ML13095A160

Email, Draft Request for Additional Information - Review of License Renewal Commitment NLS2009100-1 - Core Rim Plate Bolts

ML13095A160
Person / Time
Site:	Cooper
Issue date:	04/04/2013
From:	Lynnea Wilkins Plant Licensing Branch IV
To:	Mccutchen E Nebraska Public Power District (NPPD)
Wilkins L
References
TAC ME9550
Download: ML13095A160 (3)

Text

Lent, Susan From: Wilkins, Lynnea Sent: Thursday. April 04, 20134:34 PM To: McCutchen, Edward L.

Cc: Lent, Susan; Burkhardt, Janet

Subject:

DRAFT: RAls for Cooper Nuclear Station Re: Core Plate Hold Down Bolt Stress Analysis (ME9550)

Attachments: ME9550 Email RAls.docx Ed, By letter dated January 16, 2012, the Nebraska Public Power District (NPPD or the licensee), submitted a report on the stress analysis of the Cooper Nuclear Station (CNS) core plate rim bolts. This report was submitted in accordance with License Renewal Commitment NLS20091 00-1 , as documented in NUREG-1944, whereby the licensee committed to perform an analysis of the CNS core plate rim bolts to demonstrate the adequacy of the bolts considering the loss of bolt pre-load experienced during the period of extended operation (PEO) and submit this analysis at least two years prior to entering the PE~.

The NRC staff has determined that additional information specified in the attached Request for Additional Information (RAI) is needed for the staff to complete its evaluation. Please contact me if a clarifying teleconference is needed for the attached RAI.

Thanks Lynnea L!::fnnea Wi ({(ins, Project Manager Fort Calhoun Station, Unit 1 Cooper N udear Station Plant Licensing Branch IV Division of Operating Reactor Licensing Office of N udear Reactor Regulation US N udear Regulatory Commission Phone: 301-415-1377 1

REQUESTS FOR ADDITIONAL INFORMATION (RAIS)

NEBRASKA PUBLIC POWER DISTRICT (NPPD)

COOPER NUCLEAR STATION (CNS)

CORE PLATE HOLD DOWN BOLT STRESS ANALYSIS PERFORMED TO ADDRESS LICENSE RENEWAL COMMITMENT (NLS2009100-1)

DOCKET NUMBER 50-298 TAC NO. ME9550 EIVICB RAI 1 The example stress analysis provided in the Boiling Water Reactor Vessel and Internals Project (BWRVIP)-25, "BWR Core Plate Inspection and Flaw Evaluation Guidelines," is based on an elastic finite element analysis of the core plate and core plate hold down bolts. The information provided in Enclosure 1 (NEDC-33674P, "Cooper Nuclear Station Core Plate Bolt Stress Analysis Report") to Reference 1 does not state what type of analysis was performed to demonstrate that the CNS core plate hold down bolts (core plate bolts) will remain structurally adequate throughout the period of extended operation (PEO), considering a potential loss of preload. Please confirm that the stress analyses performed in NEDC-33674P are consistent with the approach assumed in BWRVIP-25 (Le., elastic finite element analysis).

EMCB RAI2 Section 2.0 of NEDC-33674P notes that a portion of the CNS plant-specific data was not available for this analysis and, subsequently, scaled data from Appendix A of BWRVIP-25 was used in lieu of plant-specific data. Please state what CNS plant-specific data was not available and what corresponding data was used from BWRVIP-25. Further, please provide a technical justification demonstrating that the alternative data provides a sound basis for determining that the core plate bolts will remain structurally adequate during the PE~.

EMCB RAI3 Section 7.1 of NEDC-33674P discusses the preload which was accounted for in the CNS core plate bolt stress analyses. This section notes that the original preload for each bolt was 300 plus or minus 25 foot-pound force (ft-Ibf). However, no references are provided regarding the basis for this value. Please provide the basis for the value of the preload assumed in this analysis.

EMCB RAI4 Section 8.1 of NEDC-33674P notes that the analysis performed for CNS core plate bolts calculate the shear loads on the core plate aligner pins using a different method than that used in BWRVIP-25 due to the variance in aligner pin configurations. Please describe the method used to calculate the shear loads for the CNS core plate aligner pins and provide a technical justification for this deviation from BWRVIP-25 which demonstrates that the alternative method provides an accurate means to evaluate the shear stresses imposed on the aligner pins.

EMCB RAI5 Section 8.1 of NEDC-33674P provides the results of the stress analyses of the CNS core plate bolts for three distinct scenarios. For each scenario, the bolt stress levels were compared ENCLOSURE

- 2 against applicable allowable stress values prescribed by the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, depending on the service level considered (i.e., Normal, Upset, Emergency or Faulted). The construction of the core plate results in an uneven distribution of the resultant horizontal and vertical loads supported by the core plate bolts. However, the results presented in Section 8.1 of NEDC-33674P do not specify whether these results apply to the limiting CNS core plate bolt(s). Please confirm that the results presented in this section of NEDC-33674P correspond to the limiting core plate bolt(s) (Le.,

those which support the greatest horizontal and/or vertical loads) and demonstrate that these limiting core plate bolt(s) meet the applicable ASME Code allowable stress values. If the results presented in NEDC-33674P do not correspond to the limiting core plate bolts, please present the results of the stress analyses for the limiting core plate bolt(s) which demonstrate that the stresses induced in the limiting core plate bolts meet the applicable ASME Code allowable stress values.

References

1) Letter from D. W. Van Der Kamp, Nebraska Public Power District, to NRC Document Control Desk, "Completion of License Renewal Commitment NLS2009100-1 (Revision

1) - Cooper Nuclear Station, Docket No. 50-298, DPR-46," dated January 16, 2012.

(ADAMS Accession Nos.: ML12031A248 (Incoming Letter), ML12031A249 (Non Proprietary Stress Report), ML12031A250 (Proprietary Stress Report>>