ML19256F555

Submits Responses to Specific Items Re Containment Purging & Venting in Response to NRC 790927 & 1023 Ltrs.Util Commits to Operation in Conformance W/Interim Position in NRC 791023 Ltr.Design Review of Purge & Vent Valves Performed

ML19256F555
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 7912190403
Download: ML19256F555 (3)

Text

BALTIMORE GAS AN D ELECTRIC COMPANY GAS AN D ELECTRIC BUILDING BALTIM ORE, MARYLAN D 41203 ARTHUR E. LUNOVALL,JR.

Vics Passiosm?

Suppsv 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 Purcing and Venting

Reference:

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

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

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

to R. W. Reid, same subject.

Gentlemen:

Reference (a) informed us that certain containment purge and vent valves may not be capable of shutting against DBA-LOCA pressure and dynamic loadings, according to their manufacturers. Consequently, we were 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 commits to operate in conformance with the interim position enclosed with Reference (b).

We have performed a design review 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 40 (90 being full open).

b. The inboard valves may be opened to a disc opening of 250 through u5o.

40 3 m ale 1621 079 /

Mr. R. W. Reid December 1h,2979 The following information is provided in response to specific items in References (a) and (b) as indicated.

Reference (b):

Page 2, Paracraoh 2: The Calvert Cliffs purge and vent pilot solenoids are being replaced with environmentally-qualified solenoids. Unit No. 2 is completed; Unit No. 1 vill be done during the next refueling outage.

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

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

Reference (a):

Enclosure-Ocerability Items:

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 Through Valve; /SP Across 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 design 2iP across the valve is 57 5 psi with 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 approximately a 10 angle or below (assuming a 90 angle of the disc is fully open and 00 is closed) the pressure drop across the outboard valve is close to its maximum while the spring torque and the dynamic torque due to flow are close to the lovest value. In the case of a butterfly valve the flow 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 than the maxinwn valve torque of 35,795 in-lbs at the closed position (assuming zero air pressure in the operator).

Item h. 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 14, 1979 Item 5 Accumulator Sizing - Not applicable; the valves fail shut on spring pressure.

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

Item T. Piping Fffects - The effect of piping system upstream and /.svnstream of the valve vould be to 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. How-ever, the shaft 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 containment integrity and the outboard valve experiences less maximum dynamic torque than the inboard valve. The difference in magnitude of the peak dynamic torque is negligible. The angle of disc from vertical, at which the peak dynamic torque is acting to assist closure of the valve, is 20 for the outboard valve and approximately 23 for the inboard valve.

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

Very truly,yours, f []

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5 t cc: J. A. Biddison, Esquire G. F. Trowbridge, Esquire Mr. E. L. Conner, Jr. - NRC Mr. J. W. Brothers - Bechtel

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