ML20052B755
| ML20052B755 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 03/08/1982 |
| From: | Gerrets T LOUISIANA POWER & LIGHT CO. |
| To: | Jay Collins, Morvant J, Woodward J FACTORY MUTUAL ENGINEERING CORP., LOUISIANA, STATE OF, NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| Shared Package | |
| ML20052B756 | List: |
| References | |
| NUDOCS 8205030536 | |
| Download: ML20052B755 (2) | |
Text
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March 8, 1982 WR 3 01982> 7g W3K-82-0 43 'uinm arm evv 3 Q-3-T33 E MM3#"
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% I I1982 i/ if Baton Rouge, Louisiana 70804 bL Mr. John Woodward U
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12 Perimeter Center East, Northwcut J
Suite 1200 Atlanta, Georgia 30346 Mr. John T. Collins, Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76012
Subject:
Waterford SES Unit 3 Section XI Program for the Replacement of Pressurizer lleaters Gentlemen:
Attached is the ASME/B&PV Code Section XI repair program for the replace-ment of all of the inconel sheathed heaters with Watlow supplied heaters equipped with austenitic stainless steel Type 316 sheaths in the pressurizer heater. This program has been reviewed and approved by Louisiana Power and Light for repair activitics at the Waterford SES Unit #3 Site.
C-E began an investigation in July of 1979, following the failure of twelve similar heaters used in the liigh Pressure Test Loop at the C-E Chattanooga facility due to shcath cracking.
Metallurgical evaluation of the cracks revealed the inconel 600 material to be in a highly cold worked condition, due to the fabrication process, with a hardness ranging from 27 to 30 Rockwell C.
In this condition, the ycild strength of the material is approximately 100 KSI and the residual stress (lloop direction) ranges from 25 to 50 KSI.
During operation, additional lloop atresses are caused by a radial thermal gradient due to the hot core and from thermal expansion of the magnesium oxide core. This highly stressed condition, combined with a high tempera-ture aqueous environment, has caused stress corrosion cracking (Coriou) on the 0.D. of the heater sheath.
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Coriou eracking has been dup!leated in the autoclave tests at C-E; the cracks observed t.vre identical to those in the failed sheaths.
Ikised on the high operat ing t ime capability (in access of 20,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />),
demonst rated by heaters wit h austenitic stainless steel Type 316 sheaths which are in use in C-E's Reactor Component Test Fac ility in Windsor, the decision has been made to use these heaters in lieu of the inconel 600 sheat.ber heaters.
Corion cracking has not been observed in the 316 SS.
If there are any questions regarding this repair program, please advise.
Very truly yours,
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F. Gerrets Quality Assurance Manager TFC/lb\\ll/grf L. L. Ba s s, W. M. Mo rga n, J, Wood s, L. S t i n son, I.. V. Ma urin, D. 11. Les te r,
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R. K. Stampicy, P. V. Prasankumar, F. J. Drummond, Central Records, Nuclear Records
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