ML20204G012

Forwards Safety Evaluation Supporting Amend 76 to License DPR-61 Re Operation of Plant Using Interim Acceptance Criteria for Steam Generator Tube Repair.Study Re Proposed Corrective Action Plan Requested by 860930

ML20204G012
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	07/30/1986
From:	Charemagne Grimes Office of Nuclear Reactor Regulation
To:	Opeka J NORTHEAST NUCLEAR ENERGY CO.
Shared Package
ML20204G018	List: ML20204G012 ML20204G022
References
TAC-67463, NUDOCS 8608070039
Download: ML20204G012 (3)

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• • • • • July 30, 1986 Docket No.: 50-213 Mr. John F. Opeka, Senior Vice President Nuclear Engineering and Operations Northeast Nuclear Energy Company Post Office Box 270 Hartford, Connecticut 06141-0270 ,

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SUBJECT:

TU8E PLUGGING CRITERIA FOLLOWING DISCOVERY OF UNDEFINED SIGNALS DURING STEAM GENERATOR EDDY CURRENT INSPECTION OF TUBES IN THE TUBESHEET REGION tr Re: Haddam Neck Plant ,

In a conference call on June 20, 1986, the Connecticut Yankee Atomic Power Company (CYAPCO) infomed the NRC headquarters staff and Region I that, using advanced eddy current inspection equipment, 575 steam generator (SG) tube ends were identified during the 1986 refueling as having " undefined eddy current signals" in the roll expansion region. CYAPCO stated that no actions were taken during the outage, as the nature of the signals is unknown and characterization of the anomalies could not be performed. By letter dated June 26, 1986, the NRC stated that it was appropriate for CYAPC0 to complete an evaluation which will

< serve as the basis for a license amendment to specify the acceptance criteria for the roll expansion region of the steam generator tubes. ,

By your letter dated July 24,1986, CYAPC0 stated that subsequent investigations of the undefined signals ruled out the possibility of flaws in 35 of the 575 tube Y- ends under consideration. Estimated flaw depths for the remaining 540 tube ends with undefined signals ranged from 22% to 100% through-wall. The sizing estimate assumed the entire undefined signal was due to a flaw, even though the existence of.a flaw could not be confimed in all cases.

CYAPC0 performed an analysis to detemine interim structural acceptance criteria i assuming flaws in the rolled region of the tubes'using the guidance in Regulatory Guide 1.121. " Bases for Plugging Degraded PWR Steam Generator Tubes." The proposed interim acceptance criteria includes conservative allowances for

. dynamic effects during accidents and uses safety factors consistent with

!. those described in the Regulatory Guide. On the bases of its analyses. CYAPCO r, concluded that one inch of sound roll has the required frictional resistance f for a SG tube to withstand nomal operating, test and postulated accident loads.

i Therefore, the interim acceptance criteria for the steam generator tube ends at the Haddam Neck Plant does not permit any defects in the uppemost one inch of the rolled region of the steam generator tube. CYAPC0 has identified a total of 119 tubes containing eddy current indications which did not meet the interim acceptance criteria and has plugged these tubes during the recent plant shutdown.

8600370039 DR 860730 ADOCK 05000213 PDR

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July 30, 1986 The staff has reviewed the information and analyses provided by CYAPC0 in ,

support of the interim acceptance criteria and concludes that one inch of l sound roll will provide the required frictional resistance to withstand normal operating, test, and postulated accident loads. The safety factor to withstand the pull out force is greater than 3.0 under normal operating conditions and 1.428 or more under faulted conditions. These factors of safety are in accordance with the intent of Regulatory Guide 1.121 and are in addition to an allowance of 0.1 inches for eddy current measurement errors. Additionally, the staff has concluded that the maximum calculated leakage for all tubes with flaws l which may leak will not exceed the Haddam Neck Technical Specification limit for design basis accidents (150 gallons per day per steam generator). '

Therefore, we conclude that there is reasonable assurance that the potential flaws in the rolled region of the subject 540 steam generator tubes will not result in catastrophic failure in the near term and that any propagation of existing flaws will be revealed by an increased primary-to-secondary coolant leakage rate, which is limited by plant technical specifications. On this basis, the staff concludes that operation of the Haddam Neck Plant using the interim acceptance criteria for steam generator tube repair does not present an undue risk to public health and safety for the remainder of the current fuel cycle and is, therefore, acceptable. A copy of our Safety Evaluation concerning the interim acceptance criteria is enclosed.

We believe that it is appropriate for you to continue and complete the evaluation of the undefined signals, which will serve as the basis for a future license amendment, to specify the final acceptance criteria for the roll expansion region of the steam generator tubes.

l As previously stated in our June 26, 1986 letter, we require that your study l regarding the SG tube ends, with a proposed corrective action plan, be completed no later than September 30, 1986. A license amendment, with the appropriate acceptance criteria for the tube ends, should subsequently be submitted by October 31, 1986. We again recomend that a meeting be held with the NRC staff toward the end of August 1986, to discuss your preliminary results regarding the significance of the undefined eddy current signals.

Sincerely, Original signed by Michael L. Boyle for Christopher I. Grimes Christopher I. Grimes, Director Integrated Safety Assessment Project Directorate Division of PWR Licensing - B DISTRIBUTION

Enclosure:

., Docket File PAnderson JPartlow As Stated NRC PDR' FAkstulewicz BGrimes Local PDR ACRS (10) ISAP Reading cc: See Next Page CGrimes FMiraglia EJordan CCheng Wii46 4%gy, NThompson SAP:DPL-B L EB:p) B/ gISAP:DPL-B

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4 Mr. John F. Opeka Connecticut Yankee Atomic Power Company Haddam Neck Plant l

cc:

Gerald Garfield, Esquire Kevin McCarthy, Director Day, Berry & Howard Radiation Control Unit Counselors at Law Department of Environmental City Place Protection Hartford, Connecticut 06103-3499 State Office Building Hartford, Connecticut 06106 Superintendent l Haddam Neck Plant Richard M. Kacich, Supervisor RDF #1 Operating Nuclear Plant Licensing Post Office Box 127E Northeast Utilities Service Company East Hampton, Connecticut 06424 Post Office Box 270 Hartford, Connecticut 06141-0270 Edward J. Mroczka

. Vice President, Nuclear Operations Northeast Utilities Service Company ,

Post Office Box 270 Hartford, Connecticut 06141-0270 Board of Selectmen Town Hall Haddam, Connecticut 06103 State of Connecticut Office of Policy and Management

, ATTN: Under Secretary Energy Division .

80 Washington Street Hartford, Connecticut 06106 Resident Inspector Haddam Neck Nuclear Power Station c/o U.S. NRC East Haddam Post Office -

East Haddam, Connecticut 06423 Rgional Administrator, Region !

U.S. Nuclear Regulatory Connission 631 Park Avenue King of Prussia, Pennsylvania 19406

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