fukushima: swiss action plan - nucleus-qa.iaea.org · strategy for coping with total sbo mobile am...

IAEA Technical Meeting

26-29 August 2013 – N. Cordua (ENSI)

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N. Cordua IAEA Technical Meeting on Evaluation of NPP Design Safety in the Aftermath of the Fukushima Daiichi Accident Vienna, 26-29 August 2013

Fukushima: Swiss Action Plan

Schweizerische Eidgenossenschaft

Confédération suisse

Condederazione Svizzera

Confederaziun svizra

Swiss Federal Nuclear Safety Inspectorate ENSI



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Swiss actions after Fukushima

Immediate measures

Event analyses

Design re-evaluation

Topical inspections

Backfits

Planning

Tracing

Reporting

Feb 2012

Feb 2013



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Immediate measures: Reitnau

External storage

Reitnau

(1. Juni 2011)



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Immediate measures: SFP

External AM-injection for SFP



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Event analysis

Fukushima team published four ENSI-reports

in 2011 about

Causes and consequences of the events

Analyses of the contributory HOF

Lessons Learned and specific checkpoints

radiological consequences

Action Plan



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Key issues 2012 Natural external events

Loss of safety functions

Venting and H2 Management

Emergency preparedness

Safety culture

Operating experience feedback

International activities

Central Emergency Storage Facility Reitnau

Loss of SFP cooling

Total SBO

Seismic and

flooding design



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Loss of SFP cooling

All NPPs

Backfit of alternative level and temperature

instrumentation

External hook-up points

Beznau and Mühleberg NPPs

Backfit of an alternative SFP cooling system

(designed against DBE and DBF)

Hydrogen production in SFPs

Overrated Fukushima issue

Preventive instead of mitigation measures



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Total SBO

Topical inspections (Nov - Dec 2012)

Strategy for coping with total SBO

Mobile AM equipment

AM procedures

Hook-up points

Main inspection findings

Current strategy: adequate

AM procedures: further improvement

Improvements:

○ Personal for mobile equipment

○ Storage and redundancy of mobile equipment



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Seismic and flooding

safety case

Most updated hazard profiles

Loss of offsite power

Affected dams near the plant

Safety case demonstration for 72h without

external help

Earthquake 1E-4/y

Affected SSCs

Dispersion Dose

limit

100 mSv 1 10 100

Frequenz [Hz]

0

0.4

0.8

1.2

Beschle

unig

ung [

g]

NP 1523-hor KKG

NP 1523-x SPI

NP 1523-y SPI

NP 1523-z KKG

NP 1523-z SPI



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Seismic and flooding safety:

conclusions ENSI confirmed that:

analyzed scenarios correct

dose limits observed

Backfits performed

Seismic safety demonstration to be

repeated with final hazard out of the

PEGASOS Refinement Project (PRP)



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Key issues 2013

Natural external events

Increase of safety margins

Hydrogen Management

Severe accident management

Emergency preparedness

EU stress tests’ follow-up

Operating experience feedback



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Increase of safety margins

Analysis of EU-stresstest will be extended

for all shutdown paths

External (earthquake, flooding, etc.) and

internal events (flooding, fire, etc.) with high

probabilistic importance will be reassessed.

International study of safety improvements

Definition of requirements for accident

management equipment (quality, testing,

redundancy, storage etc.)



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Hydrogen Management

Review of robustness and scope of

measuring equipment in connection with

the assessment of the H2 hazard

Updating of analyses regarding the H2

hazard and investigation of the propagation

of hydrogen from the containment into other

nuclear power plant buildings

Review of the measures and procedures in

place for protection against the H2 hazard

Review of the containment venting path in

respect of the H2 hazard.



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Schedule: Fukushima actions

2011 2012 2013 2014 2015 2016 2017 Actions

Reitnau

Flooding

Earthquakes

Extreme weather

Ext. hookup points

SFP-Instrument.

Add. SFP cooling

Diverse UHS

Licensees ENSI

KKM

KKM incl. LTO KKB



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International actions

EU stress tests (incl. Follow-up)

IAEA IRRS Mission at ENSI’s

(Nov-Dec 2011)

IAEA action plan

IAEA OSART Mission at Mühleberg-KKW

(October 2012)

WENRA

5 new Technical Working Groups

Update of Reference Levels



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Operators & Regulators

National Progress Reports

Operators & Regulators

Final

National Reports

Peers

Country Reports

xxxxxxxxxxxx

Peers

Peer Review

Summary Report

European Commission

Report to the European Council

EU stress tests and follow-up

31

.12

.20

11

31.12.2012

Peers

Additional site visits

xxxx

Regulators

National Action Plan

Peers

Peer Review

Workshop

WENRA Technical Groups 3

1.0

3.2

01

2

30.0

4.2

012

26.04.2013



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Fukushima actions: insights

Nuclear safety is a process of continuous

improvements enshrined in the Swiss law

Safety case for the Swiss NPPs:

State-of-the-art hazards

State-of-the-art det. and prob. analyses

Compliance with regulatory requirements

Margins are available

Several backfits implemented resp. on-going



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Thank you for listening!

Any questions

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