ML20085B598
| ML20085B598 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 05/15/1972 |
| From: | Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Block E US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20085B488 | List: |
| References | |
| NUDOCS 8307080213 | |
| Download: ML20085B598 (3) | |
Text
kGMCGBA CGO 1-012592A136 05/15/72 g
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UPL ATE mesWn union 003 JACKSON MICH O ZIP 60137 g
O Q 60YCE H GRIEH DIVISION OF COMPLIANCE CHICAGO OPERATIONS OFFICE O
USAEC g
GLENN ELLYN, ILLINDIS 60137 O
'O O
O CONSUMERS POWEH COMPANY r
Q PAdNALL ROAD OFFICE g
JACKSON, MICHIGAN c
5-15-72 T0-MR E J BLOCK, DIRECTOR DIRECT 03 ATE OF LICENSING t-
'a O
UNITED STATES ATOMIC ENERGY COMMISSION a
g WASHINGTON, DC O R E-DOCKET 50-255
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g LICENSE DPR-20 Q DURING AN INSPECTION OF THE INLET PLENUM OF THE PRIMARY SIDE OF THE g
NO 2 STEAM GENEHATOR AT THE PALISADES PLANT ON MAY 7,1972, A PORTION OF A BOLT WAS DISCOVERED.
AT THE TIME THE PORTION OF THE BOLT WAS O
FOUND, THE PLANT WAS IN A COLD SHUTDOWN CONDITION DURING AN OUTAGE g
SCHEDULED TO CONDUCT BOTH PRIMARY AND SECONDARY SYSTEM MAINTENANCE.
O THE BOLT WAS THE PORTION ABCVE THE THREADS OF A 5-8 INCH DIAMATER g
SHOULDER BOLT.
A DETAILED REVIEW YIELDED THAT THE ONLY PRIMARY SYSTEM COMPONENT UTILIZING A 5/8 INCH SHOULDER BOLT IS THE COMPENSAT-O ING RING SHIM (A PORTION OF THE UPPER GUIDE STRUCTURE).
THE MARK-g INGS ON THE SOLT IDENTIFIED THE BOLT TYPE AND BOLT MANUFACTURER.
THE MANUFACTURER OF THE REACTOR INTERNALS CONFIRMED THAT THIS TYPE OF Q BOLT HAD BEEN USED.
g WE BELIEVE THE CAUSE OF THE FAILURE OF THIS COMPENSATING RING SHIM Q BOLT STARTED WITH AN ACCIDENT DURING SHIPMENT OF THE UPPER GUIDE g
STR UCTUR E.
IN THIS ACCIDENT, THE UPPER GUIDE STRUCTURE AND THE COM-PENSATING RING SHIM WERE STRUCK RADIALLY.
WHILE THE IMPACT WAS NOT Q
SUFFICIENT TO SEVER THE BOLT (INSPECTIONS SUBSEQUENT TO THE ACCIDENT CONFIRMED THIS),
IT COULD HAVE CAUSED DEFORMATION TO THE SHOULDER SECTION AND INITIATED A CRACK AT THE ROOT OF THE UPPER THREAD.
THE O
INSPECTIONS PERFORMED SUBSEQUENT TO THE ACCIDENT WOULD NOT HAVE DE-g TECTED A CHACK AND SHOULDER DEFORMATION.
DURING NO AL HEATUP AND
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C00LDOWN CYCLES, THE FORCE OF THE RING SHIM DUE TO DIFFERENTIAL O
EXPANSION AGAINST THE SHOULDER BOLT INTRODUCED SUFFICIENT LOADING IN THE ALHEADY WEAKENED BOLT WHICH EVENTUALLY RESULTED IN ITS FAI LUR E.
O el THIS BOLT WAS ONE OF EIGHT BOLTS INSTALLED TO HOLD THE RING SHIM IN PLACE ON THE UPPER GUIDE STRUCTURE FLANGE DURING SHIPPING AND REFUEL-1 O ING OPERATIONS.
THESE BOLTS ARE NOT REQUIRED DURING REACTOR OPERA-gl TIONS.
O SHoutD FuaTHER BOLTS FAIL UNDER FULL FLOW CONDITIONS, THE BOLTS WOULD gl BE CARRIED BY THE FLOW STREAM DOWN THROUGH THE UPPER GUIDE STRUCTURE AND THE CORE BARREL AND PASSES OUT THROUGH THE OUTLET N0ZZLES INTO A J
_O STEAM GENERATOR.
THE HEAD OF THE BOLT PREVENTS ITS PASSAGE THROUGH g'
THE STEAM GENEHATOR.
O UNDER PARTI AL FLOW OR IF THE FLOW WERE SHUT OFF WITH A BOLT IN g
TRANSIT TO THE OUTLET N0ZZLES, THE BOLT COULD DROP DOWN AND REST ON THE TOP OF THE CORE SHROUD OR THE TOP OF FUEL ASSEMBLIES.
IT IS O POSSIdLE THAT A BOLT COULD DROP DOWN BETWEEN AN OPENING IN THE CORE gl SHROUD LATEHAL SUPPORT PLATES AND LIE TRAPPED BETWEEN THE CORE SHROUD
]
AND CORE BAdREL.
IN NO CASE COULD A BOLT DROP BELOW THE TOP PLATE O
OF A FUEL ASSEMBLY IN THE CORE REGION BECAUSE THERE ARE NO OPENINGS g'
LANGE ENOUGH TO PERMIT PASSAGE OF A 5/8 INCH SHOULDER BOLT.
O ASSUMING A BOLT WAS TO REACH THE TOP OF THE FUEL ASSEMBLY, IT IS g
POSSIBLE UNDER NO FLOW CONDITIONS THE BOLT MIGHT HOLL PAST THE POST AND GUIDE ROD NUT OF A FUEL ASSEMBLY IF THE ADJACENT CONTROL BLADE O WERE FULLY INSENTED.
IT MIGHT COME TO REST BETWEEN THE TOP OF THE g
CONTROL BLADE AND THE BOTTOM OF THE LOWER END OF THE CONTROL SHROUD.
THIS COULD CAUSE INTERFERENCE WITH THE CONTROL BLADE WHEN WITHDRAWAL j
Q WAS ATTEMPTED.
WHEN FLOW IS RESTARTED, THE BOLT WOULD BE CARRIED g
007 0F THE REACTOR INTO THE STEAM GENERATOR.
OUR REVIEW YIELDED THAT THIS WAS THE ONLY CASE IN WHICH THIS TYPE OF BOLT FAILURE COULD CAUSE O
INTEaFEHENCE WITH A CONTROL ROD DRIVE MECHANISM.
g uASED ON THE INSPECTIONS OF THE BOLT AND THE STEAM GENERATOR, WE O WOULD NOT EXPECT ANY DAMAGE TO THE STEAM GENERATORS IF FURTHER FAIL-g URES WEHE TO OCCUR.
THE BOLT EXHIBITED ALMOST NO EVIDENCE OF TUMB-LING AND HAD OBVIOUSLY BEEN INACTIVE IN THE STEAM GENERATOR HEAD.
BASED ON THE APPARENT CAUSE OF THE BOLT FAILURE AND THE NONDETRINEN-TAL EFFECT UPON INTERNALS FUNCTIONING OR REACTOR OPERATIONS OF O FURTHER OCCURRENCES, WE PLANT TO RETURN THE PLAXX PALISADES PLANT TO g
SERVICE ABOUT MAY 17, 1972.
DURING THE NEXT REFUELING OUTAGE, A MODIFICATION WILL BE MADE THAT WILL PREVENT ESCAPE OF THE UPPER PORTIONX OX l
PORTION OF A FAILED BOLT FROM THE COMPENSATING RING SHIM.
O WE WILL SUBMIT FURTHER DETAILS BY LETTER WITHIN THE NEXT TWO DAYS.
g NALPH B SEWELL l
Y O
NUCLEAR LICENSING ADMINISTRATOR
$g J g
CONSUMEHS POWER COMPANY Q
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