ML19277C607

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Summary of 830506 Meeting W/B&W Owners Group in Bethesda,Md Re Issues Raised by Reactor Vessel Internal Bolt Failures at Rancho Seco & Crystal River
ML19277C607
Person / Time
Site: 05000000
Issue date: 06/24/1983
From: Kadambi N
Office of Nuclear Reactor Regulation
To:
Office of Nuclear Reactor Regulation
Shared Package
ML19277C608 List:
References
FOIA-83-642 TAC-51432, TAC-51556, NUDOCS 8307150381
Download: ML19277C607 (75)
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JUN 2 4 W LICENSEE: B&W Owners Task Force on RV Internals Bolting Failures

SUBJECT:

SU:I4ARY OF MEETING ON MAY G,1983 TO DISCUSS THE RV IHTERIUd.S BOLTING TAILURES A meeting was held on May G,1983 in Bethesda, MD, with the B&W Owners Group to deal with the issues raised by the RV internal bolt failures that occurred at Rancho Seco and Crystal River. The purpose of the meeting was to provide the Owners Group the opportunity of discussing with the NRC staff the latest findings regarding the bolt failures, and also present their case with respect to justifying continued operation of Davis-Besse and the three Oconce Units. A copy of the attendance sign-up list is attached as Enclosure 1.

The viewgraphs used in the presentations made by the Task Force are attached as Enclosure 2.

Discussion:

The B&W Owners Group sought to provide assurance that public health and safety are maintained at undiminished levels in spite of the bolt failures.

Their arguments rested on the following three major points.

1.

The high reliability of the UT results provides confidence in the existing bolts. Field UT results correlate perfectly with labora-tory test findings with respect to good and bad bolts. There was temporary doubt regarding one bolt from Rancho Seco due to an anomalous laboratory UT indication.

(The field test gave no indication.) B&W determined that the anomaly was explained by flaws in the bolt material which did not affect strength; thus, restoring the perfect correlation between field and laboratory findings.

2 A large margin is available in the carrying capacity of the bolts.

The calculations indicate that even under severe accident condi-tions, 45 to 50 bolts would be sufficient at the upper core barrel bolt ring. The full compicment is 120 This conclusion includes consideration of preload stresses, but does also include the assumption that the failed bolts are roughly uniformly distributed around the ring.

3.

The analysis of failure consequences demonstrates that, even if bolt failures cause the core barrel to drop, the guide lugs limit the drop to 0.54 inches (hot) vertical distance. Reactor shutdown, core coolability and pressure boundary integrity are assured even under these limiting conditions.

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sunN ach CF omy OFFIC-AL RECORD COPY unc ronu sia tio403 Nacu c24a usam e -m wa

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, The Owners Group indicated that within two weeks they will provide the NRC a report that will document the infomation provided at the meeting.

The staff requested that the following items of specific additional infomation be included in the report:

1 Details of bolt preload procedure so that the uncertainty in the preload stresses can be estimated. Such details should include calibration infomation.

2.

Detailed procedures for field UT.

3.

Provide a comparison table showing the preload, nomal operating and peak accident stresses in the bolts.

4 Provide confimation of code allowables used in the analysis.

5 Provide specific documentation of the claim that 45 to 50 bolts are sufficient.

In addition, we requested that Public Power and Toledo Edison Company provide specific justification for continued operation for the three Oconec Units and Davis Besse. Since ANO-l was scheduled to restart May 14, 1983, Arkansas Power and Light Company was asked to provide prior to the startup date a justification for resuming operation of ANO-1.

M. Prasad Kadambi Project Manager, OP3 #4 Division of Licensing ORB #4:DLuf(

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omy unc ronu aia na+a nncu cua OFFICIAL RECORD COPY u= n mi-aw m

s LIST OF ATTENDEES Name Organization Prasad Kadambi NRC/0RB#4 C. W. Hendrix, Jr.,

DPC (Task Force Chairman)

Sydney Miner NRC/0RB#4 Edward D. Throm NRR/DSI Shou-nien Hou NRC/MEB Gary Abell B&W, Inspection Services John Crane Westinghouse Electric Paul Guill Duke, Licensing Gerald Vaughn Duke, Gen. Manager Nuc. Stations Robert Gill Duke, Licensing E. H. Davidson FPC, Licensing Harvey W. Slager CPCo, Materials Section Head R. S. Piascik B&W, Princ. Materials Engr.

R. Wichert SMUD, Sr. Mech. Engr /Engin. & Qual. Cont.

Frederick K. Miller TED, Nuclear Systems & Anal. Engr.

Bert Simpson FPC, Mgr. Nuc. Engineering Larry B. Tittle FPC, Mech. Engr.

Darrell R. Williams AP&L, Mech. Engr.

Dan R. Howtrd

'P&L, Lic. Sugr.

John R. Marshall AP&L, Mgr. Licensing Bill Parkinson TED, Wood-Leaver & Associates Larry D. Young Toledo Edison, Mgr. Nuc. Licensing Ted J. Myers Vice Chairman, BWDG Steering Committee (Nuclear Services Director, Telecc Edison)

H. L. 3 rammer NRC/MEB F. C. Cherny NRC/MEB B. D. Liaw NRC/MTEB G. C. Lainas NRC/AD-0R R. W. Houston NRC/DSI Ronald W. Hernan NRC/0RB#4 Alexander W. Dromerick NRC/I&E M. B. Fairtile NRC/ ORB #4 L. Connor The NRC Calendar E. Igna NRC/ACRS S. W. Gl as s Special Products & Inspec. Services, B&W J. W. Mitchem B&W C. W. Moon NRC/DL R. Riggs NPC/ DST /SPEB Guy S. Vissing NRC/DRB#4 Wm. V. Johnston NRC/DE Don Roy B&W' Jacque Lingenfelter Toledo Edison Philip C. Hildebrandt MPR Associates, Inc.

R. B. Bors um B&W Albert DeAgazio NRC/ ORB #4 L. D. Gilbert NRC/R:IV J. J. Blake NRC/ R:II K. D. Ward NRC/R:III B. J. Short B&W G. J. Vames B&W G. D. Sellers HRC/MTEB MPR Associates S. V. Weems

2-Name Organization N. M. Cole MPR Associates G. Lanik NRC/EAB M. R. Hum NRC/MTEB J. A. VanV11et NRC/ ORB #4 R. H. Wessman NRC/TA-SA J. F. Hall Combustion Engineering J. H. Taylor B&W p

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NRC - B&W OWNERS GROUP MEETitE REACTOR VESSEL INTERNALS BOLTItG MAY 6, 1983

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NRC - B&W OWNERS GROUP E ETING AGBOA REACTOR VESSEL IfGERNALS BOLTING 19.Y 6,1983 I.

INTRODUCTION A.

B&WOG ACTIONS TED MYERS-TED B.

B&WOG TASK FORCE APPROACH SKIP HENDRIX - DUKE r

II.

TECHNICAL BACKGROUND A.

PROBLBiIDBfTIFICATION DOUG LEE - P&W AND INIERNALS JOINTS DESIGN BASIS B.

INSPECTION MEllfJDS GARY ABELL - B&W III.

INSPECTION AND EXAMINATION RESULTS A.

SITE LARRY TITTLE - FPC B.

LABORATORY BOB PIASCIK - B&W IV.

SAFETY IMPLICATIONS DOUG LEE - B&W V.

PLAtff STATUS LARRY YOUNG - TED PAUL GUILL - DUKE DAN HOWARD - AP&L VI.

FLTTUPE ACTIONS

TASK FORCE MISSlai I.

MAltRAIN OTd112ANCE OF ALL ACTIVITIES RELATED TO INTERNAL BOLT FAILURES.

II.

PROVIDE FORUM FOR SHARING OF INF0 WAT10N, III.

MAlhTAIN CONSISTENT LICENSING POSlURE.

IV.

CONSIDER ALL GENERIC ASPECTS ADDRESSING BOTH SAFETY AND ECONOMIC ISSLES.

V.

EXPEDITE PERF0PFANCE OF NECESSARY ACTIVITIES.

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B8W OWNERS ACTIONS TO DATE o

INITIAL EVALUATION THERE APE LARGE DESIGN MARGINS IN THE REACTOR VESSEL BOLTING SYSTEMS CURRENT INSRCTIONS STATUS RErtALS BOLT FAILURE LE rtLS WELL BELOW THOSE REQUIRED FOR J0lfE FAILURES EVEN IF JOINT FAILURE OCCUPS THERE IS NO SIGNIFICAfR SAFtT( HAZARD ITNOLVED THEPEFOPE CURRENTLY OPERATING FACILITIES PROVIDE NO UNDUE RISK TO PlBLIC HEALTH AND SAFETY o

ESTABLISHED AN ORGANIZATION APONG THE B8W OWNERS TO CONTINUE TO ITNESTIGATE AND EVALUATE N9!

If4FORi% TION AfiD WILL CONTINUE TO RESOLVE THE PROBLEMS tE HAVE FOUND

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A 286 BOLT CHRONOLOGY DATE o

THERMAL SHIELD BOLT FAILURES JULY 15, 1981 AT OCONEE 1 o

THEPl%L SHIELD REPAIRS OCONEE 1 NOVEMBER 1981

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OCONEE 2 FEB. 22, 1982 OCONEE 3 JULY 7, 1982 AND-1 JAN, 10, 1983 RANCHO SECO UNDERWAY CR-3 UNDERWAY DB-1 1984 o

UPPER COPE BARPEL BOLT MRCH 25,1983 DEFECTS AT RANCHO SECO c

UFPER CORE BARREL BOLT APRIL 10, 1983 DEFECTS AT CR-3

NRC - B&W OWNERS GROUP IEETING PEACTOR VESSEL IfEERNALS BOLTING MAY 6, 1983 PROBLEM IDENTIFICATION INERNALS J0lfRS DESIGN BASIS DEL 5/4/83

PROBLEM DEFINITION o

LTT lt01 CAT 10NS ERE DETECTED AS EXRCTED IN THE LOWER THERIML SHIELD BOLTS IN THE PROCESS OF MAKING PLANNED REPAIRS.

o UNEXPECTED UT INDICATIONS WERE DETECTED IN THE FOLLOWING BOLTING RINGS:

- UPPER CORE BARREL

- LOWER CORE BARREL

- SURVEILLANCE HOLDER TUBE o

INDICATIONS WERE FOUND IN SA453 GR660 (A-286) BOLTS o

THE UPPER CORE BARREL AfD L0tER CORE BARREL BOLTING RINGS HAVE CORE SUPPORT STRUCTURAL SIGNIFICANCE o

CONCERNS ARE APPLICABLE TO 177FA PLATUS EXCEPT TMI-1

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BOLTED JOINTS WITH A-286 MATERIAL UPPER CORE BARREL (120 - 1 3/4 DIA.) LOWER CORE BARPEL (108 - 1/ 3/4 DIA.) FLOW DISTRIBUTOR TO LO!ER GRID (% - 1 DIA.) UPPER THERMAL SHIELD (60 - 1 1/2 die.) LOWER THERMAL SHIELD (% - 1 DIA.)

  • SURVEILLANCE HOLDER TUBE (73 - 3/4 DIA.)

SA 453 GR 660 (A-286) IS AN AGE HARDENED, HIGH STPB4GE, CORROSION RESISTANT MATERIAL. BOLTS ARE CONDITION A/ UPSET HEADED EXCEPT THE SURVEILLANCE HOLDER TUBE BOLTS WHICH ARE CONDITION B/ MACHINED.

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e. DESIGN BASIS DESIGNED TO WITHSTAND LOADINGS RESULTING FROM NORMAL AND UPSET CONDITIONS: 0 PRESTRESS 0 DEAD WEIGHT 0 THERMAL 0 OBE 8 VIBRATION DESIGNED TO WITHSTAND LOADING RESULTING FROM DESIGN BASIS ACCIDENT (FAULTED) CONDITIONS. 6 SSE O LOCA 6 DEAD WEIGHT 6 CORE BOUNCE ALLOWABLE STRESS CRITERI A FOR NORMAL AND UPSET CONDITIONS WAS SECTION Ill, SUBSECTION NB. ALLOWABLE STRESS CRITERIA FOR FAULTED CONDITIONS WAS AS PRESENTED IN FSAR. JOINT DESIGN CRITERIA WAS NO SEPARATION DURING FAULTED CONDITION LOADINGS. SIGNIFICANT MARGINS ARE INCLUDED IN THE DESIGN (ALLOWABLE STRESS AND NUMBER OF BOLTS REQUIRED TO CARRY LOADINGS). DEL 5/4/33

MINIMUM NUMBER OF BOLTS REQURIED FOR NORMAL OPERATION UPPER CORE BARREL 120 BOLTS ER RING (F BOLTS REQUIRED TO SUPPORT COPD NUMBER PLANT OF BOLTS, RANCHO SECO 8 CR-3 8 ANO-1 8 OCONEE 1 27 OCONEE 2 12 OCONEE 3 8 DAVIS-BESSE 1 8 MIDLAND 1 & 2 8 DEPENDS ON INSTALLATION TOROUE

MINIMUM NUMBER OF BOLTS REQUIRED FOR NORMAL OPERATION LOWER CORE BARREL 'IC6 BOLTS PER RING NUMBER PLANT OF BOLTS " RANCHO SECO 13 CR-3 9 AN' -1 13 3 OCONEE 1 24 OCONEE 2 13 OCONEE 3 9 DAVIS-BESSE 1 9 MIDLAND 1 8 2 9

  • DEPENDS ON INSTALLATION TORQUE

.~. NRC - B&W OWNERS GROUP EETING AGENDA REAiTO'1 VESSEL INTERNALS BOLTING MAY 6, 1983 GARY ABELL CRACK INSPECTION OF BOLTS USING ULTRASONICS o GENERIC BOLT CONFIGURATION o ULTRASONIC CALIBRATION TECHNIQUE o CALIBRATION STANDARDS o RESULTS TO DATE

GENERIC BOLT CONFIGURATION toupling Surface x Crack Site t i e s I 3 I I I I I I l l l I l 'l

ULTRASONIC CALIBRATION TECHNIQUE O POSITION TRANSDUCER ON GOOD BOLT STANDARD AND SET SIGNAL RESPONSE FROM HEAD TO SHANK AT 40% FULL SCREEN HEIGHT (FSH). RECORD DB REQUIRED FOR THIS SENSITIVITY. O REPEAT WITH TRANSDUCER ON 15% NOTCH STANDARD. O REPEAT WITH TRANSDUCER ON 50% NOTCH STANDARD.

ULTRASONIC TEST (UT) SATURATION 90 80 J g 70 5 60 2 g. 50 f 40 ~ 30 / 20 J 10 0 I f f W 2 4 6 8, 10 4 j Distance I f /r TRANSOUCER 6000 BOLT 100 90 80 70

60

$ 50 } 40 30 { 20 10 ( 0 I kt \\1 i I I I i 2 4 6 8 10 s e l Distancs = 4A,50u0s, 2mx 0 CRACKE0 10LT

t. CALIBRATION STANDARDS O BOLTS OF SAME NOMINAL MATERIAL AND SIZE. THREE BOLT STANDARDS - ONE CLEAN; ONE 15% NOTCH; ONE o 50% NOTCH. o NOTCHES CUT IN SHANK JUST BELOW HEAD. e s l A I / l 1 Crack Site E 1 ,i V l t I s-

_RESULTS TO DATE o ALL FIELD OBSERVED INFORMATION CORRELATES WITH LT RGULTS (BROKEN HEADS) I e ALL LABORATORY DESTRUCTIVE ANALYSIS OF BOLTS PULLED FROM SITES CORRELATES Willi UT RESULTS

NRC - B&W OWNERS GROUP EETING PEACTOR VESSEL INTERNALS BOLTING MAY 6, 1983 t SITE INSPECTION RESULTS L. B. TITTLE FLORIDA POWER CORPORATION

5-4-83 UT INSPECTION RESULTS (# CRACKED / # INSPECTED) BOLTED JOINT OCONEE 1 OCONEE 2 OCONEE 3 ANO-1 RANCHO SECO CR-3 (9-81) (1-82) (6-82) (5-83) (3-83) (4-83) UPPER CORE BARREL 0/21 0/30 0/30 7/120 19/120 51/120 (120 3/4 DIA.) ~ LOWER CORE BARREL 0/16 0/24 0/24 0/108 4/108 (108 3/4 DIA.) FLOW DIST/ LOWER GRID 0/22 0/25 0/25 0/93 0/96 (96 - 1 DIA.' UPPER TilERMAL SHIELD 0/25 0/20 0/20 0/60 0/60 (60 - li DIA.) LOWER THERMAL SHIELD 11/13 28/93 53/96 51/96 77/96 73/96 (96 - 1 DIA.) 94 HEADS SEVERAL SEVERAL 48 75 HEADS 69 HEADS TWISTED HEADS HEADS HEADS TWISTED TWISTED OFF TWISTED TWISTED TWISTED OFF OFF 0FF OFF 0FF SURVEILLANCE HOLDER TUBE (72 - 3/4 DIA.)* 25/72 4

  • DB-1 AND CR-3 ONLY

TOTAL UT INSPECTION RESULTS ( UCB, LCB, FL0d DISTRIBUTOR) TOTAL BOLTS TOTAL BOLTED JOINT INSPECTED INDICATIONS UPPER CORE BARREL 441 77 17.5 LOWER CORE BARREL 280 4 1.4 FLUd DIST/ LOWER GRID 261 0 0

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~ RESULTS OF METALLURGICAL EXAMINATIONS o SLM %RY OF PREVIOUS EXAMINATIONS - OCONEE I - OCONEE II o RESULTS OF CURRENT EXAMINATIONS - RANCHO SECO o OVERALL CONCLUSIONS R. S. PIASCIK PAY 6, 1983

' f? OCONEE I EXAMINATIONS 1. .LOFER THERMAL SHIELD BOLT (8) - VISUAL, PT, SEM, METALL0 GRAPHY RESULTS - INTERGRANULAR FRACTURE IN THE BOLT HFAD TO SHANK TRANSITION REGION. 2. UPPER THERMAL SHIELD RESTRAINT BOLT (3) - VISUAL, PT, SEM SURFACE EXAM RESULTS - NO CRACKING. 3. UPPER CORE BARREL BOLT (2) - VISUAL, PT, SEM SURFACE EXAM RESULTS - NO CRACKING. 4. FLOW DISTRIBUTOR BOLT (1) - VISUAL, PT RESULTS - NO CRACKING. i e e

4 C SKETCH DF LOWER TliERHAL SHIELD BOLT Si m ING LOCATION OF FRACTURE I / N/\\/\\/\\/N a h il n LOCATION OF PRINCIPAL FRACTURE \\ ./

~. I OCONEE II EXAMINATI0l4S LOWER THERMAL SHIELD BOLTS (19) VISUAL, UT, SEM,.METALLOGRAPHY RESULTS - INTERGRANULAR CRACKING IN THE BOLT HEAD TO SHANK TRANSITION REGION. e O

CONCLUSIONS (OCONEE EXAMS) 1. ALL FAILURE DUE TO INTERGRANULAR STRESS ASSISTED CRACKING. 2. ALL FAILURES LOCATED IN THE HEAD TO SHANK TRANSITION REGION. 3. BOLTS WHICH CONTAINED NO SITE U/T INDICATIONS WERE VERIFIED TO HAVE NO FLAWS (CRACKS) USING DETAILED LABORATORY EXAMINATIONS.

RANCHO SECO UPPER CORE BARREL BOLT MATERIAL - ALLOY A-286 CONDITION A PROCESSING - HOT HEADED - SOLUTION TREATED 0 1650 F FOR 2 HOURS - AGE HARDENED 0 1325 F FOR 16 HOURS - THREADS ROLLED

+ RANCHO SECO EXAMINATIONS BOLT TYPE: UPPER CORE BARREL' BOLT QUANTITY: 2 BOLTS WITH SITE U/T INDICATIONS (41,116) 1 BOLT WITH NO SITE U/T INDICATIONS (79) EXAMINATIONS: - VISUAL (ALL) - U/T (ALL) .PT (BOLT 79) - SEM/EDX FRACTURE SURFACE (BOLT 116) - SEM/EDX OF SMALL DEFECT AREA OPEN BY TENSILE LOADING (BOLT 79) - METALL0 GRAPHY (BOLT 41 & 79) 4 e

RANCHO SECO EXAMINATION RESULTS BOLT #41, #116 (CONTAINING SITE U/T INDICATIONS) ~ 1. INTERGRANULAR FRACTURE WITH EXTENSIVE SECONDARY CRACKING (BRANCHING). 2. CRACKING INITIATED IN THE HEAD TO SHANK TRANSITION REGION. 3. CRACK PROPAGATION SIMILAR TO THAT FOUND IN THE 10WER THERMAL SHIELD BOLT, l.E., FOLLOWED HAZ CURVATURE. 4. THE HEADS OF BOTH BOLTS WERE ATTACHED BY SMALL LIGAMENTS FORMED BY THE SECONDARY uRACKING. (CRACKING PROPAGATED THROUGH ~ 95% OF BOLT SHANK.)

e SKETCH OF UPPER CORE BARREL BOLT SH0NING LOCATION OF FRACTURE G k 5 d d d Nb \\ t f I / / q \\ \\ /

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p' E <vh HOT HEADING METALLURGICAL TRANSITION LOCATION OF ~ l PRINCIPAL FRACTURE Am q_ ~ SECONDAR'Y CRACKING

RANCHO SECO EXAMINATION RESULTS BOLT #79 (CONTAINING NO SITE U/T INDICATIONS) 1. FLAW CONTAINS LOCALIZED DEPOSITS 2. FLAW IS NOT INTERGRANULAR IN HATURE. 3. NO SECONDARY INTERGRANULAR CRACKING WAS OBSERVED. 4. SURFACES BETWEEN FLAWS OPENED BY DUCTILE RUPTURE WHEN PULLED APART. 5. TOTAL FLAW SIZE MUCH LESS THAN 15% SITE U/T CALIBRATION STANDARD. 6 e b

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.m RANCHO SECO EXAMINATION CONCLUSION 1. RANCHO SECO UPPER CORE BARREL BOLT FAILURES ARE TYPICAL OF PREVIOUS BOLT FAILURES. 2. BOLT #79 FLAW IS AN ANOMALLY AND NOT ASSOCIATED WITH BOLT FAILURES. THE FLAW IS METALLURGICALLY INERT SHOWING NO EVIDENCE OF PROPAGATION. e o e

OVERALL CONCLUSIONS 1. ALL BOLT FAILURES ARE DUE TO INTERGRANULAR STRESS ASSISTED CRACKING LOCATED IN THE BOLT HEAD TO SHANK TRANSITION REGION. 2. DETAILED LABORATORY EXAMINATIONS CONFIRM SITE UT FINDINGS. e e e

NRC - B&W OWNERS GROUP EETING REACTOR VESSEL INTERNALS BOLTING PAY 6, 1983 SAFETY IMPLICATIONS

~

LIKELIHOOD OF CORE DROP VERY LOW BASED ON STRUCTURAL MARGINS AND PESULTS OF UT INSPECTIONS UPPER COPE BARREL (120 BOLTS) MIN # BOLTS RESULTS OF UT INSPECTIONS PEQUIRED FOR 600D Dtrtu lvt PLANT NOPFAL OPER BOLTS BOLTS RANCHO SECO 8 101 19 CR-3 8 69 51 ANO-1 8 113 7 L0tER CORE BARREL (108 BOLTS) RANCHO SECO 13 108 0 CR-3 9 104 4

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s UPPER CORE BARREL BOLTING RING FAILURE CONSEQUENCES o BOLTS FAIL UNDER THE HEAD AS DETEPrilNED FROM LABORATORY EXAMINATIONS o CORE BARREL ASSDELY AND FUEL DROPS.54" AND IS SUPPORTED BY GUIDE LUGS o BOLT HEAD REMAINS CAPTURED BY LOCKING DEVICE PRECLUDING LOOSE PARTS ~ o BOLT SHANKS RBMIN ENGAGED (2i") IN CORE SUPPORT SHIELD THUS RESTRAINING CORE BARREL ASSEMBLY. PADIAL CLEARANCE BER!EEN SHANK AND HOLE IS.142". o NOMINAL RADIAL GAP BEREEN CORE BARREL CYLINDER AND CORE SUPPORT SHIELD IS.170". FLOW BYPASS AROUND CORE IS STs. ADEOUATE THERMAL IMRGIN EXISTS. o FUEL ASSDELY UPPER bid FITTING RBMINS ENGAGED IN UPPER GRID o CONTROL RODS CAN BE INSERTED SINCE IN FULLY tilTHDRAWN POSITION, THEY PENETRATE INTO FUEL ASSEMBLY GUIDE TUBES 6-i INCHES. o CORE BARREL BAFFLE PLATE LIKELY TO C0 TRACT PERIPHERAL FUEL ASS 9ELIES AT THE UPPER END FITTING WHICH ARE CAPADLE OF CARRYlN3 HIGH LOADS IN SHEAR. LATERALLOADSkINCLUDINGASSYMETRICLOCALOADS)ARERESISTEDBY o THE BOLT SHANKS AT THE UPPER SEVERED JOINT THE GUIDE LUGS AT THE BOTTOM

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UPPER CORE BARREL BOLTING RING FAILUPE CONSEQUENCES, Corrr'D. o VERTICAL LOADS (INCLUDING COPE BOUNCE) ARE RESTRAINED IN: THE UPWARD DIPECTION BY THE INTACT CORE SUPPORT SHIELD AND UPPER GRID STRUCTURE THE DOWNWARD DIPECTION BY THE GUIDE LUGS WITH A 30% MARGIN TO CODE ALLOWABLES o FATIGUE EVALUATION OF GUIDE LUGS RESULTS IN LOW CYCLE LOADS (3400 LBS) WHICH COULD BE TOLERATED INDEFINITELY CONCLUSION: UPPER CORE BARREL BOLTING RING FAILURE IS LIKELY TO CAUSE ECHANICAL DAMAGE BUT IT IS NOT A SAFET( CONCERN BECAUSE: CORE CAN BE SHUTD0ht CORE WILL BE RESTRAINED AND COOLED REACTOR COOLANT PRESSURE BOUNDARY L BE MAINTAINED

LOWER CORE BARREL BOLTING RING FAILURE CONSEQUB4CES o BOLTS Fall UNDER THE HEADS o FUEL AND LOWER GRID ASSEMBLY DROPS.54" AND IS SUPPORTED BY GUIDE LUGS o BOLT HEADS PB'AIN CAPTUPED BY LOCKING DEVICES o BOLT SHANKS REMAIN ENGAGED IN LOWER GRID ASSBBLY o FUEL ASSEFBLY ENGAGB E R AND CONTROL ROD INSEPTION CAPABILITIES IS MAlfRAINED o LATERAL FDTION OF THE L0iER GRID ASSEFBLY RESTPAINED BY THE GUIDE BLOCKS AND GUIDE LUGS (.020 To.040 ifJCH CLEARANCE) o VERTICAL f0T10N RESTRAINED BY THE CORE BARPEL Af1D GUIDE LUGS. o LOADINGS ON GUIDE LUGS ARE LESS SEVERE THAfl FOR UPPER CORE BARREL BOLTING RING FAILURE CONCLUSION: SAME AS FOR UPPER CORE BARREL BOLTING RING FAILURE

BASIS FOR C0t#INUED DAVIS-BESSE 0.KRATION o LARGE STRUCiUR?L PARGINS o OTHER PLANT INSFECTION RESULTS o SATISFACTORY PRESETE CONDITION NElHRON NOISE (VERIFIED ON MAY 4, 1983) LODSE PARTS COOLANT ACflVITY o JOINT LOOSENING IS DETECTABLE o ACCEPTABLE SAFETY CCNSEQUENCES DUE TO CORE DROP DURING NOFFAL OPERATION o VERY LOW PROBABILITY CF COMBINED CORE DROP PLUS HIGH LOAD (LBLOCA) ACCIDENT o ACCEPTABLE SAFETV CONSEQUENCES DUE TO CORE DROP PLUS HICfl LOAD ACCIDEfff o LIMITED PLANT OPERATION UtiflL REFUELING (JULY 29, 1983)

JUSTIFICATION FOR CONTINUED OPERATION FOR OCONEE NUCLEAR STATION e PAST UT EXAMINATIONS e LAB EXAM OF BOLT SAMPLES e SIGNIFICANT STRUCTURAL MARGIN e NNA RESULTS e ABILITY TO DETECT CORE DROP e CONSEQUENCES OF CORE DROP e LOW PROBABILITY OF DBA e FUTURE INSPECTION PLANS

UPPER CORE BARREL BOLTS INSPECTION RESULTS NUMBER NUMBER OF I STATION QUANTITY INSPECTED DEFECTS FOUND OCONEE 1 120 21 (17.5%) 0 OCONEE 2 120 30 (25%) 0 OCONEE 3 120 30 (25%) 0 NOTE 1 - INSPECTED BY ULTRASONIC TESTING

LOWER CORE BARREL BOLTS INSPECTION RESULTS NUMBER NUMBER OF STATION QUANTITY INSPECTED 1 DEFECTS FOUND OCONEE 1 108 16 (15%) 0 OCONEE 2 108 24 (22%) 0 OCONEE 3 108 24 (22%) 0 NOTE 1 - INSPECTED BY ULTRASONIC TESTING

LAB EXAMINATION OF BOLT SAMR.ES 0 REMOVED 2 UCB BOLTS FROM 0-1 DURING 1981 REFUELING OUTAGE (#1, #60) 0 FIELD UT SHOWED BOTH BOLTS IfRERACT 0 BOLT #60: HAD NO If01 CATION 3 0F CAILURE PER THE FOLLOWING TESTS: - FLOORESCEtR DYE PENETRANT - SCANNING ELECTRON MICROSCOPE O BOLT #1: HAD NO IfOICATIONS OF FAILURE PER THE FOLLOWING TESTS: - FLUORESCENT DYE PENETRANT - ENHANCED LAB ULTRASONIC TECHNIQUE

NNA RESULTS e NO ANOMALOUS SPECTRAL BEHAVIOR HAS BEEN OBSERVED FOR UNITS 2, 3. e ANOMALOUS SPECTRAL BEHAVICR HAS BEEN OBSERVED FOR UNIT 1. - NOT INDICATIVE OF A CORE DROP - ANOMALY HAS STABILIZED FOR 200 EFPD e BEAM MODE VIBRATION OF THE CORE BARREL IS PRESENT FOR ALL THREE UNITS,

ABILITY TO DETECT CORE DROP e NEUTRON NOISE SURVEILLANCE e LOOSE PARTS MONITOR e SPNDs, INf0RE T/C - POSSIBLE DETECTABLE GLOBAL CHANGE IN THESE INSTRUMENTS

PROBABILITY OF DBA o ACCIDENTS WITli POTENTIAL FOR SIGNIFICANT LOADING ON CORE SUPPORT STRULTURE ARE LBLOCA AND SEVERE SEISMIC EVENTS. o THE PROBABILITY OF OCCURRENCE OF THESE RARE EVENTS FOR THE LIMITED PERIOD OF INIERIM OPEPATION IS ACCEPTABLY SPALL. o PERIOD OF INTERIM OPERATION: - 2 WEEKS FOR UNIT 1 - 5 PG mis FOR UNIT 2 - 1 YEAR FOR UNIT 3

.c ANilCIPATED SCHEDULE FOR OCONEE NUCLEAR STATION 1 UNIT 1 SHUTDJWN FOR REFUELING AFTER CDPLETION OF UNIT 2's MAINTENANCE OUTAGE, UNIT 2 MAINTENANCE OUTAGE TO BEG!N TH1S WEEFS O, SHUTDJWN FOR REFUELING EARLY OCTOBER, UNIT 3 SHUTDJWN FOR PFJUELING APRIL 1984

t INSPECTION PLANS FOR OCONEE NUCLEAR STATION o CONTINUE NNA SURVEILLANCE - SURVEILLANCE FREQUENCY OF 3 WEEKS o PERFORM 100% LIT OF UCB DURING 01 REFUELING OUTAGE o PERFORM ADDITIONAL EXAMINATIONS BASED ON THE ABOVE RESULTS o RE-EVALUATE OPERATION OF 02, 03 BASED ON THE Ao]VE RESULTS

SUTHARY o UT's SHOW NO BOLT FAILURE o NNA RESULTS INDICATE BEAM MODE VIBRATION IS PRESENT FOR ALL THREE UNITS o SUBSTRUCTURAL UPPER JOINT FAILURE IS NOT EXPECTED FOR INTERIM FERIOD OF OPERATION o HEALTH AND SAFETY OF GENERAL PUBLIC IS NOT ENDANGERED BY A CORE DROP SCB4AR10

~ Af0-1 o PLANT STATUS SHlRDOWN FOR REFUELING 11/82 STARTUP DELAYED ON f4/25/83 TO KRFORM INSECT 10N OF UCB BOLTS INSECTION COMPLETED 5/3/83 PREPARATIONS FOR RESTART IN PROGRESS o INSECTION ESULTS 7 0F 120 UCB BOLTS EXHIBITED UT INDICATIONS o BASIS FOR RESTART FAVORABLE INSECTION RESULTS AVAILABLE MARGIN EVALUATION OF CONSEQUENCES OF POTENTIAL FAILURE o FlffURE ACTIONS CO EINUED PARTICIPATION IN TASK FORCE ACTION FUTURE INSECT 10NS/R~ PAIRS TO BE EVALUATED NEUTRON NOISE ANALYSIS E0'JIPMENT BEING INSTALLED FOR USE DilS CYCLE

FUTURE ACTIONS o THE UTILITIES PLAN TO FORMALLY D001ENT THE INFORMATION PRESENTED TODAY (WITH 2 hEEKS) o CRYSTAL RIVER AND RANCHO SECO ARE PROCEEDING WITH REPAIR PLANS AND WILL KEEP SYD MINER INFORMED o AP8L PLANS TO RESTART ANO-1 SHORTLY o OCONEE 1 WILL BE SHUTTING DOWN SOON FOR REFUELING AND INSPECTION; BOLTS WILL BE INSPECTED AND RESULTS WILL BE PROVIDED TO THE NRC o BaW O'E RS GROUP TASK FORCE IS DEVELOPING THEIR LONG RANGE PLANS WHICH WILL BE COBTiUNICATED TO THE NRC i}}

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