ML20011F173

LER 90-001-00:on 900221,RCS Leakage Calculations Indicated That Unidentified Leakage Exceeded Tech Spec Limits.Caused by Failed Packing on Block Valve.Valve Repacked During Feb 1990 Maint outage.W/900221 Ltr

ML20011F173
Person / Time
Site:	Crystal River
Issue date:	02/21/1990
From:	Boldt G, Moffatt L FLORIDA POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
3F0290-13, 3F290-13, LER-90-001, LER-90-1, NUDOCS 9003010465
Download: ML20011F173 (5)

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C OM POR AT ION February 21, 1990

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3F0290-13 U. S. Nuclear Regulatory Commiss-lon Attention: Document Control Desk >

Washington, D. C. 20555

Subject:

Crystal River Unit 3 i Docket No. 50-302 Operating License No. DPR-72 Licensee Event Report No. 90-01

Dear Sir:

Enclosed is Licensee Event Report (LER) 90-01 which is submitted in accordance with 10 CFR 50.73.  :

1 Should there be any questions, please contact this office.

Very truly yours, Gary oldt M

i Vice President, Nuclear Production l

WLR: mag Enclosure xc: Regional Administrator, Region II J Senior Resident Inspector l l

'l 9003010465 900221

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• CRYSTAL nlVEn, FLORIDA 326294219 * (904) 563 2943 A Florida Progress Company

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SYSTEM UNIDENTIFIED LEAKAGE CAUSED BY VALVE PACKING FAILURE.

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Crystal River Unit 3 was operating in MODE 1 (POWER OPERATION) at 98% Full Power on January 22, 1990. Reactor Ccolant System (RCS) leakage calculations completed earlier that day showed that UNIDENTIFIED LEAKAGE was 0.3 gpm. At 1035, Reactor Coolant System leakage calculations indicated that UNIDENTIFIED LEAKAGE had increased to 1.4 gpm. This value exceeded Technical Specification limits. At 1205 operators began plant shutdown due to excess leakage. The plant entered an Unusual Event due to excess RCS UNIDENTIFIED LEAKAGE, in accordance with the p1 ant Emergency P1an.

Plant shutdown was completed at 1550. At 1700, operators isolated the leak.

The source of RCS leakage was identified as failed packing on the block valve

• associated with the Pilot Operated Relief Valve. The root cause for the packing

) failure cannot be determined until plant personnel disassemble and examine the valve. These actions will occur during the 1990 refueling outage.

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0 l0 0 l2 oF 0l4 EVENT DESCRIPTION Crystal River Unit 3 (CR-3) was operating in MODE 1 (POWER OPERATION) at 98% Full Power on January 22, 1990. At approximately 0815, while taking logs, the Assistant Nuclear Shift Supervisor (ANSS) noticed that airborne radioactivity levels were increasing in the Reactor Building (RB) [NH]. The ANSS then noticed that the Reactor Building Sump [NH] was filling at a rate higher than normal.

The RB Sump typically fills at a rate equivalent to less than 1 gpm. The Sump fill rate at this time was 1.4 gpm. Fluid enters the Sump as a result of leakage  !

from systems within the RB, as well as condensation of moisture within the building. The increased Sump fill rate, together with increased RB radiation levels, were indicative of increased leakage in the building. 4 At 0835, Control Room 0perators began Reactor Coolant System [AB] water inventory balance calculations to determine if the Reactor Coolant System (RCS) was the leakage source. Inventory balance calculations completed earlier on January 22, 1990 showed that UNIDENTIFIED LEAKAGE was 0.3 gpm. At 1035, inventory balance calculations indicated that RCS UNIDENTIFIED LEAKAGE had increased to 1.4 gpm. 3 In accordance with the CR-3 Emergency Plan, the plant entered an Unusual Event. '

The Emergency Plan requires the declaration of an Unusual Event whenever RCS UNIDENTIFIED LEAKAGE exceeds 1 gpm.

Plant Technical Specifications require that RCS UNIDENTIFIED LEAKAGE be no more than 1 gpm. Whenever the plant exceeds this limit, Technical Specifications require that operators reduce UNIDENTIFIED LEAKAGE to less than 1 gpm within four 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, or place the plant in MODE 3 (H0T STANDBY) within the following six hours.

At 1205 operators began plant shutdown in accordance with Technical Specification requirements.

Operators could not perform additional RCS inventory balance calculations during i plant shutdown. Plant personnel monitored the RB Sump fill rate during shutdown '

in order to obtain an indication of the RCS leak rate. The fill rate increased from the initial value of 1.4 gpm to as high as 13 gpm. The plant entered HOT STANDBY at 1550. Operators continued with plant cooldown following reactor shutdown. Operators terminated cooldown and stabilized the plant at 349'F and 445 psig at 1215 on January 23.

During shutdown, operators observed indications that the RCS leak was coming from I the area around the Pressurizer [AB, PZR). In order to test for possible leakage sources, Operators closed the Block Valve [AB,SHV] associated with the Pilot Operated Relief Valve (PORV) [AB,RV]. They observed that leakage appeared to stop or decrease when they closed the Block Valve (Tag number RCV-11). Operators desired to have the PORV available during shutdown. Therefore, they reopened RCV-11, and kept the valve open until the reactor [AC, RCT] was shutdown. At 1700, operators closed RCV-ll and left it closed. With RCV-ll closed, the Sump fill rate decreased to 0.5 gpm. Operators began an RCS inventory balance

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l KRC Form 306A (649)

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UCENSEE EVENT REPORT (LER) l8ls"URlo'd8Ed'JofiiS"$dT' .#TTRY ,*o'R" 1"'$ .l

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q0 0 l3 oF 0l4 texm-.w -c w mm nn calculation at 2115. At 2315, inventory results showed that RCS' UNIDENTIFIED I LEAKAGE had decreased to 0.4 gpm. At 2315 the plant exited the Unusual Event, i

! During cooldown, and following completion of cooldown, plant personnel entered the Reactor Building in efforts to locate the exact source of RCS leakage. By 1830 plant personnel identified failed packing on RCV-Il as the leakage source.

The design of RCV-11 is such that valve packing is not exposed to RCS pressure if the valve remains closed. Therefore, utility management personnel decid^d to deenergize RCV-Il in the closed position, and intended to keep the valve deenergized for the duration of the current fuel cycle.

L On February 13, 1990 the plant shutdown and cooled down for maintenance. The plant began heatup on February 19, 1990 following completion of maintenance activities. During this outage plant personnel replaced packing in RCV-II. The valve was returned to service during plant heatup. At the time of this report, RCV-11 leakage appears to have stopped. If leakage does not resume, RCV-ll will remain in service.

. CAUSE Technical Specifications required plant shutdown due to Reactor Coolant System UNIDENTIFIED LEAKAGE in excess of 1 gpm. Plant personnel identified failed packing on RCV-ll as the source of leakage. Plant personnel have not yet determined the root cause of the packing failure.

EVENT ANALYSIS

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The RCS leakage rate never exceeded the normal flow capability of the Makeup

, System [CB]. Plant shutdown and subsequent cooldown were controlled at all l

times. All radioactive material released from the RCS was contained within the Reactor Building. No radioactive material was released to the general public.

p0RRECTIVE ACTIONS Operators closed and deenergized RCV-11 following identification of the leakage source. The valve remained closed and deenergized during plant operation. Plant personnel repacked RCV-M during the February 1990 maintenance outage. Utility engineers will investigate the packing failure to determine the root cause of the failure. Based on the results of this investigation, additional maintenance may be performed on RCV-ll during the upcoming refueling outage.

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q0 q4 oF 0 l4 TEXT fr more ansee e coeusoit. ses esMeaner N4c Form 305Caf 11h PREVIOUS SIMILAR EVENTS This is the second event in which Technical Specifications required plant shutdown due to RCS leakage. On January 28, 1982, CR-3 was forced to shutdown due to RCS UNIDENTIFIED LEAKAGE. In that event, a through wall crack developed in Makeup and Purification System piping, resulting in excessive leakage.

I M7.C Form 306A (649)