Important Elements of Review and

Assessment in Licensing of NPPs

Considering Experience Feedback of

Fukushima Accident

Zia H. Shah, DG (CS), PNRA

Technical Meeting on Novel Design and

Safety Principles of NPPs

October 03-06, 2016.

Layout

Revision of PNRA Regulatory Framework

Review & Assessment Process of PNRA

Improvements in Review & Assessment Methodology

Important Elements of Review & Assessment

Conclusion

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3

Pillars of Regulatory Body

REGULATORY FRAMEWORK

4

LAW Ordinance In the form of

Regulations

Regulatory

Guides

Industrial Codes

and Standards

RCC ASME IEEE

Administrative

Technical

Administrative Regulations defines regulatory processes i.e. Licensing process, review and Assessment process, enforcement etc.,

Technical Regulations covers technical aspects i.e. Design requirements, operational requirements, QA requirements, Siting details, etc.,

Needs to be approved by PNRA

Regulatory Framework of PNRA

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PNRA Regulations (1/2)

Regulations for Licensing of Nuclear Installations (PAK/909)

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Regulations for Licensing of Radiation Facilities other than Nuclear

Installations (PAK/908)

Regulations for Licensing of NPP Equipment Manufacturers

(PAK/907)

PNRA Enforcement Regulations (PAK/950)

Administrative Regulations

Regulations on Licensing Fee (PAK/900)

PNRA Regulations (2/2)

Regulations on the Safety of NPP Operation (PAK/913)

Regulations on the Safety of NPP Quality Assurance (PAK/912)

Regulations on Management of a Nuclear or Radiological Emergency

(PAK/914)

Regulations for the Safety of NPP Design (PAK/911)

Regulations on the Safety in NPP Site Evaluation (PAK/910)

Regulations on Radiation Protection (PAK/904)

Regulations on Radioactive Waste Management (PAK/915)

Regulations for the Safe Transport of Radioactive Material (PAK/916)

Regulations for the Licensing of Radiation Facilities other than Nuclear

Installations (PAK/908)

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Technical Regulations

PNRA communicated its regulatory requirements through directive to its licensees to revisit and re‐assess the design and safety features of NPPs in the light of the accident feedback.

PNRA reviewed its regulatory framework in the light of lessons learnt from Fukushima accident so that further improvements can be made in order to cater new areas highlighted from the accident.

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Revision of Regulatory Framework Considering

Feedback of Fukushima Accident (1/2)

Revision of Regulatory Framework Considering

Feedback of Fukushima Accident (2/2)

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Feedback of

Fukushima Accident

Identification of

Regulations that need to be revised

Thorough review of the identified Regulations i.e. Sitting, Design

and Operation of NPP

Providing recommendations on modifications

in the Regulations

Revision of Safety

requirements in

SSR-2/1, SSR-2/2,

NS-R-3

Initiated

Revision of

PNRA

Regulations on

Siting, Design

and Operation

of NPP

Modifications Proposed in Regulations

Following modifications were proposed in Regulations:

Periodic re‐evaluation and re‐assessment of site characteristics.

Strengthening the design basis for the plant for prevention of severe accidents

Introduction of passive design features in the plant systems specially the emergency core cooling systems, Hydrogen recombining systems and spent fuel pool cooling systems.

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REVIEW & ASSESSMENT

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Review & Assessment Process Licensee submissions are received

at NSD for review and assessment (R & A)

Sent to other relevant

Directorate For R&A by licensing directorate

Comments of respective

directorate on submission

Distributed to Subject Specialist / TSO

for R&A

Communicated to licensee through proper

Channel & followed up if needed

Comments by relevant

Subject specialist on submission

Assessment of comments by licensing directorate and

Meeting With subject specialist to finalize draft position

Submission

Complete?

R&A Possible

at licensing directorate?

Approval from

Higher

Management

Criteria/

Regulations

License

Conditions

Inputs from

inspections

Inputs of

consultants

No

Yes

Yes No

Yes

No

IMPORTANT ELEMENTS OF

REVIEW & ASSESSMENT

CONSIDERING EXPERIENCE

FEEDBACK OF FUKUSHIMA

ACCIDENT

Improvements in Review and Assessment

Methodology

Audit

Calculations and

Analysis

Operating

Experience

Feedback

Classic Review

(Based on codes

and standards)

Existing

PNRA

Review and

Assessment

Process

Regulatory

Models

e.g. PSA Model

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Computer Codes Available for Review &

Assessment

RELAP

ANSYS MELCOR MACCS FLUENT

GALE SAP RISK

SPECTRUM CONTAIN

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Important Elements of Review & Assessment

Considering Experience Feedback

A. Assessment of Safety Provisions for Prevention of

Accidents and Mitigation of Consequences

B. Assessment of Passive Safety Features

C. Safety Assessment of Confinements to Ensure

Offsite Releases

A. Assessment of Safety Provisions for

Prevention of Accidents and Mitigation of

Consequences

Deterministic Safety

Analysis (DSA)

• Audit calculations

Probabilistic Safety

Analysis (PSA)

• PSA Model

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Analysis

B. Assessment of Passive Safety Features

(1/2)

• No codes and standards were available for assessment of passive systems.

• Engineering judgment and knowledge based approach used for this assessment.

Performance Based

Assessment

• Integrity based evaluation was carried out as per relevant RCCM codes

Integrity Based Assessment

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B. Assessment of Passive Safety Features

(2/2)

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• Results of proto-type testing were reviewed for independent verification of safety assessment Others

Assessment of Passive safety features

The passive safety features related to decay heat removal e.g. passive residual heat removal on secondary side and passive cavity injection system assessed by the validation tests on experimental facilities and thermal hydraulic analyses. The main issues of design assessment consideration:

• Natural circulation stability during the accident conditions

• Verification of the required function during the mission time (72 hours) i.e. the core decay heat removal

• Scaling laws on experimental facilities to properly represent the actual system

• Verification of results through detailed thermal hydraulic analysis

Assessment of Passive safety features

related to containment heat removal

Passive containment heat removal system: for long term heat removal under beyond DBA conditions, including accidents associated with SBO and spray system failure.

• The startup condition, operational characteristics of system and verification of performance of key equipment

• Assessment of heat removal capability and operational performance of PCS system under the first and the second design conditions were evaluated.

• The first design condition corresponds to the early-stage of accident, and the second design condition corresponds to the long-term stage of accident

• Thermal hydraulic analysis using validated computer codes

Assessment of Hydrogen Recombiners

The passive hydrogen re-combiner is meant to

effectively reduce hydrogen risk. Review and

assessment includes:

• Calculations of hydrogen generation and distribution within the containment to verify the design basis and lay out scheme of hydrogen recombiners.

• To validate the reasonability and effectiveness of the design of containment hydrogen control system

Safety assessment of Confinements

Containment Integrity was assessed by deterministic methods applied in stress analysis/fracture mechanics

• Double containment structure analysis

• Single containment analysis against aircraft loading using ANSYS and SAP

• Two different types of aircraft crash events are considered in the design:

– Beyond design basis aircraft crash event (large commercial aircraft),

– Design basis aircraft crash event (general aircraft).

• Audit calculations regarding Impact Analysis were performed to verify the design details

Areas of Actions in Response to Fukushima

Accident

Fukushima Response

Action Plan

(FRAP)

External natural hazards

Make-shift AC power

D.C. power capacity

Fire protection

and control

Emergency cooling

Hydrogen hazard

Containment integrity

Spent fuel cooling

EOPs, SAMGs

Emergency preparedness (Off-site)

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Conclusion

• Fukushima accident highlighted need for

improvements in wide spectrum of areas that

have been carefully catered by PNRA in its

regulatory processes for granting

authorizations to NPPs

• Assessment of passive safety systems is

part of the overall safety assessment of NPPs

• International experience feedback as

important element to improve effectiveness

of regulatory processes in safety assessment

of nuclear power plants 25

Questions?

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