RBG-26442, Forwards Documentation of Info Discussed W/Nrc on 870217 & 0528 Where Agreement Reached to Defer Facility Specific Containment Venting Issues Until NRC Completed Generic Review,Per SER (NUREG-0989)

Forwards Documentation of Info Discussed W/Nrc on 870217 & 0528 Where Agreement Reached to Defer Facility Specific Containment Venting Issues Until NRC Completed Generic Review,Per SER (NUREG-0989)

ML20237L259
Person / Time
Site:	River Bend
Issue date:	08/14/1987
From:	Booker J GULF STATES UTILITIES CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
RTR-NUREG-0989, RTR-NUREG-989 RBG-26442, NUDOCS 8708200148
Download: ML20237L259 (5)

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GULF STATES UTILITICS COMPANY d -!

RIVER BEND S TATION POST OFFICE BOX 220 ST. FRANCISVILLE. LOUIS 1ANA 70775 AREA CODE 504 635 6094 - 346-6651 August 14, 1987 RBG - 26442 File Nos. G9.5, G9.27 U.S. Nuclear Regulatory Commission Document Control' Desk-Washington, D.C. 20555 '

s Gentlemen:-

River Bend ' Station -- Unit .1 Docket No. 50-458 I

Gulf States Utilities (GSU) Company submits information requested by the staff in River Bend's: Safety Evaluation Report (NUREG-989) concerning the emergency operating procedure for containment venting. The Attachment provides documentation of- information discussed with the staff on February 17, and May 28, 1987 where an agreement was reached to' defer River Bend specific containment-I venting issues until the staff has completed its generic review.

l GSU continues to actively follow the industry efforts to ensure'a

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j timely resolution of this item.

Sincerely, vt J. E. Booker ,

Manager-River Bend Oversight L. River Bend Nuclear Group JEB/ ERG / B ch cc: U.S. Nuclear Regulatory Commission 611:Ryan' Plaza Drive, Suite'1000.

Arlington, TX 76011

{ NRC Resident Inspector P.O. Box 1051 St, Francisv111e, LA 70775 l

8708200148 870814 PDR ADOCK 05000458 f OO PDR l

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i i j l *. j l ATTACHMENT

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Section 13.5.2.3 of Supplement No. 5 to River Bend Station's Safety  !

l Evaluation Report requested additional information regarding venting of j the containment. This information provides GSU's response to the I information requested by the NRC.

i NRC Request t 1. Provide information on additional flow paths for emergency venting including justification for vent path valve operability (capability l to open and reclose) and survivability of the 3-inch vent path.

GSU Response i

1. Items A, B, and C address additional flow paths which have been I evaluated for post-accident venting and item D which addresses the existing vent path and provides information regarding the j

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survivability of the 3-inch vent path.

A. Vent the containment through the Reactor Building equipment and floor drain piping. This pathway is not feasible because of the extensive operator action necessary to establish the vent. i path, limited flow area, and the large flow loss characterist!' j l of the drain piping.

B. Vent the containment through one of the containment airlocks.

l This vent path wiuld be established by deflating the airlock seals or opening the air lock doors. The mechanics of l establishing this vent path was investigated by GSU. The results of this investigation indicate that it would be possible to overcome the mechanical and electrical problems associated with establishing this pathway. The danger of potential exposure of personnel to high-temperature steam vent flow makes this option undesirable. For this reason, no further analyses using this pathway has been conducted.

C. Vent the containment through the 36-inch Containment Purge System Exhaust penetration.

This vent path has been evaluated at a pressure of 30 psig and would be established by installing a mechanical stop in the j valve actuator to limit valve position for the outboard purge l containment exhaust. In addition, it would require installation l

of plates in the ductwork necessary to isolare the Standby Gas  ;

Treatment System from high energy steam and involve the opening l of two doors at EL. 171' of the Auxiliary Building to release  !

the effluent. The mechanical stop is necessary to increase the l pressure drop across this penetration assuring the containment pressure of 30 psig is reduced to 10 psig in the Auxiliary i Building ductwork. The mechanical stop cannot be installed on a  !

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l permanent basis because it would reduce Standby Gas Treatment l l

System flow rates below the current ' design basis for this system. The containment purge system exhaust penetration valves have been analyzed to assure that these valves will open and i

reclose 'inder the venting conditions previously described. The results  ! the valve analysis indicated that the valve critical

, componei.; stresses (disk pins, bracket bolts, etc.) will be less i than the material yield strength. However, for the outboard l valve, the disk pin stress reaches 55 percent of the tensile l yield stress of the material. The standard design tensile stress limit for this material is 40 percent of the tensile. l yield strength. GSU believes that these stress levels are l

acceptable as the material does not experience any plastic deformation at this slightly elevated stress level. This analysis established valve operability under the event conditions of 100 psi air pressure at the actuator and a l Containment pressure of 50 psig.

l The selection of 10 psig as the peak pressure within ductwork in '

the Auxiliary Building was based on field test d Ja conducted by GSU. The test consisted of constructing mple duct and

, testing it to 10 psig. This test demonstrated une structural l capability of the sample ductwork. The results of this static l l test are discussed below under Item 2. I l D. Survivability of the 3-inch vent path and existing vent path, l Venting of the containment at River Bend Station is currently l

achieved by opening the inboard containment purge exha.ist i penetration and the 3-inch hydrogen purge valve. This I establishes a filtered vent path from the containment through the annulus to the Standby Gas Treatment System. The venting would be established at a pressure of 20 psig. The annulus would not be pressurized as there would be a siroifIcant pressure drop from the containment to the annulus when tons path is in operation and therefore, a low flow rate. This assures that the exhaust ductwork to the Standby Gas Treatment System would not be pressurized. The effluent from the containment is a steam / air mixture that has been-determined can be processed by the Standby Gas Treatment system.

The hydrogen purge valve was analyzed for operability during this event. The results show that this valve vill perform as required with a containment pressure of 40 psig and an annulus pressure of 0 psig. The ability to function includes opening and reclosing. This vent path is acceptable from a containment pressure and vent path operability issues because the valves necessary to establish this vent path are capable of operating at containment pressures up to 40 psig. River Bend Emergency Operating Procedures currently vent at 20 psig.

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NRC Request

[ 2. Provide information on the effects of containment venting on ductwork failure (if used as a vent pathway), and the resulting consequences of subjecting equipment near the failed duct to the steam / radiation environment. ,

I l GSU Response l

2. The structural integrity of the ductwork that would be used was l cvaluated. This evaluation is based on field test data that was obtained in the test of a typical section of ductwork at 10 psig.

The results of these test indicate the ductwork did not fail and is capable of functioning when pressurized to 10 psig. However, plastic deformation of the duct did occur. The leakage observed during this test indicates that the ductwork is not leak tight and that leakage can be expected into the Auxiliary Building. Also, the test does not simulate the actual dynamic flow conditions that would occur during an actual vent. No additional testing or analysis has been performed at this time to determine the combined effects of internal pressure and flow on the ductwork. GSU believes that l testing ductwork under actual conditions or performing an analysis i would requirs extensive effort and. be inappropriate until the generic issues involved have been sufficiently resolved to establish the success criteria to be applied.

1 If a complete ductwork failure were to occur, the area temperature would rise above 240'F. This temperature is at least 90 F above the present maximum design temperature for the area. The safety related electrical components in this area have not been evaluated to function in that environment which may render the equipment necessary for decay heat removal systems inoperable. For this s reason, GSU has concluded that it is not feasible to vent the

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containment into the Auxiliary Building.

l l NRC Request

3. Provide information on the technical basis that support the criteria used by the Emergency Director to vent containment (e.g., status of plant including anticipated rate of pressurization, existing meteorology, containment ra31oactivity, etc.) (The identification l

of an Emergency Director is not in the approved BWR Owners Group EPGs, the staff ccgsiders actions based on these parameters as l

potential deviations from the generic EPGs).

1 l CSU Response l

, 3. In accordance with previous NRC commitments, Gulf States Utilities j has incorporated a step into the current River Bend Station (RBS)

Emergency Operation Procedures (EOP's) which requires that the operator obtain permission from the Emergency Director before venting the containment. Since this commitment was made, the BWR l

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Owner's Group (BWROG) has issued Revision 4 to the generic Emergency Procedure Guidelines (EPG's). The Revision 4 EPG's do not provide 1 l guidance on activation of the Technical Support Center or on who makes the decision to vent the containment.

The NRC Staff precented this as.a generic question to the BWROC as apart of the NRC questions and comments on Revision 4 of the EPG's (ref. Letter, M.- W. Hodges to T. A. Pickens, " Comments and Questions on Revision 4 of the Emergency Procedure Guidelines", dated April 30, 1987). The BWROG response to these questions and comments (ref.

Letter, T. A. Pickens to M. W. Hodges, dated July 7,1987) stated that the syptomatic EPG's contain sufficient guidance for the proper operation and maintenance of the plant in a safe condition. Gulf States Utilities endorses the BWROG position on this question. As a result, the requirement that the operator receive Emergency Director approval prior to venting will be removed from the RBS E0P's at the next revision. This will pla~ce the GSU E0P's in compliance with l Revisions 3 and 4 of the BWROG EPG's.

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