post-fukushima actions in canada case re-examination and making ... regulatory comments on ......

AECL - OFFICIAL USE ONLY / À USAGE EXCLUSIF - EACL

Post-Fukushima Actions

in Canada

TWG-LWR and TWG-HWR Meetings

Joanne Ball

2013 June 18-20

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Short Term Actions after

Fukushima Accident: Regulatory

• CNSC (Canadian Nuclear Safety Commission) coordinated

Government of Canada response

– Domestic:

– Provided information to public, activated Emergency Operations Centre

and worked closely with other federal and provincial governments

– Internationally:

– Established links with USA, UK, FRA regulators for information exchange

and validation

– Provided experts to support the IAEA (from CNSC and AECL)

– Public communication – supplied comprehensive information from

international regulators, IAEA etc.

• CNSC key actions:

13 Mar 2011 site inspectors verified availability of key equipment

17 Mar 2011 requested to all Canadian NPP licensees to review initial

lessons learned & re-examine Safety Cases




• CNSC Task Force convened on 19th April 2011

–review criteria – to ensure that identified elements are accounted for in the reactor safety

cases and credible protective provisions have been put in place

–review elements – external hazards

– design basis accidents

– beyond design basis accidents

– accident management

– emergency measures

– regulatory framework and processes

28 Oct 2011 CNSC Fukushima Task Force Report issued

(INFO-0824) documenting review of licensees

safety case re-examination and making

recommendations

02 Mar 2012 CNSC Action Plan (INFO-0828) based on

recommendations of Task Force Report

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CNSC Recommendations to strengthen

defence-in-depth

1.0 Licensees should systematically verify the effectiveness

of, and supplement where appropriate, the existing

plant design capabilities in beyond-design-basis

accident and severe accident conditions

2.0 Licensees should conduct more comprehensive

assessments of site-specific external hazards

3.0 Licensees should enhance their modelling capabilities

and conduct systematic analyses of beyond-design-

basis accidents


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Timeline for Actions

• Many actions to be completed by end of 2012

• Majority of actions to be completed by end of

2013

• Complex actions to be completed by end of

2014 or 2015 – periodic updates on the status of activities

• Follow-up station-specific activities and

implementation of design enhancements will

take longer – to be monitored through regular compliance processes


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IRRS Mission Findings

• The CNSC‟s response was prompt, robust and

comprehensive

• Identified by the Integrated Regulatory Review Service

(IRRS) mission as a good practice that should be used

other regulatory bodies


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Short Term Actions after Fukushima Accident

Task Force Findings

• Canadian nuclear power plants are safe

and pose a very small risk to the health and

safety of Canadians or to the environment – design ensures no impact from external events that are regarded

as credible

– design offers protection against more severe external events that

are much less likely to occur

• Recommended improvements will further

enhance the safety of nuclear power in

Canada and will reduce the associated risk

to as low as reasonably practicable


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Fukushima Accident: Operators

• NPP operators required to respond to

CNSC and WANO recommendations – CANDU Industry Integration Team (CIIT) was

established

– AECL provided design assessment input to the team,

as well as to individual stations, including input to the

Romania Cernavoda plant, in response to European

regulator stress tests

– The CIIT developed a coordinated response to the

CNSC and WANO SOER-2011- 02 – „Fukushima

Daiichi Nuclear Station Fuel Damage Caused by

Earthquake and Tsunami‟


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Seismic • Design Basis for existing

plants: – Older Plants: Building Code

– Newer Plants: • 1,000 year recurrence interval

• 1980s knowledge of seismic

hazard

• Review Level Condition (RLC): – 10,000 year recurrence

– 2011 Seismic Hazard

• Results for for plants that have

completed assessment: – Plants seismically robust for an event

with 10,000 year recurrence interval


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Other External Hazards

• Applied methodology for

Screening External Hazards – Based on IAEA guidance

– Accepted by CNSC

• For specific hazards of

interest, “Review Level

Conditions” (RLC) were

established to assess

adequacy of current defences

• Confirm no cliff-edge effects


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Short Term Actions after Fukushima Accident:

National Research Universal Reactor

• Conclusions of review:

–No significant gaps found during the review of the safety cases for the

facilities at Chalk River Laboratories

–Only NRU requires immediate mitigation following a BDBA and that

equipment and processes are in place to do so

– NRU Rod bays and storage block after days/weeks

–Remaining CRL facilities reviewed do not require immediate mitigation

– the ability to cool nuclear fuel is not required

– no reliance on powered systems to remain safe

• Some generic and NRU-specific improvement areas identified

• Being addressed through an integrated implementation plan (e.g. Seismic

Re-assessment, Mobile Equipment, SAMG, Access) – This is currently an

NRU/CRL (2011-2016) license condition!


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Short Term Actions after Fukushima Accident:

Response to Regulatory Recommendations


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Technologies Adopted before

the Fukushima Accident

• Passive fuel cooling through

Steam Generators – Dousing Water System – C6 (>2,000 Mg)

– Dearator

• Additional sources for

passive fuel cooling: – Moderator System (>240 Mg)

– Shield Cooling System (>500 Mg)


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Technologies Adopted before the Fukushima

Accident: Enhancing Existing Design Capabilities

Leverage inherent design features unique to

Candu:

• Steam generators (SG) depressurized from MCR

within 40m – Enables gravity addition of water to steam generators

– Establishes a source of passive fuel cooling for at least 8h

– Provides time to setup portable diesel pumps to maintain flow

to SGs

• Emergency Mitigation Equipment (EME) for alternate

cooling to SG – Portable diesel driven pumps and generators

– Multiple different addition points from multiple locations

– “Plug-and-play”

– Portable crane to remove debris

– Stored on-site outside protected area

– Will also provide alternate water supply to spent fuel pools

• 700 Mg of water surrounding the fuel provides >24h

before corium exits vessel – Calandria Vault / Shield Tank over-pressure relief

– Water addition points to moderator and calandria vault / shield

tank to enable connection of portable diesel pumpers


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Regulatory Comments on

Licensees Response

• Licensees‟ responses to date: provided

requisite initial response, identifying proposed

plans and schedule to meet CNSC‟s request

– concluded that overall safety case remains strong

but continue to identify potential improvements

• Accelerated implementation, especially in

severe accident management and emergency

preparedness


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New Technology

Development/Deployment

Accelerated installation of Passive

Autocatalytic Recombiners – for

hydrogen mitigation

Procurement of portable diesel pumps

and generators, in addition to already

installed emergency and

backup equipment

Additional flood barriers

around fuel forwarding

pumps for emergency

generators


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New Technology


Containment Filtered Venting System;

evaluated as part of refurbishment for

events beyond the original plant

design basis


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New Technology


Bruce Power: Emergency Preparedness Services -

Merger of Security and Emergency Measures


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New Technology Development

• Modelling tools for calculating decay heat in spent fuel bays – CANDU Owner‟s Group (industry) initiative

• “Severe Accident Handbook” – Under development by CNSC and AECL – graphical display of NPP to be

used in conjunction with Severe Accident codes to aid in Emergency

Operations Planning

• Severe Accident Experimental Program for Existing

CANDUs and EC-6, – Industry initiatives:

– evaluating calandria vessel integrity and retention under SA conditions (CANDU

specific materials and geometry)

– options for base-mat materials (EC-6).

– extending data base for Passive Autocatalytic Recombiner performance under SA

conditions

– evaluating instrumentation for SA


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New Technology Development

• Regulator concluded no major gaps in knowledge but recommended increased priority of certain R&D increased

– In-vessel (in calandria) retention of core debris – core collapse, corium / calandria interaction, calandria wall CHF

–Post-accident air monitoring system

– concentration of iodine, noble gases and H2 in containment

– Instrumentation for BDBA conditions

– accident conditions and survivability criteria

– evaluation of existing instruments, alternate means of acquiring information

–Assessment of PAR effectiveness

– performance affected by surface contamination

–Participation in OECD/CSNI programs international programs:

– HYMERS (hydrogen mitigation), BIP-2 (iodine). THAI, etc. OECD


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Questions?


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1. External Hazards - Flooding RLC

• Design Basis: historically derived

• Review Level Condition (RLC):

– Probable Maximum Precipitation (PMP) event

for the region – theoretical, not historical

– Concurrent with wave overtopping due to

storm

Actions:

• Barriers installed around backup

generators (Darlington-complete;

Pickering A: Q2 2012)

• Installing water-tight doors to

Secondary Control Area tunnel at

Point Lepreau Flood Barrier Around Darlington EPG Fuel Pump

Fort Calhoun Site Flood Barrier


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Short Term Actions

CNSC Fukushima Task Force Recommendations

Within approx. 12 months:

– Complete Benefit Cost Assessment for containment venting options

– Develop strategy for assessing hydrogen risk

– Complete Benefit Cost Assessment for moderator and shield tank make-up

– Develop industry strategy for instrument survivability under severe accident conditions

– Develop a plan for a Regional Emergency Response Support Centre

– Complete multi-unit modeling options assessments

– Complete fuel bay assessing accidents

– Complete Benefit Cost Assessment to improve margins for overpressure protection


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Long Term Actions after

Fukushima Accident


– Implement Severe Accident Management Guidelines exercise

– Establish a Mutual Assistance Agreement

– Take action to satisfy provincial authorities with respect to dose projection and radiation monitoring


– Complete installation of PARs

– Complete implementation make-up to Steam Generators, Heat Transport System and fuel bays

– Establish back-up power and back-up communications for emergency centre

Oct 18, 2011 – WANO SOER 2011-03 - Fukushima Daiichi Nuclear Station Spent Fuel Pool/Pond Loss of Cooling and Makeup


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Actions after Fukushima Accident

Design Provisions

1.1 Relief capability for degasser condenser (CANDU specific)

1.2 Relief capability for calandria vessel (CANDU specific)

1.3 Protect containment and prevent unfiltered releases

1.4 Install passive autocatalytic recombiners

1.5 Hydrogen mitigation for spent fuel pool

1.6 Spent fuel bay integrity

1.7 Evaluation of make-up: boilers, reactor, spent fuel bay

1.8 Survivability of equipment for severe accident

1.9 Habitability of control facilities

1.10 Electrical power supplies: batteries, additional generators

1.11 Emergency equipment


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Actions after Fukushima Accident

Hazards and Analysis

2.1 Re-evaluation of external hazards

– original design basis did not include severe events

– later studies (e.g. seismic margin assessments) have

extended this

– approach is not uniform across sites or across hazards

2.2 Update of safety analysis

– acceleration of process to perform deterministic safety

analysis to modern requirements RD-310 Safety

Analysis for NPPs


Actions after Fukushima Accident –

SAMGs and Severe Accident Models

3.1 Implementation of Severe Accident

Management Guidelines – acceleration of existing program

– complete and implement SAMGs

– extend to spent fuel pool and multi-unit NPPs

3.2 Severe accident modelling capability for multi-

unit sites – current models are single unit

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