important elements of review and assessment in licensing ... · ansys melcor maccs fluent gale sap...
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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
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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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