ML20107C537

Special Rept:On 841226,PORV 1NC32B Opened to Relieve RCS Pressure Increase Caused by Starting Nc Pump 1A.Caused by Misinterpretation of Limits & Precautions Statement in Nc Pump Operating Procedure.Procedure Revised

ML20107C537
Person / Time
Site:	Catawba
Issue date:	01/25/1985
From:	Tucker H DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 8502210374
Download: ML20107C537 (4)

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DUKE POWER GOMPANY P.O. Box 33180 CHAMLOTTE, N.O. 28242 HAL B. TUCKER run.zenoxe

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Mr.. James P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Re: Catawba Nuclear Station, Unit 1

. Docket No. 50-413

Dear Mr. O'Reilly:

Pursuant to Technical Specification 3.4.9.3, Action Statement c, please find

-attached a Special Report concerning the automatic opening of a pressurizer

power-operated relief valve.

.Very truly yours, f$ f / 86/

Hal'B. Tucker

'RWO: sib Attachment cc: Director Office.of Inspection and Enforcement U. S.. Nuclear Regulatory Commission Washington, D. C. 20555

.NRC' Resident Inspector

• Catiawba Nuclear Station -

Palmetto Alliance' 2135 Devine Street

'Columbio,; South Carolina:E29205 Mr. Jesse L. Riley Carolina Environmental Study Group 854 Henley Place Charlotte, North Carolina 28207 Robert Guild, Esq.

P._0. Box 12097 Charleston, South Carolina 29412 DITICIAL COPY.

'B502210374 850125 ADOCK 0500 3 -gg gDR

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INTRODUCTION On' December 26, 1984, at 2201:11 hours, Pressuri::er Power Operated Relief Valve (PORV) INC32B automatically opened. It remained open for 3 seconds to' relieve;a pressure increase in the Reactor Coolant (NC) System caused by starting NC Pump 1A. Catawba Unit I was in Mode 5, Cold Shutdown, at

.the time of the-incident. This incident is reportable pursuant to Technical Specifications 3.4.9.3 and 6.9.2.

Once the NC System was filled,and vented and NC temperature was increased above Charging and Seal Injection water temperature, a steam bubble should have been formed in the Pressurizer prior to starting a NC Pump. A Limits and Precautions Statement = existed in-the.NC Pump Operating Procedure

, addressing the situation. However,:it was not clear in that its application

was misinterpreted by the Nuclear Control Operator (NCO). Therefore, this

= event is classified as a Personnel Error and an Administrative / Procedural Deficiency.n . The NC System Fill and Vent Procedure was changed to verify Lthe applicability of the Limits and Precautions Statement.

. EVALUATION

'The Pressurizer is equipped with Power Operated Relief Valves (PORV's) iwhich open when necessary to relieve Reactor Coolant (NC) System'pressura.

~The PORV?sican be placed in the MANUAL or AUTOMATIC Mode. In MANUAL,.the, iPORV can be openedbya Nuclear Control Operator (NCO). In AUTOMATIC, the

-PORV will open at either:the Upper High PressureLSetpoint (2335 psig) or

~t he: Lower High Pressure'Setpoint (400 psig) selected depending upon NC System, conditions.

. DESCRIPTION OF INCIDENT On December 26,_1984, at 2200 hours0.0255 days <br />0.611 hours <br />0.00364 weeks <br />8.371e-4 months <br />, plant conditions were as follows:

-~ Unit 'l was ;in Mode 5, Cold Shutdown'.E

'- Reactor. Coolant _ (NC) . System pres'sure 2275 psig.

x ,' NC System. temperature 1550F.f

-' Steam GeneratorT(S/G). temp 1600F.

Operat$ing Procedure OP/1/ /6150/01," Filling and Venting the Reactor _ Coolant .

E System,lwas in' progress with the' NC ' System in'a water solid condition.

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LHydrazine h'ad .been.added to the NC System.' Reactor ' Coolant was being circu-

-lated'by Residual: Heat Removal.'(_ND) System, Train A.-

?At2200'26; hours,:NCPump)1Awas.startedtorecirculatethePressurizer.

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- Coincident-with.thelpump start, NC System Pressure started increasingf /At 12201:11: hours,_PORVl1NC32B started t.o'open,! reaching the fully open position

" lin-twoiseconds. ?At 2201:141 hours, PORY INC32B closed. :During'this incident,;

PORVfINC32B was-in.th' e LLower High Pressure Mode (400 psig).

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CONCLUSIONS On December 26, 1984, at approximately 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br />, NC Pump 1A was started to Heat-up the NC System. At approximately 1420 hours0.0164 days <br />0.394 hours <br />0.00235 weeks <br />5.4031e-4 months <br />, NC Pump 1A was secured. However, af ter NC Pump 1A was secured, Charging and Seal Injection water was still being supplied to the NC System. Because the NC System temperature had previously been increased, a significant temperature difference existed between the NC System and the Charging and Seal Injection water.

When NC Pump 1A was started at 2200:26 hours, the Lower Temperature water which had accumulated in portions of the NC Loops was circulated and picked up heat from the NC System and the Steam Generators. A Pressure Transient occurred due to thermal expansion of the Charging and Seal Injection water causing NC System Pressure to increase. Since the NC System was in a water solid condition, a Pressurizer bubble was not available to dampen the effects-of a pressure transient. Because of this, PORV 1NC32B opened following the start of NC Pump 1A.

There are two Pressurizer PORV's which will open in the Lower High Pressure Mode (400 psig); INC32B and 1NC34A. Of these, only INC32B opened. This valve was able to mitigate the NC System Pressure Transient.

The Reactor Coolant Pump Operation Procedure (OP/1/A/6150/02A), which is

-referenced in Filling and Venting the Reactor Coolant System (OP/1/A/6150/01),

states that "if all Reactor Coolant Pumps have been stopped for more than 5 minutes and the Reactor Coolant System temperature is greater than Charging and Seal Injection Water temperature, the pumps cannot be started until a steam bubble has been formed in the Pressurizer". This is to ensure that a pressure transient, if it occurs, can be controlled by the Pressurizer.

The procedure also states that the condition mentioned above does not apply to fill and vent operations. The intent of this statenent was that it does not apply to the actual NC System fill and vent process which is only a portion of the fill and vent procedure. However, it does not exclude the entire fill and vent procedure.

During and following Hydrazine addition, which is included in the NC System Fill and Vent Procedure, the NC System is completely filled and vented. Therefore, since NC System temperature was increased above Charging and Seal Injection water temperature, and a significant amount of time elapsed between NC Pump runs, a steam bubble should have been formed in the Pressurizer prior to starting NC Pump 1A as required by the Limits and Precautions Statement. However, because the Limits and Precautions Statement stated that it did not apply to fill and vent operations, the application of the Limits and Precautions Statement was misinterpreted by the Nuclear Control Operator (NCO) and was not applied to the entire Fill and Vent Procedure. Therefore this event is classified as a Personnel Error, and an Administrative / Procedural Deficiency. The NC System Fill and Vent Procedure was changed to verify the applicability of the Limits and Precautions Statement.

The PORV responded as designed to relieve the NC System pressure trcusient.

There was no release of radioactive materials, radiation exposures, or personnel injuries as a result of this incident.

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m y C, ,1;' - _3 CORRECTIVE ACTION A change was made to Operating Procedure OP/1/A/6150/01, Filling and

.. Venting the Reactor Coolant System, inserting the following CAUTION Statement:

-If the temperature of the NC System or S/G's has been increased prior to stopping'NCP's, a bubble shall be formed-in'the Pressurizer prior to any further NC Pump start.. This is to prevent a possible NC Pressure

-Transient due to cold water expansion.

This 'statenent was inserted af ter the Procedure step completing the fill and vent process and prior to Hydrazine addition.

Operators will be-instructed on this incident, and the importance of the procedure changes will be stressed.

NC Pump' starts as related to system water temperature differences and pressure transients will be analyzed.

SAFETY ANALYSIS The PORV respondedfas-designed and all water relieved through the PORV went directly to and was contained in-the Pressurizer Relief Tank. The 1 health.and safety of the public was not affected by this incident.

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