Text

Draft RAI from Probabilistic Risk Assessment Licensing Branch on the Proposed Extended Power Uprate Amendment
	ML090780006
Person / Time
Site:	Monticello
Issue date:	03/18/2009
From:	Jigar Patel; NRC/NRR/DRA/APLA
To:	;
	Tam P
Shared Package
ML090780009	List: ML090780004; ML090780006;
References
	TAC MD9990
	Download: ML090780006 (3)
	v • d • e

Accession No. ML090780006 PROBABILISTIC RISK ASSESSMENT (PRA) LICENSING BRANCH (APLA) REQUEST FOR ADDITIONAL INFORMATION REGARDING MONTICELLO NUCLEAR GENERATING PLANT REQUEST FOR EXTENDED POWER UPRATE (EPU)

1. The NRC staff evaluation of the individual plant examination of external events (IPEEE) report specifically identified additional analysis is necessary to identify if single pump success is adequate for the Service Water System. The response to NRC Probabilistic Risk Assessment (PRA) Branch requests for additional information (RAI) dated February 4, 2009 - NRC Review Item (7) indicates that the current internal events Monticello Nuclear Generating Plant (MNGP) PRA Model of Record assumes that a single Service Water pump is adequate to successfully accommodate post transient cooling requirements. Describe how MNGP confirms that the single Service Water pump assumption modeled in the PRA is adequate for post-EPU requirements.

2. EPU Safety Analysis Report (SAR), Section C.3, discusses assessments for the 2003 Monticello PRA model against the American Society of Mechanical Engineers (ASME )

standard and NRC draft Regulatory Guide DG-1122 performed by Applied Reliability Engineering Inc, (ARE), in early 2004. This section does not provide information on findings and comments related to this assessment. Please identify and discuss the dispositions of any open items identified as a result of the 2004 ARE assessment, how they were subsequently addressed in the MNGP PRA, and provide justification for those open-items that affect the EPU.

3. EPU SAR, Section 4.1.1 and Section 4.5 states no significant impact on internal flooding initiator frequencies are postulated due to the EPU. Since higher flow rates can contribute to changes in initiator events for floods, please provide a more thorough justification for your conclusion on how EPU flow rates will not affect internal flooding initiator frequencies.

4. The staff notes that success criteria changes crediting Control Rod Drive Hydraulic (CRDH) by depressurizing the reactor is unique compared to boiling water reactor (BWR) EPUs previously approved. If depressurization is successful, then the low pressure injection sources would be available, obviating any need for successful CRDH injection. Further, if changes to emergency operating procedures (EOP) are required to implement this change, then this change could potentially complicate operator response to other events. The staff requests responses to the following issues to better understand the impacts of this change:

a. Was depressurization required in order to credit two CRDH pumps pre-EPU?

Describe the analyses conducted which determined that depressurization was necessary for EPU conditions.

b. Describe how the action for depressurization has been modeled in the PRA.

Explain how the human reliability analysis (HRA) for this action compares to any other actions to depressurize the reactor. Describe how the HRA dependency of this action on other operator actions was assessed.

c. Does the new requirement for reactor depressurization to allow CRDH injection create new sequences and end states? Provide the basis for this conclusion and a summary of any resulting changes to the sequences and end states.

d. Describe the risk significance of the CRDH success criteria change (i.e., Fussell Vesely Importance and Risk Achievement Worth) and contribution of the sequences associated with this change to core damage frequency (CDF) and large early release frequency (LERF).

e. Did changes to CRDH success criteria require changes to EOPs? If yes, describe the changes, operator training and validation methods, and why the changes to plant-specific EOPs remain consistent with BWR EOP guidelines or were otherwise determined to be acceptable. Your response should also discuss any potential negative impacts from the operator inappropriately depressurizing the reactor due to the new procedures.

f. Was a focused peer review performed for the PRA model changes necessary to incorporate the new CRDH success criteria including any new event tree structure and operator actions? If yes, provide the results of that peer review. If not, please justify why a peer review was not judged to be required.

5. Describe the calculation for the change in risk as a result of needing one additional safety/relief valve (SRV) to open for anticipated transient without scram (ATWS). Does the change in risk calculated for EPU include a contribution due to the SRV success criteria? Discuss how the change in SRV success criteria has been incorporated into the PRA model and include a discussion of the changes to common cause failure events and their basis.

6. EPU SAR, Appendix D, provides requantification analysis of error probability. Please describe any new operator actions developed due to the EPU that could impact the PRA and describe the methodology utilized to determine the error probability associated with the new actions.

7. EPU SAR, Section 5.6, states that the EPU change in power represents a relatively small change to the overall challenge to the containment under severe accident conditions. Please provide additional details which justify this conclusion.

8. EPU SAR, Section 4.3.1, states fire PRA results are less impacted by changes in operator actions timings than the internal events PRA results. The re-rate safety evaluation dated September 16, 1998 Section 5.3 states: The CDF contribution from internal fires increased from 8.34E-6/Year to 8.8E-6/Year. This was attributed solely to the increase in human error rates because the time available to perform various accident mitigating tasks decreases with uprate. Please provide additional justification for the conclusion stating fire PRA results are less impacted by changes in operator actions timings than the internal events PRA results.

9. The staff requests responses for the following information on Low Power and Shutdown PRA

Explain how the EPU affects the scheduling of outage activities.

Provide additional information regarding the reliability and availability of equipment used for shutdown conditions.

Explain how the EPU affects the availability of equipment or instrumentation used for contingency plans.

Explain how the EPU affects the ability of the operator to close containment.

10. EPU SAR, Section 3.3.2 indicates that the changes to EOPs and severe accident management guides as a result of the EPU were not available prior to completion of the PRA evaluation and it was assumed that the procedural changes would have a minor impact on the PRA results. The staff needs to conclude that EOP impacts are minimal, therefore, please provide a schedule for the development of the final draft of EOPs, and confirmation that the PRA results would only be minimally impacted.

11. EPU SAR Enclosure 15 provides a quantitative assessment of the risk impact of the COP credit for low pressure ECCS pump NSPH for ATWS, SBO, and internal fires events. The analysis indicates a CDF for each of these events, but does not provide a LERF metric. Please provide a LERF metric for each of the aforementioned events.

12. Based on Figures 2.6-1A, B, C and Figures 2.6-2, 3, 4, 5, 6, 6, 7 in Enclosure 7, available containment over pressure (COP) exists as a result of the accident to provide adequate net positive suction head (NPSH) for the emergency core cooling system (ECCS) pumps during fire, loss-of-coolant accident (LOCA), ATWS, and station blackout (SBO) events. Please summarize pre-EPU and post-EPU maximum pressure and duration for which containment pressure above atmospheric is required to ensure adequate NPSH. In addition, are there any operator actions required to assure overpressure conditions exist (i.e., tripping containment coolers)? If so, describe the safety significance of these actions.

v t e Letter Sequence Draft RAI
TAC:MD9990, Clarify Application of Setpoint Methodology for LSSS Functions (Approved, Closed)
Initiation Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request, Request Acceptance, Acceptance Supplement, Supplement, Supplement, Supplement, Supplement, Supplement, Supplement, Supplement, Supplement, Supplement, Supplement, Supplement, Supplement, Supplement, Supplement, Supplement, Supplement Administration Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance, Withholding Request Acceptance Meeting, Meeting, Meeting, Meeting, Meeting, Meeting Questions 16 December 2008 11 February 2009 11 March 2009 12 March 2009 18 March 2009 18 March 2009 19 March 2009 20 March 2009 23 March 2009 29 March 2009 28 March 2009 28 March 2009 6 April 2009 6 April 2009 29 April 2009 26 June 2009 2 July 2009 2 July 2009 14 July 2009 14 July 2009 5 November 2009 16 March 2011 12 September 2011 4 October 2012 8 November 2012 28 March 2013 17 May 2013 9 July 2013 26 November 2013 18 December 2008 18 December 2008 19 March 2009 25 October 2009 15 February 2013 12 March 2013 10 May 2013 24 April 2013 Answers 25 January 2010 28 September 2010 13 January 2012 21 December 2012 7 March 2013 18 March 2013 21 March 2013 10 April 2013 18 July 2013 18 July 2013 2 August 2013 18 May 2016 19 July 2012 31 January 2013 29 March 2013 10 April 2013 Results Approval, Approval, Approval, Approval, Approval, Approval Other: L-MT-08-091, Calculation 0801040.301, Steam Dryer Outer Hood Submodel Analysis., L-MT-09-002, Response to NRC Probabilistic Risk Assessment (PRA) Branch Requests for Additional Information (Rais) Dated December 5, 2008, L-MT-09-003, Response to NRC Environmental Branch Requests for Additional Information (Rais) Dated December 18, 2008, L-MT-09-004, Enclosure 1 (Continued) to L-MT-09-004, NSPM Response to Containment & Ventilation Branch RAI Number 2, Copy of MNGP Appr T0406 Data Transmittal Pages 1 of 538 Through Pages 538 of 538, L-MT-09-026, Calculation 0000-0081-6958 MNGP-PRNMS-APRM Calc-2008-NP, Rev. 1, Average Power Range Monitor Selected Prnm Licensing Setpoints - EPU Operation (Numac), L-MT-09-027, Extended Power Uprate: Response to Instrumentation and Controls Branch RAI No. 3 Dated April 6, 2009, L-MT-09-044, Extended Power Uprate: Response to NRC Mechanical and Civil Engineering Review Branch (Emcb) Requests for Additional Information (Rais) Dated March 28, 2009, L-MT-09-049, Drawing C.5-2007, Revision 15, Failure to Scram, L-MT-09-073, Extended Power Uprate: Response to NRC Containment and Ventilation Review Branch (Scvb) Requests for Additional Information (Rais) Dated July 2, 2009 and July 14, 2009, L-MT-09-083, Extended Power Uprate: Limit Curves Requested by the Mechanical and Civil Review Branch (Emcb) Associated with Requests for Additional Information (Rais) Dated March 20, 2009, L-MT-09-088, Extended Power Uprate: Revision to Clarify Text in Enclosures 5 and 7 of L-MT-08-052, L-MT-09-097, Extended Power Uprate: Acknowledgement of NRC Review Delay, L-MT-10-025, Extended Power Uprate (Epu): Response to NRC-NSPM February 25, 2010 Conference Call, L-MT-10-072, Extended Power Uprate: Updates to Docketed Information, L-MT-11-044, Uprate (Epu): Update on EPU Commitments, L-MT-12-056, WCAP-17549-NP, Rev. 0, Monticello Replacement Steam Dryer Structural Evaluation for High-Cycle Acoustic Loads Using ACE, L-MT-12-090, Westinghouse, LTR-A&SA-12-8, Rev. 1, Attachment B, Recommendations for Inspections of the Monticello Replacement Steam Dryer., L-MT-12-114, Drawing C.5-2007, Rev. 17, Failure to Scram, L-MT-13-020, Enclosure 1 - Responses to the Gap Analysis, L-MT-13-029, Enclosure 14 to L-MT-13-029 - WCAP-17716-NP, Revision 0, Benchmarking of the Acoustic Circuit Enhanced Revision 2.0 for the Monticello Steam Dryer Replacement Project., L-MT-13-091, WCAP-17716-NP, Revision 1 - Benchmarking of the Acoustic Circuit Enhanced Revision 2.0 for the Monticello Steam Dryer Replacement Project, Enclosure 14, L-MT-13-092, Extended Power Uprate (Epu): Completion of EPU Commitments, Proposed License Conditions and Revised Power Ascension Test Plan, L-MT-13-096, GE-MNGP-AEP-3304R1, Enclosure 4, NEDC-33435 Corrected Pages, L-MT-13-126, Enclosure 3, GE-MNGP-AEP-3306, Enclosure 2 GEH Response to Mella+ Eicb RAI and Affidavit, L-MT-14-023, Maximum Extended Load Line Limit Analysis Plus: Technical Specification Clarifications, L-MT-15-074, Enclosure 7, WCAP-18604-NP, Revision 0, Monticello EPU Main Steam Line Strain Data Evaluation Report., L-MT-16-017, Revised Commitment to Reconcile Analysis of Bypass Voiding for Transition to Areva Analysis Methodology, L-MT-16-071, Submittal of 2016 Annual Report of Changes in Emergency Core Cooling System Evaluation Models Pursuant to 10 CFR 50.46, ML083230111, ML083400402, ML083500575, ML083570610, ML083590127, ML090710680, ML090710683, ML090710684, ML091120578, ML091140470, ML091410121, ML091410122, ML091410123, ML091410124, ML091760769, ML092290250, ML092810554, ML093160816, ML093220925, ML093220964, ML093620024, ML100280558... further results
MONTHYEAR2009-02-24 [Table View]

ML090780006

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