ML16088A245

BVPS HRA Dependency Public Meeting - Overview Final

ML16088A245
Person / Time
Site:	Beaver Valley
Issue date:	03/28/2016
From:	Lamb T A Plant Licensing Branch 1
To:
Lamb T A, NRR/DORL/LPLI-2
References
Download: ML16088A245 (1)

Text

BVPS Joint HEP Discussion with NRC Summarize BVPS understanding of RAI o NRC is looking for adequate justification that the BVPS quantitative fire risk estimates exclude the impact of unrealistically low joint HEPs Describe BVPS approach to HRA dependency analysis o Approach follows established NFPA 805 RISKMAN process BVPS model did not translate full sequence results into minimal CDF/LERF cutsets Demonstrate that minimal CDF/LERF cutsets and full CDF/LERF sequences produce the same result, at different levels of detail Non-consequential elements of CDF/LERF sequences do not affect the total quantitative risk estimate, when quantification accounts for both failure and success terms When full CDF/LERF sequences are evaluated for dependency, minimal CDF/LERF cutsets are inherently included o All possible combinations of HEP pairs are identified from sequences and reviewed for dependency Demonstrate that accident sequence context is inherent in human action basic events (and therefore available in individual pair

-wise evaluations), since actions which may be affected by accident context are actually represented by different basic events for different contexts o Pair-wise evaluations are then applied to the longer sequence strings of joint HEPs to determine which are potentially dependent Potentially dependent joint HEPs are recorded in the dependency analyses and examined further Demonstrate that BVPS FPRA models account for HEP dependency in the construction of the model Specific details of BVPS model quantification o Compare against 1E

-05 floor Conclusion is that dependent joint HEPs are above 1E

-05 Joint HEPs below 1E

-05 are specifically justified as zero

-dependent Clarify previous RAI responses o Provided full range of values for full non-minimal CDF/LERF sequence joint HEPs Demonstrate that these values do not equate to minimal CDF/LERF cutset joint HEP values o Translate example from 2 nd round RAI response into minimal CDF cutset to show what the number would be Demonstrate justification of zero dependence in the resulting joint HEP Discuss examples of other, dependent joint HEPs in the model

BVPS Joint HEP Discussion with NRC Summarize BVPS understanding of RAI o NRC is looking for adequate justification that the BVPS quantitative fire risk estimates exclude the impact of unrealistically low joint HEPs Describe BVPS approach to HRA dependency analysis o Approach follows established NFPA 805 RISKMAN process BVPS model did not translate full sequence results into minimal CDF/LERF cutsets Demonstrate that minimal CDF/LERF cutsets and full CDF/LERF sequences produce the same result, at different levels of detail Non-consequential elements of CDF/LERF sequences do not affect the total quantitative risk estimate, when quantification accounts for both failure and success terms When full CDF/LERF sequences are evaluated for dependency, minimal CDF/LERF cutsets are inherently included o All possible combinations of HEP pairs are identified from sequences and reviewed for dependency Demonstrate that accident sequence context is inherent in human action basic events (and therefore available in individual pair

-wise evaluations), since actions which may be affected by accident context are actually represented by different basic events for different contexts o Pair-wise evaluations are then applied to the longer sequence strings of joint HEPs to determine which are potentially dependent Potentially dependent joint HEPs are recorded in the dependency analyses and examined further Demonstrate that BVPS FPRA models account for HEP dependency in the construction of the model Specific details of BVPS model quantification o Compare against 1E

-05 floor Conclusion is that dependent joint HEPs are above 1E

-05 Joint HEPs below 1E

-05 are specifically justified as zero

-dependent Clarify previous RAI responses o Provided full range of values for full non-minimal CDF/LERF sequence joint HEPs Demonstrate that these values do not equate to minimal CDF/LERF cutset joint HEP values o Translate example from 2 nd round RAI response into minimal CDF cutset to show what the number would be Demonstrate justification of zero dependence in the resulting joint HEP Discuss examples of other, dependent joint HEPs in the model