ML17285B003
| ML17285B003 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 02/05/1990 |
| From: | Samworth R Office of Nuclear Reactor Regulation |
| To: | Sorensen G WASHINGTON PUBLIC POWER SUPPLY SYSTEM |
| References | |
| TAC-75383, NUDOCS 9002130304 | |
| Download: ML17285B003 (8) | |
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t UNITEDSTATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 February 5, 1990 Docket No. 50-397 Hr. G.
C. Sorensen, Manager Regulatory Programs Washington Public Power Supply System P.O.
Box 968 3000 George Washington Way
- Richland, Washington 99352
Dear Mr. Sorensen:
SUBJECTS:
WNP-2 LOW PRESSURE TURBINE INSPECTION SCHEDULE (TAC 75383)
By letter dated November 21, 1989, Washington Public Power Supply System informed the NRC of your intent to defer inspection of the low pressure turbine (LP ¹1) at Nuclear Plant No.
2 from the scheduled 1990 refueling outage to the 1991 refueling outage.
During the 1991 outage, you will replace all three LP turbines with the fully integral disc design.
The integral design eliminates crack initiation at the bore and keyway of the conventional shrunk-on discs.
II By letter dated October 29, 1987, you committed to inspect LP ¹1 during the 1990 outage because a crack was detected in LP ¹1 during the 1987 inspection.
The turbine manufacturer (Westinghouse) recommended a 34.32-month inspection interval (actual months of operation) for LP ¹1.
As of October 17, 1989, LP ¹1 has been operated 19.8 months since the last inspection in 1987.
The remaining interval is 14.5 months.
You estimated that the operating interval from October 17, 1989 to the start of the 1991 refueling outage (tentatively April 15, 1991) is 16.5 months.
The actual deferment is, therefore, only about 2 months.
However, the 1991 outage could be delayed from April 15, 1991 to June 15, 1991, if there is a late spring run-off in the Pacific Northwest region of the U.S. If this were the case, the staff estimates a delay in the inspection of about 4 months.
The staff's concern over about the deferred inspection schedule is with crack growth during the extended 4-montII period.
You provided additional information about the crack growth in the letter dated December 14, 1989.
You had detected a 0.063 inch (in depth) crack at the governor-end outlet keyway of the No.
1 disc during the 1987 inspection of LP ¹1.
Westinghouse calculated.the critical crack size of the disc to be 2.983 inches.
Using the Westinghouse methodology which the staff has approved, the inspection interval of 34.32 months was calculated based on 50 percent of the amount of time for the existing crack to grow to one half of the critical crack size.
Adding the extended 4 months to PDR gD
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Mr. G.
C. Sorenson February 5, 1990 the 34.32 months, will extend the inspection interval to 55.8 percent of the time to reach one half of the critical crack size.
Based on the Westinghouse methodology, it would take 68 months to reach one half of the critical crack size, or 136 months to reach the critical crack size.
Based on this growth rate, the staff believes that there is sufficient safety margin left in the crack criteria after the 4 months extension.
Also from the probabi listic viewpoint, the staff believes that the 4 months inspection extension will not increase the NRC required turbine missile generation probability for WNP-2 which is 1.0E-5 per year.
For the reasons stated
- above, we have no objection to your deferring the LP 81 inspection as proposed.
Sincerely, Robert B. Samworth, Senior Project Manager Project Directorate V
Division of Reactor Projects - III IV, Y and Special Projects Office of Nuclear Reactor Regulation cc:
See next page
Hr. G.
C. Sorenson February 5, 1990 the 34.32 months, will extend the inspection interval to 55.8 percent of the time to reach one half of the critical crack size.
Based on the Westinghouse methodology, it would take 68 months to reach one half of the critical crack size, or 136 months to reach the critical crack size.
Based on this growth
- rate, the staff believes that there is sufficient safety margin left in the crack criteria after the 4 months extension.
Also from the probabilistic viewpoint, the staff believes that the 4 months inspection extension will not increase the NRC required turbine missile generation probability for WNP-2 which is 1.0E-5 per year.
For the reasons stated
- above, we have no objection to your deferring the LP Pl inspection as proposed.
Sincerely, ori gi nal si gned by Robert B. Samworth, Senior Project Hanager Project Directorate V,
Division of Reactor Projects - III IV, V and Special Projects Office of Nuclear Reactor Regulation cc:
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G. C. Sorensen WPPSS Nuclear Project No.
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CC:
Hr. C. H. Powers WNP-2 Plant Manager Washington Public Power Supply System P.O.
Box 968, MD 927M Richland, Washington 99352 Hr.
G.
E. Doupe, Esquire Washington Public Power Supply System P.
0.
Box 968 3000 George Washington Way Richland, Washington 99532 Mr. Curtis Eschels, Chairman Energy Facility Site Evaluation Council Mail Stop PY-11 Olympia, Washington 98504 Mr. Alan G. Hosier, Licensing Manager Washington Public Power Supply System P. 0.
Box 968, MD 956B Richland, Washington 99352 Mr. A. Lee Oxsen Assistant Managing Director for Operations Washington Public Power Supply System P. 0.
Box 968, MD 1023 Richland, Washington 99352 Hr. Gary D. Bouchey, Director Licensing and Assurance Washington Public Power Supply System P. 0.
Box 968, MD 280 Richland, Washington 99352 Regional Administrator, Region V
U.S. Nuclear Regulatory Commission 1450 Maria Lane, Suite 210 Walnut Creek, California 94596 Chairman Benton County Board of Commissioners
- Prosser, Washington 99350 Hr. Christian Bosted U. S. Nuclear Regulatory Commission P. 0.
Box 69
- Richland, Washington 99352 Nicholas S. Reynolds, Esq.
- Bishop, Cook, Purcell
& Reynolds 1400 L Street NW Washington, D.C.
20005-3502
ML14350A142 Provides Station Blackout (SBO) Implementation Addi Info for Plant, per NUMARC 87-00 8 890417 Response to SBO Rule. All Containment Isolation Valves Required to be Closed by Procedure During Power Operation.
Dated March 30, 1990.
431-97-0141 box P8
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