ML20080G442

Special Rept 95-01:on 950104,personnel on Unit 2 Operating in Solid Condition During Fill & Vent of Nc Sys

ML20080G442
Person / Time
Site:	McGuire, Mcguire
Issue date:	02/03/1995
From:	Mcmeekin T DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
95-01, 95-1, NUDOCS 9502070307
Download: ML20080G442 (5)

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DukeIbwerCompany T C McMinn McGuare Nuclear Generatton Department Vice Presodent 12700Hagers ferryRoad(MG01VP)

(104)8754800 Huntenville.NC280782985 (704)8754809 Fax DUKEPOWER February 3,1995 U.S. Nuclear Regulatory Commission Document Control Desk Was.11ngton, D.C. 20555

Subject:

McGuire Nuclear Station Unit 2 Special Report No.: 95-01 Problem investigation Process No.: 2-M95-0034 Gentiemen:

Attached for your information is Special Report No. 95-01, pursuant to requirements of Technical Specification 3.4. 9.3, Reactor Coolant System Overpressure Trotection System, Action e. This report documents actuation of power-operated relief valve 2NC-34 to reduce NC system pressure while operating in a solid condition during the fill and vent of the NC system on Unit 2. This actuation was determined to be appropriate by design to mitigate an increase in NC system pressure at that time. The actuation is not significant from a fatigue standpaint and of no significance with respect to the health and safety of the public.

Very truly yours, NFLN T.C. McMeekin RJD/beb Attachment cc:

Mr. S.D. Ebneter INPO Records Center Administrator, Region 11 Suite 1500 i

U.S. Nuciear Regulatory Commission 1100 Circle 75 Parkway i

101 Marietta St., NW, Suite 2900 Atlanta,GA 30339 Atlanta, GA 30323 Mr. Victor Nerses Mr. George Maxwell j

U.S. Nuclear Regulatory Commission NRC Resident inspector Office of Nuclear Reactor Regulation McGuire Nuclear Station Washington, D.C. 20555 b[(.'[..'

9502070307 950203 PDR ADOCK 05000369 g[

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B.L. Walsh (EC11C)

Zack Taylor (CNS)

G.A. Copp (EC050)

J.l. Glenn (MG02ME)

~ P.R. Herran (MG01VP)

R.C. Norcutt (MG01WC)

S.G. Bonesole (ONS Reg Compliance)

G.H. Savage (EC06E)

G.B. Swindlehurst (EC11-0842)

M.S. Tuckman (EC07H)

R.F. Cole (EC05N)

D.B. Cook (EC13A)

Tim Becker (PB02L)

P.M. Abraham (EC081)

Bruce Caldwell(MG01VP)

L.V. Wilkie (ONO3SR)

D.P. Kimball (CN05SR)

NSRB Support Staff (EC05N)

Kay Crane (MG01RC)

Rich Casler (EC05N) i i

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i DUKE POWER COMPANY McGUIRE NUCLEAR STATION SAFETY REVIEW GROUP SPECIAL REPORT This Special Report is due to requirements of Technical Specification 3.4.9.3, Reactor Coolant System Overpressure Protection Systems, Action e.

This report concerns an actuation of Power-Operated Relief Valve (PORV) 2NC-34, to reduce Reactor Coolant (NC) system pressure while operating in a solid condition during the fill and vent of the NC system on Unit 2.

This occurrence is documented on problem investigation process (PIP) 2-M95-0034.

l Special Report No.: 25-D1 Date Of Report: January 31. 1995 t

i On January 4, 1995, Operations (OPS) personnel on Unit 2 were operatir.g i

in a solid condition during the fill and vent of the NC system.

The unit was in Mode 5 (Cold Shutdown).

System venting had virtually been completed and; therefore, pressure control was very sensitive to any change in NC system mass due to a minimal amount of entrained air in the j

system at that time.

The Reactor Operators (ROs) assigned to Unit 2 stated that they had discussed the need for additional caution with control of NC system pressure and temperature during turnover. With this evolution in mind, OPS Management personnel had assigned an additional RO to assist with the performance of procedures for operation of the Unit 2 Reactor Coolant pumps. This was done in an effort to allow the RO at the controls (ROATC) to devote greater attention to the control of NC system temperature and pressure and the RO assigned to the balance of the plant (BOP)to handle any other items concerning operat,'.on of the unit.

However, as the day progressed, the level of act:Wity concerning Unit 2 became greater and greater due to restart activities in progress. The ROs stated that they were extremely busy. The ROATC as well as the RO i

assigned to the BOP and the additional RO found themselves performing multiple tasks at the same time.

At 1155, the ROATC noted a decrease in NC system pressure to less than 250 psig.

He stated that he then adjusted letdown flow to increase system pressure to approximately 275 psig.

He also stated that he had made an adjustment to the Component Cooling (KC) system flow to increase the NC system temperature.

At that time he was called to assist Instrumentation and Electrical personnel performing testing on the 2A Feedwater (CF) system pump.

Both the RO assigned to the BOP and the additional RO assigned were occupied with support of various other activities in progress at that time and were not monitoring NC system pressure or temperature. At 1204, the annunciator alarm was received for actuation or PORV 2NC-34.

The ROATC stated that the NC system i

pressure had increased to 371 psig as indicated by the control room alarm typer and the PORV had actuated as it should to reduce pressure while in the Low Temperature Overpressure Protection (LTOP) mode.

OPS personnel then took action by adjusting letdown flow to further reduce NC system pressure to within the appropriate limits. The PORV reseated properly when pressure was reduced to a level below the actuation setpoint. OPS personnel were then able to stabilize the NC system pressure and no further problems were noted.

The cycling of 2NC-34 is not significant from a safety or fatigue standpoint.

The Design Stress Report for the PORVs allows for up to 340 1

a cycles.

This limit has not yet been approached.

Also, the Pressurizer Helief Tank (PRT) is designed to withstand a pressure increase of up to 140 psig, at which time the rupture dick would relieve to reduce system pressure.

The PRT pressure did not increase significantly during this time period and no safety systems were challenged as a result.

When interviewed, the OPS personnel involved stated that they attributed the increase in NC syitem pressure to transients introduced by valve manipulations during testing ongoing at that time on the Safety Injection (NI) system check valves and consequent leakage to the check valve test header.

However, investigation into the activities associated with NI check valve testing revealed that there were no valve i

manipulations associated with this testing ongoing at that time.

Personnel involved in the check valve testing stated that they were unable to establish any flow at the time of this occurrence, and could not have induced any transient to the NC system pressure.

j The root cause for the PORV actuation is established as the sensitivity of the NC system pressure to very small changes in system mass as previously described, and the diversion of OPS personnel at the controls from paying strict attention to system pressure and temperature at that i

time.

The level of activities in progress at that time had progressed to the point of pulling the ROs from their original focus as discussed 1

in the turnover. This contributed to the pressure being allowed to increase to the point at which the PORV actuated.

In an effort to prevent recurrence of similar actuations OPS personnel will evaluate the methedology used for assignment of duties in the Control Room during evolutions such as control of NC system pressure and temperature while operating in a solid condition.

Also, in conjunction with System Engineering personnel, OPS personnel will evaluate the uce of additional control or alarm methods to assist the Control Room OPS personnel in their duties during such evolutions.

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,e ENCLOSURE 1 SIGNATURE SHEET l

Prepared By:

Gary T. Small Date: February 1.1995 v-

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