ML19268B968

RO 77-30/1P:on 771216,B&W Informed Met Ed That Software Used to Calculate Incore Imbalance Was in Error,In That Background Correction Was Misapplied as Detector Depletes. Error Will Be Corrected Prior to Cycle 4 Operation

ML19268B968
Person / Time
Site:	Three Mile Island
Issue date:	12/19/1977
From:	Ohanlon J METROPOLITAN EDISON CO.
To:
References
NUDOCS 7910250755
Download: ML19268B968 (1)

Text

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POST OFFICE BOX 480 MaDDLETOWN PENNSYLVANIA 17057 1ELEPHONE 717 944.4 041 19 December 1977 Mr. Boyce H. Grier Directorate of Regulatory Operations Region I '

Nuclear Regulatory Commission 631 park Avenue King of Prussia, pennsylvania 19406 Operating License DPR-50 Docket 50-289

Subject:

Reportable occurrence No. 77-30/1P Dcar Mr. Grier:

This telegram is to confirm the telecon between Mr. G. A. Kunder.

Unit I Superintendent. Technical Support, and Mr. P. J. Kellogg, Region I-NHC at 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> on 16 December 1977.

In accorda. ice with Technical Specification 6.9.2.A.8 we are re-porting that an error was found in the computer software methods used to calculate incore imbalance.

On 16 December 1977, Metropolitan Edison Company was informed by -

the MSS Supplier, B&W. that.the software used to calculate incorc imbalance was in error, in that the background correction was misapplied as the actcc-tor depletes throughout life.

This error could have permitted reactor operation in a manner less conservative than assuined in the safety enalynes. During the first part of Cycic 3 (0-100 ETPD) the positive operating imbalance l i m i t- should have been reduced 2.5* imbalance to assure adequate margin.

Adequate margin does exist in current posi tive imbalance set points to cover the bias induced by the software error for the remainder of the present cycle.

Corrective action which will be taken ia to correct the error prior to cycle 4 operat2on.

Very truly yours, J. P. O'Hanlon Unit I Superintendent 7910250 7 6 8 [