ML19325C814
| ML19325C814 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 10/11/1989 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | Swenson W NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| References | |
| CON-NRC-89-125 VPNPD-89-531, NUDOCS 8910170295 | |
| Download: ML19325C814 (4) | |
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(U. S.LNUCLEAR REGULATORY-COMMISSION
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Attention:
.Mr. W. H; Swenston, Project Manager Project. Directorate lII - 3
' Gentlemen::
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-DOCKET 50-266
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. POINT BEACH NUCLEAR PLANT, UNIT 1 During the 1987einservice inspection of-the-Point Beach Nuclear.
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fPlantiUnit'1 reactor' pressure vessel, Wisconsin Electric Power Company.' detected a flaw during: ultrasonic inspection m.
techniques.. This flaw.was sized in-accordance with ASME Code 94 -
Section XI methodsLand-analyzed by the< procedure provided in IWB-3600.- These analyses,were-reviewed by your?offic:,'as statedLiniMr. D. H.: Wagner's letter toiMr.
C..W.
Fay dated
- C July.,-9, 1987.. That letter further requires Wisconsin Electric.
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[3 to; provide a detailed plan of the.next inspection for review 4
six months. prior to the scheduled outage.,
The;next inspection'is scheduled forLthe spring 1990 refueling K~
' outage.- The-date-for;the examin' tion of the flaw is a
1 i
anticipat'ed to be between'Aprilf14 and' April 20, 1990, ti
-Attached is a; description of our-planned examination.
If more details;are required, please contact us.
L'y Very..truly o,a r s,
A/-
C. W. Fay-Vice President
-Nuclear-Power
' Attachment-Copies to NRC Regiol.al Administrator, Region III x
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NRC Resident Inspector I
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UNITiliREACTOR VESSEL FLAW ~
' Attachment.
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. PLAN FOR THE EXAMINATION OF.
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POINT BEACH NUCLEAR PLANT-UNIT 1
. SAFETY INJECTION NOZZLE TO SHELL WELD
.687-01-A.at-288.5*
L INTRODUCTION On June 2, 1987, Wisconsin Electric Power Company submitted to l'
the U.' S. Nuclear Regulatory Commission an evaluation of a flaw identified in the safety in]ection nozzle-to-shell weld at 288.5*
in thelPoint Beach Nuclear Plant Unit 1 reactor pressure vessel.
.This evaluation was performed according to the guidelines of ASME 1
Code"Section XI article IWB-3600.
The flaw which required evaluation was-identified during the reactor pressure vessel examination required by the ASME Code Section'XI.
The examination was performed in accordance with
'ASME Code Section XI,-1977 edition with addenda throuch
~
. Summer 1979 and the additional guidance of Regulatory Guide 1.150, Revision 1.
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-In 1987, the method used to determine the flaw size was to measure the ultrasonic transducer positional displacement that E
- produced a' response equal to 50% of the calibration amplitude.
4The transducers produced 0 and 10* refracted longitudinal waves l
to examineEthe nozzle-to-shell weld from the nozzle bore.
The l
E transducers"were 1/2" diameter with a nominal frequency of 2.25 MHz.
The ultrasonic beam size at the flaw depth was subtracted as a size correction during the evaluation of the' flaw.
The;evaluatior concluded that the flaw would not propagate during the140-year se.rvice-life of the reactor.
L iDESCRIPTION OF SYSTEM
-Southwest Research Institute (SWRI) will be the organization that performs the examination ~and sizes the safety injection nozzle-to-shell-weld flaw.
SWRI' utilizes a system comprised of three parts:
t(1) a remote transducer positioner and manipulator called the Fast
- par device, (2) an ultrasonic instrument with remote pulsers, and (3[ an:alectronic' data acquisition and analysis system called EDAS.
This-system is the same as SWRI used at Rochester Gas and Electric's Ginna Plant during'their-spring 1989 inspection and will be used during our. Unit 2 reactor vessel examination in the fall of 1989.
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UNIT l' REACTOR VESSEL FLAW Attachment Page 2 1
i LThe-Fast: par device is computer controlled to position and manipulate the ultrasonic transducer module required to scan the vessel weld volumes.
A digital output signal is provided which accurately identifies the transducer location at all times.
These signals are displayed on monitors and utilized by EDAS.
The
. Fast par is also designed to permit calibration of an ultrasonic transducer module while scanning with a second transducer module.
The ultrasonic instruments are Sonic FTS Mark II or Sonic UWA Mark III.
These instruments perform the functions of displaying i
transducer wave forms, triggering the pulsers, adjusting gain to calibrated ser. tings, and supplying signals to EDAS.
These
' instruments are similar to ultrasonic instruments commonly used in the industry.
EDAS is the SWRI data acquisition system.
This system receives the: signal from the Fast par and ultrasonic instruments and converts 1dunn to a digital format.
These signals are then stored on optical disc to preserve the raw data for further evaluation.
Other features'of the EDAS are the color displays, ability to compile multiple scan lines data on a. single display, ability to construct cross-sectional displays, and artificially gate the signals at various amplitudes.
This data manipulation is accomplished by'the EDAS without changing any information stored on the optical disc (i.e., raw data remains untouched).
DESCRIPTION OF THE EXAMINATIONS The examination of'the safety injection nozzle-to-shell weld will be conducted in two parts.
The first portion will be performed utilizing procedures and techniques consistent with ASME Code Section XI, 1977 Edition with addenda through Summer 1979 and Regulatory Guide 1.150, Revision 1.
The second portion-will utilize procedures and techniques to accurately size the flaw.
The sizing portion is based on the results of the 1988 joint flaw sizing efforts of Southwest Research Institute, EPRI, Rochester Gas & Electric, and WE. -These are the same techniques demonstrated to NRC representatives at SWRI on January 10, 1989.
The initial scans of the safety injection nozzle-to-shell weld i
will confirm the presence of the previously identified (i.e.,
l 1987). flaws and will yield size data for comparison to the 1987 data.
The scan will be conducted from the nozzle bore.
The transducers will produce longitudinal waves at 0* and a 10*
l refracted angle.
Size limits will be established at a signal response of 50% of calibration amplitude.
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- The_ sizing portion will be performed as~a separate, series of scans using ultrasonic transducers optimized for the purpose of l
_ defining; flaw edges.
The techniques tduit are planned for sizing.
the safety injection nozzle-to-shell weld flaw include focus
-transducers and tip diffraction signal analysis.
Both methods
_have been demonstrated to produce = flaw dimensions which closely reflect actual: flaw dimensions.
Focused' transducers are designed with a curved face which acts as a lense.
Thk ultrasonic energy is concentrated into a small region of the material which contains the flaw.
Flaw limits are established by the transducer positions that produce a signal amplitude of 25% of the maximum flaw amplitude.
No corrections are used or required to account for the transducer size or the beam profile._ The 25% of maximum flaw amplitude has consistently produced _ conservative _(slight over-sizing) size measurements of flaws-in the=EPRI safety injection nozzle blocks and the full scale nozzle configuration block fabricated for the 1988 joint flaw sizing effort.
'Tip diffraction technique have proven to be the most accurate sizing techniques.
The technique is dependent on the flaw producing diffracted signals and the ability of the transducers to detect these signals.
The 1988 joint flaw sizing effort showed that planer flaws with sharp edges could be sized in a configuration similar to the safety injection nozzle.
Focused transducer and tip diffraction techniques used in G
conjunction with the EDAS display capability provide reliable flaw sizing.- These-will be used to size the safety injection nozzle-to-shell weld flaw in 1990.
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