ML20024G786
| ML20024G786 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 04/26/1991 |
| From: | Robinson W PORTLAND GENERAL ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| WRR-081-91-SR03, WRR-81-91-SR3, NUDOCS 9104300340 | |
| Download: ML20024G786 (3) | |
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Portland General Electric Company Trojan Nuclear Plant 71760 Columbia River liw y.
Rainier. Oregon 97048 (503; 556-3713 April 26, 1991 WRR-081-91, SR03 U.S. Nuclear Regulatory Commission Document Control Desk Washington DC 20555 Gentlemen:
Special Report Trojan Technical Specification (TTS) 3.4.9.3, " Overpressure Protec-tion Systems," Action c, requires the submittal of a Special Report, within 30 days, in the event the Power-Operated Relief Valves (PORVs) are used to miti ate a Reactor Coolant System (RCS) pressure tran-6 sient. This letter is being autmitted to satisfy that requiroc.cnt, as, on March 27, 1991 Pressurizer PORV, PCV-455A, automatically opened to mitigate a RCS pressure transient.
Prior to the event all Reactor Coolant Pumps (RCPs) were off, the RCS was water solid, and RCS. pressure was 300 psig. At approxi-mately 0944, Component Cooling Water (CCW) flow to the
'D' Residual Heat Removal-(RHR) Heat Exchanger was stopped tc increase RCS temperature. This was required to comply with the requirements of Operating Instruction (OI) 3-4, " Reactor Coolant Pump," Step 2.16.3, which requires that the temperature difference between tho'RCS cold legs and the Steam Generator (SG) secondary water be <50*F.
At approximately 1010, these temperatures were within the limit with a maximum SG temperature of 166*F and a minimum RCS cold leg tempera-ture of 122'F.
At approximately 1015, the
'A' RCP was started to support forced oxidation of the RCS. When the
'A' RCP was started, RCS pressure started to increase.
The Solid Plant Watch Operator h.
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Document Control Desk Apell 26, 1991 l'aie _ 2 (SPWO) attempted to stop the RCS pressure increase by increasing Chemical and Volume Control System (CVCS) letdown flow. The SPWO mistakenly started closing the valve (HCV-128) controlling letdown flow, immediately recognized his mistake and fully opened the valve.
Based on a review of the RCS pressure recorder chart, the SPWO's actions did not appear to have any effect on the pressure increase. The RCS pressure increased causing PCV-455A to open and mitigate the transient at a peak pressure of 440 psig. The SPWO restored RCS pressure to approximately 300 psig. The total time of PCV-455A actuation was 2.2 seconds. The ' A' RCP continued to run during and after the event.
The Overpressure Protection System operated as designed, as PCV-ASSA opened and mitigated the pressure transient.
It was not evident-from our procedures that meeting the RCP starting requirements of Technical Specification 3.4.1.4.b, " Reactor Coolant Loops Normal Operation", would not prevent lifting of a PORV. A review of Technical Specification 3.4.9.3 Bases showed that a single PORV is capable of protecting the Plant from exceeding Title 10 of the Code of Federal Regulations, Part 50 (10 CFR 50) Appendix G 11mits with 150 degree delta T.
Note that Trojan, using this guidance, has not lifted a PORV when initially starting an RCP at the end of a refueling outage.
An initial evaluation showed two major differences between this RCP start, which occurred at the beginning of the refueling outage, and RCP starts that occur at the end of a refueling outage. Normally RCPs are started at the end of an outage when the RCS has a large volume of trarycd air in the SG U-tubos and the SGs are at ambient temperature.
For this clart the RCS was completely water solid and the SGs were acting as a heat source.
An engineering evaluation is being performed to determine require-ments for initially starting an RCP, when the RCS is completely water solid, without challenging the PORVs.
The criteria in Operating Instruction (01) 3-4, " Reactor Coolant Pump", will be revised to cover initial RCP starts when completely
'e Document Control Desk April 26, 1991 P, age 3 water solid to incorporate requirements recommended by the engineering evaluation. This will be completed by May 21, 1991 which is prior to scheduled RCP starts.
Sincerely, Ld
[ c.kww. tow W. R. Robinson General Manager Trojan Nuclear Plant c:
Mr. John B. Martin Regional Administrator, Region V U.S. Nuc1 car Regulatory Commission Mr. David Stewart-Smith State of Oregon Department of Energy Mr. R. C. Barr USNRC Resident Inspector Trojan Nuclear Plant i
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