ML20137F909

Responds to Violations Noted in Insp Repts 50-369/85-20 & 50-370/85-21.Corrective Actions:Startup Procedure Changed to More Restrictive 0.5 DPM Limit & Xenon Prediction Program Error Corrected

ML20137F909
Person / Time
Site:	Mcguire, McGuire
Issue date:	08/07/1985
From:	Tucker H DUKE POWER CO.
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 8508270123
Download: ML20137F909 (7)

Text

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DuxE POWER GOMPANY P.O. Box 33189 CHARLOTTE N.C. 28242 HAL B. TUCKER . - TE s.E PIEONE

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- nlu ., 9 y August 7, 1985 Dr. J. Nelson Grace, Regional Adminstrator U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30302

Subject:

McGuire Nuclear Station Docket No. 50-369, 50-370

Reference:

RII: CAP /PTB NRC/01E Inspection Report 50-369/85-20, 50-370/85-21

Dear Dr. Grace:

Pursuant to 10 CFR 2.201, please find attached a response to violations which were identified in the above referenced Inspection Report.

Very truly yours, Y /

Hal B. Tucker WHM/hrp Attachment cc: Mr. W. T. Orders Senior Resident Inspector - NRC McGuire Nuclear Station BSOS2701g3850807pg9 PDR ADO K 050 (

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Duke Power Company McGuire Nuclear Station Responses to NRC/0IE Inspection Reports 50-369/85-20 and 50-370/85-21 Violation 370/85-21-01, Severity Level IV Technical Specification 6.8.1.a requires that written procedures shall be established, implemented, and maintained covering general plant operating procedures.

Contrary to the above, this requirement was not met in that:

a. On May 17, 1985, at approximately 0600 hours0.00694 days <br />0.167 hours <br />9.920635e-4 weeks <br />2.283e-4 months <br />, the startup rate limit of 1.0 decade per minute (dpm) specified by procedures OP/2/A/6100/01 and OP/2/A/6100/05 was exceeded by 0.3 dpm.

b. On May 17, 1985, at approximately 1149 hours0.0133 days <br />0.319 hours <br />0.0019 weeks <br />4.371945e-4 months <br />, operating procedure, Reactivity Balance Calculations (Estimated Critical Rod Position, Enclosure 5.2, OP/0/A/6190/06), was not followed in that the dilution required by Enclosure 5.1 was not performed nor was the procedure changed to delete the dilution requirement. The reactor startup continued with a predicted critical rod position of 228 steps on bank D. The actual critical rod position occurred at 90 steps on bank D.

Response to A:

1. Admission or denial of the alleged violation:

Duke Power agrees that the violatien occured as stated.

2. Reasons for the violation:

This violation occured due to an operator pulling rods too close to the procedural limit with the start up rate indication being in an erratic range. This resulted in the excess start up rate occuring.

3. Corrective steps which have been taken and the results achieved:

The start up procedure has been changed to a more restrictive .5 DPM limit. This limit has not been exceeded in subsequent start ups.

4. Corrective steps which will be taken to avoid further violations:

Shift supervisors and operators will be reminded of the procedure change in supervisor and crew meetings.

5. Date when full compliance will be achieved:

McGuire Nuclear Station is presently in full compliance.

Response to B:

1. Admission or denial of the alleged violation:

Duke Power agrees that the violation occured as stated in Licensee Event Report 50-370/85-14.

2. Reasons for the violation:

The first criticality on 5/17/85 occurred below the hot zero power (HZP) insertion limits, and the estimated critical rod position (ECP) was missed by N1000 pcm. Because of confidence in all other data used by the ECP calculation (OP/0/A/6100/09), personnel considered xenon worth to be the factor most likely causing the large ECP error. Personnel were reluctant to immediately change the xenon worth model for two reasons. First, the xenon worth model for that cycle was based on the model for the previous cycle on Unit 1 for which there was much confindence at the time. Second, for confidence personnel generally desire to get more than one set of criticality data before adjusting reactivity param-eters. Therefore, the xenon model was not changed at that time.

Prior to the second criticality on 5/17/85, reactor coolant system boron concentration was increased to 41025 ppm for Shutdown Margin considerations.

Personnel performed an ECP calculation using this boron concentration and the same xenon model used for the first criticality of 5/17/85.

The calculation's results were that criticality probably would not occur with all-rods-out and to perform an estimated critical boron concentration (ECB) calculation. Personnel performed an ECB calculation and its results were that if criticality at 100 steps was desired a boron concentration of 942 ppm was necessary.

At that time, two alternatives appeared available. One alternative was to dilute the reactor coolant system from 1025 to 942 ppm as indicated by the ECB calculation. This alternative increased the risk of a second criticality below the insertion limits if the apparent xenon worth model error repeated itself on the second criticality. The second alternative was to remain at the current boron concentration of 1025 ppm and attempt criticality. If the apparent xenon worth model error repeated itself, criticality would probably occur at N100 steps on Control Bank D. This alternative maximized the margin for safety during the start up while allowing for criticality at a reasonable rod position if the apparent xenon worth error repeated itself.

Personnel felt that the procedure allowed either of the two alternatives without a procedure change. The second alternative was determined to be the better alternative. All the plant personnel necessary to obtain a temporary procedure change verbally approved of the second alternative.

Two licensed reactor operators, three licensed senior reactor operators (including the acting Superintendent of Operations), the Performance Engineer, and a Reactor Group member gave verbal approval of the second alternative.

The second criticality occurred at 90 steps on Control Bank D. This

provided a second set of criticality data for estimating actual xenon worth; this data confirmed the xenon model error of N1000 pcm.

3. Corrective steps which have been taken and the results achieved:

When the reactor was found to be critical with the rods below insertion limits, operators reinserted the control banks per the Unit Fast Recovery procedure. They also added boric acid to regain shutdown margin being lost by xenon decay.

4. Corrective steps which will be taken to avoid further violations:

Reactor Group personnel performed a thorough analysis of the missed ECP and found the xenon prediction program to be in error. They traced the history of the xenon prediction program back through the Unit 1 Cycle 2 period and discovered the errors that led to this event. They then corrected the program. The Reactor Group has prepared a procedure to ensure changes to the Xenon Prediction Program will be thoroughly reviewed and analyzed.

Operating procedures have been modified to limit the stable startup rate to 0.5 DPM. This cuts the previous limit in half. Operating procedures have been modified to include a blank space wherein the insertion limits must be listed. This change gives operators immediate access to this information during startup. Operating procedures have been modified to give operators the option to add boric acid and withdraw control rods to maintain criticality when it is achieved with the control rods below insertion limits. This was always allowed by Technical Specifications but the procedures were more limiting.

5. Date when full compliance will be achieved:

McGuire Nuclear Station is presently in full compliance.

Violation 369/85-20-01 and 370/85-21-02, Severity Level IV 10 CFR 50 Appendix B, Criterion V as implemented by DCP Administrative Policy Manual Section 4.2, requires that activities important to safety such as calculating critical rod position or verifying reactorshutdown margin be accomplished in accordance with instruction and procedures appropriate to the circumstances. Changes to these procedures, including curves, figures, tables and other data which are employed directly in the procedure are required to be technically valid and receive the same rigorous review and approval, including the review required by 10 CFR 50.59.

Contrary to the above requirements, on August 27, 1984, April 24, 1985, and May 17, 1985, changes were made to the Xenon Follow / Predict computer program and the computed values were utilized in an operating procedure with no nuclear safety evaluation to determine if an unreviewed safety question existed prior to use.

Response

1. Admission or denial of the alleged violation:

Duke Power agrees that the violation occurred as stated.

2. Reasons for violation:

The McGuire 1 Cycle 2 xenon worth model was changed with a McGuire 1 Operator Aid Computer Program Request dated 9/27/84. It was not a practice to prepare a Nuclear Safety Evaluation Checklist (NSEC) for changes to this model, and thus a NSEC was not prepared. However, the significance regarding nuclear safety of this change was fully understood and evaluated at the time. This change to the McGuire 1 Cycle 2 xenon worth model was in error; this faulty model was used to provide xenon worths for Shutdown Margin surveillance between 9/84 and 4/85 when Cycle 2 ended.

The original McGuire 2 Cycle 2 xenon worth model was created by 4/24/85.

This model was placed on the McGuire 2 Operator Aid Computer (OAC) on 5/8/85. A NSEC was prepared for this original xenon worth model; however, it was lost and no credit can be taken for its preparation. This model was determined to be in error on 5/17/85 after two criticalities significantly missed their ECP's. This faulty model was used to provide xenon worths for Shutdown Margin surveillance on 5/16/85 and 5/17/85.

A revised McGuire 2 cycle 2 xenon worth model was created and placed on the McGuire off-line computer on 5/17/85. This revised xenon worth model was scheduled to be put on the McGuire 2 OAC as soon as possible. Until it was on the OAC, the off-line version was availabic if needed; the off-line version was not needed and not used for Shutdown Margin surveillance.

3. Corrective steps which have been taken and the results achieved:

The revised xenon worth model was placed on the OAC and a NSEC was prepared for it on 5/22/85.

4. Corrective steps which will be taken to avoid further violations:

A procedure to change the xenon and/or samarium worth coefficients on the OAC was prepared by 5/31/85 and approved on 6/12/85. This procedure requires the preparation of a NSEC and Duke Power, Nuclear Design unit review prior to use of the new xenon and/or samarium worths from the OAC.

5. Date when full compliance will be achieved:

McGuire Nuclear Station is presently in full compliance.

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Violation 369/85-20-02 and 370/85-21-03. Severity Level IV Technical Specification (TS) 6.10.1.d requires that records of surveillance activities, inspections, and calibrations required by TS shall be retained for at least five years.

Contrary to the above, this requirement was not met in that the plant procedure used to perform the shutdown margin as required by TS 4.1.1.1.1.e in modes 3, 4, and 5 was not retained. The inspectors were unable to review the previous shutdown margin calculations for Unit I cycle two since August 1984 and Unit 2 cycle two in 1985 due to the records not be'ing

• retained.

Response

1. Admission or denial of the alleged violation:

Duke Power agrees that the violation occurred as stated.

2. Reasons for violation:

This violation occured due to a failure to recognize the necessary requirement.

3. Corrective steps which have been taken and the results achieved:

Daily surveillance PT's for both units were changed 6/7/85 to require retention of SDM calculations.

4. Corrective steps which will be taken to avoid further violations:

As requested in the report cover letter, a review of operating procedures did not reveal any other technical specification surveillance activities being performed as part of operating procedures rather than periodic tests.

5. Date when full compliance will be achieved:

McGuire Nuclear Station is presently in full compliance.

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