IR 05000237/1988006
| ML17201Q094 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 02/27/1989 |
| From: | Danielson D, Schapker F NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML17201Q095 | List: |
| References | |
| 50-237-89-06, 50-237-89-6, GL-83-08, GL-83-8, GL-88-01, GL-88-1, IEIN-88-003, IEIN-88-3, NUDOCS 8903080203 | |
| Download: ML17201Q094 (8) | |
Text
U.S. NUCLEAR REGULATORY COMMISSION REGION I II Report No. 50-237/89006(DRS)
Docket Na. 50-237 Licensee:
Corrurmnwea lth Edi son Company Post Office Box 767 Chicago, IL 60690 Facility Name:
Dresden Station, Unit 2 Inspection Pit:
Dresder1 Site, Morris~ Illinois License No. DPR-19 Inspection Conducted:
January 23, 24, 27 and February 14-16, 1989
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Inspectorr. F. Schapker *.
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ApprovE:d By:
D. H. Danielson, Chief Mat~rials and Precesses Section Inspection Summary Ins E:ction on Januar 23, 24, 27 and Februar 14-16, 1989 (Re drt No. 50-237/89006 DRS Are~s Ins ected:
Routine, unannounced inspection of inservice inspection ISI activities including review of program (73051), of procedures (73052), of observation of work and work activities (73753), of data review and evaluation (/3755); of the inspection for verification of ti'1ark l BWR Drywell Vacuum Breaker Modifications (TI 2515/96)(37828); and of IE Informatior1 ~otices (92701).
Results:
No violations or deviations were idE:ntified within the areas observe ISI activities were accomplished within the guidelines of ASME Section XI and Generic Lette:r (GL) 88-01 requirement Overlay rE:pair WE:iding and nondestructive examinations were performed to the applicable code requirement I~plementation of repairs was adequately controlled by QA~ QC requirement Licensee's actions taken on Generic Letter 88-01 and Information Notice 88-03 were adequate tc ~ssure safety w~s not compromised.
- DETAILS Persons Contacted Commonwealth Edison Company (CECo)
- C. Schroeder, Services Superintendent
- E. Netzel, QA Superintendent
- J. Achterberg, Technical Staff Supervisor
- K. Peterman, Regulatory Assurance Supervisor
- G. Whitman, ISI Coordinator
- R. Falbo, Regulatory Assurance Assistant
- J. Silady, Nuclear Licensing Assistant E. Eeni genburg, Sta ti on Jl".anager K. Miller, Senior QA Inspector M. Horbaczewski, Technical Staff, ISI R. Dyer, Technical Staff Assistant B. Wilson, Level III SMAD General Electric Company (GE)
T. Brinkman, Level III T. Kimbo. 11, Leve 1 I I W. Holasek, Level II P. Wright, Level II Hartford Steam Boiler Ir1spectiun (HSB)
K. K 11 mer, AN I I U.S. Nuclear Regulatory Commission (USNRC)
S. Dupont, Senior Resident Inspector The NkC inspector also cor.ta.cted and interviewed other licensee and contrac~or employee *Denotes thos~ present at the final exit meeting on February 16, 1989. LicE:-nsee Action Taken on Informatior; Notices (92701)
(Closed) Inforniation Notice 88-03 (83900-01) Cracks in Shroud Support Access Hole Cover Welds Backaround Jet pump BWRs are designed with access holes in the shroud support plate which is located at the bottom of the annulus between the core shroud and tile reactor ve.sse l wa 1 Each reactor vt:sse 1 hc;.s two such ho 1 e.s which are located 180 degrees aphr These holes are used for access during construction and are subsequently close~ by welding a plate over the J
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hol Th~ covers and shroud support ledge are Inconel Alloy 600 materia The connecting weld material is also Inconel 600 (Alloy 182 or 82).
The hi9!1 residual stresses resulti~g from welding, along with a possible crevice geometry of the weld, when combint:d with less than ideal water quality, present a condition conducive to intergranular stress corrosion cracking (ISGCC).
This has been recognized by General Electric and, as a result, they have developed a remotely operated ultrasonic testing capability for detecting cracks in the cover plate weld The first use of this custom ultrasonic testing fixture was at Peach Bottom Unit On January 21, 1988, intermittent short cracks were found in the weld heat-affected zone around the entire circumference of the covers at Peach Bottom Unit It is estimated that cracking exists over 50% to 60% of the circumference with cusps as deep as 70% through the wal It is believed that cover plate welds have not been inspected previously on any oth~r BW It is possible that the cracking is generic and may, therefore, affect all BWRs with jet pump Lice11see Action The licensee employed the services of GE to examine the welds utilizing ultrasonic examinatior. of the covEr plate welds for Unit 3 during the last out&9E:.
During the examinati0n of the cover plate welds, no indications associc.ted with IGSCC were recorded with the 11Smart UT" (SUT) system utiliiing 45° sliear wave and 5S 0 refrilcted longwave (RL) search unit The UT examination provides adequate assurance that the acces$ cover plate wt;lds and heat affected zones huve not degraded ar1ci will nut compromise the saf8ty of the 0peration of the reacto The licensee did not examine Unit 2 as Unit 3 did not ext1ibit any crack Unit 3 was considered most susceptib~e to cracking due to previous shroud he~d bolt cracks which were nut experienced in Unit 2, and Unit 2 has hydrogen injecticn aciditic.11 whereas Unit J does no.
Ins ection for Verificc.tion of Mark I RWR Dr 1 el"l Vacuum Breaker Modifications Closed. SIMS MPA-D2C TI 2515/96 37828 Objective To inspect those plants that have modified their drywell vacuum breakers i11 response to NRR Generic Letter 83-08, and to allow close out of this action item under Multi-Plant Action Item D-2 Background In December 1979, General Electric issued SIL No. 321 informing customers of uria nti ci pa tee cycling and damage to dry\\*1e 11 vacuur.: breakers curing LOCA tE:sts in a prototype Mark I containme:ri To assure that dr~1Wen
- vacuum breukers would be capable of withstanding chugging and conde11satiun oscillation loads, the staff issued Generic Letter 83-08 reques ti rig 1 i censees. of Mark I containments to perform pl ant-unique calculations to determine the structural adequacy of the drywell vacuum breaker The staff has received responses tu the Generic Letter and has issued Safety Evaluation Some licensees, in their response, determined that vacuum breaker modifications were required, whereas others determined that no modifications were neede The need for modifications is identified in the Safety Evaluation Repor Inspection The NRC i11spector reviewed the licensee's Technical Evaluation Report for the structural evaluation of the Vacuum Breakers and the Safety Evaluation by NR In each of the Dresden 2 and 3 Mark I Containments, there are twelve 18
external typt: vacuum breakers made by At\\\\lood - Merrill mounted on six exterior headers connecting the suppression chamber and the vent line exterior of the wetwel Loadins;s on Mark I structures and vacuum breakers are based on the General Electric Company Report, NED0-21888,
"Mark I Containment Program Load Definition Report, 11 Revision 2, dated November 198 For vo.cuwr. breakers, the loadings included are gravity, seismic, and hydrodynamic luud The hydrodynamic forcing functions were developed by ContiriLwrr Dynarr.ics, Inc. by using a dynamic model of a Mark I pressure suppression system and the full scale test facility d~ta. The system model was capable of predicting pressure transients at spE::cific locations in the ve::nt syste Loading across the vacuum breaker disc caused by pressure differentials based on test data was thus quantified as a function of tim This issue was revie\\'*ed and approved by NRC or; December 2<~, 198 Loadings were cumbi ned according to the FSAR commitment To determine the structure.*, integrity of the vacuum breakers, results from a finite element model a~~ ANSYS program analyses were compared with design limits specified in the ASME Beiler and Pressure Vessel Code,Section III, Revision I, Subsection NC, 1977 Editior and Addenda up to Sumrn~r 197 It was found that the hydrodynamic chugging force in Dresden 2 and 3 will not significantly increase the impact velocity on vacuum breukers to cause any additional loadin Since th~ 0riginal design margin does not need improvement, the licensee decided that no modifications were needed on the construction of its vacuum breaker The licensee, however, did replace the original aluminum cast discs witt1 aluminum plate material for better ductilit The NRG ins1-1ector revievied the licE:nsee's design modification records pertaining tc the replacement of tht cast alumiHum disc to wrought aluminum discs with stainless steel post The SER review by NRR determinE:d that the structural analysis indicated the existing vacuum breaker design was 6cceptable and no additional modific~tions were require Review of vacuum breaker disc modific~tion
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documentation disclosed that the disc replacement had been made with material as required by the design chang No violations or deviations were identifie.
Inservice Inspectior1 (ISI) Unit 2 (73051, 73052, 73753, 73755) Genera 1 This was the third outage of the second period in the second ten year pla Th~ licensee contracted with General Electric Corporation (GE) to perform uitrasonic (UT), magnetic particle (MT),
liquid penetrant (PT), and visual examination (VT).
Examinations were performed in accordance with ASME Section XI, 1977 Edition, Summ~r 1979 Addend ISI Procedure Rt:view The NRC inspector reviewed the following NOE procedures:
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CECo, Nondestructive Testing (lnservice Inspection) UAP 11-8, Revision CECo, 11 Preservice and Inservice Ultrasonic Inspection of Sinriiar and Dissimi"lar Metctl Pipe Welds at Nuciear Stations,
NDT-C-2, Revisio~ 15.
GE 11 Qualification and Certi.fica.tion of Nondestructive Testing Personnel,
11 QC-2, Rt:vision GE "Visual Acuity Testing, 11 QC-4, Revision CECo, 11 Ultrasonic Inspection of the Vessel Nozzle Inner Ra.dii ut Nuclear Stations," NDT-C-10, Revision 1 CECo, "Ultrasonic Inspection of Flange Ligam~nts Betwee:n Threaded Bolt Holes,'
1 NDT-C-11, Revision 1 CECo 11 Ultrasonic Exaruination of Reactor Vessel Welds to NRC Reg. Guid<:: 1.150 for Boiling Water Reactors, 11 NDT-C-30-79, Rt:vision CECo,
Bearr~ Spread and Refracted P,ngle Determination to NRC Reg. Guide 1.150 for Boiling Water Reactors, 11 NDT-C-*31-79, Revision CECo, 11 horiaqueous Red Dye Liquid Penetrant Examination for Section XI Ci iJ.SS IW8 and rnc Components for NucJ ear Statior.s 'II NDl-D-2, Revision CECo, "Visual Examinati0n -
~elds, Pressure Retair1ing Bolting, and Component Internals," VT-i-1, Revision *
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CECo, 11 Visual Examinatio11 - System Hydrostatic and Leak Tests,"
VT-2-1, R~vision CECo, 11Visual Examination - Component Supports, 11 VT-3-1, Revision CECo, 11Magne-ric Particle Examination for ASME Section XI Class IW8 and IWC Compo~ents for Nuclear Stations, 11 NDT-B-1, Revision Review of ISI Data, Material, Equipment, and NOE Personnel Certifications The NRC inspector reviewed the following documents and determined that the applicable QA/QC requirements were met:
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ISI Data Report Ultrdsonic Instruments, Transducers, and Couplant Certification Liquid Fenetrant, Cleaner, anC: Developer Certification Magnetic Particle Materials and Equipmen NOE Personnel Certifications Compliance to SNT-TC lA requirement Augmented Inspection of B~iR Stainless Steel Piping_
The licensee performed inspections of stainless steel p1p1ng as set forth in Generic Letter (GL) 88-01 and NUREG-0313, Revision There is a total population of 276 welds at Dresden Unit 2 that are governed by GL 88-0 Of those, 228 are considered to be susc~ptible to IGSCC (non-Category A).
The licensee's ausmented inspection plo.n contained a total of 145 weld Addition~l welds were added due to mechanically stress improved (MSI) welds, three previously applied overlays which were built up and surface finished this outage, and two previously unidentified welds on the Isolation Condenser System (ICS) for a total of 161 weld As a result of flaws observed in welds iri the original sample, the licensee expanded the sample to include all 12 11 recirculation riser welds, all previously applied weld overlays, both 22 11 recirculation header end cap welds, and all susceptible (non-Category 11A
) Reactor Wat~r Cleanup System weld Thus the sample size w~s expanded to a tutc.:l of 190 cf the 228 intergranular stress corrosion cracking (IGSCC)
susceptible weld Category E, F, and G welds were inspected 100% at this outag The lic~nsee performed mechanical stress improvement to 104 welds at this outag New reportable IGSCC ir1dications were identified in nineteen (19)
we1c Ten of the welds with indicatioris a.re in the 12
recirculation system risers; nine of these a.re pipe-to-elbow and one is pipe-to-reduce Two of the IGSCC indications are pipe-to-end cap welds on the 22 11 recirculation heade The remaining seven are in the
11 Reactor ~Jater Cleanup syste In addition, two previously flawed welds had significant new axial IGSCC indication The licensee repaired these flaws utilizing weld overlays. A total of 21 new weld overlays were applied at this outag In addition, three 11 leak barrier 11 weld overlays applied during a previous outage were completed and ultrasonically examine Three u11repaired welds with circumferential indications reported during the previous (198G) outage examination had been evaluated and approved for continued operation with no repairs. These welds were reexo.r.li r.ed during the current outag The results of the current UT exami r1ati ons showed no change -; n the previously* reported circumferential flaw However, t\\.;o welds on 12 11 recirculati0n risers were found to contain axidl indications in addition to the previously reported circular indications. These two welds required overlay as a result of the new axial IGSCC indicatio~s. The remaining weld which contained a circumferential flaw reported in the previous inspection was again eva1uatea by licensee engineering and determined to be acceptable without repai Due tG the significant increase in reported IGSCC indications this outage, the NRC inspector reviewed UT reports fo1* the previous three outage This review concentrated un those welds which had developed IGSCC indications at this outag UT reports for Unit 2, 1983, 1985, 1986, anti the present 1988 outages were reviewe The NRC inspector concluded tliut the UT inspection rE":~ults wert:
consistent, with no indication of inadequacy of inspecti0n techniques (1983, 1985 examinations were performed by LMT ana 1986, 1988 examinetions were performed by GE).
In discussions with the UT examiners a possible improvement in weld inspectability was made due to weid preparation prior to examinations this outag Previously, a majority of Unit 2 1 s welds were "flat topped.
This term describes the weld reinforcement which was mecha~ically prepared to smooth the weld for better UT couplan This process does not remove all the reinforcement and therefore leaves a st~p ut the toe of the wel Prior to this outage's VT exanii 11a ti CHi c. majority of thE::se steps were removed to the contour of the pip This enubles better couplant for UT examination particularly fol' circumferential scans which detect axial flaw The significu11t number cf axial indications identified duril"ig this uutage m..i:/ have been aidecl by the weld preparatior During
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discussions with the licensee at the exit meeting, the licensee's ISi representative indicated that the licensee will prepilre welds for future examinations in accordance with the recommended EPRI guideline The NRC inspector observed the application of the weld overlay The weld process was performed in accordance with the applicable weld procedure requirement Weld operators were qualified in accordance with ASME Section I Weld materials were certified to the ASME Section II, Part C requiren1ent The inspector verified the essential variables were in compliance to the welding specification requirement The NRC inspector al~o observed the auto image 11 GE Smart" ultrasonic examination of the overlay applied to the PD5-D20, 12" recirculation wel This_weld was the "worst case" of the IGSCC indications prior to overla The previous examination disclosed two circumferential IGSCC indications which were disp0sitioned in 1986 as discussed previously in this sectio The circumferentic1l flaws haC: not changed, however, twenty two additional axial ir1dications ranging from 0. 25 inches to 0. 85 inches in length and 20~~ to 92% thruwa 11 were foun After application of the overlay weld, the weld joint l/IC.S ultrasor.ically examined utilizing the automatic "GE Snwrt" system This examination revealed sixteen axial indications associated with IGSCC and ten indications associated with interbead lack of fusio Of the sixteen axial IGSCC indications, five exten~ed into the overlay material. These extensions into the.
overlay ranged from 0.06 inches to 0.20 inche The remaining eleven indications of IGSCC were contained within the top 25% of the base materia A n1anual ultrasonic examination confirmed the preseDce of the ICSC However, the_manu~l examination was noisy (grain structurE: reflections) and diffic.~lt to interpret. The resoluti0n utilizing the "GE sm&rt 11 sysif:::m was enhancec' in evaluation of the flaws ar.C: therefore was used as tilt: principle evaluator of the overlay inspectio The licer.see performed a flaw E:valuation and repair design report (SIA-89-GG4, Volume 1, Revision 1). This report documents the evaluatiur1, disposition, and repair of flawed welds found by UT examination this outag All flaw evaluations and weld overlay repair designs were performed by Structural Integrity Jl.ssociates Inc. in accordarce with NRC Generic Letter (GL) 88-01 and NUREG-0313, Revision 2, with input from discussions with NRC Headquarter The evaluation of the flaws and subsequent overlay repairs was adequate to assure thE: safety objectives as described in GL 88-Cl and NUREG 0313, Revision 2 were complied wit.
Exit Meeting The NRC i1ispector met with the licensee representatives (denoted in Paro.graph 1)
a*~ the conclusion of the inspectio The inspector summarized the purpose and findings of the inspectio The licensee represent~Lives acknowledged this informatio The insp~ctor also discussed the likely informational conter1t of the inspection report with re~ards to docun1ents or processes revie:r.ied during the "inspect"io The l icenseE representatives die riot ider.tif.Y any such documents/processes as pro pr i eta r