ML20148J609

Ro:On 730410,during Plant Startup,Difficulty Experienced w/13 of 27 Incore Thermocouples.Detailed Engineering Review Conducted.Present Plans Are to Install New Sys During Next Refueling Outage

ML20148J609
Person / Time
Site:	Yankee Rowe
Issue date:	04/24/1973
From:	Heider L YANKEE ATOMIC ELECTRIC CO.
To:	US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8011250025
Download: ML20148J609 (3)

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United States Atomic Energy Commission

'rlashington, D. C. 20545 Attention: Directorate of Licensing

Reference:

License No. DPR-3 (Docket No. 50-29)

Gentlemen:

This letter is written to inform you that during the plant startup en . april 10, 1973, difficulty was experienced with 13 of the 27 incore thermocouples. These 13 thermocouples all exit the reactor from the scuth reactor vessel head penetration. It presently appears that the 6 month flooding of the shield tank cavity resulted in moisture entering the penetratien conoseal. Readings from these thermocouples are con-tinuously improving and are presently within + 3 F of expected values. ,

A detailed engineering review has been conducted. Results of the review indicate that should the readings from the 13 questionable thermocouples become erratic or fail, adequate core performance data can be obtained. Using 1/8 core symmetry and a computer code "INCORE" accurate core performance determin,ation will be made to ensure safe reactor operation.

Results of the engineering review also indicate that experimentally determined maximum hot channel factors are signigicantly less than the predicted hot channel factors.

Manufacturing and engineering are continuing for a new incore reveable instrumentation system and thermocouples. Present plans are to install the new system during the next refueling outage presently scheduled for April,1974.

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i United: States A'tomic Energy Commission April 24, 1973 1 Attn: . Directorate of Licensing Page.Two. . i We trust.you wi11-find this information satisfactory; however,  !

should you desire additional information feel free to contact us.

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Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY

.L. H.'Heider Manager of Operations .-

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AEC DTET'RIBUTION FOR PART 50 DOCIET M) RIAL '

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. Yankee Atomic Electric Co. DATE REC'D LTR MEMO apr l oIm;a i Westborough, Massa'chusetts' 0158 lf.

I L. H. Heider 4-24-73 4-27-73'

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ENCLOSURES

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'.Ltr reporting difficulty experienced with 13'of 27.incore thermocouples on 4-10-73 1

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