ML20046C623
| ML20046C623 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 08/03/1993 |
| From: | Stetz J CONNECTICUT YANKEE ATOMIC POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9308110236 | |
| Download: ML20046C623 (3) | |
Text
.l CONNECTICUT YA N K EE AT O M IC POWER COMPANY HADDAM NECK PLANT 362 INJUN HOLL.OW ROAD e EAST HAMPTON, CT 06424-3099 August 3,1993 Re: Technical Specification 6.9.2 Docket 50-213 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Dear Sir.
Attached is a Special Report, submitted in accordance with the Haddam Neck Plant Technical Specifications 3.4.9.3, Action C and 6.9.2.
t On July 7 and 8,1993, the Haddam Neck Plant experienced two separate Reactor Coolant i
System (RCS) pressure transients which were successfully mitigated by the Low Temperature Overpressure Protection (LTOP) System spring-loaded relief valves (SLRVs).
The attached repon describes the circumstances initiating the transients, the effect of the LTOP SLRVs and the corrective actions taken to prevent recurrence.
Please contact us if you require any additional information.
Very truly yours, A kk ohn P. Stetz Vice Pn:sident i
Haddam Neck Plant cc: Mr. Thomas T. Mardn Regional Administrator, Region I 475 Allendale Road King of Prussia, PA 19406 Mr. William J. Raymond Senior Resident Inspector Haddam Neck Plant f4g'/j 090071 i.
9308110236 930803 g$
PDR ADOCK 0S000213 94 S
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Special Report LTOP Events at Haddam Neck Plant On July 7 and 8,1993, the Haddam Neck Plant experienced two separate Reactor Coolant System (RCS) pressure transients which resulted in opening the low Temperature Overpressure Protection (LTOP) System spring-loaded relief valves (SLRVs).
The first event occurred on July 7 as operators were preparing the plant for a heatup fmm Mode 5 to Mode 3,in accordance with NOP 2.1-1, "Stanup from Cold Shutdown to Hot Standby", following a refueling outage. The RCS was in a water-solid condition, with pressure control provided by manual adjustment of a Charging System flow control valve, CH-FCV-110, and the Drain System throttle valve, DH-MOV-310. CH-FCV-110 is powered from vital bus panel D.and is desigr,ed to open on a loss of power.
Before commencing the heatup, the C and D vital bus inveners required testing in accordance with special test procedure ST 11.7-127, ' Test of C and D Inveners." The purpose of the test was to demonstrate the ability to supply uninterrupted power to vital bus panels C and D from the backup power supply, via either the C or D invener, during the loss and restoration of the C and D inveners' normal power supply, MCC 12.
Vitd bus panels C and D had previously been cross-tied and were being powered from the C inverter. To start the test, the feeder breaker to MCC-12 was opened which caused the C invener's static switch to successfully transfer to the backup power supply. The feeder breaker to MCC-12 was then reclosed and the C invenets stanc switch transferred back to MCC-12.
To test the ability of the D inverter to supply power to vital buses C and D, ST 11.7-127 i
directed operators to deenergize the panel D loads, transfer the panel D power supply from panel C to the D invener and reenergize the panel D loads. As circuit #2 in panel D was deenergized, CH-FCV-110 opened fully which increased charging flow to the water-solid RCS, resulting in a pressure transient that opened the LTOP SLRVs.
Steady state RCS pressure and temperature prior to the event were approximately 320 psig and 110 degrees F, respectively. The RCS pressure limit at 110 degrees F is 750 psig.
Peak RCS pressure during the event was approximately 430 psig.
Following the LTOP event, power to vital bus panel D was restored, CH-FCV-110 was throttled closed and RCS pressure stabilized at approximately 275 psig.
A second LTOP event occurred on July 8. With the RCS still water-solid, operators were performing SUR 5.7-31," Inservice Testing of Boric Acid and RWST Check Valves,"BA-CV-320,372 & 387". They were unable to flow 30 gpm thmugh BA-CV-320 with the metering pump lined up to the charging header because the charging header was l
pressurized to approximately 2600 psig by the "B" charging pump. RCS pressure was being maintained at approximately 310 psig by manual control of the Charging System flow control valve CH-FCV-110 and Dram System thmttle valve DH-MOV-310. The operators decided to isolate the charging header from the loop fill header and repeat the flow test by flowing from the metezing pump through the fill header to the RCS.
After attempting to isolate the fill header from the charging header, operators opened the loop 4 fill valve and the fill header isolation valve. RCS pressure increased rapidly and caused the LTOP SLRVs to open. The operators quickly closed the loop 4 fill valve and 1
i restored RCS pressure. Upon review of the event. it was found that the discharge valves from the "A" charging pump to the charging and fill nc.dm had not been closed. This error in the valve lineup allowed the charging and fill headers to remain cross-connected.
in the second event, RCS pressure peaked at approximately 455 psig with a RCS temperature of 148 degrees F. The RCS pressure limit, at that temperature, is 750 psig.
RCS pressure was restored by opening DH-MOV-310 and closing the loop 4 fill valve.
The LTOP events occurred while testing plant equipment that affected charging flow while the RCS was water-solid. In the first event, a Special Test procedure was developed in a short period of time and the consequence of deenergizing circuit #2 of vital bus panel D was overlooked by the procedure developers and reviewers. In the second event, operators were having difficulty completing a surveillance procedure and attempted to place the Charging System in an unusual lineup to complete the surveillance in a timely manner.
I Immediately following the second event, mar.agement issued a stop work order on all
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testing that could affect RCS pressure. The RCS was depressurized to preclude funher events in the shon term. All required testin ; which could affect RCS pressure in the water j
solid condition was completed prior to repressurizing the RCS. The individuals involved in the inadequate procedure review end in the improper valve lineup were counseled by management on the importance of doing a job right the first time.
l On July 8,1993, the Operations Manager issued a memorandum to all Operations Department personnel, directing them to use greater care when the RCS is solid, to use properly developed procedures when manipulating plant components and to take the time necessary to assure that all activities are done correctly, regardless of the impact on the refueling schedule.
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