05000369/LER-1982-017, Forwards LER 82-017/03L-0.Detailed Event Analysis Encl

Forwards LER 82-017/03L-0.Detailed Event Analysis Encl

ML20050A941
Person / Time
Site:	McGuire
Issue date:	03/15/1982
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20050A942	List: 05000369/LER-1982-017, Forwards LER 82-017/03L-0.Detailed Event Analysis Encl 05000369/LER-1982-017-03, /03L-0:on 820212,control Room Alarms Indicated Closing of 4 Accumulator Discharge Isolation Valves, Rendering Upper Head Injection Portion of ECCS Inoperable. Cause Probably Due to Installation Deficiency
References
NUDOCS 8204020425
Download: ML20050A941 (4)

LER-1982-017, Forwards LER 82-017/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
3691982017R00 - NRC Website

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March 15, 1982 J

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I Mr. James P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission 4

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101 Marietta Street, Suite 3100 1

Atlanta, Georgia 30303

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Re: McGuire Nuclear Station Unit 1

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Docket No. 50-369

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Dear Mr. O'Reilly:

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j Please find attached Reportable Occurrence Report R0-369/82-1.

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concerns T.S.3.5.1.2, "Each Upper Head Injection Accumulator System shall be operable with: a.

the isolation valves open....".

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

e a-1 VWytrulyyours,[

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William O. Parker,.

i PBN/jfw Attachment j

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Office of Management and Program Analysis Institute of Nuclear Power Operations l

U. S. Nuclear Regulatory Commission 1820 Water Place j

Washington, D. C.

20555 Atlanta, Georgia 30339 Mr. P. R. Bemis i

Senior Resident Inspector-NRC McGuire Nuclear Station

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DUKE POWER COMPANY McGUIRE NUCLEAR STATION

' REPORTABLE OCCURRENCE REP 9RT NO. 82-17 RETORT DATE: March 15, 1982 FACILITY: McGuire Unit 1, Cornelius, NC IDENTIFICATION: The Upper Head Injection Portion of the Emergency Core Cooling System was Rendered Inoperable by the Closing of the Accumulator Discharge Isolation Valves

DESCRIPTION

At 1950 on February 12, 1982, while Unit I was operating at 50%

reactor power, control room alarms alerted operators of the closing of all four Upper Head Injection (UHI) accumulator discharge valves. Operators immediately tried to reopen the valves using control room manual actuators. Safety related Train A valves, NI-243A and NI-245A were successfully reopened, but the Train B valves, NI-242B aad NI-244B remained closed.

Noting a decreasing level in the UHI surge tank, an instrument line leak was suspected.

Investigation discovered an open-ended leak on an impulse line to UHI level switch NILS 5730, which was subsequently isolated. At 2039 the leak had been repaired, and NI-242B and NI-244B were reopened, restoring the system to its nornal configuration.

The occurrence resulted f rom the failure of a Parker-Hannifin fitting to hold an impulse line intact. The failure was apparently the result of an installation deficiency.

EVALUATION: The UHI system is independent of the remainder of the Safety Injection (NI) System.

It is designed to function in the blowdown phast of a loss of coolant accident during which UHI accumulator water delivery continues until actuation of the accumulator level switches. The level switches function to automatically close the UHI discharge '. alves to prevent injecting pressurized nitrogen (the driving force) into the reactor vessel. Thus, the safety function of the system is completely passive. The single active process involved is the isola' tion of the system at the end of the injection, when the system has ful-filled its design function. The additional cooling provided by the UHI System reduces the fuel temperature at the end of blowdown, thereby limiting the peak fuel temperature during the refill and reflood periods following blowdown.

In this event the impulse line leak rendered the UHI System inoperable. All four accumulator level switches actuated; Train A components, NILS 5720 and NILS 5740, operated to close valves NI-245A and NI-243A respectively; likewise.

l Train B components, NILS 5730 and NILS 5750, operated to close valves NT-244B and NI-242B. The valve arrangement is such that either train is capabic of isolating the water accumulator from the reactor vessel head.

The closing of the Train A valves as a result of a Train B instrument line leak was explained by the existance of a " crossover tube" which connects the Train A and Train B sensing lines within the accumulator.

Reportable Occurrence Report No. R0-369/81-171 described a related event which occurred on October 28, 1981.

In that event NI-242B and NI-244B were actuated as a result of a leak on a Train B level switch impulse line. The common train

Report No. 82-17 Page 2 level switches share the same sensing line, which allows a pressure loss o be felt at both instruments. The prior incident involved a much smaller leak in which the pressure loss was not transmitted through the train crossconnect to affect Train A componer.ts.

Both events involve the failure of similar Parker-Hannifin fittings at different locations on the same sensing line.

Parker-Hannifin fittings are used almost exclusively at McGuire and a number of failures have occurred. Of those failures, the large majority have been attributed to installation errors; failure to tighten the Parker-Hannifin nut properly (swage the line), and the installation of a reversed ferrule are the most common.

In this particular instance the repairing technician speculates that the fitting nut had not been properly tightened.

Personnel interviewed expressed a high degree of confidence in the fittings, "when they are installed correctly". With this in mind, a review of the appli-cable procedure was conducted. The procedure " Installation and Fbintenance of Instrument Line Fittings and Tubing" includes Parker-Hannifin fitting maintenance.

The procedure appears to be very complete and a contributing factor for the absence of recurring failures of particular fittings.

Self-loosening of fitting nuts was also considered as a possible mechanism for this failure.

Inspection of the system instrument lines revealed no noticeable vibration; therefore, this possibility seems remote.

Installation deficiency appears the most probable cause for the fitting failure.

At this point in McGuire's operating history, it is expected that the majority of these errors have been identified and corrected.

SAFETY ANALYSIS

The NI System was unchallenged during the event, therefore, the health and safety of the public were unaffected.

A failure of this type would not go unnoticed by the operators and appropriate action would be taken. The possibility of an instrument line failure coincident with a design basis accident is remote. The loss of the system concurrent with the design basis accident could cause an increase in the peak fuel temperatures.

CORRECTIVE ACTION

The impulse line between NILS 5730 and it's manifold valve was found disconnected from it's Parker-Hannifin fitting at the manifold valve.

The repair was made by reconnecting the line to the fitting and swagging the line. The repairing technician then loosened the fitting nut to check the threads for galling, and again tightened the fitting nut.

The line was tested for tightness and then rechecked for Icakage.

In an attempt to prevent recurrence of this incident, Parker-Hannifin fittings associated with UHI instrument lines have been verified installed correctly, in accordance with the procedure, " Installation and Maintenance of Instrument Line Fittings and Tubing".

This action was accomplished during the current Unit 1 outage.

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Report No. 82-17 Page 3 l

t Duke Power Company will analyze the significance of the physical connection of UllI instrumentation trains' relative to station design criteria to determine l

if any changes are necessary or desirable.

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