ML20097H269

Forwards Response to GE Significant Info Ltr 402 & IE Info Notice 84-17 Re Nitrogen Inerting Sys

ML20097H269
Person / Time
Site:	LaSalle
Issue date:	09/17/1984
From:	John Marshall COMMONWEALTH EDISON CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
9163N, IEIN-84-17, TAC-54150, NUDOCS 8409200220
Download: ML20097H269 (4)

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( Commonwealth Edison Oni First Nationit Pina. Chictgo, lilinois i 3 ' Address Reply to: Post Office Box 767

\, Chicago, Illinois 60690 September 17, 1984 l

Mr. Harold R. Denton,' Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555

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Sub ject: LaSalle Count ~y Station Units 1 and 2 Response.to General Electric SIL No. 402 Docket Nos. 50-373 and 50-374

Reference:

SIL No. 402, dated February 14, 1984 I.E. Information-Notice 84-17

Dear Mr.-Denton:

The attac'he'd'information is submitted in response to a telephone conversation with Dr. A. Bournia of .your staff. It constitutes Common-wealth Ediscn's plans with regard-to SIL No. 402 and I.E. Information Notice 84-17.

One signed original and 15 copies of this letter and attachments are provided for your use.

Please direct any questions you may have concerning this matter to this office.

Very truly yours, N.,

s hJA %4 M J. G. Marshall Nuclear Licensing Administrator 1m cc: Dr. A. Bournia.- NRR Region'III~ Inspector - LSCS 9163N 84j9200 Oh o 00 t P

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$e COMMONWEALTH EDISON COMPANY LASALLE COUNTY STATION UNITS 1 and 2 ATTACHMENT

1. Evaluate Inerting System Design Evaluate the design of the nitrogen inerting system. Investigate the 0

potential for introducing cold (less than 40 F) nitrogen and the orientation of the nitrogen cort relative to the vent header, down-comers, or other equipment in the wetwell and drywell which may be in the path of the injected nitrogen. Assure that temperature monitoring devices, the low temperature shutoff valve, and overall system design are adequate to prevent the injection of cold nitrogen into the containment.

RESPONSE 1 A modification proposal is under investigation to install a nitrogen inerting " Low Temperature" alarm in the main control room. This would alert operating personnel of a potential line freeze and preclude the possibility of admitting " Cold" nitrogen into the containment.

The orientation of the nitrogen inlet ports relative to other equipment has been investigated. It was shown that the introductioh of liquid nitrogen to the containment would not impinge on any equipment.

2.. Evaluate Inerting System Operation Review the operating experience of the inerting system to assure that the vaporizer, the low temperature shutoff valve and the temperature indicators have functioned properly. Evaluate the plant eclibration, maintenance and operating procedures for the inerting system. Assure that cold nitrogen injection would be detected and prevented.

RESPONSE 2 To date, the inerting system has been closely monitored by station personnel whenever it has been in use. All system components, including the temperature control shutoff valves operate satisfac-torily. A procedure change proposal is being made to include a periodic check for frost on the inerting lines during initial inerting for unit startup.

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3. Test for Drywell/Wetwell Bypass Leakage Perform a bypass leakage test as soon as convenient to confirm the integrity of the vent system. This test should be conducted during plant operation following normal plant procedures. If no procedures exist, the following is a general guide for preparing your procedure; pressurize the drywell to approximately 0.75 psi above the wetwell pressure, maintain this drywell pressure and measure the pressure buildup in the wetwell. Any bypass leak area can then be calculated (and is limited by Technical Specifications on many plants) from the wetwell pressure and the drywell/wetwell pressure difference. This will provide an indication that the vent system integrity is intact and that no gross failure exists.

RESPONSE 3 LSCS is not a BWR-4 and does not intend to perform a bypass leakage test at the next planned outage. An integrated leak test (ILRT) will be performed at the first refuel outage.

4. Inspect Nitrogen Injection Line Conduct an ultrasonic test (UT) as soon as convenient of all accessible welds in the nitrogen injection line from the last isolation valve to the wetwell and drywell penetratioiss. Also UT the containment penetrations and the containment shell within 6 inches of the penetration. UT is recommended because cracks would be most likely to initiate on the inside of the pipe or on the site of the metal in contact with cold nitrogen.

RESPONSE 4 The drywell inerting system to date, has had relatively little use.

Station personnel are confident that pipe. temperatures less than 400F have never been reached, in fact N2 delivery temperatures are maintained at approximately 90oF. LSCS does not intend to perform UT testing.

5. Inspect Containment During the next planned uutage, perform a visual inspection of the vent header, downcomers and other equipment in the containment which might be expected to be affected by the injection of cold nitrogen.

The vent header should be inspected on the outside and the inside.

Also inspect the containment shell or steel liner for at least 6 inches around the nitrogen penetration.

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- - . .  ! RESPONSE 5-Y- -A~ primary containment inspection per LTS-600-3 will be conducted priorito the next' integrated (ILRT) leak test which will be performed at;the'first refuel _ outage.

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