”

 Japan Society of Civil Engineers (JSCE) on Tsunami
 Renewed concern over Tsunami by 1983, 1993 Tsunami experiences 2002 guidelines for NPPs from the Nuclear Civil Engineering Committee of JSCE
http://committees.jsce.or.jp/ceofnp/system/files/JSCE_Tsunami_060519.pdf
1) Consideration of Tsunami sources along the plate boundary, uncertainty analysis
and verification by the use of historical record;…. At the target site, the height of the design tsunami should exceed all the
calculated historical tsunami heights.
2) “….the design tsunami is compared with the historical records …. it is confirmed
the height of the design tsunami that is obtained in this paper is twice that ofhistorical tsunamis on an average”
 Modification in 2002 based on this guideline Tsunami Probabilistic Hazard study Probabilistic Tsunami hazard analysis (TEPCo, ICONE‐14, 2006)
 Methodology guide from JSCE Nuclear Civil Engineering Com. (2009)

 IAEA DS417 (draft) Includes guide on Tsunami analysis
10BWR/3,4 generation plant
BWR/3 (460MWe, 1Fuku1)
 Mark I Containment (Drywell + Torus‐type Suppression Pool) SFP on top floor of the R/B
 Isolation condenser for passive core cooling (@Hi Pressure) Core Spray system (@Lo Pressure) after depressurization by SRV

BWR/4 (784MWe, 1Fuku 2,3,4 &5)
 Mark I Containment (Drywell + Torus‐type
Suppression Pool) SFP on top floor of the R/B
 RCIC (Reactor Core Isolation Cooling) &HPCI (High Pressure Core Injection)(@Hi Pressure) CS (Core Spray) & RHR/LPCI(@Lo Pressure) after
depressurization by SRV
11

1Fuku1
Water injection

IC

March 12 Morning ~ Rx WL decrease
15.36 Explosion on the top of R/B
20.20 Water injectionhydrogen
explosion[Based on NISA slide, IAEA Safety Convention Meeting, 2011April4]

12

1Fuku3
RCIC / HPCI

Water injection
March 1305.10 No ECCS flow,
13.12 water injectionhydrogen
explosion

13[Based on NISA slide, IAEA Safety Convention Meeting, 2011April4]

1Fuku2
RCIC operation

Water injection

March 12/13
RCIC in operation*
March 14
~midday RCIC stops operation,
HPCI in‐operable, SRV in‐operable
16.34 Depressurization of RCS
start injection (….continue)

14[Based on NISA slide, IAEA Safety Convention Meeting, 2011April4]

Unit 1

Unit 315

Why H2 explosion right after venting?
Possible Path 1 : Excessive leakage by over‐pressure at CV flange/airlocks
Possible Path 2: Vent line SGTSR/B (vent line merge with adjacentunit’s line)
Unit 1

Unit 3

SFP zone
Unit 2

1F2 blowout panel opened by
1F3 blast, which released H2

Unit 4

SFP zone

Water sample from SFP and photo indicate
16
SFs in 1F4 most probably remain intact

Current : water Injection to the reactor core
Backup: Freshwater carried by Barge Ship (Courtesy of the US)(Nearby Dam)
Non-filtrated water
Service
Water
Tank

Containment
FDW/LPCI
6-7 Tons/hr/unit

Fire Engine
Seawater

RPV~500 Tons/Day

Purified
Water
Tank

Pump

Pit
Fire Engine[SOURCE] NISA, IAEA Safety Convention Meeting, 2011April417

Current : Water Injection to SFP (Spent Fuel Pool)
2-5Tons/hr/unit

1F1,3, 4: Similarly by occasional spray from above
1F2: Using FPC‐MUW (w/o overhead spray)
18[SOURCE] NISA, IAEA Safety Convention Meeting, 2011April4

Key near‐term recovery actions
1. COOLING Flooding the containment to a certain level & installation of heatexchanger to remove heat, [challenge] working environment SFP cooling system (rather than spray and evaporation)
2. MINIMIZING AIRBORNE/LIQUID EFFLUENT Recycling of water recovered from Tb/B through removal ofradioactivity (France/US) and RO (Japan)~1200 Tons/Day treatment~500 Tons/Day treated water return to the reactors
 Storage of contaminated water Installation of R/B cover Corrosion control (Deaeration of supply water, hydrazine)
3. MINIMIZING RESIDUAL RISKS Aftershocks (Structural integrity of damaged R/B, Reliability of
power/water supply)19
 HydrogenWhat SAM (Severe Accident Management) was in place?
(OECD/NEA)
In the aftermath of Chernobyl, OECD/NEA organizeda series of meetings by SESAM (Senior Expert for
Severe Accident Management)“Severe Accident Management”: published in 1992
“Implementing Severe Accident Management in
Nuclear Power Plants”, published in 1996
(Japan) NSC recommendation for SAM preparation (1992)
 SAM study followed by SAM Guide and modifications (hardenedvent, injection to RPV and RPV‐pedestal region etc)
 Technical basis for SAM by Utility/Industry/Academia (NSRI
guideline, 1999, http://www.nsra.or.jp/safe/cv/index.html)
 Submittal of Utility report to Regulatory body after completion ofmodifications (2002) and AMG, followed by evaluation by NISA 20

What SAM (Severe Accident Management) was in place?
Stuck

Sever Accident Management
Alternative
Power source

Other Unit

SGTS

Alternative Core
injection/CV spray

EDG
Filtered Water
Storage Tank
FP system“Hardened”
scrubbing
Vent

Pedestal injection

Sea Water Pump
RHR Pump

Sea
21

What offsite emergency plan was enacted?

Zone II
Zone I(mSv)
Zone III
SPEEDI calculation March 11‐April24
Cumulative exposure to adult
http://www.nsc.go.jp/info/110425_top_siryo.pdf

Zone I (20km); “evacuation”
Zone II (North‐west): “evacuation plan (in a month)”
Zone III (20‐30km); “preparedness for evacuation”

22What offsite Emergency Actions?
March 11
16‐18: Notification of no confirmation of water injection & increase of CV pressure (TEPCO)
19:03: Government declared nuclear emergency. (Setup of Government Nuclear
Emergency Response Headquarter and Local Emergency Response Center)
21.23: PM directed evacuation (3km radius) and sheltering (10km radius) of 1F site
March 125.44 : PM directed evacuation (10km radius) of 1F site
7.45: PM directed evacuation (3km radius) and sheltering (10km radius) of 2F site
17.39: PM directed evacuation (10km radius) of 2F site
18.25: PM directed evacuation (20km radius) of 1F site
March 15
11.00: PM directed sheltering (20‐30km radius) of 1F site
Local Emergency Response Headquarter issued “direction to administer the stable Iodine
during evacuation from the evacuation area (20 km radius)” to the Prefecture Governors
and the heads of cities, towns and villages.
March 25
Chief Cabinet Secretary prompted voluntary evacuation (20‐30km radius) of 1F site
April 11
Chief Cabinet Secretary set up an area of planned evacuation within 1 month to avoid
exposure beyond 20mSv/yr and prompted preparation for evacuation (20‐30km) of 1F site(reason: just in case of large release)
April 20
Chief Cabinet Secretary set‐up of de‐fact exclusion zone for 20km radius of 1F(Nr. of residents: 7,8000) and reduction of EPZ to 8km around 2F
23

24[SOURCE] NSC, http://www.nsc.go.jp/info/20110411_2.pdf

What Ingestion control was placed?
 Control in place : March 19‐ , mostly lifted already but different
from place to place and among products
 PM can direct limitation of transfer beyond the affected area
(prefecture) Basis(I‐131)
I‐131 equivalent in drinking water/milk < 300 Bq/kg (infant:
100Bq/kg)
I‐131 equivalent in vegetable/sea‐food< 2,000 Bq/kg(Cs)
Cs in drinking water/milk < 200 Bq/kg
Cs in food< 500 Bq/kg
25

Why INES level 7? Declared by NSC/NISA on April 13th
Chernobyl:
Fukushima:

I‐131 eq.
5.2 x [10(18)] Bq
I‐131 eq. 0.3‐0.6 x [10(18)] Bq

Estimated by reverse calculation using SPEEDI and ground contamination (outside)and Severe Accident ST Analysis (inside)

INES 2.2.2.Definition of levels based on activity released
Level 7: An event …..equivalent to a release to the atmosphere of more than several
tens of thousands of tera[10(12)] Bqs of I‐131(SOURCE: INES User’s Manual 2008 Edition)

26

What Nuclear Liability system in Japan?
1. Basics: Owner/Operator owes unlimited liability for compensation of nuclear
damage, irrespective of the cause of accident
2. Two contracts: Owner/Operator‐Insurance company (Liability insurance)
Owner/Operator‐Government (Indemnity Agreement)
3. If the compensation amount exceeds 1.2B$ (assuming 100yen/$), Government
may come to support contingent on the Diet’s decision
4. Not a signatory of Amended Paris nor Amended Vienna agreements nor CSC

Owner/Operator’sinsurance[Not cover
Earthquake,
Tsunami, Volcano
Eruption]

Indemnification
Agreement
1) Case of Earthquake,
Tsunami, Volcano Eruption
2) Case of unknown cause
during normal operation
3) Case of compensation
request after 10 years

Government’s
arrangement
Case ofextraordinary
natural disasteror insurrection27

What are the potential considerations for future designs andsuccessful implementation of SAM ?
1. Design considerations against natural hazards
Personal observations
 Data compiled by reactor‐year for internal events, while by year for natural hazards
 Use of logic tree and PSA for estimation where there is scarcity of data
‐ logic tree representation of uncertain parameters‐ Tsunami source zone model‐ Probabilistic Tsunami hazard curve Building layout and elevation of Electric Equipment /EDG rooms
 ERC in robust building (seismic isolation after 2007 earthquake)

Iwate pref. Takada[SOURCE} T. Annaka et al, “A method
Of Probabilistic Tsunami Hazard Analysis”,
Earthquake Engineering Symposium, 2006
28

What needs to be considered for future designs andsuccessful implementation of SAM ?
Personal observations
2. Diversitya) Diversified Ultimate Heat Sink (UHS) of Residual Heat Removal and Emergency
Equipment Cooling Systemsb) Diversified power & water supply: Air‐cooled DG, Water from dam
3. Passive safetya) Heat removal from reactor core/containment/SFP by Isolation Condenser, PCCS,
external CV cooling, wall cooling etcb) Preparations for “what if onsite recovery actions were disabled”
4. Consideration against extended time blackout
Battery in safe place and recharger of battery by small EDG[Note] Some US plants with recharger of battery by small EDG

29

What needs to be considered for future designs andsuccessful implementation of SAM ?
Personal observations
5. Improvements of SAM (Severe Accident Management)a) Review and drill for the “use of all available resources (Apollo 13)”
 Provisions of Onsite or National Nuclear Crisis Center, under appropriatedelineation of responsibility, transportation systems and storage of mobile
equipments such as Fire Engines, portable sweater pumps, batteries,
remote sensing devices, remote spray system, robotics etc & drill for useb) Implementation of recovery actions in harsh radiation environment Provision of Temporary shielding, Remote handling machine, Remote water
spray machine, remote sensing machines and cameras by unmanned plane,
and others from National Crisis Centerc) Potential of detonation/deflagration of leaked hydrogen outside of the CV vent line pipe and SGTS line pipe “hydrogen deflagration/detonation in a BWR R/B” (NE&D 211,27‐50)d) Include “water inventory control” “water leak path analysis” (LWR)e) Recovery actions: preparation for the worst & “defense in depth”f) Structure of Emergency Management organization
30

What needs to be considered for future designs andsuccessful implementation of SAM ?
Personal observations
6. SAM Operational aids
Real‐time simulation of plant behaviour as an aid to decision‐making from
options and assess the current/future risks potentials, backed by precise
accident data tracking system by recoding every plant behaviour and remedialactions
7. Accident instrumentation (CV water level etc) and sampling capability
Very limited data available (Rx‐SC/DW pres/Rx‐SC/DW temp/Rx WL)
8. Offsite management such as the use of exposure prediction system etc
9. Design considerations for SFP
 Potential of re‐criticality of over‐moderated SFP
 Location of SFP (Accessibility, Structural integrity, Aeroplane crash) Alternative heat removal method (cooling system and UHS)
10. Amendment of International safety standards and establishing international
expert review of design/SAM (vs. national authority to license), global safety goal

31

What English information on web from Japan?
<Earthquakes and Tsunami>
Japan Meteorological Agency
http://www.jma.go.jp/jma/indexe.html
http://www.jma.go.jp/jma/en/2011_Earthquake.html
http://www.jma.go.jp/en/tsunami/
Geospacial Information Authority of Japan(partially inJapanese)
http://www.gsi.go.jp/ENGLISH/index.html<Radiation Levels>
http://www.mext.go.jp/english/radioactivity_level/index.htm
http://www.bousai.ne.jp/eng/index.html
U.S. Department of Energy Releases Radiation Monitoring
Data from Fukushima Area
http://www.energy.gov/news/10194.htm
Food and Water
http://www.mhlw.go.jp/english/topics/2011eq/index.html
Radioactive material level in tap water in Tokyo/day
http://ftp.jaist.ac.jp/pub/emergency/monitoring.tokyo‐
eiken.go.jp/monitoring/w‐past_data.html
prepared by Shuichi IWATA(iwatacodata@mac.com) the University ofTokyo & Osamu MIZUTANI (osamumztn@aol.com) UAJC on April 21,
2011 for “Twenty‐Five Years after Chernobyl Accident: Safety for the
Future”<Status of Nuclear Reactors>
Tokyo Electric Power:
http://www.tepco.co.jp/en/nu/fukushima-np/indexe.html#anchor02-Radiation Levels measured by TEPCO
http://www.tepco.co.jp/en/nu/fukushima-np/f1/indexe.html-TEPCO’s explanation paper
http://www.tepco.co.jp/en/nu/fukushimanp/f1/images/f12np-gaiyou_e.pdf-Influence of radioactive materials to the environment(prepared by TEPCO)
http://www.tepco.co.jp/en/nu/fukushima-np/f1/index2e.html-Photos for Press (TEPCO)
http://www.tepco.co.jp/en/news/110311/
Japan Atomic Industrial Forum
http://www.jaif.or.jp/english/
Japan Nuclear and Industrial Safety Agency
http://www.nisa.meti.go.jp/english/
Nuclear Safety Commission of Japan
http://www.nsc.go.jp/NSCenglish/geje/index.htm
Prime Minister’s Office of Japan
http://www.kantei.go.jp/foreign/incident/index.html
NHK World in English
http://www3.nhk.or.jp/nhkworld/
NHK World TV
http://www3.nhk.or.jp/nhkworld/r/movie/
3232What English information on web from Japan?
<Assistances>
NHK Radio provides quake‐related broadcast in 18 languages
http://www3.nhk.or.jp/nhkworld/english/radio/program/in
dex.html
Assistance Manual for Foreigners in Times of Disaster by
TICC
http://www.tokyo‐icc.jp/english/information/howto.html
Transportation
http://www.mlit.go.jp/page/kanbo01_hy_001411.html
Ministry of Defense
http://www.mod.go.jp/e/index.html
National Police Agency
http://www.npa.go.jp/english/index.htm
National Institute of Radiological Sciences
http://www.nirs.go.jp/ENG/index.html

prepared by Shuichi IWATA(iwatacodata@mac.com) the Universityof Tokyo & Osamu MIZUTANI (osamumztn@aol.com) UAJC on April
21, 2011 for “Twenty‐Five Years after Chernobyl Accident: Safety
for the Future”<Other Information Sources>
Atomic Energy Society of Japan
http://www.aesj.or.jp/en/
Japan Atomic Energy Agency
http://www.jaea.go.jp/english/index.shtml
International Atomic Energy Agency
http://www.iaea.org/newscenter/news/tsunamiupdate01.ht
ml
US Department of Energy Blog
http://blog.energy.gov/content/situation‐japan
US Nuclear Regulatory Commission
http://www.nrc.gov/japan/japan‐info.html
World Nuclear Association
http://world‐
nuclear.org/info/fukushima_accident_inf129.html
United States Environmental Protection Agency
http://www.epa.gov/japan2011/
Google Crisis Response
http://www.google.co.jp/intl/en/crisisresponse/japanquake2
011.html
Photo Service
http://cryptome.org/eyeball/daiichi‐npp/daiichi‐photos.htm
American Nuclear Society
http://ansnuclearcafe.org/fukushima/
33
33

What international supports were provided?
< International Supports for disaster recovery >135 countries and regions as well as 39 international organizations have expressed their intentions to extend assistance.
Rescue and medical support teams from 20 countries and regions (Australia, China, France, Germany, India, Indonesia,
Israel, Italy, Mexico, Mongolia, New Zealand, the ROK, Russia, Singapore, South Africa, Switzerland, Taiwan, Turkey, theU.K., the U.S.) as well as and the UNOCHA, an IAEA expert team, and the WFP have arrived Japan and have been operating
in disaster-stricken areas.
< Support from Governments>[Australia] a special pump needed for cooling Reactor[Canada] 154 radioactivity survey meters, 5,005 personal dosimeters[Finland] 50 Radioactivity measuring monitors[France] protective suits and masks(approx. 20,000 sets), 250 radiation measurement equipment, 10pumps, 5 power
generators, 5 compressors, 3 environmental survey vehicles, an environmental survey towed vehicle, approx. boron(100tons)[Korea] approx. 52 tons of boron[U.S.A] Technical support from DoE, 10,000 radioactive-proof suits from USAID; 2 fire trucks, 5 pumps, 99 protective suits
against nuclear, biological and chemical weapons, approx. 9 tons of boron, 1 large water spray pump unit, fresh-watertransportation by a barge for carrying fresh water from the U.S. Forces. 31,000 Radiation dosimeters, NRC’s experts support<Support from Industries> (Examples)[Areva] Protective suits (approx. 10,000), protective masks(3,000), 2 experts, 2 monitoring cars etc[iRobot in U.S.A] Packbot by iRobot worked inside the reactor building of Unit 3 on April 17.
[Rosatom in Russia] 400 Radiation dosimeters, protective masks(5,000)[Sany Heavy Industry in China] 62 truck mounted concrete pump[Putzmeister in Germany] Several long pumps including a 70m long pump[Westinghouse/B&W/Shaw, GE] Proposal of the mid-term & long term plan
Putzmeister pump
Packbot in reactor of
Fukushima Daiichi Unit3
Sany Heavy Industry pump

Heartful thanks to the international helping hands.

34

Never, Ever Again
anywhere in the world35
http://www.asahi.com/photonews/gallery/fukushimagenpatsu/