Strengthening Nuclear Safety in Canada:
Post Fukushima Strategies
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Fred Dermarkar Ontario Power Generation
Overview of Canadian Industry Response
Public Communication Strategy: immediate,
open, not defensive
Canadian Industry Integration Team (CIIT)
• Domestic and International participation
• Hosted two Emergency Preparedness
workshops: All three levels of
government and Military
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Comprehensive assessments with reports to the CNSC in July 2011
• Confirmed Safety of NPPs; Identified opportunities to further improve
defences for Beyond Design Basis Events
Physical improvements to NPPs have commenced
Continuing implementation of CNSC Task Force Action Plan
Five Key Learning Points 1. Systematically review and verify
defences against external
hazards
2. Increased flexibility to respond
to unexpected events to prevent
fuel damage
3. Severe accident management
(SAM) is a key part of safe
operation
4. Partner with other operators
and with the community to
enhance Emergency Response
capability
5. Regulatory framework aligned
with nuclear safety risk and
enforced through strong
regulatory oversight 3
Fukushima Site
1. 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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1. External Hazards - Seismic RLC
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 plants that have
completed assessment:
• Plants seismically robust for
an event with 10,000 year
recurrence interval
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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
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Actions:
• Barriers installed around backup generators
(Darlington-complete; Pickering A: Q2 2012)
• Installing water-tight doors to Secondary
Control Area tunnel at Point Lepreau
Fort Calhoun Site
Flood Barrier Around Darlington EPG Fuel Pump
1. External Hazards – Tornados & Man-Made Some plants not explicitly designed
for tornados
• Methodology for assessing
tornado hazards under
development
Seismically induced fires and floods
• Methodology under development
in concert with EPRI
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Man-made hazards may change
significantly with time
• Land use surrounding the site
needs to be monitored for
new or changed hazards.
2. Flexibility - Overview of CANDU (Typical)
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• 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)
2. Flexibility - Beyond Design Basis Events
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Design Basis
Beyond Design Basis
Severe
Accidents
Safety Case is well
established and
understood .
Management of DB
Events are integrated well
into Station operation
Some BDB Events have
been considered in the
Safety Case and are
explicitly considered in
the station EOPs.
Bounding Scenario1
used to determine
emergency measures
and equipment to
mitigate accident
progression
SAMG implemented
& being enhanced.
Mitigation measures
are integral to
SAMG
Consequence
Likelihood 1 Total extended loss of AC power, leading to a total
loss of normal heats sinks. Only existing cooling
water inventories are credited. Only station
batteries are credited. This approach is aligned with
the direction from WANO and INPO
2. Flexibility – Strategy to Maintain Cooling Findings:
• 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
• Steam generators proven effective as a passive heat sink
- Narora – 31 March 1993
- Pickering – 14 August 2003
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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
3. SAM - Strategy
Leverage inherent design features
unique to Candu:
• >700 Mg of water surrounding the
fuel provides >24h before corium
exits vessel
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Objective: retain corium in-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
SAM Technical Basis Documents
• Under Revision through the Candu Owners Group (COG)
• Will be used to revise station SAM Guidelines
3. SAM – Activities and Status
Containment Filtered Venting
System
• Installed at 1 NPP
• Committed as part of
upcoming refurbishment of
5 NPPs
• Under review at other
NPPs
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Hydrogen Mitigation
• All utilities are bolstering existing
Hydrogen mitigation measures (such as
H2 igniters) with Passive Autocatalytic
Recombiners (PARS)
• Installation of PARs has been completed
at 6 NPPs and will be completed on all 20
Canadian NPPs by 2015
Summary Canada has responded to the events at
Fukushima with Diligence and Urgency
The Canadian industry has risen to the challenge
• Broad collaboration domestically and
internationally
• One NPP awarded a strength by WANO for
the response
• Several key actions in the CNSC action plan
are already complete
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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.
Summary Reviews performed by the CNSC and the
Industry confirm:
• Canada’s NPPs are safe
• Canada is learning through collaboration
with others
• Canada’s NPPs are developing the
flexibility and capability to respond to
events not previously envisaged
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Canada has embraced the challenge from Jim
Ellis, CEO INPO:
“This is not a time for half-measures. We must improve the
industry we have, and shape the industry we want.”
Thank You!