ML082350350

Memo to Christine Lipa Request for Additional Information; Region III TAR Requesting Assessment of Palisades Weld Flaw Analysis for Loaded Spend Fuel Cask Msb No. 4 (TAC A10126)

ML082350350
Person / Time
Site:	Palisades
Issue date:	08/20/2008
From:	Christopher Regan NRC/NMSS/SFST
To:	Christine Lipa Division of Nuclear Materials Safety III
References
FOIA/PA-2009-0008A, TAC A10126
Download: ML082350350 (3)

Text

August 20, 2008

MEMORANDUM TO: Christine Lipa, Branch Chief Division of Nuclear Materials Safety Decommissioning, Region III FROM: Christopher Regan, Branch Chief /RA/ Division of Spent Fuel Storage and Transportation, NMSS

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION; REGION III TAR REQUESTING ASSESSMENT OF PALISADES WELD FLAW ANALYSIS FOR LOADED SPENT FUEL CASK MSB NO. 4 (TAC No. A10126)

By letter dated June 24, 2008, (ML081780224) the Nuclear Regulatory Commission (NRC) requested information to assist in their continuing review of the weld flaw analysis for loading Spent Fuel Cask Multi-Assembly Sealed Basket (MSB) No. 4, at the Palisades Nuclear Plant.

The Division of Spent Fuel Storage and Transportation staff finds that a correction to the enclosure of the above letter is required. As a consequence, the enclosure submitted herein has been changed to incorporate the correction and is indicated by change bars. Disregard and replace the previous submitted enclosure with the corrected enclosure provided.

Therefore, enclosed is a corrected request for additional information in regards to the fatigue crack growth calculation utilizing data from the specific ASTM material specification.

Please contact David Tarantino, Materials Engineer, of my staff at 301-492-3413, if you require further clarification of this issue.

Docket No. 50-255 and 072-7

Enclosure:

Request for Additional Information

August 20, 2008

MEMORANDUM TO: Christine Lipa, Branch Chief Division of Nuclear Materials Safety Decommissioning, Region III FROM: Christopher Regan, Branch Chief /RA/ Division of Spent Fuel Storage and Transportation, NMSS

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION; REGION III TAR REQUESTING ASSESSMENT OF PALISADES WELD FLAW ANALYSIS FOR LOADED SPENT FUEL CASK MSB NO. 4 (TAC No. A10126)

By letter dated June 24, 2008, (ML081780224) the Nuclear Regulatory Commission (NRC) requested information to assist in their continuing review of the weld flaw analysis for loading Spent Fuel Cask Multi-Assembly Sealed Basket (MSB) No. 4, at the Palisades Nuclear Plant.

The Division of Spent Fuel Storage and Transportation staff finds that a correction to the enclosure of the above letter is required. As a consequence, the enclosure submitted herein has been changed to incorporate the correction and is indicated by change bars. Disregard and replace the previous submitted enclosure with the corrected enclosure provided.

Therefore, enclosed is a corrected request for additional information in regards to the fatigue crack growth calculation utilizing data from the specific ASTM material specification.

Please contact David Tarantino, Materials Engineer, of my staff at 301-492-3413, if you require further clarification of this issue.

Docket No. 50-255 and 072-7

Enclosure:

Request for Additional Information

DISTRIBUTION: NMSS r/f SFST r/f DTarantino RHall SBakhsh, RIII ML OFC: SFST SFST NAME: DTarantino CRegan DATE: 08/19/2008 08/20/2008 OFFICIAL AGENCY RECORD

REQUEST FOR ADDITIONAL INFORMATION Palisades Weld Flaw Analysis for Loaded Spent Fuel Cask MSB No. 4 Model No. VSC-24

Reference:

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 welding 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 ASME Article A-4000, Material Properties. See Bamford, W. H. and Jones, D. P., "The Use of Fatigue Crack Growth Technology in Fracture Control Plans for Nuclear components," Fatigue Crack Growth Measurement and Data Analysis, ASTM STP 738, S. J. Hudak, Jr., and R. J. Bucci, Eds., American Society for Testing and Materials, 1981, pp. 281-299. Refer to the heading "Crack Growth Rate Law Considerations," Table 1 and Table 2. 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.