TXX-4820, Interim Deficiency Rept CP-86-18 Re Difficulties in Starting & Operating Safety Chilled Water Chiller Units.Initially Reported on 860321.Design Change to Control Temps Being Developed.Next Rept Expected by 860627
| ML20195B457 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 05/21/1986 |
| From: | Counsil W TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | Johnson E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| CP-86-18, TXX-4820, NUDOCS 8605290324 | |
| Download: ML20195B457 (3) | |
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File # 10110 909.4 TEXAS UTILITIES GENERATING COMPANY NKYWAY Tf)WER. 400 N(DETH OLIVE MBEU. L.E. El e DALLAS. TEXAB 75301 May 21, 1986
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Mr. Eric H. Johnson, Director Division of Reactor Safety and Projects MAY 2 312 U. S. Nuclear Regulatory Commission e"
611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76012 2
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS. 50-445 AND 50-446 SAFETY CHILLED WATER CHILLER UNITS SDAR:
CP-86-18 (INTERIM REPORT)
Dear Mr. Johnson:
On March 21, 1986, we verbally notified your Mr. R. Hall of a deficiency involving the difficulties in starting and operating the safety chilled water chiller units. We have submitted an interim report logged TXX-4769, dated April 21, 1986.
We have concluded that this deficiency is reportable under the provisions of 10CFR50.55(e). We anticipate evaluation of all corrective action and submittal of our next report by June 27, 1986.
Very truly yours, W. G. Counsil JCH/gj Attachment c - NRC Region IV (0 + 1 Copy)
Director, Inspection & Enforcement (15 copies)
U. S. Nuclear Regulatory Commission Washington, D. C.
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3 ATTACHMENT SAFETY CHILLED WATER CHILLER UNITS DESCRIPTION This issue involves difficulties in starting and operating the safety chilled water chiller units when the entering component cooling water (CCW) temperature is not maintained at or above the chilled water return temperature.
For proper operation of the safety chiller, condenser pressure must be maintained above evaporator pressure. To maintain adequate pressure differential, entering CCW temperatures must be maintained equal to or higher than chilled water return temperature. This entering CCW temperature is also necessary to ensure that the standby safety chiller will start and operate during accident conditions.
Ungernormalconditions,safetychilledwaterisdesignedtooperateat55to 65 F.
The standby chilled water loop will go to building ambient temperature g
which has a design maximum of 104 F.
To ensure that this standby chiller will start and operate during accident conditions, the entering CCW temperature must bemaintainedatorabovethebuildingambienttemperagure.
Per specification 2323-MS-49, CCW has a design outlet temperature of 105 F during normal condi-tions; however, a minimum temperatures is not specified. Gibbs & Hill calcula-tions indicate that CCW temperature is controlled primarily by station service water (SSW) temperature and thag during winter months under normal conditions CCW temperatures may average 45 F.
This failure to maintain CCW supply temperature at or above the building ambient as required to ensure that the standby safety chiller will start and operate during accident conditions is a significant deficiency in the final design and is reportable under the provisions of 10CFR50.55(e).
The concern is applicable to Units 1 and 2.
SUMMARY
OF EVENTS Date Discovered: January 23, 1986, per review of Design Modification 85-034 Date NRC Notified as Potentially Reportable: March 21, 1986.
Interim Report to NRC: April 21, 1986 Date Determined Reportable: May 21, 1986 SAFETY IMPLICATION Operability of the safety chilled water system is required to provide protec-tion for engineered safeguards equipment during normal and accident operating conditions.
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CORRECTIVE ACTION The resolation of this issue addresses CCW supply temperature as a whole and not just CC9 supply temperature to the safety chillers. As a result, a design change to control CCW temperatures out of the CCW heat exchanger is being developed.
This will consist of a by-pass line around the CCW heat exchanger and two modulating ball valves to control CCW supply temperature at 85 to 105 F.
This design change will satisfy the requirements of the operating safety chiller and other components served by CCW. An effort is still on-going to correlgte building ambient temperature with CCW temperature to verify that 85 to 105 F CCW temperatures will satisfy the requirements of the standby safety chiller.
A schedule of engineering activities will be provided by June 20, 1986.
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