ML19294B170

Ro:On 800207,control Rod Withdrawal Inhibit on Intermediate Power Level Period Recorder Found Set at Less than 30-s Setpoint.Caused by Nut Loosened During 800207 Maint Allowing Setpoint to Be Changed During Channel Check

ML19294B170
Person / Time
Site:	05000054
Issue date:	02/18/1980
From:	Ruzicka W UNION CARBIDE CORP.
To:
References
NUDOCS 8002270392
Download: ML19294B170 (2)

Text

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% UNION CARBIDE CORPORATION MEDICAL PRODUCTS DIVISION P.O. BO X 324 TUXE DO, NEW YO RK 10987 TELEPHON E: 914-351 2131 February 18, 1980 Mr. Boyce H. Grier U. S. Nuclear Regulatory Commission Office of Inspection & Enforcement, Region 1 631 Park Avenue King of Prussia, PA 19406

Dear Mr. Grier:

Mr. E. B. McCabe of your office was notified via tele-phone on February 8, 1980 of a Technical Specification re-quired Limiting Condition for Operation setpoint being out of adjustment. A confirming telecopy was also sent to you on February 8, 1980. Technical Specification 6.5. 3.a. (3) (b) re-quires this report to the Commission following any operation exceeding any Limiting conditions for Operation as established in the Technical Specifications.

At approximately 2400 hours0.0278 days <br />0.667 hours <br />0.00397 weeks <br />9.132e-4 months <br /> on February 7,19 80, 'the con-trol rod withdrawal inhibit on the intermediate power level period recorder was found to be set at less than the 30 second setpoint as required by Technical Specification Section 3.2.3.

The reactor was shut down and the on-call Senior neactor Oper-ator (in this care the Reactor Instrument Technician) was con-tacted. The Senior Operator directed that the setpoint be adjusted and tested and the reactor returned to power. During the time the reactor was operated with the out of adjustment setting, the reactor was protected by its redundant safety system design. The intermediate range 10 second reverse en,d 3 second scram setpoints were at all times correctly set.

2:ais protection along with the count rate 30 second period in-hibit and the power level reverse and scram provided adequate reactor protection.

The improper setpoint is believed to have existed during no more than six hours of reactor operation. On February 7 at 0800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br />, the reactor was shutdown for refueling and maintenance, including maintenance on the intermediate power level channel. Following this, the reactor console checklist (Reactor Standard RS-01) was completed which checked satis-factorily 'he 30 second inhibit setpoint. During subsequent operation, the console operator observed that rod withdrawal was not inhibited as it should have been when he reached a 30 0 second period. It has been postulated that a nut may have dY

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i Mr. Boyce H. Grier - Page 2 -

U. S. Nuclear Regulatory Commission February'18, 1980 L

been loosened during maintenance which then allowed the set-point to be changed during the performance of the channel check. This would have allowed the channel check to be per-

, formed satisfactorily and at the same time misadjusted the setpoint. All similar equipment has been checked for proper tightness. This has not been a recurring occurrence and is

, considered an isola' 2 event.

The Senior Reactor Operator on call should have techni-cally been present for the restart. However, he was of the understanding that the reactor was simply subcritical at the time of the call and not yet fully shutdown. After the set-point was adjusted and retested, he believed that he was authorizing a return to power and not a complete startup.

His presence at this particular startup would not have had a significant effect on reactor safety. Had this not been the case, he would have been present regardless of his under-standing of the reactor power level. This occurrence is being discussed with all operators to emphasize the import-

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ance of thorough communications and strict adherence to operating procedures.

Sincerely,

u. s. 62niJ~-

WGR:ltm J. G. Ruzicka Reactor Project Engineer cc: Mr. M. H. Voth Manager Nuclear Operations O

e e