ML18051B423

Clarifies Operability Requirements for Subcooling Margin Monitor,Per Insp Rept 50-255/85-05,NRC 831214 Evaluation of Util Response to Generic Ltr 82-28 & NUREG-0737,TMI Item II.F.2

ML18051B423
Person / Time
Site:	Palisades
Issue date:	06/10/1985
From:	Vandewalle D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	Office of Nuclear Reactor Regulation
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-2.F.2, TASK-TM GL-82-28, NUDOCS 8506170442
Download: ML18051B423 (2)

Text

.:..*._ .. consumers Power company General Offices: 1945 West Parnell Road, Jackson, Ml 49201 * (517) 788-1636 June 10, 1985 Director, Nuclear Reactor Regulation US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-255 -LICENSE DPR-20 -PALISADES PLANT -David J VandeWalle Director of Nuclear licensing CLARIFICATION OF SUBCOOLING MARGIN MONITOR OPERABILITY REQUIREMENTS Nuclear Regulatory Commission (NRC) letter dated December 14, 1983 provided _Consumers Power Company an evaluation of our response to Generic Letter 82-28, "Inadequate Core Cooling Instrumentation".

This NRC letter stated "the design of the presently installed subcooling margin_monitor is acceptable contingent on upgrading of the input range from the pressure and temperature sensors as committed by the licensee".

Due to recent concerns of our Senior Resident Inspector as documented in Inspection Report 50-255/85005, a clarification of the operabiiity requirements for the subcooling margin monitor is necessary.

Our Technical Specifications require that at least one channel of the subcooling margin be operable whenever primary coolant system temperature is above 515°F. In addition to a continuous digital display, the subcooling margin monitor also includes an alarm function which is -common _to of the two otherwise independent channels.

The alarm function of this monitor-is not addressed in our Technical Specifications, but we do calibrate the alarm during the performance of the Technical Specification surveillance procedure for the subcooling margin monitor. ' "Clarification of TMI Action Plan Requirements", NUREG-0737, section II.F.2; Instrumentation for Detection of Inadequate Core Cooling, item 5, requires that "the indication must give advanced warning of the approach of ICC (Inadequate Core Cooling)".

It is our understanding that this requirement is referencing the composite instrumentation system for detection of inadequate core cooling. This system consists of a primary coolant inventory monitoring system, core-exit thermocouples and subcooling margin monitor. Although the alarm function is 'incorporated in our subcooling margin monitor design and certainly does provide advanced warning, an operable subcooling margin monitor display, itself, also provides advanced warning of the approach of inadequate core cooling, as does the coolant inventory monitoring system. In addition, there is no specific requirement for an alarm function for the subcooling OC0685-0003B-NL02 I ADOCK )

. " Director, Nuclear Reactor Regulation Palisades Plant Subcooling Margin Monitor June 10, 1985 2 margin monitor in Appendix B of NUREG-0737, "Design and Qualification Criteria for Accident Monitoring Instrumentation".

For operability declarations as well as subsequent reportability determinations, we believe it is appropriate to take credit for the operable display. Consequently, the inoperability of the alarm function of the subcooling margin monitor, for whatever reason, does not constitute inoperability of the subcooling margin monitor provided that the subcooling margin monitor detection and display capabilities are unaffected.

The alarm function should, however, be prudently maintained in an operable condition.

Director, Nuclear Licensing CC Administrator, Region III, USNRC NRC Resident Inspector

-Palisades OC0685-0003B-NL02