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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
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Short Term Actions after
Fukushima Accident: Regulatory
• 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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Short Term Actions after
Fukushima Accident: Regulatory
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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Short Term Actions after
Fukushima Accident: Regulatory
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Short Term Actions after
Fukushima Accident: Regulatory
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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Short Term Actions after
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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Short Term Actions after
Fukushima Accident: Operators
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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Short Term Actions after
Fukushima Accident: Operators
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
Development/Deployment
Containment Filtered Venting System;
evaluated as part of refurbishment for
events beyond the original plant
design basis
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New Technology
Development/Deployment
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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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
Within approx. 24 months:
– 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
Within approx. 48 months:
– 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
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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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