ML20207P899
| ML20207P899 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 12/31/1986 |
| From: | Trevors G NEBRASKA PUBLIC POWER DISTRICT |
| To: | Gagliardo J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-3.D.3.4, TASK-TM CNSS866183, NUDOCS 8701200385 | |
| Download: ML20207P899 (3) | |
Text
i Nebraska Public Power District
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CNSS866183 December 31, 1986 g
lv E I 3E Mr. J. E. Gagliardo, Chief h
J Reactor Projects Branch U. S. Nuclear Regulatory Commission
(
3 Region IV Gil Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011
Dear Mr. Gagliardo:
Subject:
Cooper Nuclear Station Control Room IInbitability
Reference:
(1) Letter from J. M. Pflant to J. E. Gagliardo Dated January 30, 1986, NPPD Response to NRC Request for Information Concerning Control Room flabitability Reference (1) provided information about CNS Cuatrol Room habitability and identified certain short term corrective actions.
It also indicated that an evaluation would be performed and changes which would result in a significant increase in safety would be implemented. While a definitive completion schedule could not be developed until the extent of the required changes was known, the District believed that short term corrective measures could be completed during the 1986 Refueling Outage. This letter provides the status of our corrective measures and discusses future actions regarding this system.
In February of this year, an independent engineering firm was retained to review the system. The scope of the review included:
1.
Review of the Control Room ventilation system for compliance with the applicable guidance of Standard Review Plans 6.4, 6.5.1 and 0.4.1, and NUREG 0737,Section III.D.3.4.
The review included system arrangement, oystem and component capacities, controls and instrumentation, and compliance with applicable critoria.
Modifications (if any) which might result in a significant increase in the safety margins provided by the present design would be recommended.
2.
Review of the Cor. trol Hoom ventilation operation, maintenance, and testing procedurca to ensure compliance with Standard Review Plan 6.4 and Regulatory Guide 1.52.
Changes (if any) to procedures or Technical Specifications would be recommended.
0701200305 06123t DR ADOCK 0500 0
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J. E. Gagliardo December 31, 1986 Page 2 The review found that while the present system was, for the most part, as described in the Updated Safety Analysis Report and Technical Specifications, several changes may be required for it to comply with all of the criteria established in the most current guidance documents.
In consideration of the magnitude of these changes, it was determined that a phased approach to upgrading the system would be appropriate.
In this manner, modifications could be made within the physical constraints of the existing configuration to correct obvious problems. Key parameters could then be monitored to determine the results achieved, as well as the requirements for any future modifications. This approach was implemented during the 1986 Refueling Outage. The following were completed:
1.
The supply duct in the Control Room was replaced with a carbon steel pipe and the supply damper was replaced with a leak tight butterfly valve. This installation is qualified to seismic Category I criteria.
2.
The bypass line around the emergency filtration unit was removed.
Its leak tight damper was used as the filtration unit isolation damper.
3.
The exhaust duct from the Control Room was removed and plugged arch that the ventilation system now operates in the recirculation modo, with the exception of fresh idr makeup.
4.
A leak tight isolation valve was added to the exhaust duct from the kitchen and sanitary arcao.
Tht..ontrol circuitry was ali.o modified such that when the Control Room ventilation system shifts to the emergency modo, the kitchen / sanitary aren exhaust fan de-energizes and the exhaust valve isolates.
5.
The solenoid valvos that supply backup cooling wi.ter to the Control Room chillers were replaced by manual isolation valves which are suitable replacements and will reduce the potential for valve failure.
6.
The IIVAC system air flows were balanced to provide the design air flows and climinate the negative pressure in the Cable Spreading lloom.
Additionally, corresponding procedure and documentation changen are in progress.
These activities have assured that the Control Room can be maintained at a positive pressure under emergency conditions and the sources of infiltration have been minimized. The next phase consists of collecting specific performance data which will be evaluated to determine if any future enhancements are justified and cost beneficial. We anticipate completing this evaluntion well in advance of the next refueling outago to allow implementation of any necessary enhanecments.
Upon its completion, we will forward the results of the evaluation to your office.
J. E.' Gagliardo December 31, 1986 Page 3 If you have any questions concerning the above information, please contact my office.
Sincerely, G. A. Trevors Division Manager Nuclear Support j
Nuclear Power Group GAT:cbl(COMM12) 1 i
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