ML19256G095

Provides Committment to NRC Interim Position for Purge & Vent Valve Operation Pending Verification of Valve Operability Under DBA-LOCA Loadings.Design Review Indicates Valve Operation W/Adequate Shutting Torque

ML19256G095
Person / Time
Site:	Calvert Cliffs
Issue date:	12/14/1979
From:	Lundvall A BALTIMORE GAS & ELECTRIC CO.
To:	Reid R Office of Nuclear Reactor Regulation
References
NUDOCS 7912270416
Download: ML19256G095 (3)

Text

e BALTIMORE GAS AN D ELECTRIC CO MPANY GAS AND ELECTRIC BUILDING BALTIMORE, MARYLAN J 21203 ARTMum E.LUNOVALL,dm. ,

vice Passiose.'

swmv Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attn: Mr. Robert W. Reid, Chief Operating Reactors Branch #h Division of Operating Reactors

~

Subject:

Calvert Cliffs Nuclear Power Plant Unit No. 1 & 2, Docket No. 50-317 & 50-318 Containment Pureine and Ventine

Reference:

a) NRC letter dated 9/27/79 from D. G. Eisenhut to All Light Water Reactors, sa=e subject.

b) NRC letter dated 10/23/79 from R. W. Reid to A. E. Lundvall, Jr., sa=e subject.

c) BG&E letter dated 11/15/79 from A. E. Lundvall, Jr.

to P. W. Reid, same subject.

Gentlemen:

Reference (a) informed us that certain contairz:en'. purge and vent valves may not be capable of shutting against DBA-LOCA pressure and dynamic loadings, according to their manufacturers. Consequently, we vere requested to commit to implement a valve qualification program on an expedited basis, using guidelines provided by Reference (a). We provide the requested commitment in Reference (c).

Reference (b) forwarded an interin NRC position for purge and vent valve operation pending verification of valve operability under DBA-LOCA loadings and asked us to co=mit to that interim position.

Baltimore Gas and Electric Company hereby co=mits to operate is conformance with the interim position enclosed with Reference (b).

We have perfor ::ed a design reviev of the purge and vent valves for Calvert Cliffs Units 1 and 2 and have been in contact with the valve manufacturer, Henry Pratt Company. Based on these investigations, the purge and vent valves may be operated as follows with adequate shutting torque:

a. Thg outboard valves may be opened to a disc opening of 20 through ho (90 being full open).

b. The inboard valves may be opened to a disc opening of 25 0 through h5 -

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Mr. R. W. Reid December ik, 1979 The following information is provided in response to specific items in References (a) and (b) as indicated.

Reference (b): _

Page,2. Paracrath 2: The Calvert Cliffs purge and vent pilot solenoids are being replaced with environ =entally-qualified solenoids. Unit No. 2 is co=pleted; Unit No. 1 vill be done during the next refueling outage.

Pace 2, Paracrath 3: There are no override capabilities on the purge and vent valves.

Interin Position 2.b: SIAS is being added to the CIS and CRS closure signals. -

Reference (a):

Enclosure-Ocerability Ite=s :

Item 1. Valve Closure Rate VS Time - This is essentially constant.

For a duration of half a second to one second, the valve sits still due to its inertia and subsequently closes from full open to closed position at a constant rate. The valve takes five seconds to close from full open position.

Item 2. Flow Direction Throuch Valve; AP Aeross Valve - For containment purge valves, the direction of flov is from outside to inside and is reverse for vent valves. Flov stratification along the valve is not likely during LOCA due to sufficient length of inlet piping connected to each valve. The maximum designAP across the valve is 57 5 psi vith an inlet pressure of 72.2 psia.

Item 3. Establish the Worst Case for Valve Closure - In the event of a single valve closure, with the inboard valve stuck open and the outboard valve disc open to approximstely a 10 angle or below (assuming a 90 angle of the disc is fully open and Oo is closed) the pressure drop across the outbcard valve is close to its

-4mm while the spring torque and the dynamic torque due to flov are close to the lovest value. In the case of a butterfly valve the flov exerts a dynamic torque tending to close the valve. This dynamic torque is maximum at a given angle of the disc. In any case, the minimum spring torque of h0,000 in-lbs with the valve at the closed position is greater tha. the maximum valve torque of 35,795 in-lbs at the closed position (assuming zero air pressure in the operator).

Item k. Backeressure Effect - There is no backpressure effect since both sides of the operating piston bleed to containment.

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Mr. R. W. Reid December ik, 1979 Item 5 Accumulator Sizing - Not applicable; the valves fail shut on spring pressure.

Item 6. Torque Limiting Devices - Not applicable; there are no torque limiting devices.

Item 7 Piping Effects - The effect of piping system upstream and downstream of the valve vould be co decrease the inlet pressure and reduce the pressure drop across the valve. This vill assist closure of the valve.

Item 8. Dise and Shaft Orientation - The orientation of the shaft either horizontal or vertical to the fluid mixture egressing from the containment has no effect on the closure of the valve. Hov- ~

ever, the chaft in each valve is offset to the disc, and the installation of the valves is such that, in case of the inboard valve, the shaft is before the disc. and for the outboard valve the shaft is behind the disc, looking from inside the containment.

With this arrangement, any packing leakage has no effect on the contain=ent integrity and the outboard valve experiences less

- 4 m m dynamic torque than the inboard valve. The difference in magnitude of the peak dyna =ic torque is negligible. The angle of dise from vertical, at which the peak dynamic torque is acting to assist closure of the valve, is 20 for the outboard valve and approxi=ately 23 for the inboard valve.

If you have any questions on this matter, please do not hesitate to contact us.

Very truly yours, j f

gm -

y Ac u l

ec: J. A. Biddison, Esquire G. F. Trowbridge, Esquire Mr. E. L. Conner, Jr. - NRC Mr. J. W. Brothers - Bechtel 1643 299