ML19332D623

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LER 89-032-00:on 891020,pneumatic Pressure Drop for Two of Four Automatic Depressurization Sys Accumulators Discovered Greater than Max Acceptable Value.Caused by Leakage from Seat of Supply Check Valves.Seat replaced.W/891120 Ltr
ML19332D623
Person / Time
Site: Pilgrim
Issue date: 11/20/1989
From: Bird R, Ellis D
BOSTON EDISON CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
89-168, LER-89-032, LER-89-32, NUDOCS 8912050047
Download: ML19332D623 (7)
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Ralph G. Sird y senior Vice President - Nuclear November. 20, 1989 l BECo Ltr. 89- 168 1 4 U.S.iNuclear Regulatory Commission

"+ Attn: ~ Document Control Desk Hashington, D.C. 20555 y '

Docket No. 50-293

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Dear Sir:

. j The enclosed Licensee Event Report (LER) 89-032-00, " Unacceptable Pneumatic i 4, Pressure Drop for Two Automatic Depressurization System Accumulators i

. Discovered During Testing'While Shutdown", is submitted in accordance with

~10 CFR'Part 50.73..

Please do not hesitate to contact me if you have any questions regarding this W subject.

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Enclosure:

LER 89-032-00 cc: Mr. Hilliam Russell Regional Adolr.istrator, Region I .l

v. U.S. Nuclear Regulatory Commission  !

J- .475 Allendale Rd.

- King of Prussia, PA 19406 Sr.. Resident Inspector - Pilgrim Station .!

Standard BECo LER Distribution  !

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"$$[p"^1rfiSNuclear Power Station TiTLt 4 Unacceptacle eneumauc l'ressure prop for iwo AutomcElo Depressurization 1g $ 2  ; , 9; 3 il[I 6 System Accumulators Discovered Durirg Testing While Shutdown IVENT DAff (6) l- LER NUM8ER (6) REPORT DATE 471 OTHER F ACf LITIES INVOLVED it) se a n, DAY P AL;suT V NAMES DOCKET NUM8ER(S)

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. Douglas W Ellis.- Senior Compliance Engineer '" ' ^ c *

, 5,0j8 7; hi7i i 8;l 6i i 0 COMPLETE ONE LINI FOR E ACK COMPONINT F A! LURE DESCRigED IN THIS REPORT f13)

' M AIPORTA E CAU$E SYSTEM COMPONENT [g[.- "TO NP CAuSE SYSTEM COMPON E NT C- s X- L,E , , R,V K,2, 3,5 Y- '

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SUPPLEMENTAL REPORT EXPECTED (141 l MONTH DAY YEAR

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On October 20,.1989 at 1820 hours0.0211 days <br />0.506 hours <br />0.00301 weeks <br />6.9251e-4 months <br />, the pneumatic pressure drop for two of the r four At:tomatic Depressurization System (ADS) accumulators was discovered to be greater than the maximum acceptable value during testing conducted while shutdown. The pressure drop for the other two accumulators was acceptable (i.e., less than a 14 psig drop in four hours). The accumulators function to supply (store) sufficient pneumatic energy for actuating the related two-stage l Main Steam System relief valves that function to depressurize the Reactor Vessel if high pressure core cooling is not available.

The cause for the unacceptable pressure drop of the two accumulators was collective pressure boundary leakage at the seat of each accumulator's supply check valve, accumulator relief valve and drain valve. The soft seat of the check valve foi each accumulator was replaced. The relief valve for each accumulator was replaced. The drain valve for each accumulator was reworked or replaced. Post work testing was completed with satisfactory results on November 2, 1989.

The testing was performed while shutdown with the reactor mode selector switch r in the SHUTDOHN position. The Reactor Vessel (RV) pressure was zero psig with tne RV water temperature at 125 degrees Fahrenheit. The reactor power level was zero percent. This report is submitted in accordance with 10 CFR subparts 50.73(a)(2)(1)(B) and (a)(2)(vii)(D) and the unacceptable pressure drop for the two accumulators posed no threat to the public health and safety.

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j EVENT DESCRIPTION On October 20,1989 at 1820 hours0.0211 days <br />0.506 hours <br />0.00301 weeks <br />6.9251e-4 months <br />, the pneumatic pressure drop for 2 (two) of

.the 4 (four) Automatic Depressurization System (ADS) accumulators was  !

discovered to be greater than the maximum acceptable value. The discovery was made during a scheduled test performed in accordance with procedure 8.7.1.10 (Rev. 8), " ADS Accumulator Pressure Drop Test", on October 20, 1989. The test i was being performed in accordance with the surveillance program that included i a commitment made in response to NRC Inspection 50-293/88-21 (i.e., EC  ;

88-21-08).

The pressure drop test involves the isolation of the accumulators from the  ;

nonsafety grade pneumatic supplies (Nitrogen or Backup Nitrogen Supply i Systems) that normally supply the accumulators, recording the accumulator pressure after isolating the accumulator from the pneumatic supplies, and recording the accumulator pressure after four hours. The test acceptance criteria is a pressure drop that does not exceed 14 psig in four hours.

The test reve:11ed the pressure drop for accumulators T-221C and T-221D was unacceptable. The pressure, initially at approximately 80 psig, decreased to approximately zero psig during the test. The pressure drop during the four hour. test period was not monitored because of ALARA considerations. Further, the test revealed that the pressure drop for accumulators T-221 A and T-221B was acceptable with a four hour pressure drop of approximately 1 (one) psig  ;

for each of these two accumulators.

Failure and Halfunction Report 89-403 was written to document the discovery.

The NRC Operations Center was notified in accordance with 10 CFR 50.72 on October 20,1989 at 2218 hours0.0257 days <br />0.616 hours <br />0.00367 weeks <br />8.43949e-4 months <br />.

The discovery was made while shutdown with the reactor mode selector switch in the SHUTOOWN position. The Reactor Vessel (RV) pressure was zero psig with the RV water temperature at approximately 125 degrees Fahrenheit. The reactor power level was zero percent.

BACKGROUND l

The function of the ADS is to reduce the Reactor Vessel pressure to allow low pressure core cocling provided independently by the Core Spray System and the i Residual Heat Removal System (RHRS)/ Low Pressure Coolant Injection (LPCI)

I mode. The ADS depressurization function is necessary if the Reactor Vessel is isolated at high pressure and high pressure core cooling is not available.

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0 l0 013 OF O l6 l The depressurization function.provided by the ADS utilizes the Main Steam i

- System relief valves that_are part of the Pressure Relief System (PRS). The relief valves (RV-203-3A, -3B, -3C, -30) are two-stage in design. The rel,ief ,

valve's first stage (pilot assembly) provides a pressure sensing and control  ;

function while the valve's second stage (main body) provides an ADS depressurization function, or a PRS safety and overpressure protection

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function. The ADS depressurization function, initiated automatically by the '

-ADS logic circuitry or manually by_ manual switches, is accomplished by the ,

introduction of pneumatic pressure to a relief valve's first stage and results  !'

in the opening of the valve's second stage (main body) for depressurization.

Each of the relief valves is separately equipped with a safety grade pneumatic accumulator and related components. Each accumulator is provided to assure  !

4 that the related two-stage relief valve (RV-203-3A -3B,-3C,-3D) can be ,

actuated for the ADS depressurization function even if a failure of the  !

nonsafety grade pneumatic supplies (Nitrogen or Nitrogen Backup Supply Systems) occurs. Each accumulator is sized to contain (store) sufficient pneumatic energy for 20 relief valve actuations.

-The PRS safety and overpressure protection functions are accomplished by the

. relief valve's (RV-203-3A,-38,-3C,-30) spring loaded, self-actuating second stage (main body). The PRS safety and overpressure protection functions are independent of the ADS accumulator (s) and pneumatic supplies.  ;

CAUSE The cause for the unacceptable pressure drop of accumulators T-221C and T-221D

. during the test was collective leakage at portions of each accumulator's pressure boundary. Subsequent investigation and testing revealed that some of the leakage was past the seat of each accumulator's pneumatic supply check

- t valve, CK-372C (for T-221C) and CK-3720 (for T-2210). After the check valves' (soft) seats were replaced, another pressure drop test of the accumulators (T-221C and T-221D) was performed. The test revealed that the pressure drop, although improved, was still unacceptable. Additional testing revealed some leakage past the seat of each accumulator's relief valve, RV-9084C (for T-221C) and RV-90840 (for T-2210), and drain valve, H0-373C (for T-221C) and H0-373D (for T-221D).

9 Check valves CK-372C and CK-3720, manufactured by Walworth-Aloyco, are one-inch swing type valves equipped with a soft seat that has a rubber-like composition (EPDM - a synthetic, ethylene-propylene, organic substance).

. Relief valves RV-9084C and RV-9084D were manufactured by the Kunkle Valve Company (model 6000). Drain valve H0-373C (a three-quarter inch globe type),

manufactured by the Hancock Company, nameplate data includes serial number H338AAL and 5030H-1-XNC069. Drain valve H0-373D (a three-quarter inch globe p type), was manufactured by the Vogt Company, serial number 57-21577.

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CORRECTIVE ACTION Thkfo11owingcorrectiveactionhasbeentaken. For accumulator T-221C, the

, check valve (CK-372C) soft seat, and the relief valve (RV-9084C) and drain valve (H0-373C) were replaced. For accumulator T-2210, the check valve (CK-3720) soft seat and the relief valve (RV-90840) were replaced, and the  !

drain valve (H0-373D) seat area was reworked (lapped). Post work testing of  !

accumulators T-221C and T-221D was performed in accordance with procedure i (8.7.1.10) and completed with satisfactory results~on November 2, 1989. l SAFETY CONSE0VENCES j The unacceptable pressure drop for two of the four ADS accumulators posed no  ;

threat to the public health and safety. j The Core Standby Cooling System (CSCS) subsystems consist of the High Pressure  !

Coolant Injection (HPCI) System, ADS, Core Spray System (CSS), and the RHRS/LPCI mode. The Reactor Core Isclation Cooling (RCIC) System, although i not a CSCS subsystem, is capable of providing, independently of the HPC.  ;

System, high pressure core cooling if the Reactor. Vessel is itolated.

J In the unlikely event that a HPCI System failure occurred when its operation I was necessary while the RCIC System was inoperable, or if a failure of the .

RCIC System occurred when its operation was necessary while the HPCI System was inoperable, the ADS depressurization function would have been necessary to

-reduce the Reactor Vessel pressure for low pressure core coolina. The nonsafety grade pneumatic supplies to the ADS accumulators include two normally connected (in-parallel) sources of nitrogen. Assuming the nonsafety grade pneumatic systems were not available to compensate for the unacceptable pressure drop of accumulators T-221C and T-2210, the two accumulators vould not have been operable for the ADS depressurization function provided by the  !

related two-stage relief valves (RV-203-3C and -3D). The acceptable pressure drop test results for accumulators T-221A and T-221B demonstrated that these two accumulators were' operable for the ADS depressurization function provided by the related two-stage relief valves (RV-203-3A and RV-203-38). Because the loss of only one ADS (two-stage relief) valve is assumed in the Pilgrim Station accident analyses, the ADS depressurization function would have been degraded. However, the ADS wa still capable of reducing the Reactor Vessel pressure even if the nonsafety grade pneumatic supplies were not available and the depressurization function provided by the related two-stage relief valves (RV-203-3C ard -3D) was not operable because of the unacceptable pressure drop (operability impact) of the two ADS accumulators (T-221C and T-221D).

All four of the relief valves (RV-203-3A, -38 -3C, -3D), including relief valves RV-203-3C and -3D, were operable for the PRS safety and overpressure protection functions.

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0l0 0 l5 oF 0 l6 This report is submitted in accordance with 10 CFR 50.73(a)(2)(1)(B) because I the results of the pressure drop test, performed while shutdown when the ADS l is not required to be operable, indicate that two cf the four ADS accumulators and related two-stage relief valves would not have been operable for the ADS depressurization function. Technical Specification 3.5 E specifies a seven day Limiting Condition for Operation (LCO) if _one ADS (two-stage relief) valve J is inoperable when there is irradiated fuel in the Reactor Vessel and the Reactor Vessel pressure is greater than 104 psig. The last test-(procedure t 8.7.1.10) of the ADS accumulators was completed with satisfactory results on October 2, 1987. From October 2, 1987 until December 30, 1988 the plant remained shutdown. A controlled plant shutdown was completed on October 13, 1989 for planned testing and maintenance. From December 30, 1988 to October 13, 1989, operation at power was conducted for approximately 196 days. Therefore, the unacceptable pressure drop test results on October 20, 1989 indicate that Technical Specification 3.5.E may have been (unknowingly) exceeded since December 30, 1988.

This report is also submitted in accordance with 10 CFR 50.73(a)(2)(vii)(D) l

,3 because the depressurization function of two of the four ADS (two-stage 7 relief) valves was inoperable because of the unacceptable pressure drop of the related ADS accumulators.

SIMILARITY TO PREVIOUS EVENTS l

A review was conducted of Pilgrim Station Licensee Event Reports (LERs) submitted since January 1984. The review focused on LERs that involved-the ADS accumulators or other safety grade accumulators. The review identified a related conditions reported'in LERs 50-293/89-002-00 and 89-004-00.

For LER 89-002-00, a potential problem with the pneumatic (compressed air) supply for two primary containment air operated valves (AO-5040A and A0-50408) was identified on January 10, 1989 while in the startup mode with the reactor power level at approximately one percent. The redundant (in-series) check valves were capable of assuring the primary containment function and were not affected by the problem. The problem involved the 30 day mission time of the air operated valves (AO-5040A and A0-50408), and the capacity (i.e., size) of the valves' safety grade air accumulators (T-225A and T-225B) that were (then) l supplied by the nonsafety grade Instrument Air System. The discovery resulted '

from a Nuclear Engineering Departmcnt analysis of the Instrument Air System conducted as a result of NRC Generic Letter 88-14, " Instrument Air Supply i System Problems Affecting Safety-Related Equipment". The cause was attributed  !

to insufficient capacity (size) of the air accumulators (T-225A and T-2258).

~ A modification was issued and implemented that provided for the installation of two additional safety grade accumulators (X-200A and X.200B) and related p

components, including separate safety grade makeup sources of pressurized air (independent of the Instrument Air System). ]

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  • f xPIRtS: 8/31/08 FACitlTV NAME 111 pocati NUMd (21 LER NUM8tR (66 Pact (31 naa "mm -

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0l0 0 l6 or 0l6 texv u- N . -ac r ,as c.iti7, For LER 89-004-00, the pressure drop rate of the safety grade (stor'ed) air  !

supply for the same two air operated valves (AO-5040A and A0-50400) was discovered to be greater than acceptance criteria during routine (once per shift) monitoring on January 27, 1989. The discovery occurred while in the startup mode with the reactor power level at approximately one percent. The 1 unacceptable pressure drop rate resulted in declaring the two air operated I, valves inoperable, declaring an Unusual Event, and the completion of a shutdown. The redundant (in-series) check valves were capable of assuring the- f primary containment function and were not affected~by the pressure drop rate, 3 The cause for the pressure drop rate exceeding the acceptance criteria was '

attributed to collective leakage at some of the air supply connections and N leakage past the seat of the accumulator's (T-225A and T-2258) relief-valve (s).-

ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) CODES The EIIS' codes for this report are as follows:

COMPONENTS CODES

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Accumulator (T-221C, T-221D) ACC  ;

Valve (CK-372C, CK-372D) V Valve,1elltale (HO-373C, H0-373D) 1TV ,

Valve, Relief (RV-9084C, RV-9084D) RV SYSTEMS Core Spray System (CSS) BM Essential Air (Pneumatic) System LE High; Pressure Coolant Injection (HPCI)-System BJ Integrated Control System (ADS) JA }

Main Steam System SB Nitrogen Supply (Pneumatic) System LK .

Reactor Core Isolation Cooling (RCIC) System BN Residual Heat Removal System (RHRS/LPCI) B0 ,

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