ML20038A314
| ML20038A314 | |
| Person / Time | |
|---|---|
| Issue date: | 02/07/2020 |
| From: | Tekia Govan NRC/NRR/DRO/IRSB |
| To: | |
| Govan T, NRR/DRO, 415-6197 | |
| References | |
| Download: ML20038A314 (11) | |
Text
Draft Branch Technical Position 7-19, Revision 8 Public Meeting NRC Staff Presentation February 11, 2020
Agenda
- Background on Commissions Common Cause Failure (CCF) Policy
- Key Proposed Changes:
Incorporates the guiding principles from SECY 18-0090 Categorization Scheme and Graded Approach Qualitative Assessment Means to Eliminate CCF from Further Consideration Spurious Operation Assessment Re-structuring of Branch Technical Position (BTP) 2
- SRM-SECY-93-087 presents the Commissions four-point policy on how potential CCFs should be addressed in DI&C systems
- SECY-18-0090 clarifies the application of the Commissions direction in the four positions within SRM-SECY-93-087 Recognizes significant effort has been applied to the development of highly reliable DI&C systems but residual faults within digital systems may lead to CCFs Provides five guiding principles for updating the staffs guidance for addressing CCF Guiding principles were incorporated into draft BTP 7-19, Revision 8 3
Proposed Categorization Scheme and Graded Approach Safety-Related NSR Safety Significant B1 A1 Perform Qualitative Significant Perform D3 Assessment Assessment contributor to plant safety Not Safety Significant A2 B2 Perform Qualitative Not a significant Assessment contributor to plant safety 4
Proposed Qualitative Assessment Framework
- Based upon Supplement 1 to RIS 2002-22, now utilized as part of the graded approach to address CCF
- Evaluate potential CCFs and their effects in A2 and B1 systems (i.e. sufficiently low likelihood of failure)
- For B2 systems, basis for not performing an assessment should be documented 5
Proposed Guidance for Means to Eliminate CCF from Further Consideration
- Diversity - Clarifies guidance for application within the DI&C system or component
- Testing - Clarifies criteria and terminology associated with use of testing to eliminate CCF from further consideration
- Defensive Measures -
Use defensive measures to prevent, limit, or mitigate the effects of a potential CCF to eliminate CCF from further consideration Provides criteria for use of other methodologies with the provision of a technical basis and acceptance criteria Based on NRC-approved methodology 6
Proposed Spurious Operation Guidance Enhancement
- Provides bifurcated criteria for addressing spurious operation:
- Operating reactors: existing safety analysis not invalidated by the proposed digital modification
- Enhanced guidance for new and advanced reactors
- Clarifies scope and methods for performing the assessment 7
Proposed Re-Structuring of BTP 7-19
- Simplifies background and incorporates new guidance on CCF
- Maps criteria to four positions in the SRM-SECY-93-087
- Consolidates CCF guidance and corresponding acceptance criteria 8
Next Steps
- Public comment period ends March 16, 2020
- ACRS Sub-Committee scheduled for June 25, 2020
- ACRS Full Committee meeting in July 2020
- Final issuance targeted for September 2020 9
Questions 10
Acronyms BTP Branch Technical Position NSR Not safety related CCF Common Cause Failure PRA Probabilistic Risk Assessment CFR Code of Federal Regulations RIS Regulatory Issue Summary D3 Defense-in-Depth and Diversity RPS Reactor Protection System DI&C Digital Instrumentation and Control SAR Safety Analysis Report ESFAS Engineered Safety Feature Actuation SRM Staff Requirements System Memorandum MCR Main Control Room SSC Structure, System and component MP Modernization Project 11