ML18044A362
| ML18044A362 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 12/28/1979 |
| From: | Hoffman D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7912310364 | |
| Download: ML18044A362 (2) | |
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consumers Power company General Offices: 212 West Michigan Avenue, Jackson, Michigan 49201
- Area Code 517 788-0550 December 28, 1979,
Director, Nuclear Reactor Regulation Att Mr Dennis L Ziemann; Chief Operating Reactors Branch No 2 US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT - TURBINE DISC CRACKING PROBLEMS This letter is submitted by Consumers Power Company for the Palisades Plant concerning the turbine disc cracking problem.., This information was requested by*Richard Silver and William Ross of the NRC as per telephone conversation on December 13, 19 79 and December 21, 19 79.
On September 8, i979, Palisades Plant shut down for a standard refueling outage with a turbine inspection and repair.
During this outage, Westinghouse contacted Consumers Power Company (October 18, 1979) with the information that some turbine disc cracking around a keyway had been found at Zion 1.
Consumers Power requested that Westinghouse inspect the Palisades Plant turbine for this condition.
Westinghouse dispatched an inspection team to Palisades October 29, 1979.
Some indications were found on the LP turbine discs.
Consumers Power Company was insti-ucted by Westinghouse to reassemble the turbine and another inspection was to be scheduled in approximately 16 months.
On December 17, 1979, a meeting was helcf between Westinghouse and Consumers Power Company concerning this disc crack problem.
In the course of the meeting, the following summary for the Palisades Plant.turbine was provided by Westinghouse:
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2 Disc Crack Summary LP Turbine Disc No As Reported Disc Crack Depth*
Time A
B B
B 2 Generator End 2 Governor End 2 Governor End 4 Governor End 0.095" 0.236" 0.126" 0.113" 20.1 Months 16.8 Months 17.9 Months 296.0 Months
- Critical crack size for the No 2 discs is 1.928 inches from the center of the 0.750 inch diameter keyway (the radius* thus acts as a notch).
Krc for the. disc material is reported to be 209 KS! Viii":'
Ivor Johnsson of Westinghouse recommended that a reinspection of*the Palisades Plant turbine discs be performed in approximately nine months after start-up and is based on the following:
I.* 0. 060 inches is added to the "as reported crack depth" to allow for branches of the crack that do not reflect sonic energy.
This number was experimentally derived.
- 2.
Applying crack growth rates from British experience, the time to failure is calculated.
- 3.
This figure is then divided by 3 to allow for an unknown incubation time before the crack begins to grow.
- 4.
Westinghouse recommends reinspection in one half the.time interval listed above.
With this recommendation Consumers Power Company is planning a reinspection outage approximately nine months after start-up.
David P Hoffman Nuclear Licensing Administrator CC JGKeppler, USNRC