ML081970539

Follow-up Information Regarding Msb #4 Weld Flaw Analysis

ML081970539
Person / Time
Site:	Palisades
Issue date:	07/11/2008
From:	Christine Lipa NRC/RGN-III/DNMS/DB
To:	Schwarz C Entergy Nuclear Operations
References
Download: ML081970539 (2)

Text

July 11, 2008 Christopher J. Schwarz Site Vice President Entergy Nuclear Operations Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, MI 49043-9530

SUBJECT:

FOLLOW-UP INFORMATION REGARDING MSB #4 WELD FLAW ANALYSIS

Dear Mr. Schwarz:

As part of an ongoing evaluation to determine the adequacy of the Palisades weld flaw analysis for loaded spent fuel cask MSB #4, we requested a revision to the fatigue crack growth calculation (Calculation EA-FC-864-50, Appendix 2 to MSB No. 4 Structure Integrity Assessment). We have received a copy of the revised Calculation EA-FC-864-50, Appendix 2 that highlights the changes from the original revision in response to our letter dated January 23, 2008. During our review of the revised fatigue crack growth calculation, the requested fatigue crack growth data for the specific American Society of Testing and Materials (ASTM) material specification was not provided. Therefore, enclosed is a request for additional information in regards to the fatigue crack growth calculation utilizing data from the specific ASTM material specification.

In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter and its enclosure will be available electronically in the NRC Public Document Room or from the Publicly Available Records (PARS) component of NRC's document system (ADAMS). The NRCs document system is accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html.

Please contact Sarah Bakhsh of my staff at (630) 829-9816 if you have any questions regarding this matter.

Sincerely,

/RA by W. Snell Acting for/

Christine A. Lipa, Branch Chief Decommissioning Branch Docket No. 072-00007 License No. DPR-20 cc: S. Leblang, High Level Waste Manager, Entergy Nuclear Operations L. Lahti, Manager, Licensing, Entergy Nuclear Operations

Enclosure:

Request for Additional Information DOCUMENT NAME: G:\SEC\Work in progress\LettertoLicenseeCask4WeldFlawRequestforInfo#2.doc X Publicly Available Non-Publicly Available Sensitive X Non-Sensitive To receive a copy of this document, indicate in the concurrence box "C" = Copy without attach/encl "E" = Copy with attach/encl "N" = No copy OFFICE RIII RIII RIII RIII NAME SRBakhsh:mb CALipa by W. Snell for DATE 07/09/08 07/11/08 OFFICIAL RECORD COPY

REQUEST FOR ADDITIONAL INFORMATION Palisades Weld Flaw Analysis for Loaded Spent Fuel Cask MSB No. 4 Model No. VSC-24 Description and Summary of Results of Calculation EA-FC-864-50-01 Issue:

The original calculation, EA-FC-864-50, MSB #4 Structural Integrity Assessment, Appendix 2, evaluated flaws in the longitudinal weld in Spent Fuel Cask Multi-Assembly Sealed Basket (MSB) No. 4. This calculation was performed conservatively, assuming a uniform weld residual stress of 54 ksi (base material yield stress) and the parameter R=0.9 for the crack in the MSB longitudinal shim weld.

The parameter R for stress in the MSB longitudinal crack is in the range of 0.9 < R < 1.0.

Reassessment using a value of R = 1.0 would yield a higher fatigue crack growth rate.

Calculation EA-FC-864-50-01, Palisades Weld Flaw Analysis for Loaded VSC Spent Fuel Cask MSB No. 4, performed this reassessment to determine the flaw size at the end of 50-year life using the R value of 1.0, which is conservative.

Background:

The Division of Spent Fuel and Storage and Transportation (SFST) staff reviewed the fatigue crack growth calculation for an initial semi-circular surface crack present in the MSB No. 4, considering 50 years of cyclic service conditions. The calculations assumed all loading cycles had an R value of 0.9 < R < 1.0. However, the data for the specific American Society of Testing and Materials (ASTM) material specification was not used in the calculations.

It should be noted that there exists a number of fatigue crack growth models in the open literature, including the model adopted by American Society of Mechanical Engineers (ASME)

Code Case 9100. Comparisons on the crack growth rate between these models show that the ASME model is less conservative. Thus, the licensee shall obtain fatigue crack growth data for a semi-circular surface crack in ASTM SA- 516, Grade 70 ferritic steel for the R-range (0.9 < R < 1.0), in air, at room temperature to mimic the cask material and environmental conditions. Using such data, a new analysis should be performed to show that the final calculated crack sizes at the end of a 50-year service life remain stable.

Absent such data and re-analysis, the SFST staff are unable to determine if the flaw propagation after 50 years of cyclic loads would remain stable, thus assuring the integrity of the cask.

Enclosure