IR 05000271/1993017
| ML20059A149 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 09/23/1993 |
| From: | Gray E, Mcbrearty R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| Shared Package | |
| ML20059A140 | List: |
| References | |
| 50-271-93-17, NUDOCS 9310260237 | |
| Download: ML20059A149 (10) | |
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p U.S. NUCLEAR REGULATORY COMMISSION
REGION I
REPORT NO.
'50-271/93-17 DOCKFir NO.
50-271 ~
LICENSE NO.
DRP-28 7p 1,ICENSEE:
Vermont Yankee Nuclear Power Corporation RD 5, Box 169 Ferry Road
' Brattleboro, Vermont 05301 FACILITY:
Vermont Yankee Nuclear Power Corporation INSPECTION AT:
Vernon, Vermont INSPECTION DATES:
August 16 to September 2,1993
INSPECTDR:
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R. A. McBrearty, Reactor Eilgineer, Materials Date Section, Engineering Branch, DRS
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APPROVED BY:
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E. H.' Gray, Chief, Materids Section, Date Engineering. mch, DRS
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Areas Insoccted: An announced inspection was conducted of the licensee's inservice inspection program,' erosion / corrosion program and related activities. The inspection was performed to ascertain that those activities are being accomplished in accordance with applicable. Code and regulatory requirements and licensee commitments.
Results: <The programs' and their implementation are generally good. The staffs responsible for. program implementation are qualified and knowledgeable of the activities for which they are responsible.
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DETAILS
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1.0.
REVIEW OF INSERVICE INSPECTION PROGRAM (IP 73051)
Inservice inspection is mandated by the ASME Boiler and Pressure Vessel Code,Section XI
' and; because it confirms the structural integrity of the reactor coolant system and other piping systems pressure boundary, is essential to protect public health and safety.
Because of the lengthy 1985/1986 Recirculation Pipe Replacement / Refueling Outage, which kept the facility shut down for nine months, the Vermont Yankee Nuclear Power Corporation has extended the second Ten-Year Inservice Inspection Interval from November 30,1992, to L August 31,1993, as permitted by the ASME Code Section XI. The third ten-year interval
- will commence on September 1,'1993, so that the Section XI required examinations that are conducted during the current refueling outage will be credited to the third interval program, and will be governed by ASME Section XI,1986 Edition.
2.0 REVIEW OF INSERVICE INSPECTION (ISI) PROCEDURES (73052)
The Vermont Yankee nuclear facility uses nondestructive examination (NDE) procedures developed by.the Yankee' Atomic Electric Company (YAEC) to implement its ISI program.
The following procedures were selected for inspection:
YA-PE-1,~ Revision 0, " Solvent Removable Liquid Penetrant Examination" e
- e YA-PE-2, Revision 8, " Liquid Penetrant Examination"
. YA-MP-1, Revision 0, " Magnetic Particle Examination with Dry Particles and Yoke" e
.YA-MP-111, Revision 4, " Magnetic Particle Examination" e
YA-UT-1, Revision 8,." Ultrasonic Testing - General Requirements" e
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e lYA-UT-2, Revision 3, " Ultrasonic Testing of Welds"
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YA-UT-4,' Revision 3, " Ultrasonic Testing of Nozzle Inner Radius" e-co'-
- YA-UT-7, Revision 5,' " Ultrasonic Testing of Studs and Bolts"
- YA-_UT-100, Revision 2,," Ultrasonic Sizing of ID Connected Planar Flaws *
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In addition to the above NDE procedures, the following YAEC control procedures were included in the inspection:
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- YA-ISI-3, Revision 4, "lSI Requirements - Vermont Yankee" y
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. YA-DCP-1, Revision 3, " Inservice Inspection Data Control"
YA-TP-1, Revision 3, "On-Site Training for Non-Yankee NDE Personnel"
The liquid penetrant procedures permit examinations within temperatures ranging from 35 F to 250*F. YA-PE-1 incorporates temperatures from 35 F to 125 F and YA-PE-2 incorporates temperatures from 35 F to 250 F. Procedure qualification records were
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available for the appropriate temperature range and material combination and were examined by the inspector. Magnetic particle procedure YA-MP-111 permits the use of various
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techniques with visible'and fluorescent particles. Specific requirements are described for
each technique including the measurement of black light intensity for the fluorescent technique, the determination of particle concentration for wet particles, and the equations for calculating the amperage necessary to establish the appropriate magnetic field strength when using a magnetic coil for the inspection.
. The NDE implementing procedures were determined to be well written with clear, detailed instruction regarding the associated NDE method. Additionally, the procedures complied with the applicable Code and regulatory requirements.
3.0 INSERVICE INSPECTION ACTIVITIES (IP 73753)
Prior to commencing the performance of nondestructive examinations at the site, NDE personnel are required to attend a training session and to demonstrate their ability to perform j
examinations in their area of qualification.
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The inspector observed the performance demonstration by contractor personnel using liquid penetrant, magnetic particle and ultrasonic examination techniques. For the ultrasonic-l examination demonstration, the technicians were asked to examine a number of cracked
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samples selected by the YAEC Level III examiner. Those samples were obtained by the i
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licensee from the Electric Power Research Institute (EPRI) NDE Center at Charlotte, North Carolina. The samples contained manufactured defects which the technicians were required to identify and report on forms provided by the licensee. Procedures YA-UT-2, Revision 3, and YA-UT-1, Revision 8, governed the performance examinations.
The magne. tic particle and liquid penetrant demonstrations were performed using base metal-l
and welded samples containing a variety of real flaws including cracks. The contractor technicians used YAEC liquid penetrant and magnetic particle procedures incorporating solvent removable visible dye penetrant materials and an electromagnetic yoke respectively.
' Each technician _was required to examine samples selected by the YAEC Ixvel III, and to report the results on forms provided by' the licensee as they would when performing Section XI examinations in the plant. All of the performance demonstration examinations
_were performed under the supervision of the YAEC Izvel III examiner. In addition to p
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requiring performance demonstrations by contractor NDE technicians, the licensee provides instruction on the use of the YAEC procedures applicable at the site. The combination of
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training and performance demonstrations is an excellent way to assess the capability of the
' technicians to perform their assigned responsibilities.
3.1 Feedwater Nozzle Inner Radius Ultrasonic Examinations NUREG-0619, "BWR Feedwater Nozzle and Control Rod Drive Return Line Nozzle Cracking," requires that ultrasonic and liquid penetrant examinations be performed of the inner radius and bore section of feedwater nozzles. The frequency of the examinations is determined by whether or not cladding is present, and the type of sparger in use.
The Vermont Yankee feedwater nozzles contain the cladding that was applied during plant
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. construction for corrosion protection of the carbon steel vessel and to minimize rust accumulation in the vessel water. During the current 1993 refueling outage, the Vermont Yankee facility performed ultrasonic examination of the inner radius and bore section of each e
of the four nozzles. Liquid penetrant examination is not required at this time. The licensee is investigating the use of an automated ultrasonic examination system to perform the NUREG-0619 mandated examinations and, possibly, eliminate the necessity for the liquid
~ penetrant examinations required by the NUREG.
Ultrasonic examinations of the nozzles were previously performed manually from the outside surface of the nozzle, and were performed during the current refueling outage using a procedure similar to what was previously used. The procedure, YA-UT-4, Revision 3, was qualified on a full-sized feedwater nozzle mockup that contains EDM notches strategically located in base metal through cladding, in cladding and at the base metal / cladding interface.
Technique Sheet No. VY-4-93-04, Revision 1, part of the procedure, identifies the equipment, transducer, entry angle, mode of transmission and type of plastic wedge required to scan various portions of the nozzle radius and bore section Additionally, the appropriate calibration block is identified, and the calibration technique for each transducer is described.
-The' performance of what is called " scan e" requires two different wedges, a 45* flat wedge for calibration and a 19 curved wedge for scanning. After performing the system calibration using the appropriate calibration notches, the 45* flat wedge is removed and the 19* curved wedge is attached to the transducer for scanning purposes. The inspector questioned whether changing the wedge resulted in a sensitivity change that would influence examination results. Investigation revealed that a significant, approximately 12 dB, loss of sensitivity occurred. when the curved wedge was attached. The comparison was made using _
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' the response from the notch in the calibration block and a similarly sized notch in the nozzle -
' mockup. The nozzle examinations _were performed with the calibration (reference) sensitivity increased by a minimum of 14 dB. The evaluation of indications was performed at the
- higher sensitivity level'and that should compensate for the loss due to the wedge change.
The inspector concluded that the resulting examination is sufficiently sensitive to assess the
- quality of the nozzle ~section under examination. The nozzle ultrasonic examination results
. showed that no recordable indications _were detected in all four of the feedwater nozzles.
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3.2 Reactor Pressure Vessel IIcad Cladding Cracks The General Electric SIL No. 539 discussed cracking detected in the stainless steel cladding and the low alloy steel under the cladding of the reactor pressure vessel (RPV) head at Quad Cities Unit 2. In response to the SIL, Vermont Yankee performed an ultrasonic examination of its RPV head during the 1992 refueling outage. The examination revealed indications, attributed to stress corrosion cracking of the furnace sensitized stainless steel cladding, in areas of cladding inside the vessel head and on the RPV flange. Based on the 1992
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examinations, the licensee concluded that none of the cracks extended irito base material. On April 8,1992, at a meeting of Vermont Yankee and the NRC, the licensee commiaed to submit a plan for future inspections of the cladding cracks. The plan was to be submitted by the licensee to the NRC no later than 30 days prior to its next refueling outage. The licensee submitted its plan by letter dated July 1,1993, which complied with its commitment. The licensee's plans include reinspection of the eight regions of the RPV head flange that were inspected in 1992, reinspection of the flaw that was partially ground to determine the flaw depth, and to reinspect the circumferentially oriented flaws at the top of the manually clad area near the flange to dome weld and on the dollar plate weld. The reinspections are planned from the inside diameter of the flange and RPV head using ultrasonic methods to size the flaws and determine whether any have propagated into the base material.
The RPV head and flange examinations had not yet been performed at the time of this inspection, but, at the inspector's request, the examination technique and calibration was demonstrated. The block used to calibrate the ultrasonic system contains cladding similar to the cladding on the RPV head and flange and EDM notches in the cladding and through the cladding into the base metal at depths of 0.185",0.245",0.312" and 0.380". The equipment was calibrated by detecting the above listed notches from the clad surface of the block using a 60 transducer. The technique is similar to the method originally used to determine crack depth and the inspector agreed that it should be capable of showing whether any of the cracks-have grown and/or propagated into the base material under the cladding.
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3.3 Nondestructive Examination Personnel Qualification /Cedification Records Records 'of contractor personnel who are responsible for performing nondestructive
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examinations at Vermont Yankee were reviewed to ascertain that the technicians were l
properly qualified to perform their assigned duties.
The records verified that the personnel were qualified and certified in accordance with applicable provisions of SNT-TC-1 A, the governing document. Additionally, appropriate personnel were listed in the latest EPRI " Registry of Qualified Personnel for UT of IGSCC."
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3.4 Conclusions Nondestructive examinations at Vermont Yankee are performed by properly qualified technicians. The use of qualified personnel is further confirmed by the licensee by virtue of the onsite training provided by the licensee and the requirement for personnel to successfully complete a demonstration to prove their capability to perform NDE prior to performing work at the site.
The examination of the feedwater nozzle inner radius and the technique for determining the size of previously detected cladding cracks incorporate the use of qualified procedures that should provide reliable results. The licensee commitment to the NRC regarding the reactor vessel head cladding cracks was complied with in a timely manner.
4.0 EROSION / CORROSION (E/C) PROGRAM (IP 49001)
Concerns regarding erosion and corrosion in balance of plant piping systems has been heightened as a result of the December 6,' 1986, feedwater line rupture that occurred at Surry Unit 2. This event was the subject of NRC Information Notice 86-17,Bulletin 87-01 and Generic Letter (GL) 89-08. The GL specifies that all licensees provide assurances that a program, consisting of systematic measures to ensure that E/C does not lead to degradation of single and two-phase high energy carbon steel systems, has been implemented.
An effective E/C program will detect erosion of high energy carbon steel piping before the pipe wall is significantly reduced below the design or piping code minimum wall thickness.
This program should reduce risk to the plant staff and prevent unnecessary system transients
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thereby contributing to the safety of the public.
4.1 Licensee Response to Generic Letter 89-08 and Bulletin 87-01 NRC Bulletin 87-01 was issued on July 9,1987, and requested that licensees submit information concerning their programs for monitoring the thickness of pipe walls in high-energy single-phase and two-phase carbon steel piping systems. - Letters dated September 11,1987, and December 24,1987, to the NRC provided the licensee's response to the bulletin. The NRC's response was provided by letter _ dated March 17,1988, and
- stated that no further plant spv:ific action with respect to NRC Bulletin 87-01 is required.
Generic Letter 89-08 was issued on May 2,1989, and requested licensees to provide assurances that a program, consisting of systematic measures to ensure that erosion / corrosion does not lead to degradation of single-phase and two-phase high energy carbon steel systems,
-has been implemented. - The licensee's response to the GL dated July 14,1989, addressed the NRC's requests regarding its crosion/ corrosion program.
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- 4.2 Historical Information The licensee's first use of the Electric Power Research Institute (EPRI) CHEC computer
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' code for single-phase piping systems was during the 1989 refueling outage. At that time, a i
= formal program was not established although approximately 109 components were inspected.
-l The first formal E/C program was issued for use during the 1990 refueling outage when
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approximately 88 components were inspected. The first inspection of selected small bore piping (less than 3" diameter) was performed in 1992.
4.'3 Inspection Activities j
The'CHECMATE computer code is now used.for large bore piping systems and approximately 56 locations are scheduled for inspection during the current refueling outage.
Additionally,54 locations on small bore systems are scheduled for inspection.
The selection process is based on various factors including CHECMATE analysis, previous inspection results and industry experiences. Small bore piping is selected for inspection i
based on the impact on personnel safety and plant availability of the failure of a particular
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line. Approximately 6 to 8 months prior to a refueling outage, the YAEC cognizant E/C engineer at Bolton, Massachusetts, provides the E/C inspection scope to the E/C program manager at Vermont Yankee. That scope is preliminary and is subject to change based on industry and plant experiences that may occur prior to the outage.
Inspections at the site are performed by the licensee's inservice inspection contractor, and the preparation of components for E/C inspection is performed by a second contractor under-licensee supervision. Inspection results are recorded using a data logger and are then loaded
' into a computer data base. Data evaluation is performed by the YAEC engineer who is stationed at the site during the outage. A copy of the inspection results is provided to the engineer on a daily basis so that there is no backlog of data awaiting evaluation. A daily status report is issued by the YAEC engineer to the licensee's ISI Coordinator who also is responsible for managing the E/C program. Locations requiring repair or replacement are identified on the report and are discussed at outage meetings. Prior to the end of a refueling
. outage, the.YAEC engineer and the licensee's ISI Coordinator verify and document that all E/C inspections and resulting repairs and replacements are completed. Trending of inspection results, updating-the CHECMATE data base and selecting components for
- inspection during subsequent outages are performed at Bolton, Massachusetts, by the YAEC
. engineer, ' An outage final report must be issued within 90 days of the end of an outage.
. Conclusions-The licensee's erosion / corrosion program complies with NRC Bulletin 87-01 and Generic
- Letter 89-08. The program at Vermont Yankee is a comprehensive program that provides
' good control over related activities. Additionally, controls are in place to preclude starting the plant with rejectable conditions uncorrected. Inspection results are evaluated on a timely
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9 basis, and data trending and inspection location selection are performed using the
. CHECMATE computer code developed for that purpose by the E ectr c Power Research l
i Institute. The CHECMATE code is updated with current E/C data at the end of each refueling outage.
5.0 EXIT MEETING The inspector met with licensee representatives (denoted in Attachment 1) at the conclusion
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of the inspection on September 2,1993. The inspector summarized the scope and findings of the inspection. The licensee did not disagree with the findings of the inspector.
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- 4-A'ITACHMENT 1 PERSONS CONTACTED
Vermont Yankee Nuclear Power Corocration J. FitzPatrick Cognizant Erosion / Corrosion. Engineer
- D. Girroir Senior Engineer - Inservice Inspection Coordinator
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- R. P. Grippardi Quality. Assurance Supervisor R. D. Pagodin.
Operations Superintendent
- R. J. Wanczyk Plant Manager Yankee Atomic Electric Company
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C. Larson NDE Level 111
- R. Tucker -
Senior Engineer ll,S. Nuclear Regulatory Commission
- P. Harris Resident Inspector
- Indicates those present at the exit meeting on September 2,1993.
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