ML20056F706

Responds to Notice of Violation & Proposed Imposition of Civil Penalty for Insp Rept 50-271/93-09 on 930414-16 & 0511.Corrective Actions:Controlling Procedure OP-4424, CR Scram Testing & Data Reduction Revised

ML20056F706
Person / Time
Site:	Vermont Yankee
Issue date:	08/24/1993
From:	Pelletier J VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BVY-93-89, NUDOCS 9308300289
Download: ML20056F706 (5)

Text

VERMONT YANKEE NUgLEAR POWER CORPORATION Or-Ferry Road, Brattleboro, VT 05301-7002 ,

k ) ENGINEERING OFFICE

,g M0 MA;N STREET BOL TON. M A C170 (50B!?79 0711 August 24,1993 BVY 93-89 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555

References:

a) License No. DPR-28 (Docket No. 50-271) b) Letter, USNRC to VYNPC, Notice of Violation and Proposed imposition of Civil Penalty - Inspection Report No. 50-271/93-09, dated 8/2/93

Subject:

REPLY TO A NOTICE OF VIOLATION -INSPECTION REPORT NO. 50-271/93-09 This letter is written in response to Reference (b) which documents that our activities were not conducted in full compliance with NRC requirements. The violations, classified in the aggregate as Severity Level 111, were the result of a safety inspection conducted on April 14-16,1993 and completed in the NRC Region I office on May 11,1993. This inspection was conducted to review the circumstances associated with the failure to properly evaluate scram timing test data, the failure to take corrective actions for a condition adverse to quality, and the earlier occurrence of a violation of Technical Specifications (T/S) for which the plant was not shut down as required. The inspection Report was transmitted to Vermont Yankee on May 24, 1993. On June 15,1993, an enforcement conference was held in the Region I office wi+h your staff to discuss the potential violations, their causes and our corrective actions. Our response to the Notice of Violation is provided below. j VIOLATION:

10 CFR Part 50, Appendix B, Criterion XI, " Test Control," requires in part that the test results be evaluated to assure that test requirements have been i satisfied.

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U.S. Nuclear Regulatory Commission August 24,1993 i Page 2 Contrary to the above, on October 15,1992, following the scram time testing of the control rods, the test results were not evaluated adequately to assure that test requirements have been satisfied. Specifically, the average scram insertion time for one two-by-two array for notch 46 exceeded the time required by Technical Specification 3.3.C.1.2, but the subject array was considered acceptable based on a successful second scram time test without '

an adequate evaluation of the first test failure.

RESPONSE

Based on our root cause analysis, this violation occurred due to lack of specific guidance in the procedure controlling the surveillance activity combined with an approach to control rod testing that historically focused on establishing the "as-left" operability for the next surveillance interval rather than a focus on establishing the "as-found" condition of the control rod drive system.

The controlling procedure, OP-4424, " Control Rod Scram Testing and Data Reduction" was revised on April 16,1993 to require the use of "as-found" data for ,

determination of T/S compliance. Specific direction is now provided for when a -

control rod may be retested and under what conditions the retest data may be used for T/S compliance. In addition, OP-4424 now requires the preparation of an evaluation report which details the results of the test data, assesses current margin to T/S limits and requires an analytical projection of anticipated test results for the next ,

surveillance interval. Full compliance was achieved on April 16,1993 following our l evaluation of control rod scram data.

VIOLATION:

10 CFR Part 50, Appendix B, Criterion XVI, " Corrective Actions," requires, in part, that in case of significant conditions adverse to quality, measures shall assure that the cause of the condition is determined and corrective action taken to preclude repetition.

Contrary to the above, on October 15,1992, the average control rod scram  ;

time for a two-by-two array was in excess of the Technical Specification limits, l a significant condition adverse to quality, but the licensee did not take any l measures to determine the cause of the condition and corrective actions to preclude repetition. (Subsequently, on April 6,1993, the control rod scram times for core-wide average and seven two-by-two arrays exceeded the Technical Specification limits). ,

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U.S. Nuclear Regulatory Commission August 24,1993 Page 3 RESPONS_E:

The October 15, 1992 surveillance testing was the first time Vermont Yankee attempted to apply the "as-found" criteria to control rod scram data. The October test data revealed that one two-by-two array did not meet the technical specification criteria for the "as-found" condition, but did meet the criteria in the "as-left" condition.

The "as-left" data was erroneously used to evaluate CRD performance when it was combined with previous scram data onto a single historical trend plot. The condition adverse to quality was not recognized because it was not readily apparent using our historical trending methodology, that a degradation in scram time performance had occurred. Our subsequent root cause analysis has shown that our various testing and

. plotting methodologies were flawed and produced historical trends that were of questionable value.

In April 1993, because of continuing degradation of scram time data, a task team was 4

assembled in order to identify the root cause. Through extensive testing, the task team concluded the cause of the slow scram times to be degraded scram solenoid pilot valve (SSPV) components. In addition, the task team concluded that our single rod scram testing methods produced overly-conservative test data due to a test method which did not ensure simultaneous de-energization of both SSPV solenoids.

The immediate corrective action was to replace the internal components of all 178 SSPV's. All control rods were subsequently retested and marra times were verified to be within Technical Specification requirements. As stataa s.rlier, Vermont Yankee has made or has committed to make the following prograra enhancements;

, 1) OP-4424 surveillance procedure has been revised to require entry of a Work

. Order Request number on the surveillance data sheet for any control rod drive

. that was retested due to poor performance to ensure that there is proper maintenance follow-up.

2) Administrative limits have also been developed to provide early indication should the margin to T/S limits be diminished in any way. These limits are currently in review and will be added to OP-4424 by September 1993.

3) An enhanced trending / performance monitoring program for scram test data is being developed.

4) The overly-conservative test data (due to the non-simultaneous de-energization of both SSPV solenoids) will be evaluated further during the 1993 refueling outage.

. n usu,si nsu t xn mn viewi n c..m. m u nes U.S. Nuclear Regulatory Commission August 24,1993 Page 4 Corrective actions to prevent recurrence were implemented on April 16,1993 with the ,

revision to procedure OP-4424, " Control Rod Scram Timing and Data Reduction". In addition, Vermont Yankee has generated and subsequently dispositioned two (2) ,

extensive corrective action reports (CAR) with numerous recommendations being i tracked internally.

VIOLATION:

Vermont Yankee Technical Specification Limiting Conditions for Operation (LCO) Sections 3.3.C.1.1 and 3.3.C.1.2 state, in part, that the average of the scram inseition times for the three fastest control rods of all groups of four ,

control rods in a two-by-two array shall be no greater than 0.379 seconds for  :

drop-out of position No. 46.

Vermont Yankee Technical Specification LCO Section 3.3.C.3 states, in part, that if specification 3.3.C.1.2 cannot be met, the reactor shall be shut down immediately upon determination that the average scram time is deficient.

Vermont Yankee Surveillance Procedure OP-4424, " Control Rod Scram Testing and Data Reduction," Revision 15, Final Conditions No. 4 and 6 state that if the scram time results are not within the limits specified in Technical Specification 3.3.C.1.2, the reactor, if operating, will be brought to hot shutdown.

Contrary to the above, on October 15,1992, the average scram time for the  !

three fastest control rods in one two-by-two control rod array was 0.391 l seconds (thus, greater than 0.379 seconds for drop-out of position No. 46) and I the reactor was not brought to hot shutdown, but continuously operated at I power in this condition until April 7,1993, when it was shut down for an )

unrelated issue. i RESPONSE; Based on our root cause analysis, this violation resulted from an incorrect interpretation of a Technical Specification Limiting Condition for Operation.

A Potential Reportable Occurrence (PRO) was initiated on October 15,1992 because I of the failure of one (1) two-by-two array to meet the T/S notch 46 limit. During the evaluation of the PRO, Vermont Yankee learned that our cycle-specific transient analysis utilized the full core average scram time of all 69 control rods but net explicitly the two-by-two array averages. Vermont Yankee incorrectly concluded that because the two-by-two limits are not explicitly used in the transient analysis that the

.. . vunu,u vour mu m e,,w i a o,im<,n u n s U.S. Nuclear Regulatory Commission August 24,1993 Page 5 T/S 3.3.C.1.2 LCO applied only to the full core average of all 89 control rods.

Technical Specification Section 3.3.C.3, the LCO requiring shutdown, was not entered because it was incorrectly concluded that T/S 3.3.C.1.2 was satisfied.

Initially, the appropriate personnel were instructed on the correct interpretation of T/S Section 3.3. Formal training on this issue will be conducted by December 1993.

Additionally, Technical Specification Section 3.3 is being reviewed to determine if enhancements should be made to improve clarity. This activity is scheduled to be completed by October 1993. Based upon the results of the review a Technical Specification proposed change may be submitted.

The plant shutdown which occurred on April 7,1993 and the subsequent corrective actions discussed previously, returned the plant to full compliance with station ,

Technical Specifications. '

l At the earliest opportunity, a self assessment will be performed to evaluate the  ;

corrective actions implemented relative to the scram timing issue to confirm the '

effectiveness of our corrective actions taken to preclude recurrence. This is expected  ;

to occur following our Refueling Outage which begins on August 28,1993.

As instructed by the Notice enclosed with Reference b), Proposed imposition of Civil Penalty, an electronic transfer was completed on August 24,1993.

We trust that the information provided is adequate; however, should you have i any questions or require additional information, please do not hesitate to contact us.

Sincerely, Vermont Yankee Nuclear Power Corp.

w PRL Q mes P. Pelletier Vice President, Engineering cc: USNRC Regional Administrator, Region l USNRC Resident inspector, VYNPS USNRC Project Manager, VYNPS