ML20245D448

Safety Evaluation Supporting Amend 111 to License DPR-36

ML20245D448
Person / Time
Site:	Maine Yankee
Issue date:	04/24/1989
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20245D444	List: ML20245D441 ML20245D445 ML20245D448
References
NUDOCS 8904280305
Download: ML20245D448 (2)

Text

. _ . - . _ _ _ . _ _ _ _ _ _ _ _ _ - _

J f %,

• . / c UNITED STATES

['y.,[j NUCLEAR REGULATORY COMMISSION

. ; .{ * ' ,

E WASMNGTON, D. C. 20555

.]'....,/

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.111 TO FACILITY OPEPATING LICENSE NO. DPR-36 MAINE YANKEE ATOMIC POWER COMPANY MAINE YANKEE ATOMIC POWER STATION DOCKET NO. 50-309

1.0 INTRODUCTION

By letter dated (MYAPCo) February requested 3,1989, an amendment Maine to the Yankee Technical Atomic Power Specifications (TS Company) appended to the Facility Operating License DPR-36 for Maine Yankee Atomic Power Station (MYAPS). The proposed amendment would change the TS by revising the Moderator. Temperature Coefficient (MTC) limit in the TS between the 0% and 30% power levels. Between these two power levels, the current limit is a constant 0.5 E-4 delta rho per 'F. The proposed limit is a line from 0.6 E-4 delta rho per 'F at 0% power to the current limit of 0.5 E-4 delta rho per 'F at 30% power. The MTC limit above 30%

power is unchanged.

2.0 EVALUATION Currently TS limits for allowable MTC to ensure that the safety analysis assumptions are a constant 0.5E a delta rho per 'F between 0% and 30%

power levels. For power operation below 30% power, the proposed change in the MTC limit affects only the zero power CEA Ejection analysis. A reanalysis of this transient was performed increasing the MTC to a level above the proposed limit in order to conservatively determine the impact of a higher MTC. For an increase of 50% to the maximum MTC, the resulting peak radial average enthalpy increased from 177.3 cal /gm to 187.2 cal /gm. This result is well below the 200 cal /gm threshold above which clad damage is assumed to occur. This reanalysis demonstrates that sufficient margin exists in the safety analysis to accommodate an increase in the MTC as proposed in Attachment C.

While this slightly higher peak radial averaged enthalpy contributes to a very small reduction in the safety analysis margin, it has been determined not to significantly increase either the probability or consequences associated with exceeding this threshold. At zero power BOC conditions with the proposed limit, the fraction of fuel rods experiencing clad damage remains at 0% as was reoorted in the Cycle 11 Core Perfomance Analysis Report. With the proposed change in MTC limit, there remains a substantial margin to the conservative threshold of 200 cal /gm for clad damage. The safety analysis of record for Cycle 11 8904280305 890424 DR ADOCK0500g7

. . . 7 r1 full power crrditiort remains unchanned as the result of this MTC limit 4ncreasc. The probability of the MTC limiting safety analysis transient (CEA Ejection) occurring during the six and one half days per year that Maine Yankee historically crerates at less than 30% power is deemed to be small.

The proposed cherge does not affect the Uncontrolled Rod Withdrawal analysis which is rot limiting below 80f power, nor does it affect Poron Dilution analysis which is not sensitive to power levels.

3.0 ENVIRONMENTAL CONSIDERATION

This amendment involves a change in the installat.on or use of a facility component located within the restricted area as defined in 10 CFR Part 20.

The steff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that mer tc released o'+ site, and that there is oc significant increase in individaal nr cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, thdt emendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impect statement or environmental assessment need be prepared in connection with the issuance of this amendment.

a.0 CONCLUSION We have concluded, based on the considerations above, that (1) there is reasonable assurance that the Fealth and safety of the endangered by operation in the proposed manner, and (2)public such will not activities will be be conducted in compliance with the Commission's regulations, and the issuance of the amendment will not be inimical to the common defense and security or to tFe health and safety of the public.

Principal Contributed: Patrick Sears Date: March 2, 1989 l

\

_ _ _ _ _ _ _ _ - -_ -_ _ >