ML19093B067

Letter to Inform of a Delay in Final Installation of Reactor Coolant System Overpressure Protection System

ML19093B067
Person / Time
Site:	Surry
Issue date:	12/14/1977
From:	Stallings C Virginia Electric & Power Co (VEPCO)
To:	Case E, Reid R Office of Nuclear Reactor Regulation
References
Download: ML19093B067 (5)

Text

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December *14, *197T '.

. l!'inR~ OOOOl fl\I. t\lVf.

Mr. Edson G. Case,~ng Director Serial No. 446A Nuclear Reactor Regulation* PO&M/TAP :wbh U. S. Nuclear Regulatory Commission Docket Nos. 50~280 Washington, D. C. 20555 50-281 License Nos. DPR-32 Attn: Mr. Robert W. Reid DPR-37 Operating Reactors Branch 4

Dear Mr. Case:

This letter is to inform you of a.delay in the final installation of our Reactor Coolant System.overpressure protection system~ A problem with the system operation was discovered during the final installation and.testing in Surry Unit. No. 1. The investigation revealed that the air controlling solenoid valves were inco_.r_rectly specified. Other valves are on order and their delivery is expected by the end of January.* These valves will be installed and the systems tested during the first cold shutdown after the valves are received.

A .revision to the previously submitted Westinghouse prepared analysis is enclosed. This revision does not alter our system design *

.Very truly yours,

t/J. )J/). ~.di.::tt:? ;.,p,/

C. M. Stallings Vice President~ Power Supply and Production Operations 40 Copies attached of letter 4 Copies attached of Report Revision cc: ~ir. James P. O'Reilly, Region II Director, Office of Inspection and Enforcement

ATTACHMENT TO LETTER 446A *

~ .

REFERENCE:

"Pressure Mitigating Systems Transient Analysis Results,;,

July 1977. (Westinghouse Report on RCS Solid Water Over-pressurization)

Attached are three revised figures which should be substituted for the corresponding figures to be found in Appendix B of Reference 1. The revisions accommodate modifications made to the letdown isolation transients represented in these figures to upgrade the analytical basis and account for an input data correction.

Set.point pressure overshoot has not been altered in any of the transients plotted in these figures; however, *setpoint pressure undershoot has been modified in several of the letdown isolation transients. In~*.every case, the modification has resulted in an improvement in (i.e.~ smaller) set-point pressure undershoot.

In both Figures M6 and MlO, the common transient exhibiting RCS setpoint pressure undershoot response for two relief valve operation at a setpoint of 60G psig has been replotteci to reflect valve closure at a :r;eset pressure 20 psi below the setpoint. The original transient depicted in Figure M6 and Figure MlO of Reference 1 (Appendix B) represented valve closure at a reset pressure 120 psi below the 600 psig setpoint. As would be expected, the setpoint pressure under shoot has been significantly reduced to the extent that violation of the RCS pump seal pressure limit is no longer a consideration for this transient.

In Figure Ml, the setpoint pressure undershoots for both the 500 psig and 600 psig relief valve set.point transients have been adjusted to reflect a correction to the LOFTRAN input data. A reduction in set.point pressure undershoot is evident in both transients.

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