ML19308A740

Unusual Event Rept 269/75-02:on 750103,B&W Informed Util That Hot Zero Power Ejected Rod Worths Not Calculated After Control Rod Group Interchange.Caused by B&W Omission.B&W Implemented Program to Calculate Rod Worths

ML19308A740
Person / Time
Site:	Oconee
Issue date:	02/14/1975
From:	DUKE POWER CO.
To:
Shared Package
ML19308A737	List: ML19308A735 ML19308A740
References
RO-269-75-02, RO-269-75-2, NUDOCS 7912100620
Download: ML19308A740 (2)

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1 DUKE POWER COMPANY OCONEE UNIT 1 Report No.1 UE-269/75-2 Report Date: February 14, 1975

Event Date

January 3, 1975 Facility: Oconee Unit 1, Seneca, South Carolina Identification of Event: Failure to calculate the hot zero power ejected rod worth after control rod group interchange Conditions Prior to Event: Not applicable Description of Event:

On December 20, 1974, Duke Power Company was informed by the Babcock and Wilcox Company that the hot zero power ejected rod worths for the Oconee units were not calculated for core conditions after the first control rod group interchange. Af ter careful evaluation by Duke and B&W, it was determined on January 3, 1975 that this situation constituted an unusual .

event as defined by Section 1.9a of the Oconee Nuclear Station Technical I

Specificationc.

I Designation of Apparent Cause of Event:

The failure to calculate the hot zero power ejected rod worth after control rod group interchange was due to omission.

Analysis of Event:

The potential ejected rod worths in Oconee units have been measured at hot zero power and at 40 percent power during the Cycle 1 zero power physics and power escalation testing. These measurements showed that the ejected rod worths were considerably less than the limits specified by Technical Specification 3.5.2.3. An analysis of the potential ejected rod worths by B&W has shown the hot zero power ejected rod worths to be less than 1.0% Ak/k up to the time of the control rod interchange. In the case of Oconee 1, Cycle 1, this analysis also showed that the hot zero power ejected

• i rod worths were less then 1.0% Ak/k for core conditions during the entire fuel cycle. The normal unit startup procedure requires the control rod Group 5 to be partially withdrawn during criticality, fu_ther insuring that no control rod will exceed the 1.0% ak/k limit. Therefore, it is concluded that at no time have any Oconee units been in an unsafe condition with potential ejected rod worths in excess of 1.0% ak/k and that this incident did not and could not affect the health and safety of the public.

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Corrective Action:

A program has been implemented by B&W to calculate the ejected rod worths for the period after the rod interchange. In order to verify the predicted values, a test program is being developed to measure the hot zero power ejected rod worths for oconee 1, Cycle 2, at the beginning of the cycle l and at any time between 25 EFPD and immediately af ter the control rod 4

interchange. If it is not expedient to run the test between 25 EFPD and j immediately af ter the control rod interchange, the procedure for unit operation after the control rod interchange will be modified to maintain

, control rod Group 5 at a minimum of 87.5 percent withdrawn and Group 6 at 3

12.5 percent withdrawn prior to reactor criticality; this restriction will assure that Technical Specification 3.5.2.3 will not be exceeded.

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DuxE POWER COMPANY Powra Bust.orso 4aa Sourn Cucacu Srazer.CuantorTr.N.C. asaos ,

A. C. Tu n es se..o. v.a p.:s es =' P. O. Box 217e

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February 14, 1975 .

Mr. Norman C. Moseley, Director U. S. Nuclear Regulatory Commission Suite 818 230 Peachtree Street, Northwest Atlanta, Georgia 30303 Re: Oconee Unit 1 Docket No. 50-269

Dear Mr. Moseley:

Pursuant to Sections 6.2 and 6.6.2 of the Oconee Nuclear Station Technical Specifications, please find attached Unusual Event Report UE-269/75-2.

Very truly yours, a

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4. C. Thies l

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ACT:vr Attachment ec: Mr. Angelo Ciambusso 4 .

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