ML103510674

Callaway Plant, Unit 1, Email, Request for Additional Information, License Amendment Request for Technical Specification Change Regarding Risk Informed Justification (TAC No. ME4506)

ML103510674
Person / Time
Site:	Callaway
Issue date:	12/17/2010
From:	Polickoski J T Plant Licensing Branch IV
To:	Elwood T B, Maglio S A Union Electric Co
Polickoski J T, NRR/DORL/LPL4, 415-5430
References
TAC ME4506
Download: ML103510674 (4)

Text

Lent. Susan From: Polickoski, James Sent: Friday, December 17, 20104:05 PM To: Elwood, Thomas B; Maglio, Scott A Cc: Thadani, Mohan; Markley, Michael

Subject:

RAI re: LAR for TS relocation of Surv freq reqs dated December 17,2010 Attachments:

Callaway Surv Reg LAR. RAI 17 Dec 201 O.docx ScottrTom:

The NRC staff has reviewed your license amendment application dated August 5,2010 for the Callaway Plant -Union Electric Company's request for Technical Specification change regarding risk-informed justification for the relocation of specific surveillance frequency requirements to a licensed controlled program. Based on that review and as mentioned in our phone discussion on December 14, 2010, the NRC staff has identified a need for additional information as outlined in the attached request for additional information (RAI). Please review the RAI, and feel free to contact me if you would like to discuss. The staff requests a response by January 14, 2010. Thank you for your attention in this matter, Jim James 1. Polickoski Project Manager -Callaway, Diablo Canyon US NRC/NRRIDORLlLPL4 james. polickoski@nrc.gov 301-41 5-5430 REQUEST FOR ADDITIONAL CALLAWAY PLANT, UNIT UNION ElECTRIC LICENSE AMENDMENT APPLICATION (LCDN 10-0020) TECHNICAL SPECIFICATION CHANGE REGARDING RISK-INFORMED JUSTIFICATION FOR RElOCATION OF SPECIFIC SURVEILLANCE FREQUENCY TO A LICENSED CONTROLLED TAC Number The NRC staff requests additional information to complete its review of the license amendment request for Technical Specification change regarding risk-informed justification for the relocation of specific surveillance frequency requirements to a licensed controlled program. By letter dated August 5, 2010 (MLl02250056), Union Electric Company (licensee) proposed changes to adopt the Nuclear Regulatory Commission (I\lRq-approved TS Task Force (TSTF)-425, Revision 3, "Relocate Surveillance Frequencies to Licensee Control-RITSTF Initiative 5b." By email dated September 16, 2010 (MLl02590588), the NRC provided its acceptance of this amendment request which will enable the NRC to complete its detailed technical review. Following NRC staff review of the provided application, the NRC staff has a number of questions listed below: In the application, the licensee identified peer review findings from the 2000 industry peer review (Table 2 of Attachment 2 of its submittal) and findings from the 2006 Scientech assessment (Table 1 of Attachment 2 of its submittal).

In the staff's assessment of the overall technical adequacy of the internal events probabilistic risk assessment (PRA) model, the staff noted that the existing model (designated Update 4) appears to have a number of significant omissions and deficiencies, specifically: Application of an outdated and non-conservative RCP seal LOCA model Inadequate treatment of LERF Inadequate and non-conservative treatment of internal floods Inadequate treatment of system dependencies Inadequate treatment of ISLOCA The licensee further stated that an updated PRA model (Update 5) is currently being developed which will address all findings from the 2006 assessment.

This model is scheduled to be completed in the second quarter of 2011. The licensee has stated that, until that model is available, the findings from these reviews will be considered and sensitivity analyses completed as necessary.

The staff requests the following clarifications: Confirm the remaining open findings from the 2000 industry peer review will be addressed by the updated model. Some findings involve missing scope (for example, 2000 peer review finding L2-1 states that containment isolation failures and internal floods are not considered in large early release frequency (LERF) calculations).

Clarify how sensitivity analyses address missing scope items?

-2Some findings were dispositioned by stating that the updated model will be used to evaluate surveillance interval changes: Is the updated model sufficiently complete to permit its use in the Surveillance Frequency Control Program? If so, is it the intent that the revised model be applied for any required sensitivity studies required for this application? Provide the basis for the implementation of this model being delayed until 2011 if it is needed to support this application? In Attachment 2 Table 1, several items were dispositioned by sensitivity studies which show a minor impact on results. However, for findings AS-4 and SY-1, more detail is needed for the staff to conclude that the sensitivity studies bound the specific findings.

The staff requests further specification on exactly how the model was varied in the sensitivity cases, and how this bounds the deficiency being evaluated. In Attachment 2 Table 2, finding IE-7 states that the interfacing systems loss-of-coolant accident (ISLOCA) evaluation does not consider scenarios without containment bypass. The licensee has stated that it disagrees with this finding. Provide the complete peer review discussion of this item for the staff to better understand the scope of the issue and the disposition. In Attachment 2 Table 1, finding IE-8 identifies that recovery events do not have sufficient analysis or data, but there is no discussion of the significance of this finding. The staff requests further discussion of these events in more detail, identifying their probabilities, basis, and importance to the PRA results, in order to justify the adequacy of the existing PRA model. In Attachment 2 Table 1, findings associated with requirement AS-B1 identify that initiating event impacts on mitigating functions may not be properly captured.

This has been dispositioned based on a sensitivity analysis done on a prior application for Emergency Service Water. These findings point to a potential fundamental flaw in the PRA model if initiator impacts are not properly addressed in the logic. Since the scope of the findings is not identified, the staff requests additional specific details for these findings and a demonstration that the scope and impact of these findings is not significant for this application. In Attachment 2 Table 1, finding AS-4 states that the reactor coolant pump (RCP) seal LOCA model is out-of-date.

The disposition of this item identifies the use of an "older-vintage" model. a) The staff requests that the specific basis for the current seal LOCA model be identified.

b) If the updated model referred to in the submittal uses the correct seal LOCA model, identify this model and provide an assessment of its impact on the overall results compared to the existing older model. In Attachment 2 Table 1, finding QU-1 identifies that the correlated data probabilities are not accounted for during quantification, and the disposition identifies that this will be addressed by sensitivity studies. The staff requests that a discussion of the significance of this finding be provided in order to conclude that sensitivity analyses are an adequate means to address the issue.

-3In Attachment 2 Table 1, finding LE-1 identifies that some LERF contributors are not addressed by the PRA model. The staff requests identification of the missing scope items and justification be provided that their contribution to LERF would not be significant in order to conclude that sensitivity analyses are an adequate means to address the issue. In Attachment 2 Table 1, several findings against internal flooding are addressed stating that NEI 10 allows the use of qualitative or bounding analyses to address internal flood contributors. 10, Revision 1, specifies Regulatory Guide 1.200, Revision 1, as the governing document for PRA technical adequacy.

Internal flooding initiators are specifically addressed in the internal events standard endorsed by this regulatory guide. Therefore, based on this discussion, the use of a quantitative PRA evaluation is required, and from staff review of the application, qualitative or bounding evaluations are not addressed.

The staff requests licensee disposition of internal flooding findings from the peer review be re-evaluated.