ML19309C334
| ML19309C334 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 03/31/1980 |
| From: | Lundvall A BALTIMORE GAS & ELECTRIC CO. |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0578, RTR-NUREG-578 NUDOCS 8004080465 | |
| Download: ML19309C334 (2) | |
Text
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BALTIMORE GAS AND ELECTRIC COMPANY P. O. BOX 1475 BALTI M O R E, M ARYLAN D 21203 March 31, 1980 ARTHUR E. LUNDVAR,JR.
vice ensiome Suretr Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555 I
Attn:
Mr. Robert W. Reid, Chief Operating Rt s Branch #h Division of Operating Reactors
Subject:
Calvert Cliffs Nuclear Power Plant Units Nos. 1 & 2, Dockets Nos. 50-317 & 50-318 Follow-up Actions Resulting from TMI-2 Incident (Iessons Icarned)
Subcooled Marcin t'onito,r Gentlemen:
As we have discussed recently with your staff, an unexnected problen has arisen with regard to the installation of the subcooled margin monitors.
The installation of the no dual-range RIS transnitters in channel A of the RCS instrumentation induced noica on the sicnals from the renaining Rosenount transnitters of channel A.
This noise resulted in suurious High Power and TM/LP trips on channel A of RPS. Attemnts to renedy the problem with filtering were unsuccessful. Because of th*s problem, we have decided to renlace all Th and T transmitters at IC25 vith RIS transmitters due to e
their superior stability and noise immunity. Sincle channel versions of the RIS transnitters ordered for the subcooled margin monitors have been ordered, with delivery expected anproximately h/25/80.
In the meantime, the RIS transmitters ordered for the subcooled margin monitor job have been installed in channels A and B of each unit's RCS instrumentation.
In this way we can put one subcooled margin monitor in service on each unit and maintain RPS reliability.
A computer program for calculating the RCS margin to saturation is in service on both units, and serves to back-up the subcooled margin monitor. The computer program selects the higher of four in-core thermo-couple inputs as the base temperature. The in-core thermocounle innuts monitored by the program were selected on the basis of best agreement with hot leg temperature. A reference temocrature is established by selecting the saturation temnerature corresnonding to the nressurizer nressure. Two overlapping pressurizer pressure innuts cover the rance of 0-2500 psia.
The margin to saturation is deternined by subtracting the base temnerature from the reference temperature, and is' available to the control room operator vin the alarn printer.
8004080
Mr. R. W. Raid ?! arch 31, 1980 In addition'to the subcooled margin monitor and the computer program, a saturation curve is displayed in the control room for use by the operator.
When the additional RIS transmitters arrive on site the second subcooled margin nonitor on each unit vill be placed in service. This work t
is exnected to take apuroximately two vecks, and should be complete by about f
5/9/80.
7 Very tr Y yours, e
/.
Sy,gs Ja.4-cG l
i ec:
J. A. Biddison, Esquire G. F. Trowbridge, Esquire E. L. Copner, Jr.
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