ML20005F848

LER 89-039-00:on 891209,automatic Actuation of RHR Sys Portion of Primary Containment Isolation Control Sys Occurred.Caused by Hydrodynamic Transient That Actuated Protective High Pressure switches.W/900108 Ltr

ML20005F848
Person / Time
Site:	Pilgrim
Issue date:	01/08/1990
From:	Bird R, Ellis D BOSTON EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BECO-90-004, BECO-90-4, LER-89-039, LER-89-39, NUDOCS 9001170318
Download: ML20005F848 (6)

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Ralph G. Bird - .I Senior Vice President - Nuclear ,

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BECo- Ltr' 90- 004 o

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y !U.S. Nuclear Regul' atory Commission. ,

g Attn:' Document Control Desk 3 Hashington 0.C. 20555 Docket No. 50-293 >

License No. DPR-35 1

Dear Sir:

1 Th'e enclosed Licensee Event Report (LER) 89-039-00, " Automatic Closing of the Primary Containment System Group.3 Isolation Valves While Shutdown", is submitted

.in accordance with 10 CFR Part 50.73.

Please do not hesitate-to contact me if there are any questions regarding this

. report.  :

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Enclosure:

LER.89-039-00' I

cc: Mr. Hilliam Russell k

Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Rd.

1 King of Prussia, PA 19406

%m Sr. NRC Resident Inspector - Pilgrim Station Standard BECo LER Distribution 3 0 Q I g

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LICENSEE EVENT REPORT (IIR)

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Automatic Closing'of~the Primary Containment System Group 3 Isolation Valves While

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LICENGEE CONT ACT FOR THl3 LER (121 NAME TELEPHONE NUMBER ARE A CODE Douglas W. Ellis - Senior Compliance Engineer 5 10 18 71417 l- 1811 16l 0 COMPLETE ONE LINE FOR EACH COMPONENT F AILURE DESCRigED IN THis REPORT (13)

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l l I i 1 1 1 SUPPLEMENT AL REPORT EXPECTED 1141 MONTH DAY YEAR A 1 ) i YES fit ven. can'pteen Ex!ECTED SUOMISSION OATE) NO l l l ASSTi.ACT ILimit to H00 sonces. 4.s, enerommerety torteen eng+spece tvoewntsen kness (19l L

On December 9,1989 at 1245 hours0.0144 days <br />0.346 hours <br />0.00206 weeks <br />4.737225e-4 months <br />, an autonatic actuation of the Residual Heat Removal: System (RHRS) portion of the Primary Containment Isolation Control System

.(PCIS) occurred while shutdown. The actuation occurred when the RHRS was being L started for the shutdown cooling (SDC) mode of operation in accordance with procedure. The actuation resulted in the automatic closing of the Primary

, Containment System Group 3 (three)/SDC suction piping isolation valves.

The direct cause for the actuation was a hydrodynamic transient that actuated the protective high pressure (122 psig) switches for the SDC suction piping. The root

-cause is believed to have been some unvented air in the SDC suction piping. The air was most likely introduced into a section of the piping, while shutdown in October 1989, as a result of a valve bonnet leak and/or isolation that was subsequently conducted for valve sealing. The related accessible piping was inspected with satisfactory results. The PCIS logic circuitry was reset and the RHRS was satisfactorily put into service in the SDC mode of operation at 1501 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.711305e-4 months <br />. Corrective actions being planned include reconfiguring the existing vents in the SDC suction piping for improved venting.

-This event occurred while in hot shutdown with the reactor mode selector switch in the'SHUTD0HN position. The reactor power level was zero percent. The Reactor Vessel (RV) pressure was 5 (five) psig, and the RV water temperature was 230 degrees Fahrenheit with minor decay heat. This report is submitted in accordance with 10 CFR 50.73(a)(2)(iv) and this event posed no threat to the public health and safety.

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010 42 0F 0l 5 EVENT DESCRIPTION On December 9, 1989 at 1245 hours0.0144 days <br />0.346 hours <br />0.00206 weeks <br />4.737225e-4 months <br />, an automatic actuation of the Residual Heat-Removal System (RHRS) portion of the Primary Containment Isolation Control System I (PCIS) occurred while shutdown. The actuation occurred eight seconds after I starting the RHRS pump ' A' for the shutdown cooling (SDC) mode of operation. The i actuation resulted in the following desipaed responses:

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• The inboard and outboard Primaty Containment System (PCS)/ Group 3 (three) l SDC suction isolation valves (MO-1001-50 and -47), in the open position, I closed automatically. l

• The RHRS pump ' A' tripped automatically because the SDC suction valves were not fully open (i.e., the valves were closing). '

Initial utility Control Room licensed operator response was to close an RHRS injection valve (MO-1001-28A) and investigate the cause for the actuation. At approximately 1445 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.498225e-4 months <br />, the PCIS circuitry was reset and the SDC suction valves (M0-1001-50 and -47) were reopened. At 1501 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.711305e-4 months <br />, the RHRS pump 'A' was started and the RHRS was satisfactorily put into service in the SDC mode of operation.

Failure and Malfunction Report 89-476 was written to document the event. The NRC Operations Center was notified on December 9,1989 at 1515 hours0.0175 days <br />0.421 hours <br />0.0025 weeks <br />5.764575e-4 months <br />.

This event occurred while in hot shutdown with the reactor mode selector switch in the SHUTD0HN position. The Reactor Vessel (RV) pressure was 5 (five) psig with the RV water temperature at 230 degrees Fahrenheit. The reactor power level was zero percent.

. BACKGROUND Just prior to the event, steady state shutdown operating conditions existed. The Recirculation System pumps 'A' and 'B' were not in service. The Reactor Hater Cleanup (RHCU) System was in service. The RHRS was not in service in any of its operating modes.

A reactor scram had occurred on December 8, 1989 at 0308 hours0.00356 days <br />0.0856 hours <br />5.092593e-4 weeks <br />1.17194e-4 months <br />. While still shutdown as a result of the scram (LER 89-038-00), a management decision was made on December 9, 1989 to achieve cold shutdown in order to perform planned maintenance and testing. The core decay heat was minor. However, the RV water temperature was greater than 212 degrees Fahrenheit and the SDC mode of operation was to begin in order to achieve cold shutdown conditions.

The RHRS (Loop 'A') was subsequently configured for the SDC mode of operation in accordance with section 5.4 of procedure 2.2.19 (Rev. 32) Attachment 6 (six), "RHR Shutdown Cooling Operations". The procedural steps taken included flushing and venting the SDC suction piping downstream of the outboard isolation valve (M0-1001-47) and, similarly, the discharge piping up to the Loop 'A' injection valve M0-1001-29A that is downstream and in-series with valve MO-1001-28A. At 1236 hours0.0143 days <br />0.343 hours <br />0.00204 weeks <br />4.70298e-4 months <br />, the Recirculation System Loop 'B' pump (P-2018), in service at the time, was i

shutdown in accordance with procedure 2.2.84, " Reactor Recirculation System".

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0l 0 0l3 or 0 l5 text w-. <. meo mmnn Prior to commencing the SDC mode of operation, a pre-evolutionary briefing was conducted in accordance with procedure 1.3.37, " Conduct of Operations". At 1244 hours0.0144 days <br />0.346 hours <br />0.00206 weeks <br />4.73342e-4 months <br />, the RHRS Loop 'A' (throttling type) injection valve MO-1001-28A was closed and the in-series injection valve MO-1001-29A was opened in accordance with procedure (2.2.19 Attachment 6 section 5.4) steps [10] and [11), respectively. The ,

SDC suction valves (MO-1001-50 and -47) were then opened in accordance with procedure step [12). The RHRS Loop 'A' pump 'A' (P-203A) was then started and  ;

valve M0-1001-28A was jogged open in accordance with procedure step [13] and a flow of approximately 3200 gpm was attained approximately five seconds later. The actuation occurred approximately eight seconds after the start of the pump.

CAUSE A critique of the event was conducted on December 9,1989 in accordance with procedure 1.3.63, " Conduct of Critiques and Incident Investigations". The critique was held to determine the cause for the event and was attended by appropriate l

personnel including the operators on shift at the time of the event.

The direct cause for the actuation was a hydrodynamic transient that actuated pressure switches (PS-261-23A and -238) connected to the Recirculation System Loop

'A' pump suction piping. The SDC suction piping is connected to the Recirculation System Loop 'A' piping upstream of the Loop 'A' pump suction valve. The hydrodynamic transient probably resulted from some unvented air in the SDC suction piping. The setpoint for the pressure switches is calibrated at approximately 122 psig. The PCIS Group 3 logic circuitry is arranged as an interlock such that

. reaching the setpoint of either (or both) pressure switch results in a close signal to the related RHRS valves (MO-1001-50 and -47).

The root cause for the actuation is believed to have been some unvented air in the SDC suction piping. The air.was most likely trapped in a section of the suction piping between the inboard isolation valve (M0-1001-50) and the outboard isolation valve (M0-1001-47). The air was most likely introduced into this section of piping as a result of a valve (MO-1001-50) bonnet leak and/or isolation that was conducted for subsequent leak sealing performed while shutdown in October 1989.

CORRECTIVE ACTION i

The following corrective actions that have been taken include the following:

• Field inspection of accessible SDC suction piping located outside of primary containment (Drywell) was performed with satisfactory results.

The inspections revealed no evidence of piping damage or unusual piping movement.

e The related instrumentation, alarms, logic circuitry, and valves l

(M0-1001-50 and -47) were functionally tested on December 11, 1989 with satisfactory results. The inboard valve related testing was performed in accordance with procedure 8.M.2-1.5.4 (Rev. 10) Attachment 'A', "RHR Isolation Valve Control - Test A - Inboard". The outboard valve related testing was performed in accordance with procedure 8.M.2-1.5.5 (Rev. 11)

Attachment 'A', "RHR Isolation Valve Control - Test B - Outboard".

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4 'The reconfiguration of existing vents that would more effectively- 3 eliminate trapped air in the SDC suction piping is part of the Long Term Plan (Item 31).

SAFETY CONSEOUENCES

-This event posed no threat to the public health and safety. '

The RHRS/SDC mode of operation has a power generation design basis only. The SDC mode-of operation functions to reduce the RV water temperature to 125 degrees Fahrenheit approximately 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> after a shutdown for refueling or servicing activities.

If the actuation had occurred when the decay heat generation rate was greater, a gradual increase in the RV water temperature could have occurred. However, L alternate means for heat removal are available and described in procedure 2.4.25

" Loss of Shutdown Cooling", including methods for feed and letdown using the Condensate System, RNCU System, and the Main Condenser.

L This report is submitted in accordance with 10 CFR 50.73(a)(2)(iv) because the PCIS L -

logic circuitry was actuated. The SDC mode of operation is not necessary to h mitigate the consequences of an accident. The actuation was initiated by the 122 L psig RV pressure switches (PS-261-23A and -23B). The pressure switches provide a E protective function for the SDC suction piping. The SDC suction piping, extending from the Recirculation System Loop 'A' piping up to the RHRS pumps' suction valves M0-1001-43A/B/C/D, provides a flow path for the SDC mode of operation only.

SIMILARITY TO PREVIOUS EVENTS A review was conducted of Pilgrim Station Licensee Event Reports (LERs) submitted i since January 1984. The review focused on LERs submitted in accordance with D 10 CFR 50.73(a)(2)(iv) involving the closing of the RHRS/SDC suction piping isolation valves. The review identified related events reported in LERs 50-293/87-008-01, 87-015-00, and 88-025-00.

For LER 87-008-01, an unplanned actuation of the RHRS portion of the PCIS occurred during refueling on October'15,1987 at 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br />. The actuation resulted in the automatic closing of the isolation valves (M0-1001-50 and -47) and a temporary interruption in the SDC mode of operation. At the time of the event, the refueling cavity was flooded and the decay heat generation rate was negligible. The actuation occurred during a work task involving the installation of a new PCIS relay (16A-K69) in parallel with the inboard tripping relay (16A-K28) associated

-with PS-261-23A. The coil of relay 16A-K28 became de-energized during the installation of relay 16A-K69. The cause for the actuation was contractor electrical craft personnel error due to a deficient work plan.

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For LER 87-015-00, actuations of the RHRS portion of the PCIS logic circuitry occurred while shutdown on December 7, 1987 at 1438 hours0.0166 days <br />0.399 hours <br />0.00238 weeks <br />5.47159e-4 months <br /> and on December 8, 1987 at 2145' hours. The December 7, 1987 actuation resulted in a temporary interruption in the SDC mode of operation. The actuation occurred while a utility I&C

. technician was installing a jumper to circuit contacts related to PS-261-23A in accordance with procedure 2.1.8.1 (Rev. 2), " Class 1 System Hydrostatic Test".

During the jumper installation, a screw became disconnected and de-energized the coil of relay 16A-K28 that resulted in the event. The cause for the actuation was procedural inadequacy in that the procedure (2.1.8.1) did not adequately identify how the jumper was to be installed and did not contain a suitable caution regarding the potential impact to the SDC mode of operation. The December 9, 1987 actuation occurred at the beginning of the hydrostatic test when the RV pressure reached the setpoint of the pressure switches (PS-261-23A/B). The actuation resulted in the automatic closing of only the inboard isolation valve (H0-1001-50) because the outboard isolation valve (H0-1001-47) was in the closed position for the portion of

.the test (2.1.8.1 Rev. 2) being conducted. The cause for the actuation was procedural inadequacy in that the procedure (2.1.8.1) did not identify all the jumpers necessary to bypass the (122 psig) interlock for the test.

For LER 88-025-00, a low RV water level occurred while shutdown on December 3, 1988 at 0304 hours0.00352 days <br />0.0844 hours <br />5.026455e-4 weeks <br />1.15672e-4 months <br />. The low RV water level that occurred (+3 inches narrow range level) resulted in actuations that included the RHRS portion of the PCIS logic circuitry.

The isolation valves (H0-1001-50 and -47), in the open position, closed automatically. The low RV water level occurred following a local leak rate test of the SDC suction isolation valves when the outboard isolation valve (H0-1001-47) was opened (with valve H0-1001-50 in the open position). The valve was opened in accordance with procedure 2.2.86 (Rev.31), " Residual Heat Removal". The opening of valve M0-1001-47 resulted in the displacement of water from the RV (via the

' Recirculation System Loop 'A' pump suction piping) to an unfilled section of the 20 inch SDC suction piping. The cause for the actuation was utility licensed operator error.- A contributing factor was a weakness in the procedure (2.2.86 Rev. 31) approved for the activity being performed.

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

COMPONENTS CODES Pump (P-203A) P Switch, Pressure (PS-261-23A/B) PS Valve, Isolation-(M0-1001-47 and -50) ISV L

i SYSTEMS l Engineered Safety Features Actuation System (PCIS) JE Reactor Recirculation System AD Reactor Services System (RHRS/SDC mode) CF oa m.

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