EXAMINATION OF A NONREGENERATIVE HEAT EXCHANGER FROM THE U.S.S. NAUTILUS (SSN-571)
Selected components from a staianless steel nonregenerative heat exchanger removed from the U.S.S. Nautilus (SSN571) have been examined for evidence of stress-corrosion cracking. The examination was conducted on three baffle plates, all primary-face seal welds, and the tubes and the surrounding tube sheets of 7 out of a total of 35 tubes. Maximum operating temperature of the heat exchanger was 260 ction prod- F for the inlet primary water and 164 ction prod- F for the exit secondary water. Chloride content of the secondary water averaged 5 ppm, with a maximum of 15 ppm. Only one suspected stress-corrosion crack was found in the components normally in contact with the secondary water. The crack, 2.5 mils in depth, was located on a fully exposed tube. At the 95 per cent confidence level this represented a probability of finding cracking on fully exposed surfaces in 0 to 60 per cent of the rest of the tubes in the heat exchanger. Severe stress-corrosion cracking was found in tubes in the tube-sheet drain area at the juncture with the inner tube sheet at the inlet end, where secondary water seeped past the expanded tubes. Cracks were detected in five of seven tubes for a statistical probability of 25 to 96 per cent at the 95 per cent confidence level. Maximum depth of cracks was 28 mils or 80 per cent penetration of the 35-mil-thick tubing wall. Stress-corrosion cracks also were found around several holes on the drain-side tube-sheet surfaces at the inlet end. Maximum depth was 12 mils, which did not seriously threaten penetration of the 9/16-in.-thick tube sheet. Cracks were detected in 5 of 35 primary-face seal welds at the inlet end and in 11 of 35 at the outlet end. This behavior was attributed to hot-short cracking of the Type 347 stainless steel weldments rather than to stress corrosion. (auth)
- Research Organization:
- Battelle Memorial Inst., Columbus, OH (United States)
- DOE Contract Number:
- NOBS-67500, SUBCONTRACT 73-(00-929)
- NSA Number:
- NSA-14-010546
- OSTI ID:
- 4182224
- Report Number(s):
- BMI-1416
- Resource Relation:
- Other Information: For Westinghouse Electric Corp. Bettis Atomic Power Lab. Orig. Receipt Date: 31-DEC-60
- Country of Publication:
- United States
- Language:
- English
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