ML20206L556

Summary of 881117 Meeting W/Util Re Decision to Replace Rod Cluster Control Assemblies at Plant

ML20206L556
Person / Time
Site:	Wolf Creek
Issue date:	11/25/1988
From:	Pickett D Office of Nuclear Reactor Regulation
To:	Calvo J Office of Nuclear Reactor Regulation
References
NUDOCS 8811300059
Download: ML20206L556 (6)

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• UNITED STATES a ch i

/ NUCLEAR REGULATORY COMMISSION

,g WASHINGTON, D. C. 2o668

,o ; , p Novenber 25, 1988

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Docket No. 5U-482 MEMORANDUM FOR: Jose A. Calvo, Director Project Directorate - IV Division of Reactor Projects - III, IV, Y and Special Projects -

FROM: Douglas V. Pickett, Project Manager Project Directorate - IV l Division of Reactor Projects - !!!, -

IV, Y and Special Projects

SUMMARY

OF MEETING WITH WOLF CREEK NUCLEAR OPERATING CORPORATION TO DISCUSS RECENT ,

DECISION TO REPLACE THE ROD CLUSTER CONTROL ASSEMBLIES - NOVEMBER 17, 1988  ;

This meeting was held at the request of Wolf Creek Nuclear Operating Corporation to discuss their recent decision to replace the rod cluster control assemblies at Wolf Creek. In addition, brief updates of the steam generator and reactor thimble tube eddy current testing performed during the l current refueling outage were also provided. The attendees to this meeting are listed in the Enclosure.

At the outset of the meeting the licensee stressed that the information to be discussed was preliminary and that Westinghouse was still evaluating the test t' results. Mcwever, due to the significance of the action taken by the licensee and the possible generic implications, the licensee wished to discuss the preliminary results with the NRC staff.

Wolf Creek and Callaway (licensed in June,1985 and Octcber,1984 respectively) are the lead Westinghouse plants using the newly designed  !

hafnium control rods. A total of 17 Westinghouse plants (14 domestic and 3  ;

foreign) incorporate these control rods which consist of a solid hafnium rod surrounded by a stainless steel clad of approximately 18.5 mill thickness. (A 1.5 mill gap exists between the hafnium and the stainless steel clad). As a  :

licensing condition, both Wolf Creek and Callaway were required to "perform a i visual inspection of a sample of hafnium control rods during one of the first  !

five refueling outages."

Both Wolf Creek and Callaway observed hafnium in the primary coolant system  ;

during early plant operation. During the November, 1987 refueling outage [

Callaway contracted with Westinghouse to perform eddy current testing of the  !

control rods. Unexpected cladding wear was observed on the Callaway L control rods. Based upon the information gathered, Wolf Creek decided to  ;

perform eddy current testing of their control rods during the present [

refueling outace using Combustion Engineering (CE) as the contractor.  ;

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, Jose A. Calvo  ;

CE conducted eddy current testing of all rod clutter control assemblies (RCCAs). In addition, CE performed a profilometry of about half of the RCCAs. Briefly stated a profilometry is a process where eight sensors, i e

located synnetrically around the control rod circumference, measure four i diameters axially along the length of the control rod. It is used to detect i localized swelling or compression of the rods. A profilometry, which is a l l rather recent development was not performed by Westinghouse at Callaway.

• 4 preliminary results showed two, apparently unrelated phenomena. The first f finding was unexpected wear, or thinning of the contrni rod clad. Most of the  !

wear was associated with the 228 (fully withdrawn) position indicative of j

guide tube vibration. At least one of the control rods experienced through-clad  ;

i wear and several others appeared to have failed the Westinghouse acceptance i criteria Uf maintaining a minimum 50% clad volume measured circumferential1y

< around the rod. The second finding was localized, non-uniform swelling or  !

expansion on almost all of the control rods. Measured radially the expansion i j appeared to be between 5 and 30 mills (calibration of the instrumentation to measureexpansionwasinitiallylimitedto5 mills). In the axial direction  ;

j the expansion was typically limited to less than an inch. It was also pointed i Out that eddy current testing identified indications on the inside diameter of {

the c. lad at nearly every location whare swelling was observed. Expansion was ,

apparently less than 40 mills as this was the maximum clearance of the instru- ,

ment 6 tion being used.

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The cause of the expansion is currently under investigation by Westinghouse.  ;

j During the testing Westinghouse personnel who were familiar with the Callaway  !

l tests were called in to verify the validity of the CE tests. In addition, two. ,

j RCCAs that were in storage and had not been in the reactor vessel were tested f l and did not show any expansion - thus indicating it was not a manufacturing f

ancmaly. Prior to the refueling outage there had been no indication of  ;

control rod degradation (e.g., changes in red drop times or rod worth l

j measurements), t i  !

i Rather than wait for the results of the Westinghouse evaluation, the licensee i chose to replace all 53 RCCAs with new RCCAs of the origin 61 design and  !

composition. Justification for this action included:

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1 (1) Waiting for the Westinghouse evaluation (and possible NRC review) i l could adversely impact the outage schedule. Replacing the RCCAs [

] would remove time constraints on the Westinghouse evaluation. j

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! 04 ) Additional RCCAs were innediately available from the Comanche Peak

, Unit 2 site. [

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) (3) The old RCCAs are still available and on-site at Wolf Creek if the  !

l Westinghouse evaluation finds them acceptable for future use. {

l q Plans are currently underway to have Westinghouse perform a de structive I

exanination of one of the control rods at their hot cell in Pi',tsburgh, i j Results are expected by the end of the year. j 1

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Jose A. Calvo Following the current refueling outage the Wolf Creek facility will change from 12 month to 18 month cycles. The licensee stated that they expect to perform similar control rod testing during the next refuel'ng outage.

The staff concluded the meeting by rtquesting a formal report of the findings once they become finalized and available. The licensee was not willing to commit to such a report at this time citing the possib lity that Westinghouse may report this under 10 CFR 21.

Douglas V. Pickett, Project Manager Proa3Et Directorate - IV Division of Reactor Projects - 111, IY, V and Special Projects

Enclosure:

As stated cc w/ enclosure:

See next page 4

DLSTRIBUTION Wocket File NRC PDR

Local PDR I PD4 Reading I J. Calvo D. Pickett L. Rubenstein OGC-Rockville 4 E. Jordan j B. Grimes

ACRS (10)

T. Martin (Region IV)

PD4 Plant File i

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PD4/PN3 a9 DPic(et)t:sr

! 11/1V88 l

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f r .

, Jose A. Calvo l Following the current refueling outage the Wolf Creek facility will change t a from 12 month to 18 month cycles. The licensee stated that they expect to ,

perform similar control rod testing during the next refueling outage.

The staff concluded the meeting by requesting a formal report of the findings  ;

once they become finalized and available. The licersee was not willing to  !

commit to such a report at this time citing the possibility that Westinghouse  ;

may report ti.is under 10 CFR 21.

w_ A._ v eM 3 i Douglas V. Pickett, Project Manager i Project Directorate - IV  :

Division of Reactor Projects - 111, l

IV. Y and Special Projects

Enclosure:

j As stated cc w/ enclosure: l l See next page l

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- - - -- . - - . _ - _ . , . _ . - . . . . . - - . . . _ . _ - _ - - . . . - . . . . - - , . . - , . _ - _ _. -. i

, Mr. Bart D. Withers Wolf Creek Generating Station Wolf Creek Nuclear Operating Corporation Unit No. I a

cc:

Jay Silberg, Esq. Mr. Gerald Allen Shaw, Pittman, Potts & Trowbridge Public Health Physicist 1800 M Street, NW Bureau of Aie Quality & Radiation

. Washington, D.C. 20036 Control -

4 Division of Environment Chris R. Rogers, P.E. Kansas Department of Health Manager, Electric Department and Environment Public Service Commission Forbes Field Building 321 P. O. Box 360 Topeka, Kansas 66620 Jefferson City, Missouri 65102 Mr. Gary Boyer, Plant Manager Regional Administrator, Region !!! Wolf Creek Nuclear Operating Corp.

U.S. Nuclear Regulatory Commission P. O. Box All 799 Rocsevelt Road Burlington, Kansas 66839 Glen Ellyn, Illinois 60137 Regional Administrator, Region IV Senior Resident inspector / Wolf Creek U.S. Nuclear Regulatory Commission

, c/o U. S. Nuclear Regulatory Commission Office of Executive Director 4

P. O. Box 311 for Operations Burlington, Kansas 66839 611 Ryan Plaza Drive, Suite,1000

) Arlington, Texas 76011 Mr. Robert Elliot, Chief Engineer Utilities Division Mr. Otto Maynard, Manager Licensing Kansas Corporation Commission Wolf Creek Nuclear Operating Corp.

4th Floor - State Office Butiding P. O. Box 411 j Topeka, Kansas 66612-1571 Burlington, Kansas 56839 2 (

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. Enclosure Attendees i

I Wolf Creek , (

John Bailey, Vice President, Engineering and Technical Services l Otto Maynard6 Manager, Licensing

• Robert Hagen, Manager Nuclear Services i

NRC Gary Holahan

.. Jose Calvo .

Conr.d ficCracken .

!, Larry Phillips  !

j Richard Lobel .  !

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i Douglas Pickett  !

Shih-Liang Wu '

Mary Wegner j Daniele Oudir.ac ,

Paul O'Connor i l Thomas Alexion 4 j I

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