ML20125A469
| ML20125A469 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 07/03/1975 |
| From: | Siegel B Office of Nuclear Reactor Regulation |
| To: | Ross D, Rubenstein L Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9212080357 | |
| Download: ML20125A469 (3) | |
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JUL' 3 1975 h
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D. - F. Ross, Chief, Coro Perfomance Dranch, TR THRU: L. S. Rubenstein, Soction Leader, CPB, TR PUEL f AILUPES IN M0!!TICCLLO TUEL ASSD:PLICS
'l This ncno sun.ari::es the inferr.ation obtained to dato reCardin0 the fuel rod failures in Monticello fuel cosenblies.
A conferenet en11 betroen the NPC cnd representatives of :Jorthern States Power (NSP) was hold on July 1, 1975 to discuno the fuel failures observed during a recent inspection of ton dochannoled fuel assa:blics from the in-itial core loadinc ot !!onticello (see attached ' list of participants).
Three of these fuel ansemblics selected for inspection had visual' observationa of failure. There assemblies had been re-constituted i
crter the first cycle of cporation and subsequently renoved from the e
renetor after the second cyclo (l' arch 1974). The renaininc seven assmblics selected hid the larr.ont leak indications based on sipping -
results. Visual observations durant: tho inspection were cade with an-l underwater TV cr. ora and according to USP the poor quality of the pic-ture and the pheten taken soverely restricted tho detail that could bo
-seen.
In addition, the notes taken durinc, the exa.ination ucre con-taninated and could not be renoved fron tho inapoetion_ aren.
IISP is in the process of fabricatinc a borescopo mount so inproved visual o5acrvations can be r.ade within-the next few days (July -3 or 4th). Pased on our conversations with NSP the following preliminary infomation was obtained:
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Approximately 30 of the 40 corner rods had observable: failures.
The corner rod diagonally opposite the control rod blades l
(nearest the instrunent tubes) had the cost failures, l
l-The cornce rods ncarcat the blade tips had the second nost I
failures.
Few failures were obccrved on the ' corner rod adjacent to the control blade.
'i Cracks ranged in length from'approximately-1 to 36 inches.
l Claddinc cracks ranged in width from hairlino to'as cuch as 1/4 inch.
l-In'one corner rod a series of discontinuous cracks was observed extendirc almost the entire rod length.
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D. F. Roos Some indications of hydriding in the fom of hydride blisters i
were observed, however, no r.ajor blisters associated with tho l
cracks were soon.
Hairlinc cracks were observed in fuel pins adjacent to sono corner pins.
!!ost of the failures appear to be in the low enrictnent pins.
t Docause of the equi;rient, only peripheral pine of the fuel asamblics could be seen.
i As previouelv nentioned these fuel assenblics were from the initial core loadinz; and 260 of the initini 404 fuc1 asamblice still re"nin However, cil of these initini assemblics will be re-in the core.
Delivery of the placed during the scheduled October 1 refueling.
l neu fuel assocblics will etart July 15th and be completed by The remaining fuel asocablico currently in the core I
August 15th.
are ccepriced of 20 nou inproved 7x7, which have been in two cycles, and 196 reload Cx0 fuel asac: blion,116 of which have been in opera-Durinr, the lact reload (cnd of cycle 3), all the tion 1 cycle.
inproved 7x7 fuel cosentlios and 25% of the exS reload asacablies Ho indication of failurcs for any of those fuel (30) wore nipped.
i asscnblies was observed.
The plant is currently operatinf at about 835 of full power and tho power operatins level is beins controlled by the activity level at i
The plant has an augmented holdup systen the etcan jet air ejector.
that appreciably reduces the activity in the off-cas prior to stack The activity release at tho stack is approxir.ately 10,000 releaso.
ci/ soc compared to the technical specification linit of 270,000 Proconditioning procedurcs ne reccrm, ended by Cencral Electric ci/ccc.
(PCIGIR) have been in uco.
In stnrary, based on the prelininary infomation, it oppctre that failurcs are lirited to the initial ruol assemblies containinc,_ fuel rods fabricated during a timo period prior to initiation of inproved design and fabrication. procedurcs (vacuun out.-cassini; and gettering).
In particulce these failures appear to be prinarily associated with i
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Iou enrichnent rods within the asscnblies. Drcsden 2 experienced a
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larco numbor of fuel failuroc on similar vintage fuel reds; however, i
the fuel was removed earlier in life and the failures seen were not f
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D. F. Ross as extensive as those observed in !!onticello.
Additional infomation i
is nooded to explain why the failures are occurring, in the locations identified and the specific cause of failuro.
B. Siegel iiccetor Fuels Section
+
Coro Perforr.ance cronch l
Divicion of Technical Review Offico of Huelcar Reactor Roculetion i
Enclosure!
/.a Stated cc:
S. !!anauer l
F. Schrocdcr i
R. Fralcy, ACPC (21)
P. Flin-DL/i'.! ADa IE (3)
D. Duckley i
V. Stello l
L. Rubenstein i
R. l'cycr l
D. Houston
?!. Tokar DISTRIBUTION:-
Central File NRR Reading File l
CPB Reading File i
B. Siegel l
l l
TR:
TR:CPB o r,,c e,.
L. Rubens /A y
B. Sieg.
tein
.u,..,
7/J/75 7/3/75 r.,.i Arc.318 (Rev. 9 3 3) AECM 0240
- u, s. oovsRhMENT PRINTING OFFICE 11874 828-104