ML20148J624

Ro:On 721103,following Routine Insp of Shim Rod S-18,efforts to Reinsert Component in Core Unsuccessful.Insp Revealed Abnormal Wear.Vendor Insp Revealed Worn Shroud Tubes.Repair Procedure Being Studied

ML20148J624
Person / Time
Site:	Yankee Rowe
Issue date:	12/14/1972
From:	Autio H YANKEE ATOMIC ELECTRIC CO.
To:	US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8011250105
Download: ML20148J624 (4)

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. YANKEE ATOMIC ELECTRIC COMPANY

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ROWE, MASSACHUSETTS 01367 9 pt C- I yg' , .I; lj.

December, 14, 1972 .

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^U United h ates Atomic Energy Commission . .

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Attenti:n: Directorate of Licensing Referen:e: License No. DPR-3-(Docket No. 50-29)

Dear Sirs:

In accordance with ihe proposed Technical Specifications for the ' Ys:2ee Atomic Elcetric Compan;, , Section 5 7, C.a, we are reporting the felleving substantial variation from expected performance.

Following a routine inspection of shim rod S-18 on November 3, 1972, efforts to reinsert S-18 in core position JK-h5 vere unsuccessful.

Further periscope inspection of the shim rod revealed abnormal wear apIroxinstely nine inches below the normal guide block wear.

Following this evaluation of the problem, the decision was

!..ade to re.:ve the four fuel assemblies adjacent to JK-h5 to permit ins.recticn of the shim rod slot in the lower core support plate. An unde:Ja er television inspection revealed the following:

1. Aw screv vith locking cup intact was lying East  ? ,

k'est in the cruciform formed by guide blocks fcr m lover core support plate at core position HJ-h5 Tnis bo3t and locking cup assembly was later proven to be a

. y- ~ , shroud tube mounting bolt. The bolt was not obstructing

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x the shim rod hole. Subsequently, this bolt was retrieved from the lover core support plate.

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&L. g 2. Inspections through nozzle holes surrounding S-18 reveal-2 . -

%) ed crescent shapes through two nozzle holes to the East J.

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kj of the chim rod. Indications were that the shroud tube had shifted to the East.

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3. Inspections through shim rod slots of the lover core sup-port plcte revealed slots of North and South vanes nearly closed.

Upon discovery of the misaligned shroud tube and a shroud tube

( . bel-, the Ucision was made to remove all fuel from the reactor and inspect

-j the ;;rer reactor internals.

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" ' ' Unit $d States Atomic ". ergy Commission

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j, Attn: Directorateodricensing December 1h, 1972 (h[

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Durin6 the core unloading, control rod A-101 (rod #19) which

'had displayed erratic behavior during p] ant operation was_ removed from core position JK-67 for routine inspection. Later, an attempt to re-l~ insert control rod 19 was unsuccessful. The problem was believed to have

{ been caused by substantial boving of the control rod noted during the inspection. To substantiate this premise, a new control rod was inserted

.into core position JK-67; it also failed to. insert.beyond the guide block j area of the lover core support plate. Subsequent te'levision inspection l'

of this core. position revealed.a second cap screv and locking cup vedged between the Guide blocks at the extreme southern end of the South vane.

During removal.of the core components a binocular inspection I' of the lover core support plate was performed. This inspection revealed a third cap screw and locking cup resting on the Northeast guide block i of nozzle G-h.

' Following removal of all fuel elements, shim rods and control rods on Hovember 13, 1972, a thorough television inspection was commenced of the lower core support plate to shroud tube bolting. The results were as follows

1. Core position JK-h , bolt missing, cup in place.

2. Core position J h5, bolt missing, cup in place.

3. Core position K-h5, bolt and locking cup missing.

h. Core position JK-5, bolt missing, locking cup in place.

5 Core position GE-2, bolt and locking cup missins.

6. Core position G-23, bolt and locking cup missiac.

7 Core position H-23, bolt and locking cup missing.

A binocular inspection of the bottom of the reactor vessel re-vea]ed four shroud tube bolts, two with their locking cups.

On november 15, 1972, the reactor vendor representatives arrived on site and coimenced a television inspection of lower core internals.

Their findir.gs were consistent with those of Yankee with the exception of a possible loose shroud bolt at vore position G-12.

The vendor inspections resulted in the recommendation to remove the lower core support barrel to permit a more detailed inspection of the shroud tube structure. The barrel was removed on Hovember 16, 1972 and the follpving additional abnormalities were observed:

1. A sheared shroud tube tie bar between shroud tubes Ko, 24 and Ko. 25 Binocular inspection of shroud No. 25 on the Northwest side revealed a vertical '

scar one to two feet long on the outside lower quarter of the shroud tube.

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2. One bolt vaa founa missinc and one partially with- l drawn at the bottom tie plate on shroud tube Ho. 26.

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UnitedStatesAtomicf*ercyCommicsion ,

, Attn:

Directorate . of%, icensing

( December 114, 1972 The problem described in (1) aoove appears to be related to an occurrence early in plant life concerning dislodged specimen holders; no relationship has been developed relative to the currently observed shroud tube problem.

The reactor vendor is presently studying a repair which is ex-pected to result in a new unitized shroud structure. replacing the old bolted shroud structtu'e.

Very truly yours, YANKEE ATOMIC ELECTRIC CO. - ROWE F 0 Herbert A. Autio Plant Superintendent HAA:"vb cc: J. O'Reilly

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C 2 AEC DISg3UTION FOR PART' 50 000GT MATESP,,L

.(TEMPORARY FORM) CONTROL'No; 6381' 1

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FROP."j~ 5 DATE OF DOC: DATE REC'D LTR MEMO RPI OTHER

? 'Yad.ee Atc=ic Elcetric Co=pany Ro;e, Massachusetts 01367 .

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ORIG CC WHER SENT AEC PD3 y SENT LOCAL PDR I nr m 3 siened i CIASS: INPUT NO CYS REC'D , DOCKET NO:

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• 50-29 i DESCRIP2 ION: ENCLOSURES: .

Ltr repertin6 an cbnormal occurrence on 11 Do Not itemove.

72, folleving a.rcutine inspection of shim d(j.., h

' rcd S-13, it vaa revealed that the shim rod hrh, p.p. 3 ruffered abncInal year approximately ninc inchen belev the no=al guide block vear. . . . . . ,

• NOTE *PLEASE CIRCULATE INSUFFICIE:E SJPIES RECEIVED ICR FULL DISTRIBWION PLA:Q NA:GS: Yankee ,

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