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LER 89-010-00:on 891013,HPCI Sys Declared Inoperable Due to Condensate Accumulation Inside HPCI Turbine Exhaust Pipe. Caused by Drain Pipe Flow Orifice Blockage Due to Debris in Exhaust Pipe.Condensate drained.W/891113 Ltr
	ML19332B964
Person / Time
Site:	Limerick
Issue date:	11/13/1989
From:	Endriss C, Mccormick M; PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	; NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
	LER-89-010-02, LER-89-10-2, NUDOCS 8911220124
	Download: ML19332B964 (9)
	v • d • e

10 CFR 50.73 i

PHILADELPHIA ELECTRIC COMPANY LIMERICK OENER ATING ST AT!ON P. O. DOX A SAN ATOG A. PENNSYLV ANI A l9464 i

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u. 4. u.co uic a. a... e.e. November 13, 1989 m . . . 7 ".'. .".'."/.*, ." .. . . . Docket No. 50-353 License No. NPF 85 U.S. Nuclear Regulatory Commission Attn Document Control Desk Washington, DC. 20555

SUBJECT:

Licensee Event Report i Limerick Generating Station - Unit 2 This LER reports an event where the Unit 2 High Pressure Coolant Injection (HPCI) system was la a degraded condition which alone could have prevented the fulfillment of its safety function. This was due to a personnel error which resulted in condensate accumulating inside the HPCI turbine exhaust pipe.

Reference:

Docket No. 50-353 Report Number 2-89-010 Revision Number: 00 Event Date October 13, 1989 Report Date November 13, 1989 Facility: Limerick Generating Station P.O. Box A, Sanatoga, PA 19464 This LER is being submitted in accordance with the requirements of 10 CFR 50.73(a)(2)(v)(A) and (D).

Very truly yours,

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DMSich cc: W. T. Russell, Administrator, Region I, USNRC T. J. Kenny, USNRC Senior Resident Inspector, LGS 2 g pJff Q Q j, g3

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l TiiIII pne, remo.en. GR*t:tt0 SVts,rstren ca rti h0 5 I U mr n ic t it . ,= .. o.. .. . . , am .. . .... ~ n .i On October 13, 1989, the Unit 2 High Pressure Coolant Injection (HPCI) system was declared inoperable due to a condensate accumulation inside the HPCI turbine exhaust pipe resulting from

a drain pipe flow orifice (FO) blockage. This event resulted in l

the HPCI system being in a degraded condition which alone could I have prevented the fulfillment of its safety function needed to shutdown the reactor ar.d mitigate the consequences of an accident. An accident condition did not occur during the time in which the HPCI system was inoperable or could have been degraded, and HPCI was not called upon to perform its intended safety function. If HPCI had become unavailable due to the accumulation '

'of condensate in the turbine exhaust pipe, sufficient Emergency Core Cooling Systems and the Reactor Core Isolation Cooling system were available to ensure safe shutdown of the reactor. A

personnel error lead to the inadvertent overfilling of the l

suppression pool and flooding of the HPCI, turbine and exhaust i

' pipe during start-up activities. This resulted in the addition l of debris into the turbine exhaust pipe which later resulted in the FO blockage. Compressed air was utilized to unblock the FO and the accumulated condensate then drained to the barometric condenser. Weekly routine tests will be performed to verify flow through,both Unit 1 and 2 HPCI system fos. A flush of the Unit 2 HPCI drain pot will,be performed during the next appropriate HPCI outage.

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I Unit Conditions Prior to the Events ;

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Operating Mode: 1 (Power Operation) l Reactor. Power: 54.72%

i Description of the Events

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t On October 13, 1989, et 1855 hours0.0215 days 0.515 hours 0.00307 weeks 7.058275e-4 months , the Unit 2 High Pressure i Coolant Injection (HPCI) (EIIStBQ) system was declared inoperable f due to a condensate accumulation.inside the HPCI turbine exhaust i pipe resulting from a drain pipe flow orifice,(FO) (EIIS OR), FO- !

56-2D017, blockage (Refer to figure 1). This event resulted in i the HPCI system being in a degraded condition which alone could i have prevented the fulfillment of its safety function needed to shutdown the reactor and mitigate the consequences of an accident.

While performing a housekeeping inspection of the Unit 2 HPCI f pump room on October 13, 1989, at 1600 hours0.0185 days 0.444 hours 0.00265 weeks 6.088e-4 months , station Maintenance ;

personnel heard a " bubbling" sound inside of the drain pot for ;

the HPCI turLine exhaust pipe. HPCI was available but not in !

operation at this time. They immediately notified the HPCI !

system engineess.

l-The HPCI system engineers discovered that steam was leaking past i the seat of the HPCI Steam Supply Valve (HV-55-2F001) to the above valve seat drain of the HPCI Turbine Stop Valve (TV -

212). The above seat drain for FV-56-212 empties into the HPCI f

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turbine exhaust pipe drain pot, which empties to the HPCI barometric condenser.(EIIS CDU) through a 1 inch diameter drain ;

line that contains the 1/8 inch FO. The engineers observed that

the piping below the FO was not hot indicating that the leaking steam and resultant condensate was not passing through the FO. ,

The engineers concluded that the FO was clogged which resulted in i

the. collection of condensate in the exhaust piping. The leaking steam was passing through the collected condensate resulting in the observed " bubbling" sound.

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0 l1 l 0 ._ 00 nl3 er o lg nn , . ~n o.- w.nm The HPCI system engineers notified the Main Control Room (MCR) '

Shift Supervision of the problem, and Operations personnel declared the Unit 2 HPCI system inoperable on October 13, 1989 at i 1855 hours0.0215 days 0.515 hours 0.00307 weeks 7.058275e-4 months . Using'a Troubleshooting Control Form (TCF), the HPCI .

system engineers cleared the blocked FO utilizing compressed air.

The accumulated condensate then drained to the barometric condenser. The operators then placed HPCI in service in accordance with the system procedure S55.1.D, "HPCI Full Flow Functional Test." The HPCI system engineers verified that the HPCI system operated satisfactorily and that the drain pot was draining to the barometric condenser. Additionally, valve HV 2F001 was cycled opened and closed during the HPCI system operation, and the steam leakage stopped. HPCI was then declared

, operable at 2220 hours0.0257 days 0.617 hours 0.00367 weeks 8.4471e-4 months . HPCI was inoperable for less than four (4) hours. l The amount of condensate which had accumulated was estimated to

be approximately seventy-five gallons based on the observed number of cycles of operation of the HPCI barometric condenser condensate pump after the FO was unblocked. As a result, Engineering concluded that a condensate level of approximately >

ten inches existed inside the.HPCI turbine and its connecting eighteen inch diameter exhaust pipe. It is estimated that over one-half of the available HPCI turbine exhaust pipe area was filled with water prior to clearing the FO blockage.

The Unit 2 HPCI system is a single train safety system and based I

on an evaluation conducted subsequent to declaring the HPCI '

system inoperable, station personnel determined that the discovered condition could have prevented the HPCI system from '

performing its intended safety function needed to shutdown the reactor and mitigate the consequences of an accident. As a result, a notification was made to the NRC in accordance with the requipements of 10 CFR 50.72 (b)(2)(lii)(A) and (D) at 1830 hours0.0212 days 0.508 hours 0.00303 weeks 6.96315e-4 months ;

on October 14, 1989. Accordingly, this written report is being submitted in accordance with the requirements of 10 CFR 50.73 '

(a)(2)(v)(A) and (D).

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i Consequences of the Eveni , f i

The consequences of this event were minimal in that no .

radioactive material was released to the environment as a result of the HPCI system being in a degraded condition. Additionally, an accident condition did not occur during the time in which the HPCI system was inoperable or could have been degraded, and therefore HPCI was not called upon to perform its intended safety function. If HPCI had become unavailabic due to tue accumulation of condensate in the turbine exhaust pipe, sufficient Emergency ,

Core Cooling Systems (ECCS) and the Reactor Core Isolation Cooling (RCIC) system were available to ensure safe shutdown of '

the reactor and mitigate the consequences of an accident. .

The potential consequences of HPCI operating in the "as found" "

condition have been evaluated by Engireering. An initiation of r the HPCI system with over one-half of its turb!ne exhaust area l being obstructed could have resulted in any one or combination of the following.

o A HPCI turbine trip due to high turbine exhaust pressure.

o A water hammer transient in the HPCI turbine exhaust '

piping causing potential damage to the exhaust piping and its supports.

o Condensate being forced through the turbine seals and ultimately into the HPCI hydraulic lube oil system. The hydraulic lube oil system opens the HPCI turbine stop valve and regulates the HPCI turbine control valve during system operation. With water in the lube oil system, the ability of HPCI to function as designed through the

s. duration of an accident condition can not be assured.

Additionally, water in the lube oil could result in inadequate lubrication of the turbine bearings and damage to the turbine shaft.

o Inability of HPCI to achieve its required TS response time.

If this condition went undiscovered, operation of the HPCI system with the HPCI turbine and turbine exhaust pipe completely filled with condensate would increase the severity and probability of the conditions identified above.

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The cause of this event was the accumulation of small pieces of debris which blocked the 1/8 inch FO which prevented condensate ;

from draining from the HPCI turbine exhaust pipe to the barometric condenser. A personnel error lead to the addition of debris into the turbine exhaust pipe which later resulted in the FO blockage. The condensate accumulation inside the drain pot

< and the turbine exhaust pipe was a combined effect of steam leaking past the seat of HV-55-2FOO1 and the blocked FO. ;

Plant Staff and Engineering have determined the probable cause of the FO blockage to be the result of the accumulation of scale, rust, or grinding debris from original construction. This debris was introduced into the llPCI exhaust pipe when the Suppression Pool (SP) (EIIS BT) was inadvertently overfilled during Unit 2

. start-up activities on April 18, 1989 (prior to initial fuel load). This resulted in inadvertently flooding of the Unit 2 Overfilling of the SP occurred i

HPCI turbine and exhaust pipe. ;

when water was being transferred from the refueling water storage l tank to the SP for temporary storage. During this transfer, the permanent plant SP level indicators and alarms were not in .

service and temporary local level indication was installed.

However, a start-up engineer failed to open the isolation valve ,

for the temporary level indicator, and actual water level was not :

indicated. The SP water flowed through the normally open HPCI Turbine Exhaust Isolation Valve, HV-55-2F072, and leaked past the l seat of the HPCI Turbine Stop Check Valve, 55-2F021, to the j turbine. The SP water leaked past the check valve due to insufficient differential pressure to close the valve. While "

l water was being transferred from the refueling water storage tank to the SP, an individual in the Unit 2 HPCI pump room noticed ,

water flowing from the turbine shaft seals. The MCR was '

immediately notified and the transfer of water was stopped. The

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debris then settled inside the HPCI turbine exhaust pipe drain '

l pot, and later accumulated inside the FO creating the blockage.

l The condensate from the leaking steam collected in the drain pot and eventually started to fill the turbine exhaust line and l

( turbine.

The FO blockage may have existed since the Suppression Pool (SP)

(EIIS BT) overfill incident on April 18, 1989, but the accumulation of condensate probably existed only since August 20, 1989 when the HPCI system was last operated.

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t Corrective Actions:

Immediately following the discovery of the condensate accumulation inside the Unit 2 HPCI turbine exhaust pipe and

drain pot, the HPCI system engineers notified the MCR, and Operations personnel removed HPCI from service and declared HPCI :

Under a TCP, the i inoperable at 1855 hours0.0215 days 0.515 hours 0.00307 weeks 7.058275e-4 months on October 13, 1989.

HPCI system engineers utilized compressed air to unblock the FO.

The accumulated condensate then drained to the barometric condenser. The Unit 2 HPCI system was then placed in service, l and the HPCI system engineers verified that the HPCI system was ,

operating satisfactorily. HPCI was then declared cperable on October 13, 1989, at 2220 hours0.0257 days 0.617 hours 0.00367 weeks 8.4471e-4 months . Additionally, the MCR operators

, cycled valve HV-55-2F001 opened and closed, and the steam leaking past its seat was stopped. ;

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Actions Taken to Prevent Recurrencet ,

Engineering has concluded that the current design of the HPCI turbine exhaust pipe drain pot with a FO is adequate for draining of anticipated condensate. Since the debris causing the FO blockage was blown back up towards the drain pot, this problem may recur. Therefore, the following actions are being taken to verify flow through the FO and preclude further FO blocking. ,

1. For the Unit 1 and 2 HPCI systems, weekly routine tests will be written and performed to verify flow through both fos. Although the Unit 1 HPCI turbine exhaust drain '

system has not experienced any problems, the system will be inspected weekly as an added precaution. These tests

, are expected to be written and implemented by November 30, 1989.

2. For the Unit 2 HPCI system, a flush of the HPCI drain pot will be performed during the next appropriate HPCI outage.

The steam flow during HPCI system testing adequately ,

flushes the turbine casing and exhaust pipe. Since the bottom of the exhaust pipe drain pot is not in the flow path of the exhaust steam, this is a collection point for any debris, and a flush of the drain pot and its drain pipe is necessary.

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0; O 0;7 e, 0 l8 ssas w ~. . ..s w w .a sm Following the HPCI exhaust line flush, an evaluation will be made to determine whether further performance of the RTs or implementation of a modification is warranted.

Since the SP overfill incident on April 18, 1989, the Unit 2 SP water has been filtered removing the rust, scale or grinding debris. Additionally, the perman6nt Unit 2 SP level indicators and alarms are now in service to help preclude overfilling of the SP. Therefore, it is not expected that any debris from the SP will enter the turbine exhaust piping in the future.

Other industry events and HPCI system designs were reviewed and no other similar problems were identified.

Since the steam leaking past the seat of valve HV-55-2F001 stopped when the valve was cycled, no further corrective actions are planned.

The only other system that was affected by the SP overfill incident was the Unit 2 RCIC system. However, flooding of the RCIC turbine exhaust pipe did not result in any operability problems of the RCIC system. The RCIC turbine exhaust pipe drain pot is instrumented with a high level alarm which annunciates in the MCR. The RCIC drain system utilizes a 1/2 inch steam trap rather that a FO. Additionally, if blockage of the steam trap would occur, a level switch activated bypass valve allows drainage of the drain pot to prevent accumulation of condensate in the exhaust pipe. Therefore a similar problem with RCIC is not expected to occur.

Previous Similar Occurrences None Tracking Codes:

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