NUREG-0827, Safety Evaluation Supporting Proposed Installation of remotely-operated Solenoid in Pipe Tunnel Outside Containment for Offgas Vent Line

Safety Evaluation Supporting Proposed Installation of remotely-operated Solenoid in Pipe Tunnel Outside Containment for Offgas Vent Line

ML20212J964
Person / Time
Site:	La Crosse File:Dairyland Power Cooperative icon.png
Issue date:	08/06/1986
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20212J962	List: NUREG-0827, Safety Evaluation Supporting Proposed Installation of remotely-operated Solenoid in Pipe Tunnel Outside Containment for Offgas Vent Line
References
RTR-NUREG-0827, RTR-NUREG-827 NUDOCS 8608140562
Download: ML20212J964 (4)

Text

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ,

RELATING TO NUREG-0827 SECTION 4.21.3.2 0FFGAS VENT FROM SHUTDOWN CONDENSER DAIRYLAND POWER COOPERATIVE LA CROSSE BOILING WATER REACTOR (LACBWR)

DOCKET NO. 50-409

1.0 INTRODUCTION

By letter dated August 29, 1985, Dairyland Power Cooperative (DPC), licensee for LACBWR, submitted a description of a proposed design for isolation of the offgas vent from the shutdown condenser (SDC). The submittal included schedular and cost information. Discussed below is the staff's evaluation of the proposed modifications.

2.0 BACKGROUND

As part of the Systematic Evaluation Program (SEP), containment isolation provisions at LACBWR were reviewed as noted in Section 4.21 of the Intearated Plant Assessment Report (IPSAR) for LACBWR, NUREG-0827. Section 4.21.3.2 discussed isolation of the offgas vent from the SDC. As part of that review, the licensee proposed to lock closed two manual valves inside containment and to install a remotely operated valve outside containment by the end of the 1984 outage.

Subsequently, as noted in an April 8,1985 submittal, the licensee found that more extensive upgrading of the line would be needed and thus a schedule extension was requested. The staff agreed in an April 26, 1985 letter. The licensee's August 29, 1985 letter provides the details of the proposed correc-tive actions.

3.0 DISCUSSION The offaas vent is a 1-inch diameter line that connects from the primary side of the SDC to the waste pas system. The purpose of the line is to vent non-condensible cases from the SDC at the onset of SDC operations.

The original configuration of this penetration included an automatic isolation l valve inside containment which opens automatically when the SDC is actuated '

and then is automatically closed after 2 minutes by a timer. It is also 1 i capable of remote manual operation. There is a normally closed bypass around this valve. Connected to this line are a pressure instrument and a line from the fuel sipping system, with a normally open manual valve. There is also a local manual valve on the penetration line outside containment. However, this l valve may not be accessible due to high radiation if an accident occurs. l The staff's position in the IPSAR was that the pressure instrument and fuel '

sipping line valves should be locked closed and that a remotely operated solenoid valve should be installed in the pipe turbel outside containment.

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The purpose of this valve was to provide the capability to isolate this line, which is open to reactor-coolant, if the existing automatic valve should fail.

As discussed above, further licensee review determined that if the isolation boundary is considered to be at the new second valve, the line in between the two valves should be upgraded. Thus, the other manual valves in the pipe had to be replaced. The pressure gauge and valve were removed and the line tap capped.

The licensee has proposed that the new valve be a normally open, electric solenoid valve, which fails open. The valve would take its electrical supply from a non-interruptible source. Valve control and position indication would be provided in the control room.

4.0 EVALUATION The safety function of the offgas vent to remove noncondensible gases so that the SDC performs properly. The SDC serves as a heat sink when the reactor is isolated from the main condenser, such as following main steam isolation valve closure or loss of offsite power. As discussed above, the inside containment valve is normally closed, but is automatically controlled (first open, then closed) > hen the SDC is actuated. Should the valve fail open when isolation of the reactor coolant system is required, a pathway for leakage outside contain-ment could exist. This concern led to the staff recommendation to install the backup valve.

The licensee has proposed that the backup valve be normally open and fail open on loss of power. This is because the desired position of the valve during normal operation is open so that reliability of SDC venting is not adversely affected. In considering the acceptability of this design, the staff notes the following:

(1) this is a small (1") line; (2) the inboard valve is normally closed and gets a signal to close from a timer af ter SDC initiation;

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(3) power for the outboard valve is from an uninterruptible power supply; i

(4) remote controls and position indication are in the control room; (5) the SDC serves an important function and venting is desirable for maintaining its decay heat removal capability; and (6) the existing manual valve outside containment is being retained and could serve as an additional backup if closed before high radiation levels are reached.

Thus, although a fail-open valve would not oenerally be used as an isolation valve, the staff concludes that in this case, the proposed isolation 1 configuration provides adequate assurance that the penetration can be isclated I if necessary.

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As noted in the licensee's August 29, 1985 letter, the line upgrading except for installation of the solenoid valve was completed during the 1986 outage, but the valve itself would be installed during a later outage. The staff considers this schedule acceptable.

5.0

SUMMARY

Based on the above discussion, the staff finds the proposed resolution of IPSAR Section 4.21.3.2 acceptable, l

6.0 REFERENCES

1. NUREG-0827 Integrated Plant Safety Assessment Report (IPSAR), for La Crosse Boiling Water Reactor, June 1983.

2. Letter from F. Linder (DPC) to J. Zwolinski (NRC) dated April 8,1985 (LAC-10683)

3. Letter from J. Zwolinski (NRC) to F. Linder (DPC) dated April 26, 1985 (LS05-85-04-037).

4. LetterfromJ. Taylor (DPC)toJZwolinski(NRC)datedAugust 29, 1985 (LAC-11095).

Principal Contributor: E. McKenna Dated: August 6, 1986 3

'O Mr. James W. Taylor Dairyland Power Cooperative la Crosse Boiling Water Reactor

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Fritz Schubert. Esquire Mr. Lanning Smith, Chief Engineer Staff Attorney Wisconsin Public Service Commission Dairyland Power Cooperative Post Office Box 7854 2615 East Avenue South Madison, Wisconsin 53707 La Crosse, Wisconsin 54601 ,

Roy P. Lessy, Jr.

O. S. Heistand Morgan, Lewis & Rockius 1800 M Street, N.W.

7th Floor North Receptionist Washington, D.C. 20036 Mr. John Parkyn, Plant Manager la Crosse Boilina Water Reactor Dairyland Power Cooperative P. O. Box 275 Genoa, Wisconsin 54632 U.S. Nuclear Regulatory Commission Resident Inspectors Office Rural Route #1, Box 276 Genoa, Wisconsin 54632 Town Chairman Town of Genoa Route 1 Genoa, Wisconsin 54632 Chairman, Public Service Connission of Wisconsin Hill Farms State Office Building Madison, Wisconsin 53702 Regional Administrator, Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 5

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