IR 05000302/1989021
| ML20247C580 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 08/25/1989 |
| From: | Blake J, Coley J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20247C577 | List: |
| References | |
| 50-302-89-21, NUDOCS 8909140049 | |
| Download: ML20247C580 (5) | |
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>* O R UNITED STATES i
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NUCLEAR REGULATORY COMMISSION
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REGION H n
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101 MARIETTA STREET,N.W.
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% l Report No.: 50-302/89-21-Licensee:
Florida Power Corporation 3201 34th Street, South St.; Petersburg, FL 33733
, Docket No.: 50-302 License'No.: DPR-72 Facility Name: Crystal River 3 Inspection Co cted: August 8, 1989 Inspector:
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Date Signed-J.
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Approved by:
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o J/ pf Blake, Chief Date Signed rarerials and Processes Section Engineering Branch
, Division.of Reactor Safety SUMMARY Scope:
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This special, announced inspection was conducted in the area of observation and analysis of ultrasonic examination capabilities for opposite surface (outside pipe surface), initiating flaws in the various materials involved for the core flood nozzle to safe-end welds.
Results:
Babcock and Wilcox's Office of Special Products and Integrated Field Services in Lynchburg, Virginia demonstrated their ultrasonic flaw detection capabilities on a mockup for the Crystal River Unit 3, core flood nozzle to safe-end welds.
This demonstration was to' supplement information provided by the licensee to the Nuclear Regulatory Commission (NRC) Office of Nuclear Reactor Regulations' (NRR) for requested relief from the American Society of Mechanical Engineers, Boiler and Pressure Vessel (ASME BSPV) Code Requirements.
I 1E The examination capabilities and limitations for opposite surface initiating
. flaws in the dissimilar materials involved in the ultrasonic examination of the core flood nozzle to safe-ends welds are delineated in this report.
Resolution of. the information obtained as a result of this inspection is not within the
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scope of this report. The licensee will be notified by NRR as to the status of
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i their request for relief from ASME Code requirements in future correspondence.
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Within the areas examined, violations or deviations were not identified.
L 8909140049 890830 PDR ADOCK 05000302 O
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REPORT DETAILS
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Persons Contacted Licensee Employees
- J. Cooper, Nuclear Inservice Inspection, Supervisor
- D. Gulling, Nuclear Inservice, Inspection, Specialist Other Organizations B. Lewis, Authorized Nuclear Inspector Inservice (ANII) Factory Mutual Insurance Company D. Fairbrother, Babcock and Wilcox, Representative M. Hacker, Babcock and Wilcox, level III Test Examiner A. Reynolds, Babcock Wilcox, Representative D. Turner, Babcock and Wilcox, Representative
- Attended exit interview 2.
Demonstration of Flaw Detection Capability on the Core Flood Nozzle-to Safe-End Weld, Crystal River Unit-3 In May 1985. Babcock and Wilcox (B&W), performed the ten-year reactor vessel examination at the Florida Power Corporation's, Crystal River Unit-3 Nuclear Power Station (CR-3).
These examinations were conducted using the Babcock and Wilcox Automated Reactor Inspection System (ARIS-II)
utilizing immersion ultrasonic examination methods.
Included in this examination were the core flood nozzle to safe-end welds' located on the:
"W" and "Y" axes.
The applicable code for the nozzle to safe-end welds was the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI,1974 Edition with Addenda through the Summer 1975.
Section XI requires that, safe-end welds receive a volumetric examination and a surface examination. Ultrasonic examination was used for the volumetric examination method.
The examinations were conducted from the inside surface of the pipe using the shear wave mode of sound transmission and were required to penetrate the full thickness of
- the pipe wall including the inconel weld, the inconel weld butter, the 304 stainless steel safe-end and the 508 carbon steel reactor vessel nozzle forging.
The inspection zone extended for a distance of one pipe wall thickness on each side of the weld.
The examination did not detect any code recordable indications.
Although, the area required to be examined with ultrasonics included the area required to be examined by a surface examination method, the ultrasonics examination did not satisfy the code requirement to perform the surface examination.
In addition, the effectiveness of the ultrasonic examination, on the dissimilar materials l
involved in these welds, when using the shear wave mode of sound
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g propagation, is questionable because of material structural characteristics.
Subsequently, the licensee requested that B&W perform an evaluation of the
ultrasonic examination method used during the 1985 examination of the core flood nozzle to safe-end welds.
Of specific interest was the detection I
capabilities of the ultrasonic examination in the various materials for l
flaw originating at the outside surface of the pipe.
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If the ultrasonic examination proved successful or even partially successful on the outside surface of the pipe the licensee intended to use this evaluation to support a relief request for one of the core flood
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nozzle to safe-end welds that' had not received a surface examination
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during the 1985 examinations.
The primary basis for the request for
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relief was the amount of radiation dose received (approximately 16 REM)
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when the licensee performed the surface examination on the other core I
flood nozzle in 1985.
Additional considerations for the relief request,
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were that the surface examination on the subject core flood weld did not
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detect any indications and that the Office of Nuclear Reactor Regulation j
(NRR), has approved similar relief requests for licensees in the past.
j In order to ' evaluate the detection capabilities of the ultrasonic examination procedure to be used on the safe-end weld, a mockup of the
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weld joint was designed and fabricated.
The nockup was designed to simulate the core flood nozzle to safe-end weld to the maximum extent possible.
Included in the mockup were side drilled holes used to establish the calibration and EDM notches which were used to establish the
detection capabilities of the ultrasonic process. There were four sets of
four notches each on the outside diameter (0D) surface used for this detection demonstration.
Each set contained one notch located in the carbon steel base metal, one in the inconel buttering, one in the inconel weld, and one in the stainless steel safe-end.
Each set of notches were machined to a different depth.
The depths were 2.3% (34 mils), 5.6% (84 mils), 11.3% (169 mils), and 16.9% (235 mils).
To represent the worst-case orientation, the major axis of the notches was in the I
circumferential direction.
The main objective of the evaluation was to J
simulate the 1985 ARIS examination as closely as possible and scan the
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safe-end weld mockup to determine the smallest detectable flaw size that I
might be expected on the OD surface of the actual core flood nozzle to safe-end weld.
Because this is a dissimilar metal weld, it was anticipated that the detection levels would vary depending on such factors as the notch depth and location, scanning direction, and the acoustic characteristics of each of the materials.
i The results of the evaluation effort and the demonstration observed by the I
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licensee, the authorized nuclear inspector and this inspector at l
Lynchburg, Virginia on August 8, 1989 are delineated below.
a.
Opposite surface reflectors down to 2.3% through wall were detectable l
in two axial directions in the carbon steel nozzle material.
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Opposite surface reflectors down to 2.3% through wall were detectable in the inconel butter material when scanned in the safe-end direction.
c.
Opposite surface reflectors down to 2.3% through wall were detectable in the stainless steel safe-end when scanned in the nozzle direction.
Opposite surface reflectors down to 5.6% through wall were detectable in the stainless steel safe-end when scanned in the safe-end direction.
d.
None of the opposite surface reflectors, regardless of size or direction scanned, could be detected in the inconel weld material using the parameters of the 1985 ultrasonic examination procedure.
The demonstration conducted for Florida Power Corporation did demonstrate that notch reflectors in the heat affected zone of the carbon steel nozzle and the stainless steel safe-end could be detected within code recordable levels, although significant amplitude variations were noted between the two materials.
In addition to the demonstration for the relief request in the first interval examinations (1985), B&W demonstrated axial scans using a 45 degree refracted longitudinal wave transducer anticipated for use under a similar relief request from the 1986 ASME Code Section XI requirements for the second interval examinations (1995).
This transducer detected all of the notches in the carbon steel nozzle, inconel buttering, inconel weld and - the safe-end.
However, the inspector could not agree to the demonstrated technique for 1995 examinations (limiting improvements to better detectability) for the following reasons:
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a.
An examination procedure has not been developed by B&W which will discriminate between the various amplitudes observed in the different materials of this weld when the size of the notch reflector remains the same, b.
No real defects were provided in the mockup:
Cracks are generally much more difficult to detect and size, than EDM r.atches or side drills holes in the materials involved in this weld.
c.
No artificial reflectors provided in the axial or skewed direction:
Defects in these specific welds are very likely to have axial components and their detectability should be demonstrated, d.
Sizing techniques were not demonstrated: The ability to accurately size indications initiating at the OD surface in this combination of materials is essential.
Amplitude variations observed in the materials will require enhanced sizing methods.
e.
Examination techniques and new technology in equipment are presently available to perform a 100 percent effective ultrasonic examination of these dissimilar welds.
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Exit Interview The licensee acknowledged the limitations to the 1985 examinations, but expressed a significant concern over the high radiation dose that will be received in performing a surface examination on this weld..
The inspector's comments concerning demonstrating the inspectability of these dissimilar welds for the 1995 examinations were acknowledged by the licensee.
This. technical demonstration of ultrasonic capabilities was conducted in an excellent technical and professional manner by the licensee and their vendor.
Information obtained as a result of this effort should be beneficial to all participants.
Proprietary information is not contained in the report.
Dissenting comments were not received from the licensee.
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