ML20081D485

Special Rept:On 950211,actuation of PORV 1NC32B Occurred. Procedure OP/1(2)/A/6100/02 Revised to Require More Emphasis on Monitoring Pressure Indication During Sensitive Evolutions

ML20081D485
Person / Time
Site:	Catawba
Issue date:	03/13/1995
From:	Rehn D DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9503200259
Download: ML20081D485 (3)

Text

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Catawba Nxtear Generation Department ' Vice President 4800 ConcordRoad (803)&H3205 Ollice York,SC29745 (803)D13426 Fax .

l 0-- March 13,1995 U. S. Nuclear Regulatory Commission ,

Attn: Document Control Desk

• Washington, D. C. 20555.  !

Subject:

Catawba NuclearStation, Unit 1 Docket No. 50-413 ,

Special Report -

Pmssurizer Power Operated Relief Valve Actuation .l i

Pursuant to requimments of Technical Specification 3.4.9.3, Reactor Coolant System j Overpmssum Protection System, Action d, find our Special Report attached. This  ;

report documents the actuation of power-operated mlief valve 1NC32B while taking the pmssurizer water solid concurmnt with reactor coolant system .

cooldown per procedum.

Sincerely,  !

f S H

DL Rehn j KEN /SR031395. CAT Attachment xc: SD Ebneter, Region II ,

i RE Martin,ONRR RJ Fmudenberger, SRI 9503200259 950313

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.. SPECIAL REPORT f ,

CATAWBA NUCLEAR STATION 50-413, 50-414 This Special Report is due to requirements of Technical. Specification 3.4.9.3, Reactor Coolant System Overpressure Protection Systems, Action

d. This report concerns an actuation of Power-Operated Relief Valve (PORV) 1NC32B, to reduce Reactor Coolant (NC) System pressure while operating in a solid condition ~during cooldown of the NC System on Unit 1 for the C1EOC8 refuleing outage. This occurrence is documented.in Problem Investigation Process (PIP) 1-C95-0185.

On February 11,1995, Unit 1 was being cooled 'down and depressurized at the start of EOC8 refueling outage. Per OP/1/A/6100/02,. Controlling Procedurefor Unit Shutdown, Enclosure 4.4, NC System Crud' Burst Unit NC Pumps the Operator At The Controls (OATC) had:

Residual Heat Removal (ND) Train 1B inservice e NC Pump 1B inservice e B, C and D pressurizer heaters energized e Pressurizer spray initiated Per YT/1/A/4600/17, Surveillance Requirementfor Unit Shutdown, cooldown rate -

was 45.9'F/ hour. Per All Points Data (APD)information:

• Pressurizer water temperature was approximately 420'

• Pressurizer surge line temperature was approximately 409'

• NC System temperature was approximately 185*

• Charging flow was 177 gpm

. Letdown flow was 104 gpm Review of data indicated the pressurizer PORVs lifted three times. The initial lift on 1NC32B was in response to an apparent charging / letdown flow mismatch induced pressure increase. This PORV lift indicated on the Alarm Summary as "VLV NC32B PZR Power Operated Relief" OPEN. The subsequent lifts did not trigger the open limit switch, but did trigger the "Not Closed" limit switch.

The PORV(s) responded as designed to limit a low temperature overpressure .

transient with a setpoint of 400 psig. PORVs 1NC32B and 1NC34A had their-response time to open tested earlier that day. Per PT/1/A/4200/23B, NC PORV Stroke Test Using N2,1NC32B time to open was 1.9 seconds,1NC34A time to open was 2.2 seconds.

At the time of the transient, the Appendix G Cooldown Limitations (Technical Specification 3.4-3) was %5.6 psig using the 60*F/ hour cooldown line and 185*

1

SPECIAL REPORT CATAWBA NUCLEAR STATION 50-413, 50-414 NC temperature. The maximum pressure seen at the pressure instrumentation was 410.5 psig (add 4.6 psi to account for the elevation difference between the pressure instrumentation and the reactor beltline region and add 4.5. psi to account for one NC pump operation of the beltline region). The maximum pressure at the reactor beltline region was 419.6 psig which was less than the Appendix G curve by a margin of 566 psi. The cycling of the pressurizer PORVs is not significant from a safety or fracture standpoint.

The Pressurizer Relief Tank (PRT) pressure did not increase significantly during this actuation period. The maximum PRT pressure was 4.4 psig according to APD information. The PRT rupture disk setpoint of 100 psig was far from being challenged. Also, the ND suction relief valve (1ND38), which has a setpoint of 450 psig was not actuated and no safety systems were challenged as a result of this event.

In an effort to prevent recurrence of similar actuations, the use of additional control or alarm methods to assist the OATC during these evolutions was evaluated. As a result, the following corrective actions will be completed by 08/10/95.

1. Revise OP/1(2)/A/6100/02, Controlling Procedure for Unit Shutdown, to require more emphasis placed on monitoring pressure indication during sensitive evolutions. (OPS /CW Senn)

2. Evaluate the possibility of rescaling or changing the speed for at least one of the recorders in the control room which are used during these sensitive evolutions. (ESE/TM VanDeven)

3. Evaluate the possibility of modeling instrument drift on the simulator during practice sessions for these sensitive evolutions. (OPT /GE Spurlin) 2