ML25216A242
| ML25216A242 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 08/04/2025 |
| From: | Duke Energy |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML25216A235 | List: |
| References | |
| Download: ML25216A242 (1) | |
Text
Shearon Harris Nuclear Power Plant, Unit 1 Experience with Risk-Informed Process for Evaluation (RIPE)
Duke Energy Experience with RIPE 2
Submitted Exemption Request (10 CFR 50.12) utilizing RIPE Requested an exemption from certain requirements of IEEE Standard 279-1971, Criteria for Protection Systems for Nuclear Power Generating Stations Addressed a green finding and associated noncited violation of 10 CFR 50 Appendix B, Criterion III, Design Control, for Treatment of Class 1E Interfaces and Interlocks with the Turbine Trip System (TTS) Design 10 CFR 50.55a(h)(2) requires protection systems of nuclear power reactors to meet the requirements in IEEE Std 279-1968, IEEE 279-1971, or IEEE Std 603-1991 Exemption removed requirement for the reactor protection system (RPS) cables that terminate within turbine control system Cabinet G to be independent and physically separated in accordance with IEEE Std 279-1971, Section 4.6, Channel Independence
Duke Energy Experience with RIPE Quantitative Risk Characterization Non-compliant configuration assessed is the compromised requirements for single failure and interactions between control and protection systems affecting reliability of the RPS that are present by not meeting RPS independence.
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Conclusion:==
Not risk-significant and has minimal impact on safety 3
Metric PRA Base Model Risk Configuration-Specific Risk Delta Risk NRC RIPE Criteria for Minimal Safety Impact CDF 4.1459E-5 4.1475E-5 1.6E-8
< 1.0E-7*
LERF 3.5142E-6 3.5142E-6
<1.0E-10
< 1.0E-8*
Duke Energy Experience with RIPE 4
4 Timeline Submitted February 6, 2024 Acceptance on April 17, 2024
Extended Acceptance Review period (71 days)
Supplements submitted April 3, 2024 and June 7, 2024 Exemption issued on July 29, 2024 (~25 weeks)
Firsts for RIPE Process Request for Supplemental Information Structure for RIPE did not allow for requests for additional information (RAIs).
Supplemental responses were requested to remain within the RIPE process.
Request for an audit Call conducted on May 22, 2024 to address question related to Defense-In-Depth and impact a fault on the subject cables would have on the non-safety-related turbine trip on reactor trip function.
Takeaways Submittal is reviewed in a manner consistent with the principles of risk-informed decision-making outlined in Regulatory Guide (RG) 1.174, Revision 3, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decision on Plant-Specific Changes to the Licensing Basis Included Defense-In-Depth for non-safety-related systems, structures, and components Logic to be documented to the extent practicable and degree commensurate with the safety impacts and complexity of the issue Use of audit was vital to success of submittal Allowed for nuanced discussion between staff and licensee subject matter experts (SMEs) regarding the cable interface and the impact a fault on the subject cables would have on the non-safety-related turbine trip on reactor trip function 5
Duke Energy Experience with RIPE
Potential RIPE Improvements Include opportunity for remote audit Allows for open discussion between licensee and technical staff Real time response to questions Resolution of differing opinions or interpretations Subject Matter Expert involvement Allows for timely submittal of supplemental information Facilitates No Technical Objection review Additional clarity regarding level of detail required to address issues shown to have low risk and/or is non-safety-related Allows for timely development and subsequent processing of request 6
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