ML18094B448

Special Rept 90-3:on 900401,pressurizer Overpressure Protection Sys Actuations Occurred.Caused by Inadequate Procedural Direction for Identification of Reactor Coolant Protection Requirements During Mode 5 Operation

ML18094B448
Person / Time
Site:	Salem
Issue date:	04/27/1990
From:	Miller L Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
90-3, NUDOCS 9005080124
Download: ML18094B448 (4)

Text

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• Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station April 27, 1990 U.S. Nuclear Regulatory Commision Document Control Desk Washington, DC 20555

Dear Sir:

Salem Generating Station License No. DPR-75 Docket No. 50-311 Unit No. 2 Special Report 90-3 This Special Report addresses pressurizer overpressure protection system (POPS) actuations on. April 1, 1990. It is being submitted pursuant to the requirements of Technical Specification Action Statement 3.4.10.3c pursuant to Technical Specification 6.9.2.

This report is required within thirty (30) days of discovery.

Sincerely yours, L.K. Miller General Manager Salem Operations MJP:pc Distribution 9005080124 900427 PDR ADOCK 05000311 S PDC The . Energy People . .,t i-,*ibl:l*te*.

95-2189 (10M) 12-89

1 SPECIAL REPORT NUMBi990-3 PLANT IDENTIFICATION:

Salem Generating Station - Unit 2 Public Service Electric & Gas Company Hancock's Bridge, New Jersey 08038 IDENTIFICATION OF OCCURRENCE:

Pressurizer Overpressure Protection System Channel I Actuation Due To An Equipment Problem Event Date{s): 4/01/90 Report Date: 4/27/90 This report was initiated by Incident Report No.90-218 CONDITIONS PRIOR TO OCCURRENCE:

Mode 5 {Cold Shutdown)

Unit had been brought to Mode 5 at 1349 hours0.0156 days <br />0.375 hours <br />0.00223 weeks <br />5.132945e-4 months <br /> on April 1, 1990 in

.support of the initiation of the 5th refueling outage DESCRIPTION OF OCCURRENCE:

This Special Report addresses a Pressurizer Overpressure Protection System {POPS) actuation. The actuation occurred on April 01, 1990 at 1855 hours0.0215 days <br />0.515 hours <br />0.00307 weeks <br />7.058275e-4 months <br />. This report is submitted for information in *accordance with the requirements of Technical Specification Action Statement 3.4.10.3.c. which states:

In the event that either the POPS's or the RCS vents are used to mitigate an RCS pressure transient, a Special Report shall be*

prepared and submitted to the Commission pursuant to Specification 6.9.2 within thirty (30) days. The report shall describe the circumstances initiating the transient, the effect of the POPS's or vents on the transient and any corrective action necessary to prevent recurrence.

On April 1, 1990 at 1855 hours0.0215 days <br />0.515 hours <br />0.00307 weeks <br />7.058275e-4 months <br />, with the Unit in Mode 5 {Cold Shutdown), the 2PR1 valve (Power Operated Relief Valve) lifted (POPS actuation) af.ter removing No. 23 Reactor Coolant Pump (RCP) from service an4Sp;J;acing Ho. 21 RCP in service. The RCPs were swapped in support of:'/l~~~ud burst" operations. Reactor Coolant System (RCS) indicated. pj:es*sure was 320 psig at the time of swapping the RCPs.

The indicated RCS._ pressure during the POPS actuation was 360 psig.

After the first POPS actuation, three (3) additional actuations (same channel) occurred until pressure control was regained by removing No.

21 RCP from service and placing No. 23 RCP back in service at 1921 hours0.0222 days <br />0.534 hours <br />0.00318 weeks <br />7.309405e-4 months <br /> the same day (26 minutes later). The maximum RCS pressure observed, during any of the POPS actuations, was 365 psig. RCS pressure was reduced to approximately 310 psig upon regaining pressure control.

APPARENT CAUSE OF OCCURRENCE: ~ :, -- ~- Ll. ::.-*

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The "root '~cause of this event has beeri=attrf.lided to inadequate

SPECIAL REPORT 90-3. APPARENT CAUSE OF OCCURRENCE: (cont'd) procedural direction for identification of RCP requirements during Mode 5 operation.

Procedure IOP-6, "Hot Standby to Cold Shutdown" does not clearly address the phenomenon (see Analysis section} that Pressurizer spray is not adequate to maintain RCS pressure control with No. 21 RCP.

The procedure states:

"When RCS is less than 250°F, Reduce the number of Reactor Coolant Pumps to one. (If possible, maintain 23 RCP in service to provide spray flow)".

Contributing to this event has been inconsistent training in addressing Pressurizer Spray operations and the phenomenon identified in this Special Report. The Salem simulator treats RCS loops 21 and 23 as having equal capability for providing Pressurizer Spray.* The simulator training sessions are conducted in accordance with the procedural preference, however, the Operations Training lesson plans do not require discussion of the ha.sis for the pump preference.

ANALYSIS OF OCCURRENCE:

POPS is designed to protect the RCS from overpressurization by providing adequate relieving capability from the start of either one (1) Centrifugal Charging Pump or one (1) Safety Injection Pump during low temperature operation. However, since No. 21 Centrifugal Charging Pump and both Safety Injection Pumps were cleared and tagged, only No. 22 Centrifugal Charging Pump was available thereby satisfying the design of POPS.

As discussed in Westinghouse letter (PSE-86-639), "Pressurizer Spray Operation" dated December 11, 1986, RCPs may not provide Pressurizer Spray as required. Apparently, the Pressurizer surge line causes a pressure head loss (approximately 15 psi) due to the net elevation difference in raising the spray flow to the top of the Pressurizer.

This loss is apparently compensated for when No. 23 RCP is used to supply Pressurizer Spray due to the Pressurizer surge line being connected to the No. 23 RCS loop. When any of the other pumps are individually in service (including No. 21 RCP), insufficient Pressurizer Spray driving head is provided. Therefore, when No. 21 RCP

• was put .,$~ service, insufficient Pressurizer Spray was provided resulting :j;:* ""-:he POPS actuations. These actuations were not terminated., ,.:l. No. 23 RCP was put back in service.

In Mode 5, Pr~ssurizer*spray can be provided by an alternate means (other than directly from the RCS 21 or 23 loops). This other source is the charging line from the Chemical & Volume Control System (CVCS). This source is not affected by the pressure head loss caused by the surge line location. However, this source cannot be used if a differential temperature between the Pressurizer Spray line and charging return line is ~ 320°F. During this event, the differential temperature was 323°F.

The POPS functioned as designed to mitigate pressure transients caused by the lack of sufficient Pressurizer Spray. Therefore, this event did not affect the health or safety of the public. However,

SPECIAL R~PORT 90-3.

ANALYSIS OF OCCURRENCE: (cont'd) due to the actuation of POPS, this Special Report is being submitted in accordance with Technical Specification Action Statement 3.4.10.3.c, pursuant to the requirements of Technical Specification 6.9.2. .

CORRECTIVE ACTION:

Operations Department procedure(s) will be reviewed and revised to ensure that operations personnel are aware of the constraints for providing sufficient Pressurizer Spray such that mitigating actions can be taken to prevent a future POPS actuation.

This event will be reviewed by the PSE&G Nuclear Training Department to ensure existing training programs are revised to include the detail for the RCP preference when employing Pressurizer Spray. A Simulator Deficiency Report has been approved. Plans are in place to model the Pressurizer Spray function as per the actual plant response. '-

General Manager ~

Salem Operations MJP:pc SO.RC Mtg.90-043

• .. !*