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	ta s' NSP NORTHERN STATE 5 P O-W E R COMPANY		ta s'
	~		NSP NORTHERN STATE 5 P O-W E R COMPANY
	M f N N g A PQ t.3 3, M f N N g 3CTA gg4Ct March 27, 1978 Mr. James G. Keppler .		~
	Director - Region III Office of Inspection and Enforce =ent United States Nuclear Regulatory Com=1ssion 799 Roosevelt Road Glen Ellyn, Illinois 60137		M f N N g A PQ t.3 3, M f N N g 3CTA gg4Ct March 27, 1978 Mr. James G. Keppler Director - Region III Office of Inspection and Enforce =ent United States Nuclear Regulatory Com=1ssion 799 Roosevelt Road Glen Ellyn, Illinois 60137

	==Dear Mr. Keppler:==		==Dear Mr. Keppler:==

	MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 The following report is submitted in accordance with Ite: 6 of IE Bulletin No. 78-03, " Potential Explosive Gas Mixture Accu =ulations Associated with L'R offgas Syste= Operations." Our response to I: ems 1 through 5 of the bulletin is as follows:		MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 The following report is submitted in accordance with Ite: 6 of IE Bulletin No. 78-03, " Potential Explosive Gas Mixture Accu =ulations Associated with L'R offgas Syste= Operations." Our response to I: ems 1 through 5 of the bulletin is as follows:
	Item 1 Operations and maintenance procedures related to the Offgas Syste= have been reviewed and found to be adequate to assure operation in accordance		Item 1 Operations and maintenance procedures related to the Offgas Syste= have been reviewed and found to be adequate to assure operation in accordance with all design parameters.
	, with all design parameters. Measures which prevent inadvertent actions vaich might cause ignition of the =ixture of gases con:ained in the off-gas piping include:		Measures which prevent inadvertent actions vaich might cause ignition of the =ixture of gases con:ained in the off-gas piping include:
	a.		Special procedures have been written to purge por: ions of a.
	Special procedures have been written to purge por: ions of offgas syste= piping which nay contain concentrations of		offgas syste= piping which nay contain concentrations of
	. hydrogen above the explosive 11=10.		. hydrogen above the explosive 11=10.
	: b. Operating procedures require considera: ion of additional local purging and =onitoring for hydrogen where necessary.		b.
	~~: c.~~ Per:1:s are required for each velding operation in :he plant to assure tha: special precautions and purging prior to velding are performed.		Operating procedures require considera: ion of additional local purging and =onitoring for hydrogen where necessary.
			Per:1:s are required for each velding operation in :he c.
			plant to assure tha: special precautions and purging prior to velding are performed.
	I:ee 2 The ventila: ion of spaces and areas through which offgas syste piping containing explosive =ixtures of gases pass has been reviewed and found		I:ee 2 The ventila: ion of spaces and areas through which offgas syste piping containing explosive =ixtures of gases pass has been reviewed and found
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			8301100121 821207 l
			PDR FOIA i
			HIATT82-545 PDR L

	,a . ,v. ,		,a.
			,v.
	NORTHERN CTATED POWER ' COMPANY		NORTHERN CTATED POWER ' COMPANY
	, .Mr. James G. Keppler March 27, 1978 Page 2 to be adequate. In all of these areas, the pressure inside the syste=		.Mr. James G. Keppler March 27, 1978 Page 2 to be adequate.
	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 alar =s 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 volu=e 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.		In all of these areas, the pressure inside the syste=
			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 alar =s 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 volu=e 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 i= mediate automatic shutdown of the recombiner train.		Loss of dilution steam to an operating recombiner results in an i= mediate 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 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 syste= cannot be bypassed during operation.		The recombiner syste= cannot be bypassed during operation.
	Item 3 As described in Item 2 above, the potential for accu =ulation of explosive cixtures is negligible. Therefore, no further actions are considered to be necessary. Th'e exhaust air from these areas is =enitored continuously for air-borne radioactivity. In the unlikely event of an offgas leak, these monitors would initiate control room alar =s at concentrations far below those which would be equivalent to a de: enable =1xture.		Item 3 As described in Item 2 above, the potential for accu =ulation of explosive cixtures is negligible.
			Therefore, no further actions are considered to be necessary. Th'e exhaust air from these areas is =enitored continuously for air-borne radioactivity.
			In the unlikely event of an offgas leak, these monitors would initiate control room alar =s at concentrations far below those which would be equivalent to a de: enable =1xture.
	Item 4 The portion of offgas system containing hydrogen in detonable concentra: ion does not have any loop seal drains.		Item 4 The portion of offgas system containing hydrogen in detonable concentra: ion does not have any loop seal drains.
	Item 5 Operating and energency procedures have been reviewed and found :o provide adequate guidance in the event of a hydrogen detona ion in the offgas syste=.		Item 5 Operating and energency procedures have been reviewed and found :o provide adequate guidance in the event of a hydrogen detona ion in the offgas syste=.
	Yours very truly, V		Yours very truly, VAh$Y&
	Ah$Y&		L. J. Wachter Vice ?residen: - Power ?rodue:icn and System Operation cc:
	L. J. Wachter Vice ?residen: - Power ?rodue:icn and System Operation		Mr. G. Charnoff i
	; cc: Mr. G. Charnoff i NRC Office of Inspection and Inforcenent Washington, D.C.		NRC Office of Inspection and Inforcenent Washington, D.C.
	L' m .		L' m
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{{Adams
| number = ML20028C428
| issue date = 03/27/1978
| title = Responds to IE Bulletin 78-03, Potential Explosive Gas Mixture Accumulations Associated W/Bwr Offgas Sys Operations. Operating & Emergency Procedures Provide Adequate Guidance in Event of Offgas Sys Detonation
| author name = Wachter L
| author affiliation = NORTHERN STATES POWER CO.
| addressee name = Keppler J
| addressee affiliation = NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
| docket = 05000000, 05000263
| license number =
| contact person =
| case reference number = FOIA-82-545, REF-SSINS-6820
| document report number = IEB-78-03, IEB-78-3, NUDOCS 8301100121
| package number = ML20027A594
| document type = CORRESPONDENCE-LETTERS, INCOMING CORRESPONDENCE, UTILITY TO NRC
| page count = 2
}}

=Text=
{{#Wiki_filter:_ -
ta s' NSP NORTHERN STATE 5 P O-W E R COMPANY
~
M f N N g A PQ t.3 3, M f N N g 3CTA gg4Ct March 27, 1978 Mr. James G. Keppler .
Director - Region III Office of Inspection and Enforce =ent United States Nuclear Regulatory Com=1ssion 799 Roosevelt Road Glen Ellyn, Illinois 60137

==Dear Mr. Keppler:==

MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 The following report is submitted in accordance with Ite: 6 of IE Bulletin No. 78-03, " Potential Explosive Gas Mixture Accu =ulations Associated with L'R offgas Syste= Operations." Our response to I: ems 1 through 5 of the bulletin is as follows:
Item 1 Operations and maintenance procedures related to the Offgas Syste= have been reviewed and found to be adequate to assure operation in accordance
, with all design parameters. Measures which prevent inadvertent actions vaich might cause ignition of the =ixture of gases con:ained in the off-gas piping include:
a.
Special procedures have been written to purge por: ions of offgas syste= piping which nay contain concentrations of
. hydrogen above the explosive 11=10.
: b. Operating procedures require considera: ion of additional local purging and =onitoring for hydrogen where necessary.
: c. Per:1:s are required for each velding operation in :he plant to assure tha: special precautions and purging prior to velding are performed.
I:ee 2 The ventila: ion of spaces and areas through which offgas syste piping containing explosive =ixtures of gases pass has been reviewed and found
.u ".s~ o-~ e, 1 I C 8301100121 821207 l PDR FOIA i HIATT82-545 PDR L

,a . ,v. ,
NORTHERN CTATED POWER ' COMPANY
, .Mr. James G. Keppler March 27, 1978 Page 2 to be adequate. In all of these areas, the pressure inside the syste=
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 alar =s 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 volu=e 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 i= mediate 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 syste= cannot be bypassed during operation.
Item 3 As described in Item 2 above, the potential for accu =ulation of explosive cixtures is negligible. Therefore, no further actions are considered to be necessary. Th'e exhaust air from these areas is =enitored continuously for air-borne radioactivity. In the unlikely event of an offgas leak, these monitors would initiate control room alar =s at concentrations far below those which would be equivalent to a de: enable =1xture.
Item 4 The portion of offgas system containing hydrogen in detonable concentra: ion does not have any loop seal drains.
Item 5 Operating and energency procedures have been reviewed and found :o provide adequate guidance in the event of a hydrogen detona ion in the offgas syste=.
Yours very truly, V
Ah$Y&
L. J. Wachter Vice ?residen: - Power ?rodue:icn and System Operation
; cc: Mr. G. Charnoff i NRC Office of Inspection and Inforcenent Washington, D.C.
L' m .
.}}

ML20028C428 - Revision history

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