ML20213C789
| ML20213C789 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 03/11/1986 |
| From: | Tucker H DUKE POWER CO. |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 8611100280 | |
| Download: ML20213C789 (2) | |
Text
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DUKE POWER Goxiwxy 18.0. HOX 33180 CIIAHLOTTE, N.C. 28242 n^i.a.-
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March 11, 1986 i
Dr. J. Nelson Crace, Regional Administrator U. S. Nuclear Regulatory Comaircion Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Ret Catawba Nuclear Star on. Unit 1 Docket No.
M icalgcificationLCO
Dear Dr. Grace:
4 This letter constitutes written followup of a request for temporary waiver of Technical Specification requirements which was made (and subsequently granted) via telecons between Duke Power Company personnel and members of your staff on March 10, 1986. This) temporary emergency relief from compliance with Technical Specification Limiting Conditions for Operation (LCO) was requested to avoid unnecessarily shutting down Catawba Unit I since the LCO would have been exceeded at 9:30 A.M. on March 11, 1986.
The proposed relief request was a result of the need to replace the carbon bed in the Unit 1. Train B, Auxiliary Building Filtered Exhaust (VA)
System. The amount of time needed to replace the carbon bed would have exceeded the Technical Specification allowed outage time (reference specification 4.7.7.C).
The carbon bed was identified as defective at 9:30 A.M. on March 10, 1986 when the sample results from the laboratory analysis showed that the methyliodide removal efficiercy was 98.64% instead of the
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required 99%. The amount of time needed to replace the carbon bed and functionally test it would have exceeded the allowed outage time.
Providing an additional 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> allow the carbon bed replacement to be made and the system to be restored to operability status without having to place the unit in Mode 4.
The sole function of the VA system is to filter the airborne radioactivity released from coolant leakages associated with the ECCS equipment in the Auxiliary Building, following a LOCA involving severe fuel damage.
The off-aite doses associated with ECCS leakages post LOCA have been evaluated in the Catawba FSAR (Section 15.6.5 and Table 15.6.5-10).
The contribution of ECCS leakages to the off-site doses, post LOCA, is not significant with or without VA filtration before release to the environment. Furthermore, during the period of inoperability of the B Train carbon bed, the 100% capacity, totally redundant A Train carbon bed will remain operable and capable of filtering the safety train ECCS pump rooms for Unit 1.
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'Dr. J. Nelson ca, Regionni' Ad::inictrctor March 11, 1986 Page 2 The duration of operation without Unit I having its VA Filtered Exhaust System totally operable would be small (less than 120 hours0.00139 days <br />0.0333 hours <br />1.984127e-4 weeks <br />4.566e-5 months <br />). The probability of occurrence of a LOCA during this time is extremely small.
l For example, the LOCA frequency for a large break with potential for core heatup is 4.7xE-5 per reactor year (see Sequoyah RSSMAP-NUREG/CR-1659).
The probability of a large break LOCA during a 120 hour0.00139 days <br />0.0333 hours <br />1.984127e-4 weeks <br />4.566e-5 months <br /> period is less than 9.0xE-7.
The probability of excessive ECCS leakages subsequent to a LOCA is even smaller. Therefore, granting this request does not pose undue risk to the health and safety of the public. An equally important reason for granting the proposed change is that one thermal cycle on the reactor and associated systems is avoided. This has real benefits in terms of availability, component lifetime and safety.
A permanent change to the Catawba Technical Specifications will be pursued.
Justification will be provided which will allow the VA System to be inoperable for up to 7 days. This allowed outage time is consistent with the NRC's Standard Technical Specifications, Revision 4 and Draft Revision 5.
Very truly yours, 8/
n Hal B. Tucker 1
RWO: sib i
l cc:
Mr. Harold R. Denton, Director l
Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555 NRC Resident Inspector Catawba Nuclear Station l
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