akira omoto.pdf

Akira OMOTO, Professor, Tokyo Institute of Technology([email protected])

Fukushima accidentWhat happened in Japan and why?

Outline

What happened?

Why?- What Fukushima accident tells us about weakness in the context of Defense in Depth

Issue of cultural attitude behind decision-making Organization Nuclear community National

A. Omoto, IVA, 2013Nov29 2

Government Report to the IAEA, June2011 Initiation from B, then propagated westwards to area A, and further to the North and South down to Ibaraki

Source area of the 3.11 earthquake (multi-segment rupture)


Tb/B R/B

[SOURCE] http://www.tepco.co.jp/cc/press/betu11_j/images/110618l.pdf and TEPCO May 23 report

Flooding of Electric Equipment Room in turbine building (Metal-clad, Power Center, Control Center, DC battery)

Hx/B

Inundation height14-15mAssumed Tsunami

height 5.7m

Tb/B

R/B


Failure of AC-independent systems as timeCore melt, hydrogen generation and explosion

3.11 PM Earthquake and Tsunami left the plant underComplete SBO (AC/DC) + Isolation from Heat Sink

Long termDepressurize reactor systemActivate Low Pressure water injection systems

Accident Management

Short term Core cooling by AC-independent systems: use of decay heat

as driving force

automatic response

Sequence of accident (Unit 2 & 3)


What happened?




Recent Tsunamis (1933 Okujiri, 1993 Okujiri, 2004 Smatra)and advent of plate tectonics study triggered re-evaluation

of design basis Tsunami

Level 1 Defense in DepthPrevention of abnormal operation and failures


History of re-evaluation of Tsunami height by TEPCO

Design basis(1966)

3m

5.7mRe-evaluation of Design basis Tsunami using JSCE code(2002)

Probabilistic Tsunami hazard study (2006): 10(-5)/year for 10m

Hypothetical analysis (2008)15.7m

TEPCO studies: Tsunami deposit, Tall Tsunami wallTEPCO organized experts panel for review.


However, deposit study did not helpmodel construction very much

In this annex, an outline is presented of: the methodology, namely the Tsunami Assessment Method for Nuclear Power Plants in Japan published by the JSCE (Japan Society of Civil Engineers) in February 2002.

Historical tsunami study The first step is to conduct literature surveysfor dominant historical tsunamis affecting the target site, and then the validity of recorded tsunami heights needs to be examined. On the basis of the results, fault models for numerical simulations for historical tsunamis can be set up.

ANNEX II: ASSESSMENT OF TSUNAMI HAZARD:

Current practice in some states


1) Implicit assumptions in professional societys guide need scrutiny

2) Deposit study does not necessarily lead to a complete model3) When uncertainty is very high, prepared by thinking;

- Where is cliff edge ? - What is possible to increase distance to cliff edge?

Technical lessons

Dialogue/critical review among experts in different disciplinary areas

Lack of critical thinking, questioning attitude Listening to alternative/opposing views Lack of preparedness to beyond assumed conditionWaiting, expecting uncertainty will be reduced

Relevant cultural attitude issues

Level 1 Defense in DepthPrevention of abnormal operation and failures


Storegga slide

Amongst the largest known landslideStudy of deposited sediment8,000 years agoAround 10% of Tsunami by landslide?

Storegga tsunami deposits,Scotland


Accident Management (AM) was prepared after Chernobyl, butnot assuming extensive damages by external /security eventsdamages to System, Structure, Components Offsite power Heat Sink

AM was not robust enough, especially against external event, SBOIndependence of each layer of Defense-in-Depth Nexus between safety and security

Level 4 Defense in DepthControl of accident beyond Design Basis

Lack of critical thinking, questioning attitudewhy not assume? Waiting by expecting until uncertainty will be reduced

Technical lessons


Communication system Team


Overall offsite actions (evacuation and food control) helped reduce health risks

Identified problems Offsite centers function was lost Confusion in implementation of EPR Delineation of responsibility including PM,

communication among decision-makers

Needs to revisitDelineation of responsibility, command line, coordination Design and function of offsite centerOffsite emergency plan (zoning and others)

Technical lessons

Level 5 Defense in DepthEmergency Preparedness and Response (EPR)

Complacency Accident will not happen here



Not intended to say Accident like Fukushima is only uniquely happening in a unique natural and social environment


What happened?



A WARNING in Sec. overview, Kemeny report, 1979

We have stated that fundamental changes must occur in organizations, procedures, and, above all, in the attitudes of people.

No amount of technical "fixes will cure this underlying problem.


In a culture where it is impolite to say no and where ritual must be observed before all else, I think that Western style safety culture will be very hard for the Japanese to accept.

But there were also extraordinary even heroic efforts made by the brilliant dedicated engineers, operatorsI do not doubt that the Japanese Nuclear industry has the capability to transform to a nuclear operations safety culture.

Prof. D. Klein, Ex Chairman of USNRC, The Ripon Forum, Summer 2011

Influence of national culture?


This was a disaster Made in Japan.: Its fundamental causes are to be found in the ingrained conventions of Japanese culture (our reflexive obedience; our reluctance to question authority; our devotion to sticking with the program; our groupism; and our insularity)

Prof. K. Kurokawa in chairmansmessage to the Diets Investigation Committees Report (2012 July)

[source] http://naiic.go.jp/wp-content/uploads/2012/07/NAIIC_report_lo_res2.pdf

Influence of national culture?


6. Priority of risk management (Utility) Business environment (vertical integration, cost-plus

tariffs, relations with local governor & mayor)

Where do we need transformation in attitude?

7. Continuous safety improvement, being trusted by the society

2. Complacency Accident cannot happen here

5. Parochialism Vertical silo when multi-disciplinary issues involved

3. Professionalism and responsible useHeavy outsourcing (Utility) Lack of expertise (Regulation)

1. Critical thinking and listening to alternative views

4. Imagine what may happen if assumption was wrong


University of Tokyos Nuclear GCOE studyWhy nuclear community in Japan failed to prevent this accident by interviews to 24 well-recognized experts in nuclear community

Why nuclear community in Japan failed to prevent this accident?

[SOURCE] A. Omoto et al, Global 2011, December 2011


Focus on internal events in PSA No question to US origin designs in early phase (Electric

Equipment room in UG of Turbine Building) Lack of tension between Regulators/Operators No question asked to NE programme implemented

under the National Policy

1. Collectivism (as versus Individualism) Structure of sentence: subject + noun + verb Think/Act as a group No serious debate Not much speaking out:

Tall trees much windBetter bend than break

Some salient features of national culture

2. Less critical/reflective thinking, questioning attitude Education is, more or less, for transfer of knowledge

rather than teaching how to think Difference in traits of safety culture: raising concern

[INPO Fukushima LL report] decision-making approach did not provide for independent challenge or second checks by other groups within the organization.


[SOURCE] http://geert-hofstede.com/japan.html

Power Distance(hierarchical society)

Individualism

Masculinity(driven by competition, Achievement) Uncertainty

avoidance

Long-termorientation


3. Lack of big-picture thinking, lose sight of substance :being distracted by formality and details [Ex] independence of regulatory body to enable safety-first

decision-making Forget what independence is for and strict independence is leading to isolation

Although Nisbetts The geology of thoughts argues Asian see object as an integral part of environment (see forest that tree)

4. Culture in Engineering : Heavy emphasis on component reliability/quality, while weak in system thinking; [Ex] why B5b was not considered in Japan? [Ex] Construction of tall Tsunami breakwater wall what about

preparedness beyond design basis Tsunami?

Some salient features of national culture


1. Dedication INPO special report on the nuclear accident, Nov. 2011

Some workers lost their homes and families to the earthquake and tsunami, yet continued to work

Generally speaking, Utilities employee have mentality of dedication through work for the better of the society, whereas the society does not think so

Look at positive side

2. Compassion

4. Hard-working

3. Politeness (though being lost)


Assessment Impact of cultural attitudes (organization,

professional society, national) on decision-making, clarifying causal relationship

Socio-technical structure to control risks

International comparative study

For better decision-making & risk management

Future actions?


.thank you for your attention

Supplementary slides


Why 11 out of 14 NPPs along the coastal line affected by Tsunami had escaped from core melt?


1) Tsunami height and

Elevation of facilities

2) Availability of power

a) Offsite power

b) Location of Power

Distribution Equipment

& Battery room

c) Air-cooled EDG

3) Accident Management

using then-available

resources including

availability of resources

Onagawa 1F1-3 1F5-6 2F1-4 Tokai


1. Loss of safety function was caused by SBO (in this case, complete loss of AC/DC power) combined with LHS (loss of heat sink). LOOP (Loss of offsite power) by earthquake* was a part of the cause leading to SBO. However, LOOP itself does not lead to accident, since onsite emergency power sources are installed as backup. In case of Fukushima, flooding (by Tsunami) of Electric Equipment Room in Turbine Building was the cause of SBO, where power from emergency power sources cannot supplied to safety equipments needing power.

*All the 7 offsite power lines to 1F were lost due to failure of breaker, cable damage and collapse of transmission line tower.

Was Fukushima accident triggered by damage caused by Earthquake rather than Tsunami?

2. TEPCO estimates no significant damage was given to systems to perform safety function by earthquake itself, since: 1) Transient response shows no indication of failure of safety-

related systems, 2) Walk-down of similar units found no sign of damage, and3) Seismic response analysis supports no damage to safety systems

would have been given by earthquake

3. The level of acceleration by the 3.11 earthquake was almost the same as design basis. It is know from inspection of damages at KK NPS at earthquake (2007) and of damages at Onagawa NPS at 3.11 earthquake (2011), SSC (Structure/System/Component) at NPS shows robustness against earthquake. In case of KK, even to 2-3 times the magnitude of design basis earthquake.

Nr. MWe 3.11 Observed (max. gal) Design (Ss) (max. gal)

N-S E-W Vertical N-S E-W Vertical

1Fuku1 460 460 447 258 487 489 412

1Fuku2 784 348 550 302 441 438 420

1Fuku3 784 322 507 231 449 441 429

1Fuku4 784 281 319 200 447 445 422

1Fuku5 784 311 548 256 452 452 427

1Fuku6 1100 298 444 244 445 448 415

Comparison of Design Basis and plant response on 3.11 at the Basement of Reactor Building

Reactor Scram by the earthquake Set points : Horizontal=135 gal, Vertical=100 gal

akira omoto.pdf

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