05000369/LER-1982-015, Forwards LER 82-015/01T-0.Detailed Event Analysis Encl

Forwards LER 82-015/01T-0.Detailed Event Analysis Encl

ML20050C054
Person / Time
Site:	McGuire
Issue date:	03/24/1982
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20050C055	List: 05000369/LER-1982-015, Forwards LER 82-015/01T-0.Detailed Event Analysis Encl 05000369/LER-1982-015-01, /01T-0:on 820212,both Centrifugal Charging Pumps (CCP) Declared Inoperable When Hydrogen from Reciprocating Charging Pump Suction Dampeners Entered CCP Suction,Causing Cavitation
References
TAC-48395, NUDOCS 8204080073
Download: ML20050C054 (4)

LER-1982-015, Forwards LER 82-015/01T-0.Detailed Event Analysis Encl

Event date:
Report date:
3691982015R00 - NRC Website

text

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i DUKE Powan COMPANY Powru Dunwim 422 Sourn Cnuncu Srazer, Cruumriz, N. C. 2a242 WILLIAM Q. PAR M ER, J R.

I V vc, p.c. orw, March 24, 1982 ruc.-o~e4.ca7o.

Sicaw P.ooucTeow 373-4083

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Mr. James P. O'Reilly, Regional Administrator g

U. S. Nuclear Regulatory Commission O

Region II p' C g

y 101 Marietta Street, Suite 3100 SigD

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Atlanta, Georgia 30303 9'

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1#w Wi, ~ ?.f* j Re: McGuire Nuclear Station Unit 1 Docket No. 50-369 A

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Dear Mr. O'Reilly:

Picase find attached Reportable Occurrence Report R0-369/82-15. This report concerns T.S.3.1.2.4, "At 1 cast two charging pumps shall be operable...";

T.S.3.1.2.2, "At least two of the following three boron injection flow paths shall be operable..."; and T.S.3.5.2, "Two independent ECCS subsystems shall be operable with each subsystem comprised of:

a. one operable centrifugal charging pump."

This incident was considered to be of no significance with respect to the health and safety of the public.

An update to this report will be provided when the final corrective action has been determined.

Very truly yours, N

W0 William O. Parker, Jr.

PBN/jfw Attachment cc: Director Records Center Office of Management and Program Analysis Institute of Nuclear Power Operations U. S. Nuclear Regulatory Commission 1820 Water Place Washington, D. C.

20555 Atlanta, Georgia 30339 Mr. P. R. Bemis Senior Resident Inspector-NRC McGuire Nuclear Station

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8204080073 820324 PDR ADDCK 05000369 S

PDR hl

l, DUKE POWER COMPANY McGUIRE NUCLEAR STATION

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REPORTABLE OCCURRENCE REPORT NO. 82.5 1

REPORT DATE: March 24, 1982 FACILITY: McGuire Unit 1, Cornelius, NC IDENTIFICATION: Loss of Both Centrifugal Charging Pumps (CCP) When Fydrogen (11 ) from the Reciprocating Charging (PD) 2 Pump Suction Dampeaers Entered the Suction of the Centrifugal Charging Pumps DISCUSSION: On February 12, 1982, during an attempt to fill and vent the PD pump suction piping in preparation for returning the pump to service, opening valve IU-217 (suction isolation to the PD pump) resulted in cir and 112 in the PD pump suction piping flowing into the common suction of the two CCP's.

Con-trol room personnel noticed that CCP 1A motor current and charging flow had begun to oscillate, indicating cavitation, and thus subsequently swapped to CCP IB and tripped CCP 1A.

Approximately 30 seconds later, CCP IB began to cavitate and was tripped. This resulted in charging and letdown being secured.

Both CCP's were declared inoperable at 2058 while unit I was in mode 1, 50%

power operation. This incident is reportable pursuant to Technical Specifi-cations 3.1.2.4, 3.1.2.2, and 3.5.2, When the Nuclear Equipment Operator (NEO) who had opened the valve heard a page announcement that charging had been terminated he imnediately called the control room. As a result,of his call, the control operators then suspected that gas from the PD pump suction was entering the CCP suction, and instructed him to reclose the valve.

The Shift Supervisor and three NE0's vented CCP IB and 1A through the overflow piping, llowever, when CCP IB vas restarted it immediately began cavitating, and was again tripped. After donning anti-C's and shoe covers, the Shift Supervisor entered the pipe chase and vented the suction pipes for both pumps, one at a time, for a total of approximately five minutes. During this time, the NE0's revented CCP IB.

Pump IB was restarted and verified to operate properly after which charging and letdown were re-established.

EVALUATION: Due to the pulsating suction flow, characteristic of recipro-cating pumps, the FD pump is equipped with a suction dampener consisting of a vertical section of twelve inch pipe with H2 gas overpressure. The water level iP controlled by *w'9 solenoid valves which supply gas when the water level is too high and vent off gas when the water level is too low.

These valves can be controlled automatically by level switches, or manually by i

switches mounted on a local panel.

l After the event, a check of the dampener level control system found the refer-ence pot and leg empty. An empty reference leg would indicate high water icval to the Icvel switches which would result in a continuous supply of H to the 2

1

- Report No. 82-15 Page 2 dampener. The_ glass cover and meter movement of the IcVel switch for valve INV-838 were also found damaged, but the effect of the damage on switch opera-tion could not be determined. The means by which the reference leg was drained could not be determined. No leaks were found when the reference leg and pot were refilled.

The PD pump was isolated and drained in order to install instrument taps and pressure sensing devices for a station modification. After draining, the vent and drain valves were closed.

Level in the reference leg was apparently lost while the piping was isolated since it had worked properly before but not after this period. When the NE0's attempted to fill the system, a slight hiss was heard. The NEO was not concerned because he knew that H2 gas was inv.olved in the dampener operation. Actually, this indicated that the level controls might not have been working properly (supplying H2 when it should have been vented).

The NEO was likewise not concerned by the sound of water flow when he opened the PD pump suction valve because he expected water to flow into the PD pump suction.

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Hydrogen header pressure supplying the dampener was approximately 110 psig which could easily displace water in the charging pump suction piping. ' Judging by the volume control tank level changes during the event, it is estimated.that about fifty cubic feet of water was displaced by the gas.

VCT overpressure generally ranges from 50 - 30 psig.

The H2 released to atmosphere did not fill any of the areas to concentrations sufficient to cause combustion as a result of a spark. Hydrogen and air in the piping was in no danger of combustion due to the absence of an ignition source.

SAFETY ANALYSIS

When the CCP's were inoperable, no emergency core cooling was available above 1500 psig (safety injection pump shutoff head). Emergency boration and reactor coolant makeup were also not available during this period.

- Any significant decrease in T would have resulted in a corresponding drop in ave pressurizer level but system pressure could have been maintained by the pressur-izer heaters until level dropped below 17%.

It was essential that the unit be maintained in a steady state condition until charging and letdown could be.

restored.

The unit remained in a steady state condition during the incident and the health and safety of the public were not affected.

If the restoration of makeup coolant flow had been delayed until'after the pressurizer inventory was' lost, or had a transient occurred forcing a loss of pressurizer inventory, a reactor trip would have ensued. With the loss of pressurizer water, loss of pressure control.would occur. The_ lower limit of the pressure excursion would be determined by. system hot spot saturation-pres;ure. Forced core cooling would continue unless' system pressure loss or system voiding required stopping the pumps at which time natural circulation 6

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Report No. 82-15 Page 3 would provide the.means for core heat removal.

Reactor coolant temperature trends would be dependent on steam generator heat transfer rates and core decay heat generation.

When reactor coolant. system pressure decreased to below 1500 psig, the safety injection pumps would begin to refill the system. Safety injection would con-tinue until pressurizer pressure control was regained.

Steam generator water level, steam flow, and feed flow affect steam generator heat transfer and the reactor coolant natural circulation rates. The steam generator parameters are relatively simple to control; therefore, the recovery from the postulated loss of nakeup flow incident is considered to be within the capabilities of the station.

CORRECTIVE ACTION

The immediate corrective action was to secure the CCP's, isolate the PD pump suction, vent the CCP's and suction piping, and to return CCP IB to service. CCP 1A was tested and returned to operable status later the same day.

Due to several incidents including this one, a memorandum to standardize the practice of isolating and draining equipment has been distributed. Effective February 25, it is required that at least one drain and/or vent be red tagged open when any component is isolated for maintenance. Although such action may not have prevented this incident, it is good operating practice which was not followed in this instance.

The PD pump and suction dampener have been isolated from the charging system.

Duke Power Company is evaluating the system design to determine what temporary and/or permanent changes are necessary to prevent recurrence of this type event.

The PD pump will not be returned to service until such a temporary or permanent change is made. A followup report describing any temporary changes made to the system and permanent changes planned will be submitted when these evaluations are complete.