ML20029A704
| ML20029A704 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 02/27/1991 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20029A702 | List: |
| References | |
| NUDOCS 9103040083 | |
| Download: ML20029A704 (3) | |
Text
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jg UNITE D sT ATEs NUCLE AR REGULATORY COMMISSION g
W A&HING T ON, D. C. 70666
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$AFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION i
RELATED TO AMENDMENT NO.117 TO FACILITY OPERATING LICENSE NPF 9 1
AND AMENDMENT NO. 99TO FACILITY OPERATING LICENSE NPF-17 1
DUKE POWER COMPANY MCGUIRE NUCLEAR STATION, UNITS 1 AND 2 DOCKET N05. 50 369 AND 50 370
1.0 INTRODUCTION
By letter dated December 19, 1990 as supplemented February 15, 1991, Duke Power Company (the licensee) requested amenoments to the Technical Specifications (TSs) appended to facility Operating License Nos. NPF-9 and NPF-17 for the McGuire Nuclear $tation, Units 1 and 2.
The proposed amendments would reduce from 751 to 50% the number of moveable incore detector thimbles required for the Moveable Incore Dctection System to be operable. The amendments are applicable only to McGuire Unit 1, Cycle ?.
The supplemental inf ormation provided by letter dated February 15, 1991, was clarifying in nature and did not affect the scope of the noticed action or the staff's proposed no significant hazards consideration determination.
These changes would allow continued operation of Unit I should the current problem with sticking detector thimbles become worse.
2.0 EVALUATION Essentially all PWR Technical Specifications contain a requirement for operability of 75% of the incore detector locations for periodic mapping of the core power distribution. On a number of occasions, for various reasons, failures of thimbles in operating PWRs have approached or exceeded the 25%, and relaxation of the 75% requirement has been permitted for the duration of the affected operating cycle.
The licensee's proposed change allows for the increase in the moveable incore map measurement uncertainty on Fq above the 5% normal allowance by the relationship 5% + [3-T/12.5)2%, where T is the number of unfailed detectors.
d This relationship increases the uncertainty allowance to 7% when half the
-thinibles are used. The uncertainty in the measurement of F delta H is 41 and is proposed to increase to 5% if only half of the detectors are used.
These allowances are similar to those used for other reactors.
9103040083 910227 PDR ADDCK 05000369 P
2 The licensee has provided the results of recent core maps which show that thare currently is erproximately 5% margin in F delta H to the Technical Specification limits for steady state operating conditions.
Since the unit does not loed follow and the peaking factors normally tend to decrease with burnup, we would expect the cargin to increase from now till the end of cycle.
Recently, the licensee has had to take additional penalties on the measured total peaking factors Fq.
These penalties are an approximate 5% for uncertainty in the LOCA analysis and a 2% penalty due to Technical Specification 4.2.2.2.(e).
There will be the additional penalty due to using fewer than 75% of the incore detectors. The licensee has stated that, in spite of these, the total Fq limit will be met by reducing the axial cffset limit. Furthermore, the licensee stated that the measured Fq will continue tc decrease throughout the remainder of the cycle, and that the Westinghouse analysis for operation with fewer than 75% thimble detectors is still valid with the additional LOCA analysis penalty and the 2% penalty.
Another safety concern relating to degradation of incore mapping ability is the ability to detect anomalous conditions in the core.
One of these is inadvertent loading of a fuel assembly into an improper position.
Since this is a loading problem, it is not of concern for the remainder of the operating cycle. Other anomalous conditions are conceived to produce either an axial or radial effect, which woulo cause either a change in quadrant tilt ratio or axial offset ratio.
These are mcaitored by the excore detectors that would help identify problems not fully detectable with reduced incore mapping capability. Furthermore, the core exit thermocouples in the reactor provide a useful supplement to the incore detectors to octect problen.s.
Jf one of the power range neutron flux detectors (excore detector) is inoperable power operation n.ay continue if the power level and the trip setpoint are reduced or the quadrant tilt is monitored by the incore detectors every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
During operation with fewer than 75% of the incore detectors operable, the lower power option must be the one used.
Our review of the suitability of operation of the McGuire Nuclear Station Unit i reactor for the remainder of the Cycle 7 with a reduced number of movable incore thimble locations to as few as 50% indicated that adequate margin exists at this time in Cycle 7 and sufficiently increased uncertainty allowances have been made to ensure that Technical Specification peaking f actor limits will be met.
In addition, there are adequate supplemental indicators of anomalous conditions to preclude an unsafe condition from escaping detection in the absence of f ull incore detector mapping capability.
Based on the above considerations we conclude that the proposed Technical Specification changes are acceptable.
The licensee has agreed to go to the lower power option if one excore detector is inoperable. Also the licensee will use all available thimbles on each map taken.
.3 3.0 (NVIRONkfNTALCONSIDERATION r
lhese aniendments involve changes in requircments with respect to the installation or use of frcility components located within the restricted area as defined in 10 CFR Part 20 and changes in surveillance requirements.
The staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, cf any effluents that may be released offsite and that there is no significant increase in individual or cumulative occupational 4
radiation exposure.
The Comission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public coment on such finding.
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental imptet statement or environntental assessment need be prepared in connecti(1 with the issuance of these amendm(nts.
4.0 C0kCLUSION 4
The Commission's proposed determination that the amendments involve no significant hazards consideration was published in the Federal Register (56 FR 2957) on January 25, 1991.
The Comission consulted with the State of North Carolina.
- he public coments were received, and the State of North Carolina did not heve any comments.
The sta'r has concluded, based on the consiocrations discussed above, thats (1) thers is reasonable assurance that the health and safety of the-public will not Le endangered by operatiun in the proposed manner, and (2) such activities will be conducted in compliance with the Comission'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 Contributors it. Chatterton, DST /SRXB Dated February 27, 1991 1
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