IR 05000327/1993004
| ML20034F141 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 02/19/1993 |
| From: | Blake J, Coley J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20034F125 | List: |
| References | |
| 50-327-93-04, 50-327-93-4, 50-328-93-04, 50-328-93-4, NUDOCS 9303020323 | |
| Download: ML20034F141 (10) | |
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%,0,f cf UNITL3 STATES NUCLEAR REGULATORY COMMISSION y
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. REGION 11
" r 101 MARIETTA STREET, N.W.
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ATLANTA, GEORGl A 30323 o,
Report Nos.:
50-327/93-04 and 50-328/93-04 Licensee: Tennessee Valley Authority
3B Lookout Place 1101 Market Street i
Chattanooga, TN 37402-2801
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Docket Nos.:
50-327 and 50-328 License Nos.: DPR-77 and DPR-79'
Facility Name:
Sequoyah 1 and 2
Inspection Conducted:
February 1 - 5, 1993
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Inspector: k.M lid a c2 - / 8-33
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~JN..Coley,tJg Date Signed
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Approved by:
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Dafe Signed
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J f. Blake, Chief aferials and Processes Section
Engineering Branch Division of Reactor Safety
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SUMMARY
Scope:
This special announced inspection was co. ducted in response to a flow assisted '
corrosion blowout in a 3 inch target tee on an operating vent pipe line :
running from the moisture separator reheater to the extraction steam system.
In addition to investigating the cause of the failure the. inspector conducted an in depth audit of TVA's erosion / corrosion (E/C) program, procedures,
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drawings, work activities, and recorded data for both Units 1 and 2.
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Corrective actions on previous NRC inspection findings were also evaluated.
j Results:
In the areas inspected, violations or deviations were not identified primarily
because the erosion / corrosion program addresses high energy-piping in non-
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safety related systems. The inspector's audit however, revealed that TVA's
E/C program is not effective in controlling E/C at the Sequoyah Plant particu-larly in smaller bore piping (10 inches in diameter and smaller). This
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finding on small bore piping is apparent when comparing the token results obtained by E/C ultrasonic examinations to the 118 through-wall piping E/C -
failures experienced at the site and repaired using liquid sealants with
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clamps or cans since mid-1988.
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9303020323 930219 PDR ADOCK 05000327
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t Although TVA's program correctly focuses on large bore piping (10 inches and
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greater) the inspector identified weaknesses in.that program which if;not properly addressed by the licensee could result in plant piping failures
(large bore and small bore) that may challenge safety related systems, cause unnecessary shutdowns, and injure personnel or damage equipment in-the vicinity of the' failure.
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Report ~ Details 1.
Persons Contacted Licensee Employees
- B. Anderson, Project Management i
- L. Bryant, Maintenance Manager u
- L. Bush, Operations Manager (Acting)
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- W. Goins, Site E/C Engineer
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- J. Hamilton, Quality Audit and Assessment Manager
- M. Miller, Quality Control Manager
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- J. Proffitt, Licensing Engineer
- F. Scalise, Non Destructive Test Specialist
- J. Smith, Manager, Regulatory Licensing i
- G. Strickland,. Corporate E/C Engineer
- P. Wallace, Manager, Site Support L;
- J. Ward, Manager, Engineering and Modifications
- K. Whittenburg, Manager, Public Relations
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- T. Woods, Corporate Lead Metallurgical Engineer i
- J. Mathis, NRC'(Acting) Resident Inspector i
- Attended exit interview
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Acronyms and initialisms used throughout this report are listed in the last paragraph.
2.
Review and Evaluation of the Sequoyah Flow - Accelerated Corrosion Monitoring Program - Units 1 and 2 (49001)
Background
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Erosion / corrosion of carbon steel piping systems has occurred in the turbine cycle (two-phase systems) of both fossil and nuclear power plants
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for a number of years.
Several licensees had established monitoring i
programs to examine for this phenomenon in wet steam systems in the late-70's.
However, until the 1986 catastrophic failure at the Surry facility, single phase piping systems were net considered susceptible to i
erosion / corrosion. The Surry failure prompted NRC to request all licensees to institute special programs for controlling erosion / corrosion (Bulletin 87-01 and Generic Letter 89-08).
TVA's E/C program for the Sequoyah two phase piping started in late 1984-for Unit 1, and 1985 for Unit 2.
Single phase piping was added in early 1988. Both programs were basically inspection programs based on engineering judgement and some analysis. The selection of components for examination reflected a very small sample of susceptible piping when using this concept to determined which components would be likely to fail-
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i In the Spring 1992, during cycle 5 outage for Unit 2, TVA utilizci the Electric Power Research Institute (EPRI) computerized program CHECKMATE for the first time.
However, only a small portion of the components examined at this time were selected using this method.
The results of tnis small sample were fairly favorable in'that two components were identified as requiring repair or replacement using this technology.
CHEC was never used in its entirely by TVA because early evaluations 1f the program by the licensee revealed a lack of conservatism in the early revisions of the program.
EPRI had developed CHEC for single-phase piping and CHECKMATE for two-phase piping to help plant E/C engineers in identifying the most suscep-tible locations for inspection, thereby minimizing the amount of inspec-
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I tion required.
CHEC and CHECKMATE approach this issue in two distinct yet similar fashions for single-phase and two-phase analysis.
For single-phase lines, a plant specific model of the condensate feed water and heater drain lines is developed. This mNel is then analyzed
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using the " Pass 1" analysis mode in CHEC. CHEC P.ss I results provide information for planning the initial inspection in that it ranks the
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susceptibility of all components to E/C.
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For two-phase analysis (CHECMATE), individual models must be developed
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for all lines that need to be analyzed.
Lines experiencing significant.
E/C in the past should be given a higher priority for analysis. CHECMATE output consist of three ranking lists that can be used for planning the initial inspection. The first list is a ranking by erosion rate for all the components in the line. The second list ranks these components by.
the predicted time to reach a minimum acceptable thickness. The third list provides the predicted wear and thickness for all components.
Based on these lists and past experience with a given line, the E/C engineer has enough information to determine the inspection locations for the line.
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Evaluation of the January 28, ima, Pipe Failure On January 29, 1993, TVA notif a NRC that they had experienced a blowout on Unit 2 in a 3 inch target tee located in an )perating vent pipe line which ran from the moisture separator reheater to the extraction steam system.
The failure was apparently caused by E/C of the target tee fitting.
On February 1, 1993 the inspector arrived at the Sequoyah facility to investigate the failure and to examined the licensee's E/C monitoring program. The inspector investigation into the failure revealed that the licensee had a significant history of E/C on operating vent lines with target tees. This history included replacing 3 operating vent lines with stainless steel on Unit 2 and replacing 6 lines with stainless steel on Unit 1.
In addition, Unit I was operating with 2 operating vent lines repaired with liquid sealant in cans attached to I
them. These lines however, were not in E/C program because the E/C-l engineer had incorrectly identified the operating vent lines on his marked up drawings as only operating 2% of the time therefore, exempt from E/C.
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On February 3, 1993, while the inspector was at the_ site the licensee experienced another blow-out on an elbow downstream of the first failure.
This line was repaired with a can and liquid sealant.
Ultrasonic examinations of the adjacent piping revealed that it had eroded from.200 inch nominal to.080 inch.
However, the licensee performed the necessary calculations on the pipe and elected to continue operating' the plant until the next outage in September.1993.
After the first pipe failure on January 28, 1993, the licensee did not elect to examine similar piping on Unit 1.
However, after the 2nd pipe failure, and also after experiencing a liquid sealant can come loose on a leaking fitting on Unit 1, the licensee decided to bring this Unit down and examine the applicable lines. These examinations revealed that' out
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of 30 pipe runs examined and evaluated,14 runs of pipe required material replacement, this included 6 tees and -10 elbows. Two Scab plate repairs were also required, as well as one overlay weld repair.
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Review and Evaluation of TVA's E/C Monitoring Program The inspector held discussions with corporate E/C engineers, site E/C engineers, and the Quality Assurance (QA) nondestructive examination (NDE) supervisor concerning the E/C program at the Sequoyah facility.
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i These discussions and the subsequent review of records and documents listed below were conducted in order to determine whether or not manage-l ment control problems or generic weaknesses existed relative to the
licensee's implementation of its long-term E/C monitoring program.- The
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records and procedures listed below also encompass the basis for the E/C
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program, the E/C program, and implementing procedures used to monitor i
Units 1 and 2 for flow-accelerated corrosion at the Sequoyah Nuclear Power Plant.
Documents Reviewed Document Identifier Title
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MEB-84-1115T0309, Memo Moisture Separator To: J. Darling, Manager Reheater (MSR) Low
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of Nuclear Power Pressure Drain Pipe From: R. Cantrell, Manager, Failure - Design Study of Engineering Dtd. 11-5-84 Request No. S-028 Results and Recom-mendations L29-841203-983 Metallurgical Sequoyah Nuclear Plant Report Dtd. 11-30-84 Unit 2 Inspection of Crossaround Piping, Target Tees, and Extraction Steam Piping for Wall Degradation
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Documents Reviewed Cont'd
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Document Identifier Title
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B25-870127-028, Memo Preliminary. Report on the To: H. Abercrombie, Site Condensate - Feedwater.
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Director Piping Inspection From: D. Wilson, Project (Suspected E/C Areas)
Engineer, Dtd. 1-27-87 j
B25-870408-067, Memo Sequoyah Nuclear Plant i
To: H. Abercrombie, Site Unit 2, Wall Thinning
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Director Assessment Program Final
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From: D. Wilson, Project Report Engineer, Dtd. 4-8-87 l
L44-870918-806 TVA's Thinning of Pipe Walls in
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Response to NRC Bulletin Nuclear Power Plants
87-01, Dtd. 9-18-87
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SNP-00-D052 Dtd. 12-14-87 Sequoyah Nuclear Plant Design Study for Single-Phase Flew E/C-
L44-890719-803 TVA's Erosion /Corrosien-Induced
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Response to NRC Generic Pipe Wall Thinning Letter 89-08 Dtd.7-19-89 r
General Engineering Speci-Corporate Erosion /
fication No G-97B Dtd.4-5-91 Corrosion Program
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Memo To: R. Lumpkin,-QA Manager Priority E/C Monitoring from: P. Trudel Engineering Sites For Unit'1 Based
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Manager Dtd. 10-4-91 on Previous examinations
Sequoyah Nuclear Plant (SNP)
Unit 2 Extraction Steam Periodic Instruction Pipe Wall Degradation
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2-PI-SXX-005-001.0 Dtd.1-23-92 Monitoring Program l
t SNP Periodic Instruction Unit 2 Wall Degradation
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2-PI-SXX-003-001.0 Dtd.1-23-92 Monitoring Program For Feedwater/ Condensate Piping, Turbine, and
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Heater Drain Lines SNP Periodic Instruction Unit 1 Wall Degradation 1-PI-SXX-003-001.0 Dtd.9-21-92 Monitoring Program For The Feedwater/ Condensate'
i Piping, Turbine, and-i Heater Drain Lines
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Documents Reviewed Cont'd
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Document Identifier Title SNP Periodic Instruction Unit 1 Extraction Steam 1-PI-SXX-005-001.0 Dtd.9-21-92 Pipe Wall Degradation Monitoring Program NDE Procedure No. N-GP-22 Grid Marking of Rev. O, Dtd. 1-4-93 Components for E/C Examination NDE Procedure No. N-UT-26 Ultrasonic Examination
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Rev. 12, Dtd 1-4-93 For The Detection of
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ID Pitting, Erosion, and l
Corrosion As a result of the above discussions and reviews, the inspector identified the following E/C program weaknesses:
(1) TVA's Program has been far two small considering all susceptible piping have not been modelled to determine their ranking' for E/C.
The programs for next outage on both units has increased the sample modelled some, but at this point it appears that E/C in'the plant is exceeding the parameters of the monitoring program.
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Plant history is not being properly used to supplement the E/C program. The 118 thoughwall repairs made since mid - 1988 utilizing-liquid sealant in cans on piping ranging from 10 inches to 1/2 inch in diameter have not been factored in the E/C program. Mapping these repairs on system drawings could have assisted the E/C engineer in predicting many of these plant failures before hand.
(3)
Expansion examinations are not being performed properly and in many i
cases not at all.
Expansion examinations should include fittings
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upstream and downstream of a failure, similar trains, and similar piping on the other Unit.
It is not uncommon at Sequoyah to see where multiple repairs (three and more) have been made within a very short run of piping, and similar trains on the other Unit had not been examined, but subsequently failed.
(4) There is no second party review of input or output data, particularly from plant operations personnel. This was apparent where the E/C engineer incorrectly assumed that the operating vent lines for the MSR's only operated 2% of the time. Therefore, excluded them from the program.
(5) The E/C program is fragmented. The E/C engineer at the site only performs this duty part time. Time spend on E/C detection and prevention has been totally inadequate.
When there is a pipe failure as the inspector witnessed.
Instructions for component
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examination and sample expansion come from individuals not familiar
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enough with the E/C phenomenon to correctly identify how best to examined for it, record it so that the information can be effectively used in the E/C program, and bound it to insure no-subsequent blowout occurs.
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(6) Although, TVA has implemented Code Case N-480 for ASME Code Class 1, 2, and 3 carbon and low alloy steel piping in their Corporate E/C
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Program Prc:edure No. G-978. Only one component (a 1 1/2 inch steam generator blowdown piping vent fitting) is in TVA's program for examination on each Unit. The licensee is expected to monitor safety related systems for known types of piping degradation. This
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token inspection of these carbon steel systems is inappropriate.
(7)
Preservice examination on replacement piping and fittings is not done at Sequoyah regardless of the replacement material.. However preservice inspection is required in TVA's Corporate E/C Program Procedure No. G-97B and other industry standards.
(8) Component Grid size for ultrasonic examination delineated in NDE Procedure No. N-GP-22 is different than that delineated in Corporate
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Procedure No. G-97B and the site programmatic Periodic Instructions.
In addition, the only document that defines pipe component layout is
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N-GP-22.
However, this document uses the intrados (inside radius)
of an elbow as the zero point for starting the grid.
It appears that if a 2" grid band was required and the layout started on the
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intrados of an elbow, the outside radius of the grid would far exceed the required grid size.
As delineated above, the licensee's E/C program has technical control problems and generic weaknesses which has allowed E/C failures to exceed the licensee's efforts to control it. However, the primary failure of the E/C program is due to the lack of commitment by the licensee for establishing an adequate inspection scope and failure to adequately establish component and examination priority for the susceptible components.
The ineffectiveness of this E/C program is illustrated in
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the fact that during the 1991 Unit I cycle 5 outage only one component was found deficient and required repair. During the 1992 Unit 2 cycle 5 outage 4 components were detected which required weld repairs. However, during this same period many throughwall failures occurred and were repaired with liquid sealant. These failures reflect not only an
inadequate E/C program but also an inadequate plant maintenance program.
Within the areas examined, no violations or deviations were identified.
3.
Licensee Actions on Previous Inspection Findings - Units 1 and 2 (92701 and 92702)
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(Closed) Violation 50-327,328/92-09-02, Inadequate Procedural Requirements for Repair and Replacement Activities
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This violation involved an inspector finding that a in-service inspection
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(ISI) weld map that did not reflect two welds depicted on the corresponding plant weld map. The two welds had been added during a maintenance activity. Following the maintenance activity that added the'
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welds, ISI personnel were not notified in order that they could update
their weld maps. The procedure that controls maintenance activities did
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not contain sufficient positive controls for ASME Section XI components
to ensure that ISI would be notified of weld replacements or addition of
new welds by the maintenance craft.
l The licensee's corrective action for this item consisted of performing a 100% review of-the 81 total ISI weld maps verses the plant weld maps (no additional missing welds were identified). The licensee also revised the ISI repair and replacement procedure to ensure that the responsible section will notify ISI when ISI maps are affected by
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maintenance activities.
In addition the licensee conducted a formal
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qualification program for individuals involved in planning Section XI maintenance activities to ensure that ISI requirements are
properly implemented.
(Closed) Violation 50-327,328/92-09-04, Failure to follow Procedure for j
Placement of Lead Letter "F" on Radiographic Film i
This item dealt with the fact that TVA's Radiographic Procedure NRT-I
required that the lead letter "F" be placed adjacent to the radiographic
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penetrameter. An inspector's review however, revealed that TVA was placing the lead letter "F" on top of the penetrameter so close to the essential 4T hole that it nearly obscured resolution of the hole.
TVA's corrective action included issuing a procedure change to clarify l
that the "F" may be placed on the penetrameter provided the image of the letter does not obscure the requisite hole or the edge of the penetrameter.
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i (Closed) Inspector Followup Item 50-327,328/92-09-03, Improper Surface i
Preparation for Ultrasonic Examination of Erosion / Corrosion Weld Overlay i
Repairs. This item dealt with an inspector's observation that TVA had
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not prepared the overlay weld repairs on A and B Main Feedwater Pumps for
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a baseline Ultrasonic examination after application of the overlay. This repair had been applied during a previous outage and was not installed at that time as a temporary repair.
Therefore, a baseline for monitoring
E/C in this susceptible area was necessary. The licensee was notified and a work authorization was issued to prepare the welds for examination.
The inspector reviewed the ultrasonic examination reports for the
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subsequent examinations and held discussions with the licensee's E/C engineer to ensure that no other weld overlay repair had similar problems. As a result of these discussions and the review of examination data this item is considered closed.
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Within the areas examined, no violation or deviation was identified i
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Exit Interview t
The inspection scope and results were summarized on February 5, 1993, j
with those persons indicated in paragraph 1.
The inspector described the
areas inspected and discussed in detail the inspection results.
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Proprietary information is not contained in this-report.
Dissenting comments were not received from the licensee.
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Acronyms and Initialisms
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ASME -
American Society of Mechanical Engineers l
B&PV -
Boiler and Pressure Vessel CHEC -
Chexal Horowitz Erosion Corrosion
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CHECMATE - Chexal Horowitz Erosion Corrosion Methodology for analyzing Two-phase Environment
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Dated
E/C -
Erosion and Corrosion EPRI -
Electric Power Research Institute ISI
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-Inservice Inspection
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MSR -
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NDE -
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NOS -
Numbers
NRC -
Nuclear Regulatory Commission
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Quality Assurance
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Rev. -
Revision
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SGB -
Steam Generator Blow-down l
SNP -
Sequoyah Nuclear Plant l
TVA -
Tennessee Valley Authority i
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