ML20148J386
| ML20148J386 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 12/12/1972 |
| From: | Autio H YANKEE ATOMIC ELECTRIC CO. |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20148J385 | List: |
| References | |
| NUDOCS 8011210758 | |
| Download: ML20148J386 (3) | |
Text
w-l YANKEE AT@MIC ELECTRIC COMPMY-
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YAhMEE ROWE, MASSACHUSETTS 01367 i
Y December 12, 1972 United States Atomic Energy Commission Washington, D. C.
20545 Attention: Directorate of Regulatory Operations s.:
Reference:
License No. DPR-3 (Docket No. 50-29)
Dear Sirs:
[
Relative to the reporting requirements specified in 10 CFR 20 Part
)
20.403 (b) (4), Yankee Atomic Electric Company - Rowe reported on November 13, 1972 that two control rod shroud tubes were displaced.
s The following written report is submitted in accordance with 10 CFR 20.405 (a) (2).
Following a routine inspection of shim rod S-18 on November 3, 1972, cfferts to reinsert S-18 in core position JK-45 were unsuccessful.
Furthe.
periscope inspection of the shim rod revealed abnormal wear approxicately mine inches below the normal guide block wear.
1;h Following this evaluation of the problem, the decision was made to
.pp receve the four fuel assemblies adjacent to JK-45 to permit inspection of the di shic rod slot irf the lower core support plate.
An underwater television in-g pection revealed the following:
T M
1.
A cap screw with locking cup intact was lying East and l:#
West in the cruciform formed by guide blocks for the lI%
lower core support plate at core position HJ-45.
Th1s bolt and locking cup assembly was later proven to be a
' 'f shroud tube mounting bolt.
The bolt was not obstruct-ing the shim rod hole.
S ub s equen tly, this bolt was re-
.w trieved from the lower core support plate.
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2.
Inspections through nozzle holes surrounding S-18 reveal-
- pfk ed crescent shapes through two nozzle holes to the East f
of the shim rod.
Indications were that the shroud tube jtZ had shifted to the East.
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y, je; 3.
Inspections through shim rod slots of the lower core sup-g port plate revealed slots of North and South vanes nearly j@r closed.
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paited Statn3 Atomic Energy' Commission A;:ent. Dirnctorats of Rr atory Opsrations
{J ctmber 12, 1972 7
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4 Upon discovery of the misaligned shroud tub.e and a shroud tube bolt, k!
the decision was made to remove all fuel from the reactor and inspect the low-l er reactor internals.
T (1
During the core unloading,' control rod A-101 (rod,#19) which had dis-i
- played erratic behavior during plant operation was removed from core position JK-67 for routine inspection.
Later, an attempt to reinsert control rod 19
?
(i was. unsuccessful.
The problem was believed to have been caused by substantial bowing 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
[. l failed to insert beyond the guide block area of the lower core support plate, g l Subsequent television inspection of this core position revealed a second cap tf, screw and. locking -cup wedged between the guide blocks at the extreme southern end of the South vane.
44 i
During removal of the core components a binocular inspection of the lower core support plate was performed.
This inspection revealed a third cap f
screw and locking cup resting on the Northeast guide block of nozzle G-4.
f 7
Following removal of all fuel elements, shim rods and control rods on November 13, 1972, a thorough television inspection was commenced of the lower core support plate to shroud tube bolting.
The results were as follows:
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4 1.
Core position JK-4, bolt missing, cup in place.
2.
Core position J-45, bolt missing, cup in place.
T 3.
Core position K-45, bolt and locking cup missing.
i 4.
Core position JK-5, bolt missing, locking cup in place.
5.
Core position GH-2, bolt and locking cup missing.
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6.
Core position G-23, bolt and locking cup missing.
7 7.
Cors position H-23, bolt and locking cup missing.
t er A binocular in'spection of the bottom of the reactor vessel revealed four shroud tube bolts, two with their locking cups.
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s On November 15, 1972, the reactor vendor representatives arrived on ki site and commenced a television inspection of lower core internals.
Their findings were consistent with those of Yankee with the exception of a possibic k
loose shroud bolt at core position G-12.
h The vendor inspections resulted in the recommendation to remove the y
lower core support barrel to pemit a more detailed inspection of the shroud g
tube structure.
The barrel was removed on November 16, 1972 and the follow-gg ing additional abnormalities were observed.
m 1.
A sheared shroud tube tie bar between shroud tubes No. 24 and No. 25.
Binocular inspection of shroud R
No. 25 on the Northwest side revealed a vertical h,
scar one to two feet long on the outside lower g
quarter of the shroud tube, t
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~3-Unitrd*Stetrs Ato ic Ernr y Commission
.'c tri:* Directorats of h atory Operntions mber 12, 1972 a
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One bolt was found missing and one partially with-drawn at the bot'tbm tie plate on shroud tube No. 26.
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The problem described in (1) above appears to be related to an k
occurrence early ir. plant life concerning dislodged speciv.cn holders; no l ([,c relationship has been developed relative to the currently observed shroud
' E tube problem.
h The reactor vendor is presently studying a repair which is expect-
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H ed to result in a new unitized shroud structure replacing the old bolted fj.(
shroud structure.
Very truly yours, W
YANKEE ATOMIC ELECTRIC CO. - ROWE fan'u-<Y hY bcd$f l [i i
Herbert A. Autio.
Plant Superintendent g
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