ML20058L642
| ML20058L642 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 03/15/1978 |
| From: | Wachter L NORTHERN STATES POWER CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-78-04, IEB-78-4, NUDOCS 9106060344 | |
| Download: ML20058L642 (1) | |
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.[s NORTHERN STATES POWER COMPANY MIN N E A PO LI S. MIN N E S OTA 55400 March 15,1978 Mr. James G. Keppler Director - Region III Office of Inspection and Enforcement United States Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137
Dear Mr. Keppler:
MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 As requested in IE Bulletin No. 78-04, the use of NAMCO D2400X or EA-170--302 SNAP LOCK switches in safety-related equipment in the primary containment of the Monticello Nuclear Generating Plant has been reviewed. No switches of this type are used or planned for use at this facility.
Yours very truly, L. J. Wachter Vice President Power Production and System Operation ec:
Mr. G. Charnoff NRC Office of Inspection and Enforcement Washington, D.C.
i:~7 I ~is78 9106060344 780315 CF ADOCK 05000263 CF
&Ae/ >/W NSP NORTHERN STATES POWER COMPANY M IN N E A PO LI S, MIN N E S OTA 55401 March 27, 1978 t
Mr. James G. Keppler Director - Region Ill Office of Inspection and Enforcement United States Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137
[
Dear Mr. Keppler:
MONTICELLO NUCLEAR GENERATING PLANT I
Docket No. 50-263 License No. DPR-22 The following report is submitted in accordance with Item 6 of IE Bulletin No. 78-03, " Potential Explosive Gas Mixture Accumulations Associated with B'4 Of fgas System Operations." Our response to Items 1 through 5 of the bulletin is as follows:
Item 1 Operations and maintenance procedures related to the Offgas System have been reviewed and found to be adequate to assure operation in accordance with all design parameters. Measures which prevent inadvertent actions which might cause ignition of the mixture of gases contained in the off-gas piping include:
Special procedures have been written to purge portions of a.
offgas system piping which may contain concentrations of hydrogen above the explosive limit.
l b.
Operating procedures require consideration of additional local purging and monitoring for hydrogen where necessary.
c.
Permits are required for each velding operation in the plant to assure that special precautiens and purging prior to welding are performed.
Item 2 Theventilationofspacesandareasthroughwhichoffgap[sstempiping containing explosive mixtures of gases pass has been M'j wed and found o n b 01- -
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IPR 2 D 1978
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-r NORT:.ERN CTATES POWER COMHANY Mr. James G. Keppler March 27, 1978 Page 2 to be adequate.
In all of these areas, the pressure inside the system piping is maintained well below atmospheric pressure during nor=al operation. Therefore, any leakage would be from the area into the offgas system. High pressure alarms will alert the operator in the event of a malfunction. The system automatically isolates when the pressure reaches about 20 psia. The ventilation in these areas provides at least three volume changes per hour. This is adequate.
to prevent an accumulation of hydrogen gas during any brief period of time that the system pressure would be greater than atmospheric pressure.
Loss of dilution steam to an operating recombiner results in an immediate automatic shutdown of the recombiner train.
The portion of the offgas system containing a concentration of hydrogen above the detonable limit does not contain loop seal drains or rupture discs.
The recombiner system cannot be bypassed during operation.
Item 3 As described in Item 2 above, the potential for accumulation of explosive mixtures is negligible. Therefore, no further actions are considered to be necessary. The exhaust air from these areas is monitored continuously for air-borne radioactivity.
In the unlikely event of an offgas leak, these monitors would initiate control room alarms at concentrations far below those which would be equivalent to a detonable mixture.
Item 4 The portion of offgas system containing hydrogen in detonable concentration does not have any loop seal drains.
Item 5 Operating and emergency procedures have been reviewed and found to provide adequate guidance in the event of a hydrogen detonation in the offgas system.
Yours very truly, L. J. Wachter Vice President - Power Production and System Operation cc:
Mr. G. Charnoff NRC Office of Inspection and Enforcement Washington, D.C.
.