Strengthening Nuclear Safety in Canada:

Post Fukushima Strategies

1

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!