05000263/LER-1977-027

LER 77-27:on 770923,RHR Torus Cooling Valve Body Seat Ring Threads Found to Be Stripped.Caused by Rotation of Plug Which Unscrewed Seat.Mod in Process to Hold Seat in Place Using Bolding Ring Welded to Valve body.W/771021 Ltr

ML20056B863
Person / Time
Site:	Monticello
Issue date:	10/21/1977
From:	Mayer L, Tilly D NORTHERN STATES POWER CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
LER-77-27, NUDOCS 9102130520
Download: ML20056B863 (2)

LER-2077-027,

Event date:
Report date:
2632077027R00 - NRC Website

text

6 LICENSEE EVENT REPORT CCNTAOL BLOC < l l l l l l l (PLEASE PRINT aLL REQUIRED INFORM ATION) 1 6 4 Eu Et tcf NSE f. TNT N;.vt LCfNSE NUMB (A T v nt T,PE i c1 ! M l N l Ml N l P l 1l l0 l0 l-l 0l 0l0 l 0 l 0l-l0 l 0 l l 4l 1l 1l1 l1 l l0 l3 l 7 89 14 15 25 26 30 31 32 C AT E cou, T(( :$, "[A$[ DoCati Nuvet A fttNT DATE winosa cATE O1 CON T l l l W l Ll lo l 5 l 0l-l0 l2 l 6 l 3] l0 l 9 l 2 l 3l7 l774l l1 l0 l2 l1 l 717l 7 8 57 56 59 60 61 68 69 75 80 EVENT CE SC AiPT 3CN EE IUpon disansembly of RHR torus cooling valve, MO-2008, for stem replacement the valvej 7 89 go

@ lbody seat ring threads were found to be stripped. Upstream isolation valve MO-2006 l 7 89 eo

@ lwas operable at time of occurrence. Modification in process to hold seat in place l 7 89 80 0 lusine a holdine rine welded to the valve bodh No previous similar occurrences. l 7 89 80 DH l (M-RO-77-27) l 7 89 psave 80 t CO E COMPONENT CCCE S IEA M J5 if R VOLATON C

lS l D l [f_] l V l A l Ll Yl E l Xl d43 l Al 3l 9l 5l (_Nj

/ S9 10 11 12 17 44 47 48 CAUSE DESCRIPTION BE IPrevious problems with shearing of valve stem clamp set screws allowed stem and plug l 7 89 80 BE lto rotate during attempts to operate the valve. Rotation of the plug unscrewed the l 7 89 80 EE lseat which resulted in damage to the valve body seating ring threads, Anchor 10-inchl 7 89 80 F a cit 'T v VETHOD OF STATUS  % DOAEA OTHER STATUS D:SCOvf RV DISCOvf Av DESCAIPTON 1 (y,j l0l0l0l l NA l d45 l NA 80 l

7 8 9 10 12 13 44 46 ACTwT[ CcNT E NT AELf ASf D OF AELIASE AM(JuNT 08 ACT'wT v LOC ATON OF AttE ASE ll 7 8 9

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11 NA 44 l

45 l NA 80 l

PERSONNEL EXPOSURES NUVBf A 'vrE CESCFaPTON BE l0 l 0l 0] W 7 89 11 12 l NA 13 7 80 l

l PE ASONNEL INJUA;ES l Navet A otSCA+ von -- _q BE lo l 010 l I NA 5  ? l 7 89 11 12 80

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OFFSITE COtJSEQUENCES l l' 8 lNA 7 89 s

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80 l

LCSS DA DAMAGE TO FACILITY  ;

T w pE DE SC A,PT ON 7 1

7 89 W 10 l NA 'M 90 l j PUBLICIT Y l 3 lNA 7 89 go l l ADDITIONAL FACTDAS I

g lCause Description Continued: 300-Pound Globe Valve. Holding ring being installed l eO 9102130520 7710 )

- @.j to hold seat in place. CF ADOCK 050 p 7 ea eo NAME: D ' Tilly PHo. 612/295-5151 j

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M IN N E A PO La s. MIN N E S OTA 55401

?$ h October 21, 1977 h u licy I oil P Y:.

Q N

\A Mr J G Keppler, Director, Region III Office of Inspection & Enforcement f Ull O U S Nuclear Regulatory Com:nission 799 Roosevelt Road Glen Ellyn, IL 60137

Dear Mr Keppler:

MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 RHR Test Line Isolation Valve, MO-2008. Seat Ring Separation The Licensee Event Report for this occurrence is reproduced on the back of this letter. Enclosed are three copies.

Yours very truly, u8 rom L 0 Mayer, PE Manager of Nuclear Support Services LOM/DMM/deh cc: Director, IE, UShTC (30)

Director, MIPC, USNRC (3) j G Charnoff MPCA Attn: J W Ferman bbI 2 7977 over 7730d0216

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