ML20055E684

Discusses Generic Implications & Resolution of Control Element Assemblies at Plant.Util Should Submit Plans & Justification for Any Continued Use of Old Style Control Element Assemblies Beyond Current Cycle for NRC Review

ML20055E684
Person / Time
Site:	Cooper
Issue date:	07/09/1990
From:	Dudley R Office of Nuclear Reactor Regulation
To:	Gates W OMAHA PUBLIC POWER DISTRICT
References
NUDOCS 9007120238
Download: ML20055E684 (4)

Text

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g-f NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 l

1 N ? / July 9,1990

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DobketNo.50-298 Mr. W. Gary Gates Division Manager - Nuclear 0perations '

l Omaha Public Power District l

~444 South 16th Street Mall l Mail Stop BE/EP 4 l Omaha,-Nebraska 68102-2247

SUBJECT:

GENERIC IMPLICATIONS AND RESOLUTION OF CEA FAILURE AT MAINE YANKEE On June 7, 1990, while conducting cold functional testing of the control element assemblies (CEAs) following the cycle 12 refueling outage at Maine ,

Yankee, one CEA could not be fully inserted in the core. Subsequent inspection l

'of the CEA-revealed that the end cap was missing from the center CEA finger, R the lower stainless steel spacer and boron carbide pellets had fallen out of l the center finger and an axial crack existed at the lower end. The upper stainless steel spacer.was cocked in the bottom of the CEA finger and was causing the center CEA finger to bind against the guide tube. The CEA could not be fully inserted in the core during cold functional testing due to interference fron; boron carbide pellets that had fallen into the center CEA

_-_ guide tube.

On' June 25, 1990, the NRC staff ~ met with the Combustion Engineering Regulatory a g , Response Group (CERRG) to discuss the generic implications and proposed L resolution of the CEA failure that occurred at Maine: Yankee.. The CERRG -

l concluded-that the CEA failure was most likely due to irradiation assisted stress corrosion cracking (IASCC).. The CERRG also concluded that the failure mechanism was only ap)11 cable to the older Combustion Engineering (CE) CEA design which did not lave an absorber plug (other than boron-carbide pellets) at the bottom of the center CEA finger. In order to' resolve this issue, the  :

CERRG proposed specific Action Programs for each affected'11censee. The CERRG submitted its report to the NRC addressing this issue by letter dated June 26, 1990.

l' l It is our understanding that Fort Calhoun currently is operating with two CEAs  !

1. of the old design with an exposure of approximately 1150 effective full power l days (EFPD). Recently, degradation of one Maine Yankee CEA was identified with l only 2732 EFPD exposure. _ Additionally, one Maine Yankee CEA with only 3415

l. EFPD exposure failed with loss of end cap and absorber material from the middle finger and loss of full insertion capability. Therefore, you are requested to submit your plans and justification for any continued use of the old style CEAs beyond the current cycle for our review. Please provide your response within 60 days of the date of this letter.

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' The reporting and/or recordkeeping requirements contained in this' letter affect

. ofewer than ten respondents; therefore, OMB clearance is not required under  !

-Pub. L.96-511.

t Sincerely.

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e' Richard F. Dudley, Acting Director Project Directorate IV-1  ;!-

Division of Reactor Projects - III. --'

IV, Y and Special Projects .

Office of Nuclear Reactor Regulation

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The reporting and/or recordkeeping requirements' contained.in this letter affect 5 fewer than ten respondents; therefore, OMB clearance is not. required under -t Pub. L.=96 511.. I g Sincerely, p e i: Orig!nal signed by l Richard F. Dudley, Acting Director n ll Project Directorate IV-1 1 L Division of Reactor Projects - III,. ,

IV, V and Special Projects Office of Nuclear Reactor Regulation cc: See next page l" DISTRIBUTION I

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0FFICIAL RECORD COPY Document Name: LTR FT CALHOUN.- j

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, *; . Mr. W. Gary Gates Omaha Public Power District Fort Calhoun Station Unit No. I cc:-

Harry H. Voigt. Esg.

LeBoeuf, Lane, Leiby & MacRae 1333 New Hampshire Avenue, NW Washington, D.C. 20036 Mr. Jack Jensen, Chairman Washington County Board of Supervisors Blair, Nebraska 68008 Mr. Phillip harrell, Resident Inspector U.S. Nuclear Regulatory Comission P.O. Box 309 ,

Fort Calhoun, Nebraska 68023 Mr. Charles 0. Brinkman, Manager

+ Washington Nuclear Operatinus Combustion Engineering, Irc.

12300 Twinbrook Parkway, Suite 330 P.ockville, MD 20852 -

Regional Administrator, Region IV U.S. Nuclear Regulatory Comission Office of Executive Director for Operations 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 70011 Harold Borchert Director Division of Radiological Health Department of Health 3nl Centennial Mall, South P. O. Box 95007 Lincoln, Nebraska 68509 Mr. G. R. Peterson,tianager Fort Calhoun Station P. O. Box 399 Fort Calbcun, Nebraska 68023