ML20205F586
| ML20205F586 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/20/1987 |
| From: | Hukill H GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 5211-87-2056, NUDOCS 8703310206 | |
| Download: ML20205F586 (3) | |
Text
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o GPU Nuclear Corporation 0, Nuclear
- ,omgr8o Middletown, Pennsylvania 17057 0191 717 944 7621 TELEX 84 2386 Writer's Direct Dial Number:
5211-87-2056 March 20, 1987 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C.
20555 Gentlemen:
Three Mile Island Nuclear Station Unit 1 (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 EFW Turbine Inlet Relief Valve Operation In GPUN letter 5211-85-2212, dated December 20, 1985, we discussed the implications of the lifting of the Emergency Feedwater Turbine Driven Pump (EF-P1) main steam inlet relief valves (MS-V22A/B) during automatic starting of EF-Pl. We discussed the short term modifications to be made for Cycle 5 operation to preclude MS-V22A/B lifts and to allow for acceptable performance of EF-Pl. Finally, GPUN identified that a permanent solution to reduce challenges to MS-V-22A/B would be investigated by the end of Cycle 6 refueling.
GPUN has investigated a permanent solution. The solution was discussed with Messrs. J. Thoma, R. Blough and J. Wermiel of NRC on December 23, 1986, via telephone conference.
This letter serves to document this conversation and to identify the solution to the relief valve lifting.
A discussicn of the modifications and the testing done to ensure a proper solution is provided in the attachment to this letter.
Sincerely,
. D.
ill Vice President & Director, TMI-l HDH/JCA/jh:0833A Attachment 8703310206 G70320
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cc:
R. Volmer PDR ADOCK 05000289 P
PDR J. Thoma g\\s R. Conte D. Crutchfield
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T. Murley GPU Nuclear Corporation is a subsidiary of the General Public Utilities Corporation
ATTACHMENT The cause of the lifting of MS-V22A/B was identified as being attributable to a combination of; 1) a narrow margin between MS-V22A/B setpoints and the pneumatic pressure controller (PC-5) setting for the turbine pump inlet steam regulating valve MS-V6, and 2) the inability of the MS-V6/PC-5 control loop to respond fast enough to the increased steam supply which results with the simultaneous opening of the steam supply valves MS-Y13A/B.
To resolve the problem of inlet relief valve lifting during auto-initiation of EF-P1, the following modifications have been made:
1)
New main steam inlet relief valves, MS-V22A/B, were installed. The new valves have higher lift setpoints (260/280 psig) than the old valves (200/220 psig).
It should be noted that the higher setpoints will not adversely impact the EF-P1 turbine integrity.
2)
The pneumatic pressure controller (PC-5) for the pump inlet steam pressure control valve (MS-V6) has been changed. The new proportional plus integral (P&I) type cor. troller has the capability to control inlet pressure at a desired value under a wider range of operating conditions.
3)
The control logic for the steam supply valves MS-V13A/B has been modified to delay the opening of the second valve (MS-Vl3B) by no greater than 60 seconds but no less than 40 seconds.
By analysis, we have concluded that a 60-second delay in the opening of the second steam supply valve (MS-V138) is acceptable for the limiting design basis accident (DBA) - main feedline break inside containment.
To ensure that the above noted modifications would resolve the problem of inlet relief valve lifting, several tests were performed with the modifications temporarily installed.
Both pump minimum recirculation and full flow tests were performed. These tests are described below:
1)
Pump Minimum Recirculation Flow Test - During this test both cold and hot starts of EF-P1 were performed using a 60-second delayed opening for the second MS-V13 valve.
During the cold start of EF-P1, no safety valve lifts occurred. EF-P1 accelerated smoothly and reached stable operation.
During the hot starts of EF-P1, MS-V22A lif ted once each time.
In each case of MS-V22A lift, the safety valve reseated after a single lift without operator intervention.
EF-P1 was operated at a stable condition after reseat of the safety valve.
The safety valve reseated prior to the opening of the second MS-Vl3 val ve.
Opening of the second MS-V13 had no noticeable effect on the system aperation.
We do not consider the opening of MS-V22A during hot start to be a problem because a hot start of EF-P1 would occur only on pump start immediately following surveillance testing, or on pump start immediately following pump trip on turbine overspeed, or on pump start immediately following manual trip by an operator.
2)
Full Flow Test To Pressurized 0TSG - A cold start of EF-P1 was performed using main steam.
EF-Pl accelerated smoothly and obtained stable operation without a relief valve lift.
Once full flow was stabilized, the flow was reduced in steps from 100% to 60% and then from 60% to 30%.
In both reduction cases, EF-P1 operation was sati sfactory.
Based on the above listed modifications and testing, GPUN believes that a satisfactory solution to the lifting of the steam inlet relief valves has been identified. The modifications required to support this solution have been implemented.,
_