ML20127P254

Ler:On 750711,visible Cracks Observed in Several Corner Pins of Ten Initial Core 7X7 Fuel Assemblies.Caused by Hydride & pellet-clad Interaction Mechanisms.Leaking Fuel Has Been Identified & Replaced Each Fueling Outage

ML20127P254
Person / Time
Site:	Monticello
Issue date:	07/21/1975
From:	Mayer L NORTHERN STATES POWER CO.
To:	Giambusso A Office of Nuclear Reactor Regulation
References
LER-LER-750721, NUDOCS 9212020170
Download: ML20127P254 (2)

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l NORTHERH STATE 5 POWER COMPANY MIN N E A PO LI S. MIN N E S OTA 95401

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July 21, 1975 -_

Regulatory Dcchet Fila _ _

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Mr A Gia:nbusso, Director D Division of Reactor Licensing U S Nuclear Regulatory Commission .,

Washington, DC 20555 ' ' L-- ; -

Dear Mr Giambusso:

HONTICELLO NUCIIAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 Licensee Event Report to the NRC Observed Cracks in Failed Fuel Assemblies The Licensee Event Report for this occurrence is reproduced on the back of this letter.

Yours very truly,

& h, Y L 0 Mayer, PE Manager of Nuclear Support Services -

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[_TJ l L l (_ Ol 510 l-l Ol 216 l 3 l 59 60 l Ol711 lll 71 Sl [0. l 712 l 1l 7 l 5 l 61 68 69 74 75 80 EVENT DESCR:PTION gg l On July 11, 1975, Region III NRC I&E requested that the visible cracks observed 7 89 j

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@l in several corner pins of ten initial core 7x7 fuel assemblies be reported as an l 7 89 80

@ [ AO. Assemblies are leakers removed from core after cycles 2 and 3. Leaks have 7 89 l 80 Ql 7 e9 been identified in 158 of 484 initial core assemblies to date. No leaks have l 80 g[ been identified in 7x7 or 8x8 reload fuel. We plan to replace remaining initial l 7 89 m,q 80 DE cost coupoNENT coot surNn MIENuNu viotAfoN

@ lR) Cl [Ej l Fl UlE l LlX lX l lNl l Gl0 l8 [ 0 l [NJ 7 89 to 11 12 17 43 44 47 48 CAUSE DESCRIPT:ON 28 ( Fuel pin f ailures believed Caused by hydride and pellet-Clad interat tion l 7 89 80 EE l mechanisms. Leaking fuel has been identified and replaced each refueling outage. l 7 89 80 8l l stAIus' s powin OTuta STAfus oscovtav orscovtav OtscnietoN 7 8 (E_j 9

l0 l8 l 3 l lNA l d45 l TV Camera Inspection l 10 12 13 44 46 80 HEtt SED OF Att St AMOUNT of ACTMTV tocatioN OF REif ASE IO 7 8 l__Zj 9

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45 NA l 80 PERSONNEL EXPOSunES NUMBE R t v Pt DISCRIPfiCN 8 l_01 0101 La_] I NA 7 89 l 11 12 13 80 PERSONNEL INJURIES E -l 0l l0l l 7 89 l

11 12 80 OFFSITE CONSEQUENCES Eg l NA l

7 89 80 LOSS OR DAM AGE TO FAClllTY typt otscnieticN

@ [L,j l Reactor power reduced to decrease activity release. l 7 89 10 BV PUBLICITY DE I NA l

7 39 80 ADDITIONAL FACTORS 18 l Event Description (contd.) core 7x7 fuel during refuel outage scheduled to 7 89 l 80 DE l begin in September, 1975. (A0 50-263/75-11) 1 7 89 80 NAME M H Clerftv PHONE: 612/295-5151 po esi.e.,

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