Safety Challenges for New NPP A. Viktorov, Canadian Nuclear Safety - - PowerPoint PPT Presentation

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Canadian Regulatory Perspective on Safety Challenges for New NPP

• A. Viktorov,

Canadian Nuclear Safety Commission IAEA Technical Meeting June 22-26, 2015

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How this presentation works..

• 1. CNSC outline
• 2. Preparation for new build in Canada
• 3. Canadian requirements related to the TM scope
• 4. Special case – small reactors

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• 1. Canadian Nuclear Safety Commission
• Established May 2000, under the

Nuclear Safety and Control Act

• Replaced the AECB, established in

1946, under the Atomic Energy Control Act

• The CNSC regulates all nuclear-

related facilities and activities

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• 1. Our Mission

To protect the health, safety and security of persons and the environment; and to implement Canada’s international commitments on the peaceful use of nuclear energy To disseminate objective scientific, technical and regulatory information to the public concerning the activities of the Commission and the effects on the environment and on the health and safety of persons

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• 1. CNSC Core Activities
• Develop regulatory framework
• Carry out licensing and certification
• Assess baseline compliance
• Support Canada's international
• bligations
• Engage stakeholders through public

hearings and consultations

Commitment to continuous improvement

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• 2. Preparation for New Build
• Site preparation licence

issued in August 2012 for Darlington B

• Technology not specified

– But several specific reactor designs considered

• Decision is contested in

courts

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Act Regulations Licences, Certificates, Licence Conditions and Orders

Requirements “must meet” Enabling Legislation

Requirements Guidance

• 2. Mature regulatory framework for new NPP
• Most of regulatory

documents for nuclear power reactors updated recently

• Coherent approach for

all nuclear facilities

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• 2. CNSC Licensing Process

Site preparation under Licence to Prepare Site Construction under Licence to Construct

Five stages in the lifecycle of a nuclear facility

Operation under Licence to Operate Decommissioning under Licence to Decommission Release from licensing under Licence to Abandon

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• 2. Licensing process independent of reactor

technology or size

• Estimated licensing time

~ 9 years from the initial trigger to the

• perating licence
• In addition to design and
• perational requirements, guides

explain the licensing process in Canada

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• 2. Vendor Design Review - test of readiness
• VDR is a high level review of design to evaluate whether there

are fundamental barriers to licensing in Canada

– Tool to determine whether the vendor is ready for potential deployment in Canada – Standardized process – Requires design to be essentially complete

• Outcomes help the vendor have discussions with potential

customers and the regulator on the path forward

• Vendor Design Review is optional and not part of licensing

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• 2. Vendor Design Review outcomes
• Several designs have gone through the all
• r some stages of review – ACR, EC6,

AP1000, EPR, ATMEA

• No fundamental barriers for licensing of

considered designs in Canada

– That is, no safety challenges that could not be resolved based on the current knowledge and technology

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• 2. VDR – examples of potential challenges
• Reflection of lessons learned from the Fukushima Daiichi accident
• Beyond Design Basis Accidents (BDBA) and Severe Accidents (SA)

prevention and mitigation

• Classification of Structures, Systems and Components
• Application of Single Failure Criteria
• Containment Leak Rate and Filtered Venting provisions
• Robustness against malevolent acts, physical and cyber security
• Digital control systems, sharing of instrumentation and measurements

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• 2. Being prepared for safety challenges
• New reactors would not be licensed for construction with any

substantive safety issues outstanding

• Substantive issues – are those which may require multi-year effort to

achieve satisfactory resolution

• Regulatory requirements and acceptance criteria should be

developed in anticipation of substantive issues or safety challenges

• Need to identify potential safety challenges

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• 2. Where challenges lie
• The reactors in Canada are re-licensed every 5 years based on

the outcomes of regulatory assessments

– Reactors are safe to operate – safety challenges are understood

• Safety requirements are in place for new NPP

– at least, for the traditional technologies

• Largest challenges for new NPP are not related to safety but

– Economics – Public acceptance – Regulatory readiness, for novel technologies

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• 3. Emerging safety challenges
• Some safety challenges are relatively novel

– Malevolent acts – Cyber security – Counterfeit, fraudulent or suspect items – Digitalization of plant control – Loss of know-how in countries with established programs – Acquiring expertise, in countries starting to develop nuclear energy

• Not the focus of this discussion

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• 3. Focus on Defence in Depth
• CNSC perspective on Principle of DiD and

– Assessment of DiD – Design Extension Conditions – Emergency Mitigating Equipment – Engagement with IAEA

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IAEA Summary Report on Fukushima Daiichi Accident

• “The defence in depth concept remains valid, but

implementation of the concept needs to be strengthened at all levels by adequate independence, redundancy, diversity and protection against internal and external hazards. There is a need to focus not only on accident prevention, but also on improving mitigation measures.”

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• 3. Three key messages CNSC takes away
• Re-balancing capability for prevention and for mitigation

– Design features to deal with DEC – SAMG – Increased understanding of safety margins in DEC

• Attention to external hazards

– Quantification of site specific hazards – PSA

• Refinement of regulatory requirements

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• 3. CNSC requirements for DiD
• REGDOC-2.5.2, Design of Reactor Facilities: Nuclear Power Plants

– This documents sets requirements for New NPP – Used as guidance in conduct of Periodic Safety Reviews

• Based on IAEA NS-R-2 and SSR-2/1 and reflects Canadian best practices

The concept of defence in depth shall be applied to all organizational, behavioural, and design-related safety and security activities to ensure they are subject to overlapping provisions. The levels of defence in depth shall be independent to the extent practicable.

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• 3. Assessment of DiD
• Guidance on performing a systematic assessment of DiD is given

in IAEA safety reports series No. 46, Assessment of Defence in Depth for Nuclear Power Plants

– Logical and comprehensive approach – Very cumbersome in application

• Effort to strengthen DiD principle should be accompanied by

effort to develop an approach for evaluation

• CNSC currently undertakes a project to develop a simplified

assessment approach

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• 3. Design Extension Conditions
• High level requirements in REGDOC-2.5.2, Design of Reactor

Facilities: Nuclear Power Plants

– The design authority shall identify the set of design-extension conditions (DECs) ... These DECs shall be used to further improve the safety of the NPP by enhancing the plant's capabilities to withstand accidents that are … more severe than DBAs …

• Standard CSA N290.16 will provide more specific requirements

related to BDBA

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• 3. Canadian standard N290.16 (in development)
• Sets Canadian requirements for both existing and new reactors
• Clarifies terminology (for example “BDBA” versus “DEC”)

– Based on the Plant State diagram – next slide

• Describes functional requirements for different types of systems

used in BDBA

• Defines objectives and requirements for analysis and

management of BDBA

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• 3. Plant states, according to CNSC

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• 3. Design principles for DEC
• Design basis not to be compromised
• Features necessary for accident management to be provided
• Containment performance requirements to be specified for DEC
• Complementary design features, fixed and portable

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• 3. Design principles for DEC
• Interfaces / connection points to be designed to the highest

safety class of interfacing systems

• Portable SSC shall have an approved design process and specific

criteria

– Includes inspection, testing and maintenance requirements

• DEC SSC to be assessed for survivability and habitability

– Reasonable confidence in functionality of SSC under harsh conditions

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• 3. Assessment principles for DEC and BDBA
• Objective – evaluate design ability to withstand challenges

posed by DEC, to reasonable degree of confidence

• Use of best estimate method and integration with PSA
• PSA – main, but not the only, source for identification of DEC
• Uncertainties to be considered
• Ongoing hazard assessment, recognizing that site hazard change
• ver time, especially man-made

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• 3. Emergency mitigating (portable) equipment
• Additional features to supplement fixed SSC if needed
• EME is currently provided at, or close to, NPP sites

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• 3. Emergency Mitigating Equipment
• Design requirements for EME to be

developed, supported and documented

– Could be commercial grade

• New NPP could employ the concept
• f additional mobile equipment to

strengthen independence of safety provisions

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• 3. CNSC engagement in refinement of DID concept
• NEA/CNRA STG Green booklet on DiD – final stages of

preparation

• IAEA SSR-2/1 and TECDOC “Considerations on the Application of

the IAEA Safety Requirements for Design of Nuclear Power Plants”

– Active Canadian participation – Few notable differences in interpretation of high level requirements

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• 3. DiD aspects where differences persist
• Definition of Design Basis and cascading effects on

interpretation of Design Basis Accidents, Safety Systems, design and analysis rules, etc

• Splitting of Level 3 of DiD (and/or sometimes Level 4)
• Place of DEC relative to the Design Basis
• Scope of events included in DEC

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• 3. Design Basis vs Design Extension
• In Canadian framework, DB and DEC are distinct part of the
• verall “Plant Design Envelope”
• Different rules apply – less conservative for DEC
• Bringing some DEC (no significant core damage) into level 3 DiD

creates confusion by having different rules within same level

• Having DEC in levels 3a and 4 requires independent two sets of

independent equipment for DEC

• Consideration of DEC as part of Design Basis along with DBA

leads to confusion in terminology

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• 4. Small Modular Reactors

Stress-test of the regulatory framework, including identification and resolution of safety challenges

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• 4. What makes SMR different
• Large variety of technologies

– Loop-based, integrated or pool-type LWR – Sodium, lead, gas cooled

• Novel features

– Factory fuelled – Remote operation

• Features may challenge existing licensing approaches

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• 4. “SMR” safety requirements
• Requirements should be founded on well-understood,

technology neutral scientific bases

• Risk-informing specific requirements is inevitable given the wide

variety of SMR

• Graded application of requirements under different

circumstances and risk scenarios becomes essential

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• 4. Example: autonomous operation of reactors
• Technology allows remote operatoin of a facility, but needed:

– better understand the state of the art and its safety case – examine public acceptability (i.e. develop a position and plan to show how confidence will be developed) – review existing requirements, codes and standards for applicability – assess whether any additional requirements (i.e., security, human factors, emergency response, etc) needed – understand sensitivity to external hazards

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• 5. To sum up
• Canada is actively involved with IAEA in development of

requirements and guides

• Canada cooperates with several international frameworks

examining challenges that future NPP will face

– MDEP – SMR regulatory forum – INPRO – Gen IV Forum

• Early identification of potential challenges and common

approach helps resolution

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• 5. To sum up – readiness for New NPP
• Canadian regulatory framework has been updated and ready to

face challenges posed by new nuclear construction

• Level of safety already achieved by the current NPP is high but
• pportunities exist for safety improvements

– Safety is not the biggest challenge

• New technologies are likely to bring novel challenges

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nuclearsafety.gc.ca

Questions are welcome