RS-10-084, Additional Information Supporting Application for Technical Specification Change Regarding Risk-Informed Justification for Relocation of Specific Surveillance Frequency Requirements to a Licensee Controlled Program
| ML101160374 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 04/26/2010 |
| From: | Simpson P Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RS-10-084 | |
| Download: ML101160374 (13) | |
Text
Exelon Generation www.exeloncorp.com 4300 W~nfieldRoad Nuclear April 26, 2010 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 LaSalle County Station, Units 1 and 2 Facility Operating License Nos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374
Subject:
Additional Information Supporting Application for Technical Specification Change Regarding Risk-Informed Justification for the Relocation of Specific Surveillance Frequency Requirements to a Licensee Controlled Program
Reference:
Letter from P. R. Simpson (Exelon Generation Company, LLC) to U.S. NRC, "Application for Technical Specification Change Regarding Risk-Informed Justification for the Relocation of Specific Surveillance Frequency Requirements to a Licensee Controlled Program (Adoption of TSTF-425, Revision 3j,"dated February 15, 2010 In the referenced letter, Exelon Generation Company, LLC (EGC) requested an amendment to Facility Operating License Nos. NPF-11 and NPF-18 for LaSalle County Station (LSCS), Units 1 and 2, respectively. The proposed change modifies the LSCS Technical Specifications (TS) by relocating specific surveillance frequencies to a licensee-controlled program. Attachment 2 of the referenced letter provided documentation with regard to probabilistic risk assessment (PRA) technical adequacy. Table A.2-1, "LaSalle PRA 2008 Peer Review Results," included information regarding the gaps that were identified during the peer review cf the LSCS PRA.
During a conference call with the NRC on April 15, 2010, the NRC indicated that with respect to Table A.2-1, a more detailed discussion of the identified gaps was needed, rather than the associated supporting requirement descriptions. As a result, EGC is providing a revised version of Table A.2-1 that includes a discussion of the gaps identified during the peer review.
EGC has reviewed the information supporting a finding of no significant hazards consideration, and the environmental consideration, that were previously provided to the NRC in Attachments 6 and 1, respectively, of the referenced letter. The additional information provided in this submittal does not affect the bases for concluding that the proposed license amendment does not involve a significant hazards consideration. In addition, the additional information provided in this submittal does not affect the bases for concluding that neither an environmental impact
April 26, 2010 U.S. Nuclear Regulatory Commission Page 2 statement nor an environmental assessment needs to be prepared in connection with the proposed amendment.
There are no regulatory commitments contained in this letter. Should you have any questions concerning this letter, please contact Mr. Kenneth M. Nicely at (630) 657-2803.
I declare under penalty of perjury that the foregoing is true and correct. Executed on the 26th day of April 2010.
Manager - Licensing 84
Attachment:
Additional Information Supporting Probabilistic Risk Assessment Technical Adequacy cc: NRC Regional Administrator, Region lii NRC Senior Resident Inspector --- LaSalle County Station Illinois Emergency Management Agency - Division of Nuclear Safety
ATTACHMENT Additional Informa1:ion Supporting Probabilistic Risk Assessment Technical Adequacy TABLE A.2-1 LASALLE PRA 2008 PEER REVIEW RESULTS SUPPORTING ASSESSMENT IMPACT ON BASE PRA IE-A7 Although a detailed plant-specific precursor review was not reported, Supporting Documentation issue. No impact.
industry wide initiating evlent precursors are considered and Requirement Met No additional IE categories would documented where appropriate in the LaSalle initiating event (IE) Capability be identified. Peer reviewers analysis (e.g., loss of station cooling, ISLOCA, loss of multiple DC Category (CC) I. desired greater buses, reference leg brea~k,and the various LOCA categories). discussionldocumentation of IE Additionally, plant-specific precursors i ~ specifically e considered in the precursors.
plant water intake evalual.ion provided in Appendix G.l of the component data notebooli.
IA jump from Category I to Category Ill could be achieved by
]supplementing the initiating event identification process with additional
]documented evidence that plant-specific operating experience
]precursors were considered (perhaps with reference to operations landlor system manager interviews that considered near misses, or IE-D3 The LS-PSA-013 notebook discusses the industry '%ey sources of uncertainty" per Electric Power Research Institute (EPRI) guidance.
However, the current analysis does not fully meet tile requirements of Supporting IRefer to the impact discussion for Requirement Not Supporting Requirement QU-E4.
Met.
Regulatory Guide (RG) 1.200, which requires a discussion of sources
/of model uncertainty and related assumptions. Also, there may be
]some piant-specifi&assurnptions made that may not be fully captured Iby the generic list of potential sources of uncertainty.
Expand the existing treatrnent of sources of uncertainty to consider sources of model uncertainty and related assumptions. Consideration should also be given to potential plant-specific assc~mptionsthat should also be noted as stourcesof uncertainty. NUREG-1855 and an upcoming EPRI Treatment of Uncertainty report should provide more guidance on how to meet this supporti~~g requirement (SR) in the
-future.
ATTACHMENT Additional 1nformat:ionSuppol-ting Probabilistic Risk Assessment Technical Adequacy TABLE A.2-1 LASALLE PRA 2008 PEER REVIEW RESULTS OF GAP P a the industry '"key sources of ver, the current analysis does
.200, which requires a discussion of sources of rnodel uncertainty and related assumptions.
Also, there may be some plant-specificassumptions made that may not be fully captured by the generic lisi of potential sources of Expand the existing treatrnent of sources of uncertainty to consider sources of model uncertainty and related assumptions. Consideration should also be given to potential plant-specificassumptions that should also be noted as sources of uncertainty. NLJREG-1855 and an upcoming EPRI Treatment of Uncertainty report should provide more guidance on how to meet this SR in the future.
While the LS-PSA-003 notebook provides some selected comparison Supporting Documentation issue. No impact.
of RMIEP MELCOR results to more recent MAAP runs, there is no Requirement No1 The LaSalle PRA Success Criteria documented comparison of how the LaSalle success criteria compare Met. Notebook compares MAAP and to those used for sister plants or other similar comparisons as required MELCOR runs. The peer review for this SR. However, the success criteria used for LaSalle appear to team desired more comparisons be consistent with those of other similar boiling water reactors (BWRs). with other plants and other codes.
The LS-PSA-003 docume!ntation should be enhanced to include a section that compares the LaSalle success criteria .to those used in the PRAs of other similar BWRs.
ATTACHMENT Additional 1nformal:ionSupporting Probabilistic Risk Assessment Technical Adequacy TABLE A.2-1 LASALLE PRA 2008 PEER REVIEW RESULTS DESCRIPTION The LS-PSA-(413notebook discusses uncertainty" per EPRl guidanc not fully meet the requirernent discussion of sources of rnodel uncertainty and related assumptions.
Also, there may be some plant-specific assumptions made that may not be fully captured by the generic list of potential sources of uncertainty.
Expand the existing treatrnent of sources of uncertainty to consider sources of model uncertainty and related assumptions. Consideration should also be given to potential plant-specificassumptions that should also be noted as sources of uncertainty. NUREG-1855 and an upcoming EPRl Treatment of Uncertainty report should provide more guidance on how to meet this SR in the future.
7 system engineer interviews are docunlented in the respective system Supporting Documentation issue. No impact.
notebooks. Operator interviews are documented in the Human Requirement Met The majority of the LaSalle PRA Reliability Analysis (HRA) notebook. Each system notebook contains (CC 1) System Notebooks include an appendix documenting interviews with system managers, however, documented Operator Interviews there is little mention, if any at all, of walkdowns pel-formed in support and Walkdowns. The peer review of the system analyses. The impression received is that walkdowns team desired that every System were performed some time ago for a niuch earlier revision but have not Notebook include such been retained in the system notebooks. documentation and that walkdowns Interview with plant engineers has been documented. However, plant be performed with both Ops and walkdown details are not provided in the Standby Liquid Control, Core Systems personnel on the Standby Cooling, High Pressure Core Spray, and Reactor Core walkdown.
Isolation Cooling system notebooks.
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ATTACHMENT Additional Information Suppo~tingProbabilistic Risk Assessment Technical Adequacy TABLE A.2-1 LASALLE PRA 2008 PEER REVIEW RESULTS discusses the industry '
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ATTACHMENT Additional 1nforrnat:ionSupporting Probabilistic Risk Assessment Technical Adequacy TABLE A.2-1 LASALLE PRA 2008 PEER REVIEW RESULTS SUPPORTING REQUIREMENTS I DESCRIPTION OF GAP I ASSESSMENT PEER I IMPACT ON BASE PRA Table 5.1-2 summarizes the post-initiator HEPs in tabular form, but no Supporting Documentation issue. No impact.
consistency check is discussed in the analysis. Requirement Not The EGC HRA best practices direct The final HEP values need to be compared against each other to Met 1 performance of a reasonableness check their reasonableness. Table 5.1i-2 appears to have assembled and this was performed for for this purpose, but the ainalysis contains no discussion of any such PRA. Peer Review consistency check. team desired to see a detailed discussion of the reasonableness The LS-PSA-013 notebook discusses the industry "key sources of Supporting Refer to impact discussion for uncertainty" per EPRl guidance. However, the current analysis does Requirement Not Supporting Requirement QU-E4.
not fully meet the requirements of RG 1.200, which requires a Met.
discussion of sources of rnodel uncertainty and related assumptions.
Also, there may be some plant-specific assumptions made that may not be fully captured by the generic list of potential sources of uncertainty.
Expand the existing treatment of sources of uncertainty to consider sources of model uncertainty and related assumptions. Consideration should also be given to potential plant-specific assi~mptionsthat should also be noted as sources of uncertainty. NUREG-1855 and an upcoming EPRI Treatment OF Uncertainty report should provide more guidance on how to meet this SR in the future.
DA-C8 Basic events used to model the standby status of various plant Supporting Nan-significant impact. The LaSalk systems use a mixture of plant-specific operational data and Requirement Met PRA uses primarily plant-specific engineering judgment. For the plant S'ervice Water system and (CC I). information for configuration several other systems, standby estimaites have been determined from probabilities. Peer Review team procedures and operating data (see Appendix G of LS-PSA-010). For desired that glJ configuration other components, assunlptions are used (e.g., 50% probability of probabilities used in the PRA be either of two pumps in a system is in standby). So, overall LaSalle has based on plant-specific data.
some Category II attributes and some Category I attributes.
Collect plant-specific data for all of the basic events that reflect standby status to meet C,ategory I1 requirements.
ATTACHMENT Additional Information Supporting Probabilistic Risk Assessment Technical Adequacy TABLE A.2-1 LASALLE PRA 2008 PEER REVIEW RESULTS fSCRlPTlONi OF GAP
--- d -
l ~ h documentation e should describe how tests were counted to fully meet the requirements of this SR.
The LS-PSA-013 notebook discusses .the industry '"ey sources of Supporting to impact discussion for uncertainty" per EPRl guidance. However, the current analysis does Requirement Not Supporting Requirement QU-E4.
not fully meet the requirements of RG 1.200, which requires a Met.
discussion of sources of rnodel uncertainty and related assumptions.
Also, there may be some plant-specific: assumptions made that may not be fully captured by the generic lisi of potential sources of uncertainty.
Expand the existing treatment of sources of uncertainty to consider sources of model uncertainty and related assumptions. Consideration should also be given to potential plant-specificassumptions that should also be noted as sources of uncertainty. NlJREG-1855 and an upcoming EPRl Treatment of Uncertainty report should provide more guidance on how to meet this SR in the future.
IF-C3b Appendix D addresses flow through drain lines (e.g., 314 and 3J5) and Supporting Documentation issue. No impact.
addresses doors as well. RG 1.200 appends the Category II Requirement Met Flood barrier unavailability is requirements to include the potential for barrier unavailability, including (CC I). considered and including in the maintenance. Barrier unavailability does not appear to have been internal flood analysis. Peer review discussed; however, given the nature of the major flooding scenarios it team desired to see more extensive will probably make little difference. discussions on this topic; however, In order to meet the Category II requirements of RC; 1.200 one must the team expected any resulting address potential unavailability of barriers that affect the propagation oi changes to the model results would water. be non-significant.
ATTACHMENT Additional Informa1:ionSupporting Probabilistic Risk Assessment Technical Adequacy TABLE A.2-I LASALLE PRA 2008 PEER REVIEW RESULTS SUPPORTING PEER REVIEW REQUIREMENTS DtfSCRlPTlON OF GAP ASSESSMENT IMPACT ON BASE PRA
- # - a .\-
IF-F3 The LS-PSA-013 notebook discusses .the industry 'key sources of Supporting Refer to impact discussion for uncertainty" per EPRl guidance. However, the current analysis does Requirement Not Supporting Requirement QU-E4.
not fully meet the requirements of RG 1.200, which requires a Met.
discussion of sources of rnodel uncertainty and related assumptions.
Also, there may be some plant-specific assumptions made that may not be fully captured by the generic list of potential sources of uncertainty.
Expand the existing treatment of sources of uncertainty to consider sources of model uncertainty and related assumptions. Consideration should also be given to potential plant-specific ass~imptionsthat should also be noted as s,ources of uncertainty. NCJREG-1855 and an upcoming EPRl Treatment of Uncertainty report should provide more auidance on how to meet this SR in the future.
QU-Dla ER-AA-600-1015 Attachment 2, "Review of Updated PRA Model," Supporting ~ocumentationissue. No impact.
contains specific guidance for reviewing a sample of accident Requirement Not Cutset review is performed as part sequences/culsets to determine that the logic of the cutset or Met. of the PRA update quantification sequence is correct. Sections 6.3.1 and 6.5 of LS-13SA-014 discuss and documentation process. Peer the top 10 core damage frequency (CDF) and large early release review team desired to see greater frequency (LERF) cutsets, respectively. The model appears to be documentation of such a review.
reasonable based on these discussions. However, the top 10 CDF cutsets represent only about 31% of the total CDF. The review team felt that additional cutsets, representing more % of the total CDF should be reviewed and cliscussed.
In response to a query from the review team, the LaSalle PRA team stated that additional cutsets were reviewed, but were not documented. The PRA team should provide evidence that such a review was performed by documenting it in the Quantification
ATTACHMENT Additional Informat.ionSupporting Probabilistic Risk Assessment Technical Adequacy TABLE A.2-1 LASALLE PRA 2008 PEER REVIEW RESULTS SUPPORTING REQUIREMENTS DEiSCRIPTION OF GAP QU-D4 ER-AA-600-1015 Attachment 2, "Review of Updated PRA Model,"
contains specific guidance for reviewing a sample of accident sequences/cutsets to determine that the logic of the cutset or sequence is correct.
Section 2 of LS-PSA-014 Quantification Notebook documents a review of top 10 cutsets; however, there is no documentation of a review of non-significant cutsets.
In response to a query from the review team, the LaSalle PRA team stated that additional non-significant cutsets were reviewed, but were not documented. The PR.A team should provide evidence that such a review was performed by documenting it in the Quantification Notebook.
The Summary Notebook includes documentation of key sources of Refer to impact discussion for uncertainty; however, with the changes to eliminate "key" from the SR Supporting Requirement QU-E4.
definition, this SR cannot be considered met.
Expand the existing treatrnent of sources of uncertainty to consider sources of model uncertainty and related assumptions. Consideration should also be given to potential plant-specific assumptions that should also be noted as sources of uncertainty. NUREG-1855 and an upcoming EPRl Treatment of Uncertainty report should provide more guidance on how to meet this SR in the future.
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ATTACHMENT Additional Information Supporting Probabilistic Risk Assessment Technical Adequacy TABLE A.2-I LASALLE PRA 2008 PEER REVIEW RESULTS PEER REV'EW ASSESSMENT I lMPACT ON BASE PRA Supporting The LaSalle PRA Summary Requirement Not Notebook provides an extensive Met. discussion of both parametric and model is affected (e.g., introduction of a new basic event, changes to modeling uncertainty and sensitivity basic event probabilities, change in success criterion, introduction of a studies for the base PRA.
new initiating event)." Given that the requirements QU-E2 have not The peer reviewers assessed the been met, this SR is consequently not met. sources of uncertainty as not met in The changes to this SR as identified by the NRC via a Federal anticipation of the NUREG-I855 Register Notice in July 2007 indicate that for all sources of uncertainty, [Reference 101 and EPRl 1016737 respectively, identify how the PRA model is affected. [Reference II ] specific process yet Once items for QU-El and QU-E2 are identified per the new to be issued at the time of review.
requirements, identify how the PRA model is affected (e.g. introduction The LaSalle uncertainty and of a new basic event, changes to basic event probabilities, change in sensitivity discussions in the base success criterion, introduction of a new initiating event) for each item. PKA are judged to be consistent with, or exceed the recently issued NUREG-1855 guidance; however, each ST1 change assessment will follow the NUREG-1855 construct.
A detailed description of accident sequences is provided for the top 10 Supporting Documentation issue. No impact.
accident sequences which equates to -70% of the CDF. To meet this Requirement Met Such information is documented in SR, a detailed description of significant accident sequences is (CC I). the PRA Quantification Notebook.
required. Since no definition of significant is provided in QU-F6, then a Peer review team desired to see detailed description for up to 95% of the accident sequences is more detailed documentation.
required to meet this SR.
Provide a detailed description for the remaining accident sequences that comprise up to 95% of the CDF. Note that providing this information would also s~~pport meeting SR QU-Dla.
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ATTACHMENT Additional lnformaltion Supporting Probabilistic Risk Assessment Technical Adequacy TABLE A.2-1 LASALLE PRA 2008 PEER REVIEW RESULTS that the requirements QU-E4 have not been met, this SR is consequently not met.
cumentation issue. No impact.
SR is not met.
Document the quantitative definition used for significant basic event,
)k discusses the industry ' fer to impact discussion for Page 10
ATTACHMENT Additional Information Supporting Probabilistic Risk Assessment Technical Adequacy TABLE A.2-1 LASALLE PRA 2008 PEER REVIEW RESULTS ASSESSMENT
- IMPACT ON BASE PRA-Supporting Documentation issue. No impact.
(ASME) standard for the significant sequence is most likely used in the Requirement Not LaSalle LERF analysis. tiowever, the fact that this definition may be Met.
used is not documented in the notebooks.
IDocument the definition in the Level 2 notebook for significant accident progression sequence (also refer to QU-F6)
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