IR 05000301/1990023
| ML20024F981 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 12/17/1990 |
| From: | Danielson D, Schapker J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20024F974 | List: |
| References | |
| 50-301-90-23, NUDOCS 9012270201 | |
| Download: ML20024F981 (6) | |
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U. S. NUCLEAR REGULATORY COMMISSION
REGION III
- Report No.:
50-301/90023(DRS)
Docket No.:
50 301 License No.:
DPR-27 Licensee: Wisconsin Electric Power Company 231 West Michigan Street-P379
. Milwaukee, WI 53201 Facility Ncme:
Point Beach Nuclear Plant - Unit 2 Inspection At:
Point Beach Site Two Rivers, WI 54241 Inspection Conducted: October 17-19, 24 25, and December 5 6, 1990 Inspector:
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, F. Schapter Daq6
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,. h 7 Y M A 4 w m I-t w d // f'8 Appro m By
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H. Danielson, Chief Dite'
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d terials'and Processes Section Inp oe c tion. s_..me nry Insoection on October 17-19. 24-25. and December 5-6. 1990 (Recort No.
50-301/90023(PRS))
Areas Inspected:
Routine announced inspection of inservice-inspection (ISI)
activities including review of program'(73051), procedures-(73052),
observation of work and -work --activities -(73753), ISI-data review and evaluation (73755), and review of'licenseo action on NRC Information Noticos (92704).
Results: Of the areas inspected, no violations or deviations were identified.
During the course of the inspectivn, the following were noted:
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Based on the areas reviewed, the licensee appears to have an effective ISI Program. The licensee contracts for ISI services and performs.ISI activities to ASME Section XI requirements, utilizing state of the art ISI equipment and procedures.
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The. licensee's action in response to NRC Information Notice 90-04 was complete-and comprehensive with respect to accomplishing safety objectives.
l 9012270201 901220 ADOCK05000g01 PDR G
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DETAILS 1.
Persons Contacted Wisconsin Electric Power Company (WEPCol
- C, Sherwood, ISI Engineer
- J. Kohlway, Nuclear Engineer K. Crowly, Nuclear Engineer J. Michaelson, Quality Assurance
- R. Seizert, Superintendent, Regulatory and Support Ser" ices Hartford Steam Boiler Encineerine and Insurance Company (HSB)
R. Motguin, ANII-j U.
S. Nuclear Regulatory Commission (NRC)
- C, Vanderniet, Senior Resident Inspector The inspector also contacted and interviewed other licensee and contractor employees.
- Denotes those present at the exit interview on December 6, 1990.
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2.
Licensee Action on Information Notices (92704)
(Closed) NRC Information Notice 90-04:
Crackinc of the Unoer Shell-to-Transition Cone Cirth Welds in Steam Generators a.
Backerg.MDd Cracks and linear indications on the inner circumference of Westinghouse (H) steam generators (SG) transition cone girth welds
'have-been. detected in 18 SGs in the United States. The degree of cracking ranges from severe (Indian Point, Unit 2) to isolated and-
-dispersed (Zion Station,-Unit 1).
Flaws have been observed only in H Models 44 and 51 vertical recirculating U-tube SGs with the feedwater ring design.
Root cause of the cracking has not been established. A common factor was the general corrosion pitting on the inside surface of the flawed SGs. Meta 11agraphy found that the surface pits served as crack initiation sites. The current information indicates that the degradation probably results from corrosion-assisted thermal-fatigue.
The flaw indications can be detected-with enhanced ultrasonic (UT)
. procedures. Due to the structural design of.the transition cone weld inherent geometric features commonly result in innocuous reflectors.
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b.
Inspection The NRC inspector observed the UT of the SG "A" transition girth weld.
One hundred percent of the veld was examined utilizing a 1/2" X 1", 2.25 MHZ transducer for detection.
The weld was scanned from both sides using 45' and 60' angles.
Eleven indications were identified within the inner 1/3 of the weld volume.
The indications were plotted and shown to be subsurface.
To confirm that the indications closest to the inside surface (ID)
were embedded, a visual (VT) and magnetic particle examination (MT) was performed.
No surface indications were identified.
The NRC inspector performed an independent examination of the ID surface (VT and MT) and concluded that the~UT indications were subsurface and were apparently not open to the ID surface. No pitting was observed on or adjacent to the weld as observed by the NRC inspector at the Zion Station where ID cracking was identified.
The UT indications were sized using a 1" round, 2.25 MHZ transducer, with 45' at.d 60* angles.
All indications that were 250% Distance Amplitude Correction (DAC) were sized using the 1/2 maximum amplitude technique.
Since all indications were $100%
DAC, this sizing method was more conservative than the ASME Code technique which requires sizing indications to 50% of DAC.
Five of the indications sized were found to be in excess of ASME Code Section XI, IWB 3511, requirements.
These five indications were evaluated in accordance with IWB-3600 of ASME Section XI and found acceptable for continued operation with linear elastic fracture mechanics analysis.
The NRC inspector also reviewed the previous ultrasonic examination performed by another contractor.
In 1983, Southwest-Research Institute (SWRI) performed a UT exam of weld SG-A-4 and had determined that there was no recordable indications at that time.
During the'1990 exam of weld SG-A 4, the examination by SWRI was repeated by EBASCO, utilizing-similar techniques and-transducers. A 1/2" round, 2.25 MHZ transducer with 45' and 60*
angles was used.
- 11 indications could be seen at less than the Code recording level with the 1/2" round, 2.25 MHZ transducer l
(i.e., <50% DAC).
Since the indications were seen al less'than
50% DAC, ' sizing would not be specifically required t y the Code.
l-This would explain why no recordable indications were found in
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The indications found in steam generator girth weld SG-A 4 are embedded and appear to be small areas of embedded slag.
Based on L
an evaluation of the indications in accordance with IWB 3600,
"A"-
steam generator can resume operation. A successive exam, as required by IWC 2420b will be performed during the next inspection period of weld SG-A-4.
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s0 The licensee's actions taken in response to the information notice is adequate to assure the SGs transition girth welds have not
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degraded.
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Inservice Insocetion (73051)
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General The NRC inspector reviewed the second ten year Inservice Inspection-(ISI) Plan for the third period, second outage.
The ISI Plan conforms to the American Society of Mechanical Engineers
.(ASME) Boiler and Pressure Vessel Code,Section XI, 1977 Edition, Summer 1979 Addenda, Relief requests in accordance with 10 CFR-50.55a(g)(5)(iv) had been applied for and accepted by the Office of Nuclear Reactor Regulation (NRR) for those inservice examinations the licensee was ur.able to perform during this period. The services of an Authorized Nuclear Inservice Inspector (ANII) were procured and the ISI procedures and personnel certifications have been reviewed by the ANII,
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The.licenseo contracted EBASCO Services, Inc., and WEPCo Quality
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Assurance departments to perform the ISI.
Westinghouse Electric Company _(WEC) was contracted to perform eddy current examination
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'(ET) of the steam generators' tubing, b.
ISI Documentation Review (73052. 73755)-
q The NRC inspector reviewed documents relating to the following:
Nondestructive examination (NDE) procedures' utilized for ISI, NDE personnel certifications in accordance with SNT-TC 1A.
NDE equipment calibrations and examination reports.
Eddy current- (ET) equipment: calibration,
Ultrasonic instruments (UT), calibration blocks, transducers
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and UT couplant certifications.
Liquid penetrant material certification.
ET examination reports and plugging material certification reports.
- ET data analysis guidelines, No violations or deviations were identified.
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Observation of Work Acrivities (73753)
The NRC inspector observed work and discussed examinations with NDE examiners. -These activities included observation of calibrations and examination performance, and review of documentation of the following NDE:
Ultrasonic examination of the SG transition girth welds for
SG "A".
- Liquid penetrant examination (PT) of the pressurizer spray
nozzle and piping velds.
- Visual examination (VT) of pressurizer. relief valve bolting e
and pressure retaining components,.and SG A-4 girth weld ID surface.
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Magnetic particle examination of the SG-A-4 girth weld.
- Eddy current examination of SG tubes.
Work activities were performed in accordance with approved procedures. utilizing calibrated NDE equipment, and certified
. Detection and' resolution of flaws detected by NDE personnel.
procedures were completed in accordance with ASME Code and regulatory requirements.
Resolution of NDE flaws is discussed in Paragraphs 2 and 4 of this report.
4.
Eddy Current Examination (ET) of Steam Generators (73753. 73755)
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General i
The licensee employed H to perform ET of the SG tubes as required bytthe Point Beach Technical Specifications (TS). H-utilized the MIZ.18 digital multi frequency acquisition and analyzer system to conduct the examinations.
Inspection results in the "A" SG hot leg showed four tubes degraded 240% wall, five tubes with undefined signals, and 40 tubes with axial indications within the tubesheet.
In the "B" SG, a total of 19 tubes had indications 240% wall, 16 tubes with undefined signals and'32 tubes with axial indications within the tubesheet.
The axial indications within the tubosheet were evaluated with the motorized rotating pancake coil (HRPC) probe.
Initial indications with the bobbin probe displayed distorted signals (DI).
Further evaluation using the MRPC probe disclosed the axial indications.
The licensee plugged all the tubes with the above indications.
In addition, the licensee expanded the scope of the inspection per TS 15.4.2.A.2.b., Table 15.4,2-1.
The total number-of tubes examined
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this outage, including the expanded sample, was SG
"A", hot leg 1,830, cold leg 590; SG
"B",. hot leg 1,665, cold leg 2,157.
i Approximately 20% of all inservice tubes were full length inspected, all hot leg unsiceved tubes not included in the full
. length sample were inspected to the first support plate, and a 20%
sample of cold leg sleeved tubes was examined.
The licensee has been utilizing MRPC to define distorted indications for several outages.
This practice is not required by regulatory requirements but is more conservative and enhances safety when the MRPC data is utilized appropriately.
The licensee demonstrated this commitment to safety by plugging all the indications in the tubesheet which displayed axial indications using the MRPC probe, b.
Inspection
.The NRG inspector observed the ET of the SG tubes in progress, verified calibration / certification of ET equipment, calibration standards, and reviewed the examiners / analyst qualification
. certifications. The NRC inspector also reviewed the ET Data Analyst Guidelines for the Unit 2 SGs and observed the analyst
. data sheets and evaluations of indications in progress.
TFe licensee's ET program and tube degradation preventive maintenance program appear to be conservative in assuring the safe oporation of the SGs for Unit 2.
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Exit Inte rview The inspector met with licensee representatives (denoted in Paragraph 1)
at the conclusion of the inspection on December 6, 1990.
The inspector summarized the purpose and findings of the inspection.
The licensee
representatives acknowledged this information. The inspector also-discussed the likely informational content of the inspection report with regard to documents or processes reviewed during the ir,spection.
The-licensee representatives did not identify any such documents / processes as proprietary.
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