iaea technical meeting on evaluation of nuclear power plant … · 2013-08-29 ·...

nuclearsafety.gc.ca

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Implications of the Fukushima Daiichi Accidents for the New Builds Design Requirements in Canada

R.P. Rulko (Canadian Nuclear Safety Commission)

IAEA Technical Meeting on

Evaluation of Nuclear Power Plant Design Safety in the Aftermath of the Fukushima Daiichi Accident

Vienna, Austria, 26—29 August 2103

2 Canadian Nuclear Safety Commission

Outline:

• Fukushima Feedback - Background

• Fukushima Feedback and New Builds Design Requirements

• New Builds Vendor Design Assessment

• Vendor Design Assessment - Fukushima Feedback

• Conclusions


Fukushima Feedback - Background

• CNSC has issued its Fukushima report – posted on the CNSC website on October 28, 2011

• Main emphasis on:

Capability of Canadian NPPs to withstand conditions similar to those that triggered the Fukushima nuclear accident

Emergency preparedness and response in Canada

Effectiveness of the CNSC regulatory framework

• Implications for New Builds design requirements


Fukushima Feedback - Background

• Main Conclusion: The report makes 13 recommendations to further enhance the safety of

nuclear power plants in Canada

• 13 recommendation were divided into TWO categories: Technical and operational recommendations: design and operational

enhancements that strengthen reactor defense in depth and technical cooperation at the international level to be implemented through existing regulatory oversight operations

Regulatory recommendations, which require Commission approval to amend the regulatory framework (new requirements in RD-337, Design of Nuclear Power Plants) and Commission approval and direction to enhance emergency preparedness. Implementation will be through revised priorities by CNSC staff.


Fukushima Feedback and New Builds Design

Requirements

• REGDOC-2.5.2, Design of Reactor Facilities: Nuclear Power Plants (replaces RD-337) has been drafted to:

Update requirements for the design of new water-cooled NPPs

Implement findings from the Fukushima Task Force Report

Provide guidance to licensees in understanding and complying with requirements

• Intended to assist applicants, licensees and reactor vendors in their design activities and preparations for potential construction of new NPPs, and CNSC staff with their review of applications to construct new NPPs


Fukushima Feedback and New Builds Design Requirements

• REGDOC-2.5.2 implements Fukushima Recommendations:

Improved requirements for spent fuel storage

New requirements for portable equipment for use during emergency situations, including:

Redundant connection points to provide water and electrical power in severe accident situations

Setting the time for which the plant must be self-sufficient without mobile equipment

More comprehensive coverage for design extension conditions (DEC)



• DECs are a subset of beyond-design-basis accidents (BDBAs) that are considered in the design process of the facility

Releases of radioactive material must be kept within acceptable limits

• A DEC is an unlikely event and may include fuel melt

An extended loss of AC electrical power is an example of a DEC



• DECs are a subset of BDBAs, specifically those BDBAs considered in the design

In version 1 of RD-337, DECs were referred to using

terminology such as ‘selected BDBAs’

DECs do not extend the design basis – the conservative rules that address design basis accidents continue to apply but only inside the design basis



• Complementary design features are components in the design of NPPs that are necessary to address DECs:

Different design requirements than those features considered for

design-basis accidents (DBAs)

• Examples of complementary design features: Provisions to cool core debris

Provisions to remain in a safe shutdown state to prevent criticality

Recombiners and igniters for hydrogen control

Provisions to preclude unfiltered releases

In-vessel retention or core catcher to retain the core debris

An alternate AC power supply or an alternative water supply

• Complementary design features are classified relative to their safety significance


New Builds Vendor Design Assessment

• Voluntary Pre-Licensing 3 step process:

Phase 1: Assessment of compliance with regulatory requirements to confirm that the design intent complies with CNSC design requirements (RD-337, RD-367), and related regulatory requirements

Phase 2: Identification of potential fundamental barriers to licensing the reactor design in Canada

Secondary objectives of Phase 2 review:

Significant level of assurance that vendor has taken CNSC design requirements

into account Attention on new design features & approaches (to ensure that adequate testing

& analysis were performed or are planned) Attention on successful resolution of generic and outstanding safety issues

• Phase 3: Pre-construction follow-up on one or more focus areas covered in Phase 1 and 2. Vendor’s anticipated goal is to avoid a detailed revisit by CNSC during the review of the construction licence application

• Construction License Application detailed review

11 Canadian Nuclear Safety Commission 11 11


High-Priority Topic

# Focus Topic

1 General NPP Description, Defense-in-Depth, Safety Goals, Dose Acceptance Criteria

2 Classification of Structures, Systems & Components

3 Nuclear Design of Reactor Core

4 Fuel Design & Qualification

5 Control Systems & Facilities

6 Means of Reactor Shutdown

7 Emergency Core Cooling & Emergency Heat Removal Systems

8 Containment & Civil Structures Important to Safety

9 BDBAs & Severe Accident Prevention & Mitigation

10 Safety Analysis

12 Canadian Nuclear Safety Commission 12 12


# Focus Topic

11 Pressure Boundary

12 Fire Protection

13 Radiation Protection

14 Out-of-Core Criticality

15 Robustness & Seismic Issues

16 Safeguards & Security

17 Vendor R&D Programs

18 Management System of Design Process & Quality Assurance in Design & Safety Analysis

19 Human Factors

20 Incorporation of Decommissioning Design Considerations


Vendor Design Assessment - Fukushima Feedback

• Three vendor design pre-project reviews carried out to date: EC6 (Phase 3), AP1000 (Phase 2) and ATMEA (Phase 1)

• CNSC added an extra “special topic” on Fukushima lessons learnt to the standard set of 20 review topics

• CNSC provided to vendors the CNSC Fukushima Task Force report

• CNSC Fukushima Task Force report conclusions have been added to the new version of RD-337 regulatory doc on design requirements for new NPPs – REGDOC 2.5.2

• CNSC review of all three designs’ features relevant to the Fukushima Task Force report conclusions is positive at the level of reviews



• Scope of verification of design provisions:

Relief capability for degasser condenser (CANDU specific)

Relief capability for calandria vessel (CANDU specific)

Protection of containment and prevention of unfiltered releases

Provision of passive autocatalytic recombiners (PAR)

Provision of Hydrogen mitigation for spent fuel pool

Assessment of spent fuel bay integrity

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

Survivability of equipment for severe accident

Habitability of control facilities

Electrical power supplies: batteries, additional generators

Emergency equipment



• Scope of evaluation of external hazards, Sever Accident Management (SAM) and modeling:

External hazards design provisions for severe events (e.g. seismically induced fires and floods, robustness of spent fuel pools under seismic events, external floods, tornados, extreme weather, industrial accidents)

Provision of Severe Accident Management Guidelines for spent fuel pool and multi-unit NPPs

Provision of severe accident modelling capability for multi-unit sites



• Scope of evaluation of equipment for emergency situations:

Provision of portable equipment

Provision of makeup water pumps (SG, calandria, shield tanks, spent fuel pools, vault coolers)

Provision of portable generators/batteries to power critical equipment

Provision of hoses, cables, manifolds

Verification that plant design facilitates multiple connections

Provision of storage facilities

Deployment procedures and practices

Maintenance and testing programs



• Scope of evaluation of design provisions for protecting containment:

Hydrogen hazards (provision of PAR, provision of igniters at

multi-unit plants)

Venting (dedicated venting for severe accident conditions)

Cooling (provision of cooling water to air-coolers)

Modelling (multi-unit containment model)



• Scope of evaluation of design provisions for spent fuel pools:

Confirmation of structural strength

thermal stress analysis (boiling of water)

seismic robustness (Review Level Earthquake of 10,000 y)

Consideration of need to install PAR

Provision of SAM to events in spent fuel pool


Conclusions

• Canada has analyzed in-depth the Fukushima accident and determined its implications not only for the operating but also the New Builds

• The existing regulatory framework was updated to include the new design requirement for the New Builds – draft REGDOC 2.5.2

• Recently conducted pre-project vendor design reviews of the three technologies (EC-6, AP1000, ATMEA) included the special review topic of the Fukushima and assessed the proposed designs according to the updated requirements

iaea technical meeting on evaluation of nuclear power plant … · 2013-08-29 ·...

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