ML20029B518
| ML20029B518 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 03/06/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20029B516 | List: |
| References | |
| NUDOCS 9103110328 | |
| Download: ML20029B518 (4) | |
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NUCLEAR REGULATORY COMMISSION S-k WASHINoToN, D.C. 20E6 ya y
SAFETY EVALUATION 6Y THE OFFICE OF NUCLEAR REACTOR REGULAT[0N, 0
RELATED TO AMENDMENT NO. 85 JO FACILITY OPERATING LICENSE NFF-35 AND AMENDMENT NO. 79 TO 12ACILITY OPERATING LICENSE NPF-52 DUKE POWEd COMPANY, ET AL.
CATAWBA NUCLEAR STATION, UNITS 1 AND 2 DOCKET h05. 50-413 AND 50-414 1.0 _ INTRODUCTION By letter dated February 28, 1991, Duke Power Company, et al. (the licensee) requested amendments to the Technical Specifications (TSs) appended to facility Operating License Nos. NPF-35 and NPF-52 for the Catawba Nuclear Station, Units 1 and 2.
The proposed amendments would revise Technical Specifications (T5s)
Table 3.3-6, Item 3, (Action 31) and TS 4.7.6.e(2).
The change is to reflect celetion of thc automatic closure of the control room area ventilation system (CRAVS) air intake isolation valves upon receipt of a High Radiation-Air Intake or Smoke Density-High signal.
The licensee requested that the proposed amendments be granted on an emergency basis.
The Catawba Nuclear Station Units 1 and 2 CRAVS was declared to be inoperable and Limiting Condition for Operation 3.0.3 was entered at about l
1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on February 25, 1991, when the licensee determined that the system could not meet its intended function under all postulated conditions. Telephone-authorization for a Temporary Waiver of Compliance from TS Table 3.3-6, Item 3 (Action 31), 4.7.6 n(2) and TS 4.7.6.e(5) was granted on February 25, 1991, and confirmed by letter dated February 27, 1991, 2.0 EVALUATION The control room area is normally maintained at a positive pressure by taking makeup air from either or both of two outside air intakes. Each intake is monitored for the presence of radioactivity, smoke and chlorine.
Isolation of the intakes should, as currently described in the Final Safety Analysis
-Report (FSAR), occur automatically upon detection of one or more of these conditions.
Consistent with this design approach, should both intakes close, the operator could override the intake monitors and open the desired intake based upon plant conditions to ensure the capability for control room pressurization. The capability for pressurization is necessary to ensure control room habitability and compliance with GDC-19 " Control Room" following a design basis accident.
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. Recently, the licensee identified design inconsistencies wherein, on combinations of a loss-of-coolant-accident (LOCA), loss-of-offsite-power (LOOP) and the f eilure of a diesel generator, the air intake isolation valves would close and could not be reopened in a timely manner to enable meeting the GDC 19 design basis accident analysis dose limit. This condition derives from the smoke detector and radiation detector control power being provided from a non-class 1E battery backed power source.
in the event of loss of power to these devices, which would occur during a LOOP, a close signal to the CRAVS outside air intake valves may be generated causing the four CRAVS outside air intake valycs to go closed. This in conjunction with a simultaneous LOCA and failure of an Emergency Diesel Generator to start could preclude the re-opening of either outside air intake path to the CRAVS and pressurization of the control room under this condition may not be fully assured and the GDC 19 limit may be exceeded.
This information was reviewed by the licensee with the result being that on February 25, 1991, the licensee declared both trains of the CR ventilation systems iroperable because the system could not meet its intended function under all postulated conditions and entered TS 3.0.3 which would require unit shutdown.
The licensee also requested a Temporary Waiver of Compliance on February 25, 1991, from the associsted Technical Specifications which would allow (1) the isolation valves to be maintained in an open position by removing power from their actuators, (2) the implementation of certain compensatory measures, and (3) the-processing of an amendment to the TS to effect a permanent resolutiqn to the problem.
The NRC staf f orally granted the Temporary Waiver of Coq 'iance (TWC) on February 25, 1991.
The staff's letter of February 27, J 1, documenting the TWC, providtd the staff's assessment of items (1) and (2) above.
This amendment deals with item (3) above.
As noted above, the potential for the closure of the CRAVS outside air intake valves during a Loss-of-Offsite Power (LOOP) concurrent with a Loss-of-Coolant Accident (LOCA) and a single failure of an emergency diesel generator resulted in the potential for exceedance of GDC 19 dose limits to personnel inside the control room. -The licensee's permanent resolution to this concern is to remove the design feature wherein the CRAVS air intake valves automatically close upon receipt of smoke or radiation signals. This would preclude the valves from closing upon a LOOP. Annunciation / alarm from the smoke and radiation detectors would continue to-be provided in the control room.
In addition, in order to irrprove the availability of the subject monitors, the licensee will assure the reliability of the non-1E battery backed monitor power source and assure that the monitors will perform the required monitoring function in the event of a LOOP.
This modification would assure that the position of the CRAVS outside air intake valves can be manually controlled as required in response to the postulated accident condition from the control room.
The licensee states that the-Catawba control room radiation dose analysis assumes that the outside air. intake valves remain open for the duration of the accident.
Therefore, the staff finds it acceptable to modify the TS such that these valves will be normally open and will be operated manually as required by operators since this condition would be bounded by the accident analysis assumption in this regard. Manual operation of the isolation valves for protection from smoke is also consistent with the NRC staff review guidance in the Standard Review
. Plan.
The licensee plans to implement this modification shortly after issuance of this amendment to the TS.
The chlorine parameter was involved in the licensee's request for a Temporary Waiver of Compliance only because the interim solution taken by the licensee, removal of motive power from the air intake valves, also rendered automatic response to detection of chlorine inoperable for the short interim period until the permanent modification is completed.
Compensatory measures for this condition were provided by the licensee and evaluated by the staff in the consideration of its issuance of the Temporary Waiver of Compliance.
Upon implementation of the permanent modification, to delete the automatic closure signals on smoke or radiation from the intake valves, the automatic response including system isolation in response to chlorine will be as it is currently described in the FSAR.
Based on the NRC staff's review of the licensee's analysis of and the proposed schedule for implementing the permanent modification, as discussed above, the staff finds the licensee's action to mitigate the consequences of radiation, chlorine and smoke on the habitebility of the control room to be acceptable.
3.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION
DETERMINATION The State of South Carolina was informed by telephone on March 04, 1991, of the hRC staff's no significant hazards consideration determination. The State i
contact had no comments on the determination.
The staff has reviewed the licensee's request for the above amendments and has deterrrined that, should this request be implemented, it would not (1)' involve a significant increase in the probability or consequences of an accident previously evaluated because the proposed permanent mode of operation of the system is bounded by the previously existing accident analysis. Also, the licensee's proposed amendments would not (2) create the possibility of a new or different-kind of accident from any accident previously evaluated because changing the CRAVS fron, automatic to manual response to sn.oke _or radiation does not introduce-
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any new accident initiators.- Finally, the proposed amendments would not (3) involve a significant reduction in a margin of safety because the consequences of the control room GDC 19 dose analysis are unchanged and the-protection cf operators from smoke is not significantly changed. Accordingly, the Commission finds that this request does not involve a significant hazards consideration.
4.0 FINDING 0F-EMERGENCY WARRANTING AN AMENDMENT WITHOUT-NOTICE i
The licensee's application-for the TS change has been timely. The problem was ir.itially identified based on a similar problem having been identified at another facility _and the situation causing the emergency situation at Catawba was not known until investigation of that similar problem. -The licensee states that the Catawba Nuclear Station Units 1 and 2 were subject to TS 3.0.3 at about 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on February 25, 1991, when the CRAVS was declared to be inoperable. The interim response includes removal of motive power from the valve operators, thus providing for manual control by operators as required.
The permanent response involves a modification which cannot be implemented until the Technical-Specifications are amended.
4 The staf f finds that f ailure to grant the Temporary Waiver of Compliance and the essociated amendment in a timely n.anner would have resulted in the shutdown of both units on February 25, 1991, until such time as the proposed changes to the TS could be granted.
We also find that the licensee could not reasonably have avoided this situation, that the licensee has responded in a timely manner, and has not delayed its application to take advantage of the Energency Licensee Amendments provision of 10 CFR 50.91. Accordingly, the staff concludes that the licensee has satisfied the requirements of 10 CFR 50.91(a)(5) and that a valid-emergency exists.
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4.0 CONCLUSION
The staff has concluded, based on the considerations discusseo above, that (1) the amendment does not (a) significar,tly increase the probability or consequences of an accident previously evaluated, (b) create the possibility of a new or different kind of accident from any previously evaluated or (c) significantly reduce a safety margin and, therefore, the amendment does not involv significant hazards consideration; (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conaucted in compliance with the Commission's regulations, and the issuance of these amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
P. Madden, PSB R. Martin, PDII-3/DRPE Dated: March 6, 1991
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