IR 05000331/1993011
| ML20058M390 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 09/30/1993 |
| From: | Jeffrey Jacobson, Schapker J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20058M380 | List: |
| References | |
| 50-331-93-11, NUDOCS 9310050155 | |
| Download: ML20058M390 (9) | |
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U.-S. fiUCLEAR REGULATORY COMMISSI0fd
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REGI0f1 III
'I Report fio. 50-331/930ll(DRS)
Docket flo. 50-331 License fio. DRP-49 l
Licensee:
lowa Electric Light & Power Company
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Post Office Box 351
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Cedar Rapids, IA 52406 I
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Facility flame: Duane Arnold Energy Center
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Inspection At:
Pal o, IA-Inspection Conducted: July 26-29, August 17-20, 24-26, and September 14-15,
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1993 l
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j~ f61 M6/9 $
Inspector:
F FI Sdhapker Date
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Approved By:
IIM %
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- J. M. Jacotison,' Chief Date Materials and Processes Section
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Insoection Summary I
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Insoection on July 26-29. Auaust 17-20. 24-26. and September 14-15. 1993 (Report f40. 50-331/930ll(DRS))
Areas Inspected:
Routine, announced safety inspection of the implementation i
of. inservice inspection (ISI) activities including review of program (73051),
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procedures (73052), observation of work activities (73753), data review and
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evaluation (73755), observation of jet pump set screw repairs (37700), review l
of ultrasonic examination data for the shroud support access hole cover welds
(92701), inspection of the
"D" outboard main steam isolation valve (MSiV)
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nondestructive examir.ation (f4DE) indications (73753), and review of the
.j erosion / corrosion program (49001).
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Results: Of the areas inspected, no violations or deviations were identified.
- During the course of the inspection, the following were noted:
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The licensee's request for Code relief for repair of the MSIV "D",
j CV4421, indications was initially rejected by f4RR. The licensee failed to pursue the indications to the limitation of the Code for stress l
rel ie f.
Additional probing of the indications removed one indication
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(#1) for which no Code relief was required, and the remaining indication j
(73) was reduced to faint magnetic particle detection and the Code radiograph could not detect the indication after weld repair. 11RR subsequently granted Code relief for the #3 indication to avoid necessitating stress relief.which could distort the valve body.
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l-Inspec' tion Summary
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The licensee has committed additional resources to the erosion / corrosion (E/C): program and is implementing state-of-the-art E/C computer
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programming system analysis (Checkworks) and utilizing the EPRI tailor collaboration to upgrade the program.
l-The licensee's ISI program 14DE data reports showed marked improvement, details of examination coverage, parameters, calibrations, and results -
i exceeded Code requirements and were professionally documented.
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DETAILS
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1.
Persons Contacted
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1pwa' Electric Liaht and Power Company
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- D. Wilson, Plant Superintendent
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- M. Huting, Qua'lity Control Supervisor
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- K. Young, Manager, Nuclear Licensing
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- M. McDermott, Manager, Engineering
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- P. Bessette, Regulatory Cor..munication Superintendent i
- F. Dohmen, Corporate Level 111'
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- S. Shangari, Corporate Welding Engineer
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- G. Park, ASME Specialist, Codes and Materials t
- A. Thomas, Erosion / Corrosion Engineer l
S. Russel, Quality Assurance Auditor l
General Electric Comnany (gel
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i P. Bailey, Project Manager l
H. Schlort, Level Ill UT
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J. Oysley, level 11 PT
r U. S Nuclear Reaulatory Commission (NRCl-
J. Hopkins, Senior Resident inspector
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- C. Miller, Resident Inspector l
- Denotes tFose participating in the exit interview on Septembsr 15,
1993.
Other plant and contractor technical personnel were contacted during the
course of the inspection.
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2.
Licensee Action Taken on Information Notices (92701)
i information Notice 88-03: Cracks in Shroud Access Hole Cover Welds l
a.
Backaround
Jet pump BWRs are designed with access holes in the shroud support
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plate which is located at the bottom of the annulus between the l
core shroud and the reactor vessel wall.
Each reactor vessel has
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two such holes which are located 180 degrees apart.
These holes
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are used for access during construction and are subsequently l
closed by velding a plate over the hole.
The covers and shroud
support ledge are inconel Alloy 600 material.
The connecting weld'
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material is also inconel 600 (Alloy 182 or 82).
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The high residual stresses resulting from welding, along with a possible crevice geometry of the weld, when combined with less
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than ideal water quality, presents a condition. conducive to
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intergranular stress corrosion cracking (IGSCC).
This has been
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recognized by GE, and as a result, they have developed a remotely operated ultrasonic testing (UT) capability for detecting cracks in the cover plate welds.
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Licensee Action l
The licensee employed the services of GE to ultrasonically examine i
the cover plate welds in 1988 (reference NRC inspection report 50-
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331/88012(DRS)). At that time, the UT capability was oriented for circumferential cracking only. No relevant indications (cracks)
were identified. Subsequent examinations at foreign BWRs have identified radial cracking propagating into the reactor vessei
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wall.
GE issued a Rapid Information Communication Service Information Letter informing all BWRs with. access hole cover
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plates of these findings and recommended further UT to identify cracking in the radial plane.
I The licensee employed the services of GE to perform the examination using a new technique with the capability to identify
circumferential and radial cracking.
The circumferential exams, looking for radial indications, were performed 360 degrees from
the shroud ledge weld toe, across the weld crown, to 1.4. inches on the access hole cover side of the weld.
The axial exams, looking for circumferential indications, were limited on the shroud ledge side of the weld due to proximity of the shroud and reactor
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pressure vessel wall. The UT exam did identify the same type of
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nonrelevant indications as the previous exam but no cracking was apparent.
The UT examination provides adequate assurance that the access
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cover plate welds and heat affected zones have not degraded and will not compromise the safety of the operation of the reactor.
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3.
Inservice Inspection (ISI) (73051)
a.
Backaround The NRC inspector reviewed the licensee's inspection plan and relief request for the current refueling outage.
The ISI plan
conforms to the American Society of Mechanical Engineers (ASME)
t Boiler and Pressure Vessel Code,Section XI,1980 Edition through
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the Winter 1981 Addenda. The services of an Authorized Nuclear
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Inservice Inspector (ANII) was procured and the 151 procedures and
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personnel certifications were reviewed by the ANII.
The licensee contracted GE to perform selected ISI nondestructive examinations.
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ISI Documentation Review (73052. 73755)
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The NRC inspector reviewed documents relating to the following:
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NDE personnel certifications in accordance with SNT-TC-1A
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and Generic Letter (GL) 88-01 recommendations (where
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required).
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NDE procedures utilized for ISI.
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NDE data reports, including calibration records.
Ultrasonic instruments, calibration blocks, transducers and UT couplant.
l Liquid penctrant and magnetic particle material
certification.
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The documentation reviewed complied with the applicable Code and
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regulatory requirements. The ISI NDE data reports were of
exceptional quality and professionally prepared.
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c.
Observation of Work Activities (73753)
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The NRC inspector observed the following ISI work activities in progress:
UT of primary coolant system recirculation overlayed piping using automatic scanning GE " Smart 2000" with special designed transducer (welds RRFJ4-C-20 and RRF-J004-4A).
See Section 4 for additional details.
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Manual UT of recirculation suction piping welds (RCAJ-43 and
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J-18) in accordcnce with GL 88-01 recommendations (IGSCC
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examination).
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Magnetic particle and UT of main steam piping welds (MSA-
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J036 and J038).
Liquid penetrant examination of recirculation piping weld
(RCAJ043).
Visual examination of reactor vessel internals with remote
television cameras of the shroud welds. The licensee l
performed an augmented visual examination of 100% of the l
shroud welds from the inside diameter. (ID) of the shroud.
This inspection was performed in response to industry and NRC concerns of weld cracks recently identified at Carolina
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Power and Light's Brunswick Station. No degradation or
cracking indications were identified.
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The observed licensee's work activities were in compliance with
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the ASME Sections XI and V, and applicable NDE procedure
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requirements. No indications in excess of Code acceptance l
requirements were identified.
No violations or deviations were identified.
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4.
Ultrasonic Examination of Overlays (7375')
The NRC inspector identified an unresolved item (331/90013-01) during-a previous inspection.
The unresolved item concerned the surface o
conditions of some weld overlays in the recirculation piping, of which some were not conducive to achieving adequate UT inspection coverage in j
accordance with GL 88-01 recommendations.
t Past practi, in achieving the required surface condition was to grind ~
and flar 'he weld to smooth and flatten the weld surface.
This was not desirabis 'o the licensee as the overlays were near theli minimum
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required thicknesses and grinding the surface could necessitate
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additional welding which could be deterious to the overlay and pipe I
weld.
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As an alternative to mechanically improving the surface of the overlays,
the licensee contracted for the services of a nondestructive examination.
laboratory to develop UT inspection equipment and technique which would
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be able to effectively detect and size flaws in overlays with surface conditions as those found at DAEC.
This UT system and procedure was developed and tested with favorable results (reference NRC inspection
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report 50-331/92004(DRS)).
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The licensee changed the ISI NDE contractors for this refueling outage,
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and therefore necessitated the requalification of the UT system being l
employed to examine the overlays this outage..The NRC inspector
observed the calibration and automated UT (GE Smart 2000) in progress.
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Adequate penetration and resolution was apparent, coverage of the
overlay weld and a minimum of twenty-five percent of the base material
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was achieved as recommended by GL 88-01. No growth of the overlayed
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cracks was observed and no new indications were identified.
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No violations or deviations were identified.
The unresolved item is
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considered closed.
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5.
Observation of the Reactor Vessel Jet Pomos Set Screw Repair (377001
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The licensee identified jet pump restrainer set screw tack weld cracks
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at three locations (JP 1, 3, and 11) during~ the last refueling outage (reference NRC inspection report 50-331/92004(DRS.)).
GE, the equipment
designer., developed 'a remote automatic welding repair to secure the set
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screws.
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The repair secures the set screw by application of a fillet weld on the
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screw threads to jet pump restr.iner.
The welding process is performed
underwater using remote high re:.olution video cameras and a Gas Metal
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Arc Welding (GMAW) pulse spray welding process. A special cup type cover containing the weld head with sealing capabilities is lowered in place to cover the set screw threads. When manipulated into the proper position, the fixture is secured and the water is evacuated by purging the cup with Argon-Helium-carbon dioxide.
Immediately after purging, the welding is initiated and two welds are deposited 180 degrees apart on the thread to jet pump restrainer. A visual examination is performed, via remote video camera to assure adequate penetration and-
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deposit of weld material to sect.re the set screw.
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inspection
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The NRC inspector reviewed the Weld Procedure Specification (WPS) P8-M-VW-1, the Procedure Qualification Record (PQR) P8-M-UW, and observed the purging, welding process, and visual inspection for jet pump restrainer l
set screw number 14. All essential variables as required by ASME Code Section IX were adhered to.
The visual examination confirmed the' weld was sound and secured the set screw.
The licensee demonstrated their
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commitment to safety by repairing all the jet pump restrainer set screws
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regardless of the original tack weld soundness. Only three tack we.os
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were observed to have cracked, as a preventive measure the licensee elected to assure all set screws were secured.
No violations or deviations were identified.
6.
Observation of the Main Steam Isolation Valve (MSIV) Repair and Examinations (73753)
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The licensee machined the bore of the outboard MSIV "D" after unacceptable as-found leak rate test results were obtained this
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refuelire ;atage. A magnetic particle (MT) examination conducted following this machining identified three unacceptable linear
indications in the valve body.
Indication number 1 was 1/4"; number 2
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was 2" intermittent, and number 3 was 1-1/4" in length.
Number 2
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indication was subsequently removed by grinding.
The remaining two
indications, after grinding to a depth of.304" and.312" respectively, i
were 1/4 inch and 1-1/8 inch in length. All these indications were
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determined to be subsurface shrinkage defects (radiograph review) from
the original casting process which were brought to the surface by the
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machining.
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Code repairs of these defects require the defects to be reduced to en
acceptable size before depositing weld metal.
Following the weld
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repair, a post weld heat treatment could be required.
The licensee's previous experience with such repair and heat treatment results in excessive valve body distortion which causes the valve's leakage
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performance to degrade. For this reason, the licensee requestied relief
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from the Code requirement to reduce the indication to acceptable limits prior to weld repair to avoid necessitating heat treatment of the weld repair.
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The licensee's initial repair to MSIV "D",
prior to NRC Code relief
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approval, ground the indications to depths up to 10X wall thickness and
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weld repaired prior to reducing the indications to Code acceptable sizes. ~ However, the licensee had not approached the 20% wall thickness
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Code limit of repair depth requiring post weld heat treatment after welding.
This approach was presented to the NRC with a request for Code relief and acceptance of the repair as performed.
r A conference call was held on September 16, 1993, with the.0ffice of -
Nuclear Reactor Regulation (NRR) and the licensee concerning this relief request.
The Region Ill NRC inspector ~was present during the conference call. NRR informed the licensee that they could not accept.the request for Code relief because the licensee had not pursued the removal of the-indications to the limit of the Code requirement where stress relief would be required.
It is possible that the indications could be. removed ~
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and Code relief would not be necessary.
In addition, the licensee had not MT inspected each weld layer as deposited to assure the flaw did not
propagate into the weld material.
The licensee subsequently probed the indications and attempted to remove
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the flaws without exceeding the Code limits for post weld heat l
treatment. The number 1 indication was removed and weld repaired, complying with Code requirements.
The number 3 indication was probed to
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a depth of.593", which resulted in the presence of three more
indications. These were weld repaired with each weld pass being
visually and MT inspected to assure the. indications would not propagate
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into the weld material. Radiography of both weld repairs were performed which verified that no defects existed in the weld and that the casting i
around the repaired area meets the requirements of the original
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construction Code. The final radiographs revealed only very minor
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shrinkage indications and represents a significant improvement in this
area, compared to the original fabrication radiograph.
l The licensee performed an engineering evaluation to determine the j
bounding flaw depth of subsurface defects for the CV4421 -(MSIV "D")
valve body per ASME Section XI requirements.
The results of this evaluation concluded the as-left flaws prior to welding are bounded by the assumed flaw sizes in this analysis, and those assumed flaw sizes were evaluated using a series of conservative assumptions and were determined to be acceptable for 40 years of operation per the
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requirements ASME Section XI, IWB-3600. This engineering evaluation was submitted to NRR with.the Code relief request for their review. The NRC j
inspector conferred with NRR and the licensee subsequent to the
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September 16th conference call and confirmed the licensee's subsequent
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repairs and engineering evaluations were acceptable.
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No violations or deviations were identified.
However, the licensee did.
not pursue the removal of the indications to the limits of the Code-i
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requirement, where post weld heat treatment would be required, without 4'
NRC prompting.
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7.
' Erosion / Corrosion (E/C) Prooram Review (49001)
The licensee's E/C program is conservative and is currently in the process of being upgraded.to the state-of-the-art EPRI Checkworks program.
This new EPRI program improvement removes interfaces of components, enhances the structural evaluations and provides more a
accurate line correction factors.
The licensee has also committed j
additional resources to the upgrading and implementation of the E/C
program by adding additional personnel.
In addition, the licensee is i
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utilizing the resources of EPRI's tailored E/C program.
This program:
provides specific " tailoring" of the Duane Arnold E/C susceptible i
components and systems into the Checkworks E/C program.
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The NRC inspector observed the UT data recording and input to.the computer program, reviewed current and previous outage reports and j
implementing procedure. The licensee inspected 133 components this
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outage. A total of twelve replacements were made this outage due to the
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identification of wear in excess of minimum wall or projected to exceed
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minimum wall prior to the next refueling outage.
In addition, two
components are scheduled for replacements for the next refueling outage
based on predicted wear calculations.
l The licensee's dedication to upgrade the E/C program and the demonstrated effectiveness of the program provides the necessary conservatism to assure the mitigation of the possibility of a i
catastrophic rupture, which could jeopardize plant safety systems and i
human lives.
i No violations or deviations were identified.
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8.
Exit Interview i
The inspector met with licensee representatives (denoted in Section 1)
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at the conclusion of the inspection on September 15, 1993. The
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inspector summarized the scope and findings of the inspection
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activities.
The licensee acknowledged the inspection findings.
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inspector also discussed the likely informational content of the
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inspection report with regard to documents or processes reviewed by the'
j inspector during the inspection. The licensee did not identify any such
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document / processes as proprietary.
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