ML20148G242

Final Deficiency Rept CP-86-18 Re Safety Chilled Water Sys Chiller Units.Initially Reported on 860521.Component Cooling Water (CCW) Sys & Chiller Mods Made,Including Addition of Water Regulating Valve in Condenser CCW Outlet Piping

ML20148G242
Person / Time
Site:	Comanche Peak
Issue date:	01/18/1988
From:	Counsil W TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
CP-86-18, TXX-88103, NUDOCS 8801260449
Download: ML20148G242 (3)

Text

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EE log i TXX-88103 L r file # 10110 r C 909.4 1UELECTRIC

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I,$',,7Sd5,"$,,, January 18, 1988 U. S. Nuclear Regulatory Coninission Attn: Document Control Desk Washington, D.C. 20555

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION DOCKET NOS. 50-445 AND 50-446 SAFETY CHILLED WATER SYSTEM CHILLER UNITS SDAR: CP-86-18 (FINAL REPORT)

Gentlemen:

On May 21, 1986, we notified you via our report logged TXX-4820 of a reportable deficiency involving the Safety Chilled Water Chiller units. Our most recent interim report was logged TXX-7109, dated December 17, 1987. The following is submitted to clarify our previous transmittals and discuss our final corrective actions.

DESCRIPTION OF DEFICIENCY Our previous correspondence on this subject discussed a deficiency originally identified as a result of operaticnal problems associated with the Safety Chilled Water Chiller units. The problem was a result of the failure to consider the effects of minimum Com)onent Ccoling Water (CCW) supply temperature on operation of these caillers. This temperature can be as low as 40 degrees F (CCW supply) during winter operation.

, This deficiency identified the need to evaluate the potential adverse effects of minimum CCW supply temperatures on all cooled components. Additional review indicated adverse effects of low CCW supply on non-safety ventilation chillers and the non-safety instrument air compressors.

SAFETY IMPLICATIONS Operability of the Safety Chilled Water System is required to provide protection for engineered safeguards equipment during nonnal and accident operating conditions, f>$ b DOC S

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TXX-88103 January 18, 1988 Page.2 of 3 CORRECTIVE ACTION Corrective actions under consideration were either a system approach (involving modification to the CCW system such that outlet (supply) temperature could be controlled) or an individual component approach such that ability to operate under the minimum CCW temperature would be confirmed or component modification implemented. The individual component approach as described below was selected as the best solution:

1. Safety Chilled Water System Chiller Units The safety chilled water chiller unit vendor has advised that the safety chillers will operate satisfactorily both during operation and upon startup from the standby to full load conditions with 40 degree F CCW supply temperature af ter implementation of the following chiller and CCW system modifications: (1) The addition of a water regulating valve in the condenser CCW outlet piping to maintain condenser refrigerant pressure above evaporator pressure. This modification will also require the addition of a pressure controller on the refrigerant side of the condenser to control the operation of the water regulating valve; and (2)

That CCW not be allowed to circulate through the condenser prior to chiller startup to avoid low oil pressure trips resulting from refrigerant boiling out of the oil due to a sudden decrease in refrigerant pressure caused by circulating cold CCW through a standby chiller. This operation will be accomplished by automatically closing the water regulating valve when the chiller is on standby (off).

Should loss of Instrument Air Systems occur, each water regulating valve will be equipped with a 30-minute (minimum) air accumulator tank and a handwheel for manual control of CCW flow after the accumulator instrument air has been exhausted.

2. Non-Safety Ventilation Chillers A similar modification was made to the affected non-safety chillers except air accumulators were not provided.

TXX-88103 January 18, 1988 Page 3 of 3

3. Non-Safety Instrument Air Compressors A bypass line was added to the non-safety instrument air compressor to bypass the instrument air compressor jacket af ter-cooler, as appropriate.

The Design Basis Document for the CCW system (DBD-ME-229) and associated cooled components (DBD-ME-311, "Safety Chilled Water System") will preclude recurrence of this deficiency if future equipment substitutions or additions requiring CCW cooling are made.

Unit 1 corrective actions are scheduled for completion by February 26, 1988.

Unit 2 corrective actions will be completed prior to Unit 2 fuel load.

Very truly yours,

/. [Mkk W. G. Counsil GLB/grr c-Mr. R. D. Martin, Region IV Resident inspectors, CPSES (3) s