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17th TWG-LWR and 13 th TWG-HWRIAEA Headquarters, Vienna, Austria

18 - 20 June 2012

Katsumi YamadaNuclear Power Technology Development Section

Division of Nuclear Power

Summary of CM on “Applying Lessons Learned from the Fukushima Accident to

WCR Technology Development” and Proposal for Next Steps

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International Atomic Energy Agency2

• IAEA HQs, 23 - 26 April 2012;• Attended by 8 consultants and 11 IAEA staff members ;• The first step for

Action12 “Effectivelyutilize R&D” inthe IAEA Action Planon Nuclear Safety;

• To share informationand discuss LessonsLearned; and

• Suggestions for IAEAactivities.

Consultants Meeting on “Applying Lessons Learned from the Fukushima

Accident to WCR Technology Development”

International Atomic Energy Agency

Background

• The Great East Japan Earthquake has highlighted a number of challenges to Nuclear Power Plants, especially those caused by external events;

• Several reports have been published by various organizations to discuss the cause and sequences of the accident at Fukushima Daiichi and to learn lessons from the accident; and

• It is strongly required to apply the lessons to existing and future NPPs and to enhance their tolerance to severe external events.

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Goal

• To share information on and assessment of the Fukushima accident; and

• To discuss the lessons to apply to WCR technology development.

Ultimately, to develop WCR technologies by applying Lessons Learned from the Fukushima accident.

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Specific Tasks� Share information on actions which MSs have

taken or are going to take against events similar to Fukushima Accident;

� Share information on and an assessment of Fukushima Accident based on the interim report of the Investigation Committee of Japan;

� Discuss Lessons Learned from the accident and how to apply them to WCR technology development; and

� Discuss international collaboration for applying Lessons Learned to WCR technology development and roles of the IAEA.

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Work Done (0/4)

�Organize lessons and recommendations in various reports into a table and provide it to the consultants in advance of the meeting:

Scientific Secretary � created a comprehensive and concise table of

Lessons Learned from Fukushima Accident; and

� sent the Integrated Lessons Learned Table to the consultants for their reference one week before the meeting.

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Integration of Lessons Learned

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Strengthen measures against extreme external events and subsequent events

Findings

Lessons orRecommendations

IntegratedLessons

Categories Design and Siting

…….

…...


Work Done (1/4)

� Share information on actions which the IAEA and MSs have taken or are going to take against events similar to the Fukushima accident:

� The IAEA introduced its activities on Fukushima Accident; and

� Consultants made presentations on post-accident situations and actions in their countries.

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Work Done (2/4)

� Share information on and an assessment of the Fukushima accident based on the interim report of the Investigation Committee of the Japanese Government (Government Committee);

� Prof. Koshizuka, the University of Tokyo, made a presentation to describe the causes, responses and assessment of the Fukushima accident to provide the factual basis for the discussion of lessons learned from the accident.

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Work Done (3/4)

�Discuss Lessons Learned from the accident and how to apply them to WCR technology development;

� Consultants discussed Lessons Learned from the Fukushima accident and elaborated their own lessons mainly from the technical points of view; and

� The lessons were incorporated into the Integrated Lessons Learned table and checked that there were no major discrepancies.

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External Hazards:There is a need to ensure that in considering external natural hazards: • the siting and design of nuclear plants should include sufficient protection against infrequent and complex combinations of external events and these should be considered in the plant safety analysis – specifically those that can cause site flooding and which may have longer term impacts; • plant layout should be based on maintaining a ‘dry site concept’, where practicable, as a defence-in-depth measure against site flooding as well as physical separation and diversity of critical safety systems; • common cause failure should be particularly considered for multiple unit sites and multiple sites, and for independent unit recovery options, utilizing all on-site resources should be provided; • any changes in external hazards or understanding of them should be periodically reviewed for their impact on the current plant configuration; and • an active tsunami warning system should be established with the provision for immediate operator action.

IAEALesson 1

Strengthen measures against earthquakes and tsunamis:we will consider the handling of plurally linked seismic centers as well as the strengthening of the quake resistance of external power supplies. Regarding tsunamis, from the viewpoint of preventing a severe accident, we will assume appropriate frequency and adequate height of tsunamis in consideration of a sufficient recurrence period for attaining a safety goal. Then, we will perform a safety design of structures, etc. to prevent the impact of flooding of the site caused by tsunamis of adequately assumed heights, in consideration of the destructive power of tsunamis. While fully recognizing a possible risk caused by the flooding into buildings of tsunamis exceeding the ones assumed in design, we will take measures from the viewpoint of having defenses-in-depth, to sustain the important safety functions by considering flooded

JapaneseGovernment

Lesson 1

CategoryIntegrated Lessons Learned/ CM Lessons (April 2012)

1.1 Strengthen measures against extreme external events and subsequent events- Excess of design basis earthquake did not cause any known significant damage- Design basis tsunami height is less than actual- Extensive tsunami and explosion damage and debris created significant logistical difficulties and inhibited response actions- Over-conservatism over earthquakes led to under-conservatism for tsunamis (Location of emergency D/Gs)- Repeated earthquakes and tsunami threats stopped work on occasions

[Note] Positive lessons Negative lessons Neutral lessons

Individual Lessons Learned and Recommendations

Sources1.

Des

ign

and

siti

ng

Lessons Learned Table

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Work Done (4/4)

�Discuss international collaboration for applying the lessons to WCR technology development and roles of the IAEA;

� Consultants discussed the key functions for nuclear safety deteriorated in the accident and possible technology developments based on the lessons; and

� Consultants elaborated a list of highly prioritized activities in which the IAEA should take the lead.

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Highly Prioritized IAEA Activities1. Japanese led international collaborative efforts on

plan for collection and analysis of Fukushima datato gain insights on BWR accident progression => CRPs

2. International information exchange meeting relat edto the different actions taken to manage theaccident and their effectiveness => Technical Meeting(s) / Workshop(s)

3. Definition and treatment of additional class ofprobabilistically negligible, but physically realiz ableevents that have extremely detrimental effects=> Guidelines

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Highly Prioritized IAEA Activities(continued)

4. Technical and managerial control of plant under severe accident/disaster conditions=> Guidelines

5. Means and assurance of containment cooling andheat rejection to UHS following severe accidents=> CRP

6. Filtered containment venting, effectiveness andimpact on evacuation=> CRP

7. Hardened, reliable instrumentation => CRP

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Outputs

• A table of Lessons Learned from the Fukushima accident to apply to WCR technology development; and

• A list of suggestions for international collaborative activities in which the IAEA should take the lead.

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Proposal for Next Steps- Project Scope -

• Project Title: “Analyses of WCR Technologies to Cope withFukushima-type Accidents”

• Scope:

Analyse and assimilate information on:

– technologies to cope with Fukushima-type accidents, including those already proven and under R&D; and

– their assessment of the features, effectiveness and challenges in the light of the Fukushima Daiichi nuclear accident.

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Proposal for Next Steps- Main Activities -

• Technical Meeting (@Tokyo, May 2013)– to collect, share and discuss information on the

technologies to prevent and/or mitigate severe accidents among experts and designers

• Workshop (@Vienna, November 2013)– to disseminate the information on technologies

to cope with Fukushima-type accidents and their effectiveness

• Preparatory and Follow-up CMs

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Proposal for Next Steps- Topics -

• Design and siting to prevent and/or mitigate Fukushima-type accidents:– Measures against extreme external events and subsequence events;– Measures to prevent and/or mitigate hydrogen explosions;– Containment venting system;– Design of safety-related structures, systems and components; and– Consideration on design and siting of multi-unit sites.

• Emergency preparedness and response:– On-site emergency response facilities, equipment and procedures;– Reliable on-site and off-site electricity supplies; and– Off-site infrastructure resilience.

• Effective utilization of PRA methodologies to prevent severe accidents:– Risk assessment and management with PRA; and– Consideration on beyond design basis events.

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Proposal for Next Steps- Expected Outputs -

• Sharing of experiences and identifying lessons learned on system performance and improvement to address Fukushima-type accidents;

• Sharing of information on technologies to cope with Fukushima-type accidents and their assessment; and

• Technical documents to disseminate the information to all Member States.

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Highly Prioritized IAEA Activities1. Japanese led international collaborative efforts on

plan for collection and analysis of Fukushima datato gain insights on BWR accident progression => CRP (?)

2. International information exchange meeting relat edto the different actions taken to manage theaccident and their effectiveness => Technical Meeting(s) / Workshop(s)

3. Definition and treatment of additional class ofprobabilistically negligible, but physically realiz ableevents that have extremely detrimental effects=> Guidelines

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Highly Prioritized IAEA Activities(continued)

4. Technical and managerial control of plant under severe accident/disaster conditions=> Guidelines

5. Means and assurance of containment cooling andheat rejection to UHS following severe accidents=> CRP

6. Filtered containment venting, effectiveness andimpact on evacuation=> CRP

7. Hardened, reliable instrumentation => CRP

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…Thank you for your attention!

e-mail: [email protected]

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