05000369/LER-1982-003, Forwards LER 82-003/03L-0.Detailed Event Analysis Encl

Forwards LER 82-003/03L-0.Detailed Event Analysis Encl

ML20040H568
Person / Time
Site:	McGuire
Issue date:	02/01/1982
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20040H569	List: 05000369/LER-1982-003, Forwards LER 82-003/03L-0.Detailed Event Analysis Encl 05000369/LER-1982-003-03, /03L-0:on 820102,average Temp in Upper Containment Was Reduced Below Temp Requirement.Caused by Cold Weather Cooling Bldg.Temp Increased Using Dihydrogen Recombiner Heaters
References
NUDOCS 8202180394
Download: ML20040H568 (3)

LER-1982-003, Forwards LER 82-003/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
3691982003R00 - NRC Website

text

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DUKE POWEH COMPANY da

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' i 422 Sourn Cucucu STHEET, CHAHLOTTE, N[ 063-Q R '.

WI LLI AM O. PA R M E R, J R.

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Strau PaoovcTion Mr. James P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303 Re: McGuire Nuclear Station Unit i Docket No. 50-369

Dear Mr. O'Reilly:

Please find attached Reportable Occurrence Report R0-369/82-03. This report concerns T.S.3.6.1.5, " Primary containment average air tempera-ture shall be maintained:

a. Between 85 F and 100 F in the containment upper compartment...".

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

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'l Very truly yours, 2!UCyp,.

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v William O. Parker, Jr.

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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 McGuire Nuclear Station

hyFICIAL Cul'Y 8202180394 820201 PDR ADOCK 05000369

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4 DUKE POWER COMPANY McGUIRE NUCLEAR STATION REPORTABLE OCCURRENCE REPORT NO. 82-03 REPORT DATE: February 1, 1982 FACILITY: McGuire Unit 1, Cornelius, NC IDENTIFICATION: The Average Air Temperature in Upper Containment Decreased Below the Minimum Average Air Temperature Requirement

DESCRIPTION

In order to meet the requirements of Technical Specification 3.6.1.5(a), the primary containment average air temperature must be maintained between 850F and 100 F in the containment upper compartment, but the lower limit may be reduced to 600F in modes 2, 3, and 4.

On January 1, 1982 Unit 1 was in the process of starting up (in mode 3 proceeding to mode 1) when it was noticed that upper containment temperature was close to the mode 1 limit of 85 F.

The only means of heating upper containment that could be found was to operate the hydrogen (H ) recombiners (installed in containment 2

to burn excess hydrogen in the event of an accident) which was done by per-forming the periodic test "H2 Recombiner lA & IB Operability Test".

After the H2 recombiners were run for approximately five hours, the upper containment temperature had increased above the lower limit and the test was terminated.

Early on January 2, the H2 recombiners were operated again for about 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> to increase upper containment temperature above the lower temperature limit.

Between the time the recombiner test was run the first time and completed the second time, other attempts were made to increase the upper containment tem-perature by opening some of the shield plugs between upper and lower containment.

Approximately four and one-half hours after entering mode 1, the average tem-perature in upper containment was 85 F.

The Upper Containment Cooling System (VU) return fans were run in order to get a more representative average air temperature.

It was thought that since the Unit was in mode 1 the temperature would increase; however, the temperature dropped to approximately 830F. There-fore, on January 2, the Unit was in an action statement pursuant to Technical Specification 3.6.1.5(a).

The H2 recombiners were again run to return the temperature above the 850F limit, and within 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> the technical specification action statement was satisfied.

The H2 recombiners were run one more time after this to maintain temperature above the lower temperature limit.

There has been no trouble maintaining temperature since this incident.

EVALUATION: The unit was in the process of heating up after an extended outage.

During the month of December, Unit I had been out of service due to an incident involving the turbine generator (see LER/RO-369/81-183). No heat was generated in the Reactor Building during this time, and thus the cold weather was able to slowly cool the building. Also, the equipment hatch to the outside was briefly opened to allow some equipment to be taken into containment. Due to the great amount of thermal mass in the reactor building, it took a period of time for the cold to affect the temperature in containment. When the VU fans were started, upper containment was already at the lower temperature limit of 85 F.

The Unit had entered mode 1 so it was expected that the temperature in containment would increase. The opposite effect was observed, however, because the Unit was not in operation long enough to heat-up the thermal mass of the building.

The temperature apparently dropping more quickly after the VU fans were run could

e Report No. 82-03 Page 2 be due to increasing the warmer air flow across the cooler concrete, thus transferring the heat more quickly.

Or, the movement of air by the VU fans could have made the average temperature reading a more accurate indication.

Removing the shield plugs between upper and lower containment did not alleviate the low temperature problem in upper containment. The plugs were removed and returned within the maximum time limit' allowed by Technical Specification 3.6.5.5.

When the H2 recombiners were operated, they were able to increase the average air temperature in containment.

This action. brought the temperature within limits in less than three hours. After this, the H2 recombiners had to be run once more to stay above the limit.

SAFETY ANALYSIS

The low temperature limit is set because of the density of air at the prescribed temperature.

In an accident condition, the volume increase which would result in heating-up dense air could significantly increase the pressure in containment.

It was found that the lower temperature limit could be maintained using the H2 recombiners before the actual incident occurred.

Therefore, when the temperature dropped below the limit, the action statement was able to be satisfied within three hours. Even though the Unit was in mode 1, the reactor power level at the time of the incident was only 25%. Due to the low level and short time of operation at that level, it can conservatively be stated that the energy that would determine the maximum containment pressure in an accident was far below the values used_in the accident analysis. Thus, the health and safety of the public were not affected by this incident. A review of the various containment integrity analyses revealed that the minimum temperature assumed in these analyses was 750F. Thus, the current technical specification limit of.850F is unnecessarily conservative.

CORRECTIVE ACTION

When the average temperature in containment began reaching the lower limit and af ter it dropped below the limit, the temperature was increased by using the H2 recombiner heaters.

The temperature in upper containment is measured in several places and averaged.

This temperature is available on the computer and gives an alarm when the limits are reached. The temperature was verified to be within specification on the Operator Aid Computer.

Duke Power Company is presently looking at possible heat sources in the reactor building, and will also apply for a change in the Technical Specifiestions to reduce the minimum containment average air temperature from 850F to 75 F.