ML17251A536

Responds to NRC Bulletin 88-009, Thimble Tube Thinning in Westinghouse Reactors. Worst Case Thimble Tube Only Experienced 3% Degradation Between Two Tests.Util Intends to Conduct Third Test During 1990 Refueling Outage

ML17251A536
Person / Time
Site:	Ginna
Issue date:	06/06/1989
From:	Mecredy R ROCHESTER GAS & ELECTRIC CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-88-009, IEB-88-9, NUDOCS 8906140272
Download: ML17251A536 (3)

Text

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. REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:8906140272 DOC.DATE: 89/06/06 NOTARIZED: YES DOCKET N

FACIL:50-244 Robert Emmet Ginna Nuclear Plant, Unit 1, Rochester G

05000244 AUTH.NAME AUTHOR AFFILIATION MECREDY,R.C.

Rochester Gas 6 Electric Corp.

RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Responds, to NRC Bulletin 88-009, "Thimble Tube Thinning in Westinghouse Reactors."

DISTRIBUTION CODE:

IE18D COPIES RECEIVED:LTR ENCL SIZE:

TITLE: Bulletin 88-09 Thimble Tube Thinning xn Westi ghouse Reacto NOTES:License Exp date in accordance with 10CFR2,2.109(9/19/72).

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ROCHESTER GAS AND ELECTRIC CORPORATION

~ 89 EAST AVENUE, ROCHESTER, N.Y. 14649.0001 June 6,

1989 TCa.CowOqt A%LA CODL 716 5c6.2700 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C.

20555

References:

a.

b.

License No.

DPR-18 (Docket No. 50-244)

NRC Bulletin No.

88-09:

Thimble Tube Thinning in Westinghouse Reactors Gentlemen:

Rochester Gas and Electric Corporation has completed its inspection of the R,E.

Ginna Nuclear Plant incore neutron monitoring system thimble tubes as required by NRC Bulletin 88-09 'his inspection was conducted on May 8, 1989 prior to restart from the first scheduled refueling outage since receipt of the bulletin in accordance with Item 2d of "Actions Required" of Reference (b) above.

The thimble tube inspection was conducted using the methodology specified in RG&E Procedure NDE-500-10, Revision 0,

"Multifrequency Eddy Current Examinations of 316 Stainless Steel Incore Flux Thimble Tubing."

This procedure requires the use of a

Zetec MIZ-18 Multifrequency Eddy Current Testing

System, or its equivalent, with all testing results to be stored using RG&E guidelines for permanent record retention.

The May 8, 1989 inspection results were evaluated against an acceptance criterion of 65% through-wall wear, This value is based on an analysis performed by Altran Corporation for RG&E (Technical Report 88105A-C-01')

and assumes that the wear is uniform over a 90'ircumference.

It is also consistent with the criteria for ASME Boiler and Pressure Vessel

Code,Section III, Subsection NB, Class I components.

This value contains all necessary uncertainty considerations.

All thimble tubes inspected during the May 8, 1989 test met the 65% acceptance criterion.

A thimble tube inspection similar to the May 8,

1989 test was also conducted during February 1988 in response to NRC Information Notice No. 87-44, "Thimble Tube Thinning in Westinghouse Reactors" (dated September 16, 1987).

However, the February 1988 test did not set up an inspection program, meeting the requirements of NRC Bulletin 88-09, Consequently, RG&E conducted the May 8, 1989 test to satisfy these requirements and with the intent of determining the thimble tube wear rate between the two tests and subsequently establishing an appropriate testing frequency, This testing frequency is to be based on the maximum thimble tube through-wall wear detected between tests and applied to the thimble tube whose wear is closest to the 65% acceptance criteria.

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However, RG&E does not consider two tests to be an adequate basis for determining the proper testing frequency.

As

such, RG&E intends to conduct a third test during the 1990 refueling outage for Ginna.

This time between tests is considered acceptable since the largest thimble tube through-wall wear rate between the 1988 and 1989 refueling outage tests was 10%,

Applying this wear rate to the worst case defect of 50%

through-wall wear indicates that the 65% acceptance criteria will not be exceeded prior to the 1990 refueling outage.

This is further supported by the fact'hat the worst case thimble tube only experienced a

3%

degradation between the two tests.

The. results from this third test will be analyzed and compared with the previous two tests to establish an appropriate testing frequency.

RGEE willnotify the NRC of these results following our review.

Very truly yours, Robert C. Mecr y

General Manager Nuclear= Production Subscribed and sworn to before me on this 6th day of June, 1989 Notary Public'AMES C. McGUIRE NOTAIIYPUSUC, SoLto ot Now Y04 CkuMieIinhbeoe Cary q,rt M)Ccc'Ass'ea &piss Ooc.28, IO " i MDFK017 XC:

Allen R, Johnson (Mail Stop 14D1)

Project Directorate I-3 Washington, D,C.

20555 U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406 Ginna Senior Resident Inspector