ML070880519
| ML070880519 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 04/09/2007 |
| From: | Gordon Bjorkman NRC/NMSS/SFST |
| To: | Jamnes Cameron Division of Nuclear Materials Safety III |
| Chuang, J NMSS/SFST 301-492-3321 | |
| References | |
| TAC A10126 | |
| Download: ML070880519 (3) | |
Text
April 9, 2007 MEMORANDUM TO:
Jamnes L. Cameron, Branch Chief Division of Nuclear Material and Safety, Region III FROM:
Gordon Bjorkman, Branch Chief
/RA/
Spent Fuel Storage and Transportation Division, 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 The Division of Spent Fuel Storage and Transportation (SFST) staff finds that additional information is required in order to complete the ongoing TAR for assessing the adequacy of the Palisades weld flaw analysis for loaded spent fuel cask MSB No. 4.
During our review of the fatigue crack growth calculation, it was noted that one input variable was fixed at a possibly non-conservative value. As a consequence of this assumption, the associated fatigue crack growth rates could also be non-conservative. The result could thus under-predict the eventual flaw size, possibly by a very significant margin. Consequently, attached is a request for additional information in regards to this calculation.
Please contact Jerry Chuang, Senior Structural Engineer, of my staff at 301-415-8586, if you require clarification of this issue.
Enclosure:
Request for Additional Information
April 9, 2007 MEMORANDUM TO:
Jamnes L. Cameron, Branch Chief Division of Nuclear Material and Safety, Region III FROM:
Gordon Bjorkman, Branch Chief
/RA/
Spent Fuel Storage and Transportation Division, 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 The Division of Spent Fuel Storage and Transportation (SFST) staff finds that additional information is required in order to complete the ongoing TAR for assessing the adequacy of the Palisades weld flaw analysis for loaded spent fuel cask MSB No. 4.
During our review of the fatigue crack growth calculation, it was noted that one input variable was fixed at a possibly non-conservative value. As a consequence of this assumption, the associated fatigue crack growth rates could also be non-conservative. The result could thus under-predict the eventual flaw size, possibly by a very significant margin. Consequently, attached is a request for additional information in regards to this calculation.
Please contact Jerry Chuang, Senior Structural Engineer, of my staff at 301-415-8586, if you require clarification of this issue.
Enclosure:
Request for Additional Information DISTRIBUTION:
NMSS r/f SFST r/f JChuang MDebose GHornseth BWhite MGryglak ML070880519 OFC:
JChuang MDebose GHornseth GBjorkman DATE:
04/05/2007 04/05/2007 04/05/2007 04/09/2007 OFFICIAL AGENCY RECORD
REQUEST FOR ADDITIONAL INFORMATION Palisades Weld Flaw Analysis for Loaded Spent Fuel Cask MSB No. 4 Model No. VSC-24
Reference:
Licensee supplied calculation EA-FC-864-50, Appendix 2 to MSB No. 4 Structure Integrity Assessment, page 18.
Issue:
The fatigue crack growth analysis set a fixed value of R at 0.9 in a fatigue crack growth law provided by ASME Section XI, Article A-4000 for all stress cycles. Provide fatigue crack growth data for a surface crack in ASTM SA-516, Grade 70 ferritic steel for the range of 0.9 < R < 1.0 and re-analyze the case using the data to demonstrate that the final crack length determined by the referenced calculation 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 a constant R value of 0.9. However, due to the level of residual stresses imposed in the assumptions, it appears to the staff that most of the loading cycles are in the range of 0.9 < R < 1.0.
It is well known that higher values of R yield a larger crack growth rate per cycle for a fixed stress amplitude. Thus, fatigue crack growth data for a semi-circular surface crack in ASTM SA-516, Grade 70 ferritic steel for this R-range (0.9 < R < 1.0), in air, at room temperature are needed. 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.