ML19257A317

Submits Info Re Deficiency Found on 791207 Re Nonconservatism in Method Used to Generate Power Distributions & Rod Worths for Dropped Rod Events.New Analysis Performed Using More Conservative Model

ML19257A317
Person / Time
Site:	North Anna
Issue date:	12/11/1979
From:	Brown S VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
References
1116, NUDOCS 8001030725
Download: ML19257A317 (2)

Text

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VIRGINS A ELECTRIC AND POWER COMP ANY, RICMMON C. VI RGINi a 23261

- [ q l3 A j; 24 December 11, 1979 Mr. James P. O'Reilly, Director Serial No. 1116 Office of Inspection & Enforcement PSE&C/JCHjr:mac: wang U.S. Nuclear Regulatory Comission Region II Docket No. 50-339 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303

Dear Mr. O'Reilly:

On December 7,1979 a report was made under the provisions of 10CFR50.55(e) concerning the Departure from Nucleate Boiling Ratio (DNBR)

Limit.

In accordance with the reporting requirements of 10CFR21, the following information is submitted:

A. Name and address of reporting individual:

Mr. E. A. Baum, Executive Manager Licensing and Quality Assurance Virginia Electric and Power Company P. O. Box 26666 Richmond, Virginia 23261

8. Facility, activity and/or component affected:

North Anna Power Station, Unit 2

. DNBR Limit C. Name of firm constructing the facility or supplying the component, activity or service:

Westinghouse Electric Corporation, P. O. Box 355 Pittsburgh, Pennsylvania 15230 D. Description of defect, deficiency, or failure to comply:

A nonconservatism was found in the method used to generate power distributions and rod worths for dropped rod events. New analyses have been performed using a more conservative reactivity feedback model and the results indicate that certain multiple rod drop events may not trip the reactor as previously assumed.

E. Date of determination of reportability: -  %

December 7, 1979 lffg 3j4 WT 8 0 010 3 0 [$m4;.cnev $~~^

, F. Similar components, activities, or services: >

, North Anna' Unit 1 G. Corrective action which has been, is being or will be taken, the individual responsible and the length of time to complete the action:

The corrective action is to implement the following procedural solution when applicable.

Manual Rod Control 0-100% Power: No change from current rod insertion limit.

(i.e., Technical Specification 3.1.3.6, North Anna 2)

Automatic Rod Control 0 to 90% Power: No change from current rod insertion limit.

(i.e., Technical Specification 3.1.3.6, North Anna 2) 90 to 100% Power: D bank greater than 215 steps.

The benefit of this solution is that it will minim'ze a power overshoot for rod drop events and preclude potential DNBR limit violations. We are also continuing our review of this problem for possible implementation of

, long term solutions which may be more desirable.

H. Other information:

None Any information not available at this time will be submitted in a follow-up letter as a 30-day report.

Should you require further information, please contact this office.

Very truly yours fYV/ W h.< --s dI Sam C. Brown, Jr.

Senior Vice President - Power Station Engineering and Construction cc: Director, Office of Inspection and Enforcement (3) 1668 315 e

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