ML20133Q397
| ML20133Q397 | |
| Person / Time | |
|---|---|
| Issue date: | 08/09/1985 |
| From: | Richardson J NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Liaw B Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20133Q399 | List: |
| References | |
| NUDOCS 8508150120 | |
| Download: ML20133Q397 (1) | |
Text
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t0A usoq'o, UNITED STATES e['
' 'g NUCLE AR REGULATORY COMMISSION p
WASHINGTON, D. C. 20555
%,.....f muw MEMORANDUM FOR:
B. D. Liaw, Chief Materials Engineering Branch Division of Engineering, NRR FROM:
J. E. Richardson, Chief Mechanical / Structural Engineering Branch Division of Engineering Technology, RES
SUBJECT:
TRANSMITTAL 0F DRAFT REPORT "PROBABILISTIC TREATHENT OF STRESS CORROSION CRACKING IN SENSITIZED 304 STAINLESS STEEL WELDMENTS IN BWR PIPING" The subject draft report was prepared in May 1985, by Failure Analysis Associates under contract to Lawrence Livermore National Laboratory.
Table 7 on page 75 of the report indicates that rupture probabilities in large diameter BWR piping are several orders of magnitude greater thar. ir PWR primary loop piping. Moreover, the authors conclude that " Analysis of the limited available data on cracking in alternative austenitic BWR piping materials (304 NG, 316, 316 NG) indicates that these materials would not provide substantial improvements in piping reliability unless they can be counted upon to be significantly less weld sensitized."
(See page 78 of the subject report).
These results embody many conservative assumptions. With respect to the 316 NG materials, high temperatures for long times were assumed during welding and repair and, in addition, high sulfate concentration was assumed to be continuously present. We believe these input assumptions are grossly conservative and have led to the wrong conclusions. More realistic input will undoubtedly show that 316 NG material is must less susceptable to stress corrosion cracking than 304. For example, the assumption of the continuous presence of sulfates and 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> of welding tire is totally unrealistic. A revision to the draft report which incorporates more realistic modeling inputs is being contemplated.
We understand that personnel from Failure Analysis Associates, Lawrence Livermore National Laboratory and Argonne National Laboratory now agree that the first draft report now being transmitted by this letter can be significantly improved in terms of realism. Thus, the previously cited results will no doubt be substantially revised.
. E. Richardson, Chief Mechanical / Structural Engineering Branch Division of Engineering Technology, RES
Enclosure:
As stated 8508150120 e50009 h81 0
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