ML110190637
| ML110190637 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 01/14/2011 |
| From: | Gillespie T Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LAR 09-010 | |
| Download: ML110190637 (23) | |
Text
Duke T.PRESTON GILLESPIE, Jr.
President Pk~ukeVice OrEnergya Oconee Nuclear Station Duke Energy ON01 VP / 7800 Rochester Hwy.
Seneca, SC 29672 864-873-4478 864-873-4208 fax T.Gillespie@duke-energy.corn January 14, 2011 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555-0001
Subject:
Duke Energy Carolinas, LLC Oconee Nuclear Station (ONS), Units 1, 2 and 3 Renewed Facility Operating Licenses Numbers DPR-38, -47, -55; Docket Number 50-269, 50-270 and 50-287; Response to Request for Additional Information Regarding License Amendment Request to Relocate Specific Surveillance Frequency Requirements to a Licensee Controlled Program License Amendment Request (LAR) No. 2009-10, Supplement 1 On March 17, 2010, Duke Energy Carolinas, LLC (Duke Energy) submitted a LAR requesting Nuclear Regulatory Commission (NRC) review and approval to relocate specific surveillance frequencies to a licensee-controlled program. The LAR adopts Technical Specification Task Force (TSTF)-425, Revision 3, and would modify ONS technical specifications by relocating specific surveillance frequencies to a licensee-controlled program with the implementation of
.Nuclear Energy Institute (NEI) 04-10, "Risk-Informed Technical Specification Initiative 5B, Risk-Informed Method for Control of Surveillance Frequencies." The NRC electronically transmitted a Request for Addition Information (RAI) to Duke Energy on November 12, 2010. The Enclosure provides Duke Energy's response.
If there are any questions regarding this submittal, please contact Boyd Shingleton of the ONS Regulatory Compliance .Group at (864) 885-4716.
I declare under penalty of perjury that the foregoing is true and correct. Executed on January 14, 2011.
Sincerely, T. Preston Gillespie, Jr., Vice President Oconee Nuclear Station A-.o0w www. duke-energy. corn
U. S. Nuclear Regulatory Commission January 14, 2011 Page 2
Enclosure:
Duke Energy Response to NRC Request for Additional Information
Attachment:
Revised TABLE 2-1, Status of Identified Gaps to Capability Category II of the ASME PRA Standard Through Addenda RA-Sc-2007
U. S. Nuclear Regulatory Commission January 14, 2011 Page 3 cc w/
Enclosure:
Mr. Luis Reyes, Regional Administrator U. S. Nuclear Regulatory Commission - Region II Marquis One Tower 245 Peachtree Center Ave., NE, Suite 12 00 Atlanta, Georgia 30303-1257 Mr. John Stang, Project Manager Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 0-8 G9A Washington, D. C. 20555 Mr. Andy Sabisch Senior Resident Inspector Oconee Nuclear Site Ms. Susan E. Jenkins, Manager Radioactive & Infectious Waste Management Division of Waste Management South Carolina Department of Health and Environmental Control 2600 Bull St.
Columbia, SC 29201
ENCLOSURE Duke Energy Response to NRC Request for Additional Information
January 14, 2011 Page 1 Enclosure Duke Energy Response to NRC Request for Additional Information RAI I NEI 04-10 industry guidance document states in Step 12-A4 that the cumulative change for all surveillance test interval (STI) changes remains below 1E-05/yr core damage frequency (CDF) and 1E-06/yr large early release frequency (LERF). In addition, the total CDF must be reasonably shown to be less.than 1E-04/yr and the total LERF must reasonably shown to be less than 1E-05/yr. Please explain how Oconee meets the associated NEI 04-10 guidance.
Duke Energy Response to RAI 1 The Oconee Probabilistic Risk Assessment (PRA) is a full scope PRA, including both internal and external events (i.e., external flood, seismic, fire, high winds [tornado]). In the current PRA model of record for Oconee, the total CDF is less than 1 E-04/yr and the total LERF is less than 1 E-05/yr.
Industry guidance document Nuclear Energy Institute (NEI) 04-10 discusses Regulatory Guide (RG) 1.174 guidelines in Steps 12-A3 and 12-A4. In Step 12-A3, the total CDF and LERF changes from the individual Surveillance Test Interval (STI) change being assessed are compared to RG 1.174 limits for CDF and LERF changes; namely, CDF increase < 1ET.06/yr and LERF increase < 1E-07/yr. If the RG 1.174 limits for CDF and LERF changes are not met for any individual STI change, then either the process ends or a revised STI is considered for re-evaluation until the limits are met.
In Step 12-A4, the cumulative CDF and LERF changes from all of the individual STI changes are compared to the RG 1.174 limits for CDF and LERF changes and must be below 1E-05/yr for CDF and below 1 E-06/yr for LERF. Additionally, the total CDF must be reasonably shown to be less than 1E-04/yr when using the 1E-05/yr ACDF criterion and the total.LERF must be reasonably shown to be less than 1 E-05/yr when using the 1 E-06/yr ALERF criterion. If the RG 1.174 limits for CDF and LERF changes are not met, the process ends or a revised STI is considered for re-evaluation until the cumulative limits are met.
The Duke Energy plant program for control of surveillance frequency changes has been explicitly developed in accordance with the NEI 04-10 industry guidance document and contains the same requirements, RG 1.174 limits, and restrictions as set forth in NEI 04-10 regarding individual STI and cumulative STI changes. Should the Oconee model of record not meet required- limits for total CDF and LERF, or should RG 1.174 limits, as stated in NEI 04-10, be exceeded for individual or cumulative STI changes, actions will be taken as noted above in accordance with NEI 04-10 guidance. Additionally, since the plant program for control of surveillance frequency changes is directly based on NEI 04-10, should any part of the process not meet a requirement of the NEI 04-10 methodology, action will be taken consistent with that described in NEI 04-10. In this manner, Oconee meets the associated NEI 04-10 guidance.
RAI 2
Table 2-1 of Attachment 2 identifies specific unresolved "gaps" of the Oconee Nuclear Station probabilistic risk assessment (PRA) internal events model to meeting the American Society of
Enclosure - Duke Energy Response to NRC Request for Additional Information January 14, 2011 Page 2 Mechanical Engineers PRA standard Capability Category II supporting requirements. In the column labeled "Importance to 5b Application", the licensee asserts, for some specific supporting requirements which are not met at Capability Category II, that:
i) Certain gaps will be assessed on a case-by-case basis ii) The gap has no or minimal impact on surveillance testexceptions.
Asserting that certain gaps are to be assessed on a case-by-case basis is inconsistent with Nuclear Energy Institute (NEI) 04-10, Revision 1, which specifically requires Capability Category II. Further, NEI 04-10, requires all gaps to Capability Category II to be accessed via sensitivity studies. This position was accepted by the staff in its safety evaluation of NEI 04-10 Revision
- 1. Therefore, notwithstanding the assertions in Table 2-1 regarding Capability Category I, each supporting requirement not meeting Capability Category II must be further evaluated by sensitivity studies when applying the internal events PRA model for this application.
With regard to item ii above, the gaps cannot be dispositioned a priori, since this would also conflict with NEI 04-10 which did not identify any supporting requirements that were not required for this application. Again, such gaps must be evaluated by sensitivity studies for each surveillance frequency change.
The licensee is therefore requested to confirm that their plant program for control of surveillance frequencies includes a requirement to assess all open gaps to Capability Category II of the standard via sensitivity studies for each application of the NEI 04-10 methodology, and does not rely upon any a priori assessment of the relevance-of the supporting requirement.
Duke Energy Response to RAI 2 All open gaps to Capability Category IIof the standard will be addressed via sensitivity studies a priori for each application of the NEI 04-10 methodology, and will not rely upon any assessment of the relevance of the supporting requirement. The Duke Energy plant program for control of surveillances has been revised to clarify the rbcluirement to assess all open gaps to Capability Category II of the standard via sensitivity studies for each application of the NEI 04-10 methodology, and does not rely upon any a priori asses-sment of the relevance of the supporting requirement.
Table 2-1 has been revised to remove wording that indicated gaps will be assessed on a case-by-case basis or that gaps have no or minimal impact on the surveillance frequency change.
The revised table is provided in the Attachment to this Enclosure.
RAI 3
Table 2-1, Attachment 2 of the McGuire and Catawba Surveillance Frequency Risk-Informed Change submittals identifies gap #14 as having initiating event supporting requirement deficiencies to the model. The Oconee submittal assumes these supporting requirements are Capability Category II by not being placed in Table 2-1. Since PRA models for all three plants are very similar, please confirm to the staff that initiating event supporting requirements for the Oconee PRA are Capability Category II and provide dispositions if they are not Capability Category II.
Enclosure - Duke Energy Response to NRC Request for Additional Information January 14, 2011 Page 3 Duke Energy Response to RAI 3 Gap #14 from Table 2-1, Attachment 2 of the McGuire and Catawba Surveillance Frequency Risk-Informed Change submittals is not applicable to Oconee since the Oconee Initiating Events analysis has been revised to meet the ASME PRA Standard initiating event supporting requirements at the Capability Category II level.
ATTACHMENT Revised Table 2-1 Status of Identified Gaps to Capability Category II of the ASME PRA Standard Through Addenda RA-Sc-2007
Attachment January 14, 2011 Page 1 Revised Table 2-1 Status of Identified Gaps. to Capability Category II of the ASME PRA Standard Through Addenda RA-Sc-2007 Title Description of Gap Applicable Current Status / Comment Importance to 5b
- i. SRs Application Gap #1 Accident sequence notebooks and AS-B3 Open. Phenomenological For each surveillance system model notebooks should effects are considered in the frequency change document the phenomenological model, although these evaluation, any conditions created by the accident considerations are not always phenomenological.
sequence progression. documented. conditions created by the accident sequence progression will be identified, included and documented in the analysis.
Gap #2 Revise the data calc. to group DA-B1 Open. Partitioning the failure Each surveillance standby and operating component rates represents a refinement frequency change data. Group components by service to the data analysis process. evaluation will include condition to the extent supported by Previously, generic data sensitivity studies to the data. sources often did not provide consider the impact of standby and operating failure grouping data into rates. NUREG/CR-6928 does operating vs. standby provide more of this data, and failure rates and by will be used going forward. service condition.
Attachment - Revised Table 2-1 January 14, 2011 Page 2 Title Description of Gap Applicable Current Status / Comment Importance to 5b SRs Application Gap #3 Enhance the documentation to DA-D4 Open. As part of the Bayesian Each surveillance include a discussion of the specific update process, checks are frequency change checks performed on the Bayesian- performed to assure that the evaluation will verify updated data, as required by this SR. posterior distribution is that the Bayesian reasonable given the prior update process distribution and plant produces a experience. These checks reasonable posterior need to be formally distribution. (See the documented. example tests in DA-D4.)
Gap #4 Provide documentation of the: DA-D6 Open. Generic CCF Each surveillance comparison of the component probabilities are considered for frequency change boundaries assumed for the generic applicability to the plant. CCF evaluation will ensure common cause failure (CCF) probabilities are consistent with that CCF probabilities estimates to those assumed in the plant experience and are consistent with PRA to ensure that these boundaries component boundaries, component are consistent. although the CCF boundaries and plant documentation needs to be experience.
enhanced to discuss component boundaries.
Gap #5 Enhance the human reliability HR-A2 Open. Based on evaluations Each surveillance analysis (HRA) to consider the using the EPRI HRA calculator, frequency change potential for calibration errors. calibration errors that result in evaluation will identify failure of a single channel are and consider the, expected to fall in the low 10.' impact that equipment range. Relative to post-initiator calibration errors HEPs, equipment random could have on the failure rates and maintenance results and unavailability, calibration HEPs conclusions.
are not expected to contribute significantly to overall equipment unavailability.
Attachment - Revised Table 2-1 January 14, 2011 Page 3 Title Description of Gap, Applicable Current Status / Comment Importance to 5b i SRs Application Gap #6 Identify maintenance and calibration HR-A3 Open. Based on evaluations Each surveillance activities that could simultaneously using the EPRI HRA calculator, frequency change affect equipment in either different calibration errors that result in evaluation will identify trains of a redundant system or failure of multiple channels are any work practices diverse systems. expected to fall in the low that could 10-5 range (or smaller). simultaneously affect Relative to post-initiator HEPs, equipment in either latent human error probabilities, different trains of a equipment random failure rates redundant system or and maintenance unavailability, diverse systems.
calibration HEPs and misalignment of multiple trains of equipment are not expected to contribute significantly to overall equipment unavailability.
Gap #7 Develop mean values for pre-initiator HR-D6 Open. Pre-initiator HEPs are Each surveillance HEPs. . generally set to relatively high frequency change screening values, which bound evaluation will use the mean values. Even so, mean values for pre-pre-initiator HEPs are not initiator HEPs.
significant contributors to risk.
Gap #8 Document in more detail the HR-G3 Open. Performance shaping Each surveillance, influence of performance shaping factors are accounted for in. the frequency change factors on execution human error development of human error evaluation will use probabilities, probabilities, although detailed HEP values that have documentation is not always been quantified with available for every HRA input. consideration of plant-specific and scenario-specific performance shaping factors.
Attachment - Revised Table 2-1 January 14, 2011 Page 4 Title Description of Gap Applicable Current Status / Comment Importance to 5b SRs Application Gap #9 Enhance HRA documentation of the HR-G4 Open. T/H analyses, simulator Each surveillance time available to complete actions. runs and operator interviews frequency change are used in developing the time evaluation will use available to complete operator HEP events with time actions. The time at which the available inputs based cue to take action is received is on plant-specific specified in the HEP thermal/hydraulic quantification. However, the analyses or HRA documentation needs to simulations.
be enhanced to provide a traceable path to all analysis inputs.
Gap #10 Document a review of the HFEs and HR-G6 Open. HFEs are reviewed by For each surveillance their final HEPs relative to each other knowledgeable site personnel frequency change to confirm their reasonableness to assure high quality, evaluation, post-given the scenario context, plant However, this review needs to initiator HEPs will be history, procedures, operational be better documented. reviewed against each practices, and experience, other to check their reasonableness given the scenario context, plant procedures, operating practices and experience.
Gap #11 Develop mean values.for post- HR-G9 Open. The use of mean values Each surveillance initiator HEPs. for HEPs instead of lower frequency change probability median values can evaluation will use affect the PRA results. mean values for post-initiator HEPs.
Attachment - Revised Table 2-1 January 14, 2011 Page 5 Title Description of Gap Applicable Current Status / Comment Importance to 5b SRs p Application Gap #12 Develop more detailed HR-H2 Open. Operator recovery Each surveillance documentation of operator cues, actions are credited only if they frequency change relevant performance shaping are feasible, as determined by evaluation will credit factors, and availability of sufficient the procedural guidance, cues, operator actions only if manpower to perform the action. performance shaping factors they are feasible, as and available manpower. As determined by the noted for HR-G3, -G4, and -G6 procedural guidance, above, the documentation of cues, performance these considerations needs to shaping factors and be enhanced. available manpower.
Attachment - Revised Table 2-1 January 14, 2011 Page 6 Title Description of Gap Applicable Current Status / Comment Importance to 5b SRs Application Gap #13 Various enhancements to the IF-B3 Open. A plan and schedule internal flood analysis: IF-C2c are in place for
" Identify the release characteristic IF-C3 addressing internal and capacity associated with each IF-C3b flood issues related to flood source. IF-E5 the PRA Standard for
" Discuss flood mitigative features. IF-E5a ONS. In the interim,
- Address the potential for spray, jet IF-E6b for each surveillance impingement, and pipe whip IF-F2 frequency change, we failures. will evaluate all SRs
- Provide more analysis of flood not meeting CCII with propagation flowpaths. Address sensitivity studies and potential structural failure of doors refer to the updated or walls due to flooding loads and MNS flood analyses the potential for barrier for insights.
unavailability.
" Address potential indirect effects.
" If additional human error failure events are required to support quantification of flood scenarios, perform HRA in accordance with the applicable HRA SRs.
" For all human events in the internal flood scenarios, include scenario-specific impacts on the performance shaping factors identified in supporting requirement IF-E5a.
" Enhance the documentation to
.address all of the SR details.
Attachment - Revised Table 2-1 January 14, 2011 Page 7 Title Description of Gap, Applicable Current Status / Comment Importance to 5b SRs Application Gap #14 Explicitly model RCS LE-C6 Open. This issue affects Each surveillance depressurization for small LOCAs certain small LOCAs. frequenHcy change and perform the dependency However, since the small evaluation will include analysis on the HEPs. LOCA contribution to LERF is a sensitivity study to small, there is no significant assess the importance impact on the PRA results. of explicitly modeling RCS depressurization for small LOCAs.
Gap #15 Various enhancements to the, LERF LE-G3 Open. Each surveillance documentation. LE-G5 frequency change LE-G6 evaluation will document:
- the relative contribution of contributors to LERF and any limitations in the LERF analysis that would impact the 5b evaluation
- the use of the quantitative definition for significant accident progression sequence provided in the "Acronyms and Definitions" section of the PRA Standard.
Attachment - Revised Table.2-1 January 14, 2011 Page 8 Title Description of Gap Applicable Current Status / Comment Importance to 5b SRs Application Gap #16 Perform and document a comparison LE-F3 Open. Comparisons performed Each surveillance of PRA results with similar plants and QU-D3 for the Mitigating System frequency change identify causes for significant' Performance Index and other evaluation will perform differences. Identify the contributors programs help identify causes and document a to LERF and characterize the LERF for significant differences, comparison of CDF uncertainties consistent with the However, to fully meet this SR, and LERF results with applicable ASME Standard the model quantification those of similar plants.
requirements. documentation needs to be enhanced to provide a results comparison.
Gap #17 Perform and document sensitivity LE-F2 Open. This is addressed with Each surveillance analyses to determine the impact of LE-G4 each Surveillance Test Interval frequency change the assumptions and sources of QU-E4 assessment. evaluation will include model uncertainty on the results. sensitivity analyses to determine the impact of the assumptions and sources of model uncertainty on the 5b analysis results.
Attachment - Revised Table 2-1.
January 14, 2011 Page 9 Title Description of Gap Applicable Current Status / Comment Importance to 5b SRs Application Gap #18 Expand the documentation of the QU-F2 Open. These SRs pertain to Each surveillance PRA model results to address all QU-F6 the model quantification frequency change required items. documentation. evaluation will document:
- the model integration process, recovery analysis, and uncertainty and sensitivity analyses
- the use of definitions for significant basic event, significant cutset, and significant accident sequence provided in the "Acronyms and Definitions" section of the PRA Standard.
Gap #19 Provide evidence that an SC-B5 Open. Oconee success criteria Each surveillance acceptability review of the T/H are consistent with those of frequency change analyses is performed. sister plants included in the evaluation will check PWROG PSA database. and ensure the However, to fully meet this SR, reasonableness and the success criteria acceptability of the documentation needs to be T/H analyses results enhanced to include a results used to support the comparison, success criteria.
Attachment - Revised Table 2-1 January 14, 2011 Page 10 Title Description of Gap Applicable Current Status / Comment Importance to 5b SRs Application Gap #20 Expand the documentation of the SC-Cl Open. These SRs pertain to Each surveillance success.criteria development to SC-C2 the success criteria frequency change address all required items. documentation. , evaluation will ensure that:
- success criteria are documented in a manner that facilitates the 5b application, model upgrades and peer review
- the processes used to develop overall PRA success criteria and supporting engineering bases,-including inputs, methods and results are documented.
Attachment - Revised Table 2-1 January 14, 2011 Page 11 Title Description of Gap Applicable 1 Current Status I Comment Importance to 5b SRs Application Gap #21 Enhance the system documentation SY-A4 Open. To support system Workplace procedure to include an up-to-date system model development, XSAA-115, PRA walkdown checklist and system walkdowns and plant personnel Modeling Guidelines, engineer review for each system. interviews were performed. has been revised to
,However, documentation of an require documentation up-to-date system walkdown is of a system walkdown not included with each system and system engineer notebook. interview. A plan and schedule for updating the system models with the revised guidance is in place.
Until each system notebook is updated, the impact of this gap will be evaluated for each surveillance frequency change.
Attachment - Revised Table 2-1 January 14, 2011 Page 12 Title Description of Gap Applicable Current Status I Comment Importance to 5b SRs Application Gap #22 Enhance the systems analysis SY-A8 Open. Basic event component Each surveillance documentation to discuss component boundaries utilized in the frequency change boundaries. systems analysis are consistent evaluation will use with those in the data analysis. definitions for SSC In addition, component boundary, boundaries are consistent with unavailability those defined inithe generic boundary, failure failure rate source documents, mode, and success such as NUREG/CR-6928. criteria consistently Dependencies among across the systems components, such as and data analyses.
interlocks,. are explicitly modeled, consistent with the PRA Modeling Guidelines workplace procedure. There is no evidence of a technical problem with component boundaries, just a need to improve the documentation.
Attachment - Revised Table 2-1 January 14,.2011 Page 13 Title Description of Gap, Applicable Current Status / Comment Importance to 5b SRs Application Gap #23 Provide quantitative evaluations for SY-A14 Open. There is no evidence of For each surveillance screening. a technical problem associated frequency change, the with the screening of component and failure components or component mode screening failure modes, just a need to performed in the document a quantitative systems analysis will screening. It is expected that be verified to meet the conversion to a more quantitative quantitative approach would requirements provided not change decisions about in SY-A14.
whether or not to exclude components or failure modes.
- A review of our qualitative screening process confirms this expectation. For example, transfer failure events for motor-operated valves (MOVs) with .24 hr exposure times may not be modeled unless probabilistically significant with respect to logically equivalent basic events. For Oconee, the MOV transfers failure probability is less than 1% of the MOV fails to open on demand probability. In cases likethis, not including the relatively low probability failure mode in the PRA model does not have an appreciable impact on the results.
Attachment - Revised Table 2-1 January 14, 2011 Page 14 Title Description of Gap Applicable Current Status / Comment Importance to 5b SRs Application Gap #24 Per Duke's PRA modeling SY-B8 Open. As noted for SY-A4, The impact of this gap guidelines, ensure that a walkdowns (which look for will be evaluated for walkdown/system engineer interview spatial and environmental each surveillance checklist is included in each system hazards) have been performed, frequency change.
notebook. Based on the results of although up-to-date walkdown See Gap #21.
the system walkdown, summarize in documentation is not included the system write-up any possible with each system notebook.
spatial dependencies or environmental hazards that may impact multiple systems or redundant components in the same system.
Gap #25 Document a consideration of SY-B1i5 Open. The impact of adverse For each surveillance potential SSC failures due to adverse environmental conditions on frequency change, environmental conditions. SSC reliability is considered but potential SSC failures is not always documented. due to adverse However, there is no evidence environmental of a technical problem conditions will be associated with components identified, included that may be required to operate and documented in in conditions beyond their the analysis.
environmental qualification, just a need to improve the documentation.
Attachment - Revised Table 2-1 January 14, 2011 Page 15 Title Description of Gap Applicable Current Status / Comment Importance to 5b SRs Application Gap #26 Enhance system model SY-C2 Open. This SR pertains to the Workplace procedure documentation to comply with all systems analysis XSAA- 115, PRA ASME PRA Standard requirements. documentation. Modeling Guidelines, has been revised to provide guidance on meeting the Standard's supporting requirements. A plan and schedule for.
updating the system models with the revised guidance is in place. Until each system notebook is updated, the impact of this gap will be evaluated for each surveillance frequency change.