ML20236N132
| ML20236N132 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 02/11/1998 |
| From: | Battige C NRC |
| To: | NRC |
| Shared Package | |
| ML20236J176 | List: |
| References | |
| FOIA-98-164, RTR-NUREG-CR-5985 NUDOCS 9807150021 | |
| Download: ML20236N132 (5) | |
Text
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Note To :
Weld Team From:
Ken Battige O
Subject:
Summary of NUREG/CR-5985, PNL-8g19, Supplement.1, j
" Review of P-scan Computer Based Ultrasonic inservice inspection System" i
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- P-scan is short for Projection Image Scanning Technique. The equipment is built and operators trained by the Force Institute (the Danish Welding institute). Force recommends Level ll personnel to operate equipment, and Level lli personnel to interpret and evaluate results Primarily intended for inservice inspection at nuclear power plants, semi-automatic operation can be conducted remotely after set-up.
1 A scanning unit is attached to the object to be examined, and scans in the "X"and "Y" directions.
i The weld centerline is typically Y= 0, with a reference point set at X = 0, and the length of the weld along the X axis.' The "Z" axis is depth into the object. See Attachment 1, Section 5.1.
P-scan stores images, rather than raw ultrasonic data., on 3 %" diskettes. Visual output via color printer for permanent, reinspectable, records. (samples available) f P-scan has a very large dynamic range ( >100dB with the logarithmic amplifer), so no gain settings are used during data acquisition. No minimum threshold is set for signal recording I
(gating levels set during interpretation).
i P-scan scans are done with multiple transducers concurrently.
Evaluation of indications according to amplitude is performed primarily during post-processing with a separate software program.
l The P-scan data set includes three views: top, side, and end i
l' Side and End are relative to the weld, not the component (the reverse of normal).
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All three views, along with other information, are presented for detection, sizing, and l
evaluation of flaws. A computer cursor is available to pin-point indications.
See Attachment 1, Section 5.2 for diagram.
P-scan system capabilities have been established through the qualification process.
Review Checklist for NRC Inspectors: See Attachment 2 l
[
ANO has used the P-scan technique to examine the top portion of the MSB walls for 10 casks.
This NUREG review based on one month of laboratory use at PNL. The NUREG is intended as a guide for NRC inspectors, and does not present any conclusions or 4
recommendations on the system.
9907150021 990630 PDR FOIA DUMS98-164 PDR p
p-
P-scan i
k 5.0 Image Interpretation
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5.1 P-scan Axis Dennition and Z exes for inspection of a circumferential weld.
Typically the weld centerline will be taken as Y=0. X-0 4
is preferably at a known reference point. Z increases toward the center of the pipe A circular saw cut is shown in the outer surface of the weld zone.
figures 5.lB D show the meaning of" Side view" and "End view"in P-scan terminology. Figure 5.lB shows side and and views of the same pipe shown in Figure 5.1A. Figure 5.lc shows the side and and views of the Y
circular saw cut. Figare 5.lD shows the P-scan side and end views ofindications from the saw cut. Note that the X
terms are reversed from what might be expected; this is because the words " side" and "end" refer not to the pipe, V
but to the weld itself.
l Z
5,2 P-scan Axis Display Figure 5.2 is a diagrammatic presentation of a P scan image. Figures 5.2A, B, and D diagram the axis orien-tations for P-scan presentations. P-scan uses a rec'. angular 5ide End coordinate system (in the case of a pipe, treating the outer surface as though it were a plane), presented with the Z-axis down (larger positive Z means greater depth into the part). The X and Y axes may begin at any number, Pipe positive, negative, or zero; the Z-axis normally begins at B
0 or a positive number (a negative Z value indicates data above the surface of the part). The Top View (A)is a C-scan view, showing the stepping (magnetic wheel crawler) axis (X) across and the scanning axis (Y arm) up, looking at the outside of the part, with the positive Z-axis point-ing into the paper. The Side View (B) is a B-scan end j
l Scan i
A view, showing the stepping axis (X) across and the depth C
axis (Z) down, with the scanning axis pointing into the paper. Figure 5.2C shows an ultrasonic amplitude presen-tation called an Echo View, aligned with the side view.
The End View (D) is a B-scan side view, showing the scanning axis (Y) across and the depth axis (Z) down, p-scan i
with the stepping axis pointmg into the paper. Figure O
5.2E is an Echo View aligned with the End View. A screen display will show views A, B, and C or A, D, and Figure 5.1 P-sess amis deflaition E; a printed display may show the screen display or all five views.
Figure 5.1 diagrams the P scan axis and view definitions.
Figure 5.l A shows the typical orientation of the X, Y.
S t.17 NUREG/CR 5985, Suppl.1
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P-scan
. 1 01 234 5.4 P-scan Imaging Mode
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Figure 5.3 shows a P-scan image of test block UT-RPT-1 TOP VIEW CIRC 1 (see Section 7.3 for notes on the geometry of the 0
block). It has been reproduced as 90% of actual size to
-I y_,m3 allow a venical orientation on the page (scales for other images range from 55% to 100%).
234
~
O x-Axis 5.4.1 Top of Image 1
SIDE VIEW e
At upper left, the print is identified as a P-scan image, as 2
2-^US distinct from A-scan or T-scan. De small numbers (0.000, 4.808, 4.985, 5.117, 5.205) printed vertically 1 01 234 above the image are X-axis ranges for indications. De 60 eB v.- Axis numbers *0.00 in" and "$.51 in" above the image (far left c 40 eB ECHO VIEW and right respectively) indicate the X-axis (crawler axis) 20 dB ApuTUDE Axl5 values at the left and right edges of the image, arid also indicate that the dimensions are in inches rather than 321 0 -1 millimeters. De three other numbers 'X 0.926," "Y 0
0.417," and "2 2.334" above the image give the X, Y, y.gns and 2 axis coordinates of the location marked by the
)
cross-hairs.
2 Z-^*5 5.4.2 Top View Identification 321 0 -1 60 es At the hfi side, " TOP VIEW" indicates that the view is Y-"S E 40 eB in the planc (or a flattened representation of the cylinder, ECHO VIEW sphere, or other surface) on which the probe travels.
20 eB AuouTuoE Ans
" Top 5.00 in" means that the Y axis (scanner axis) extent of the TOP VIEW is 5.00 in. (12.7 cm), but it does not indicate the lower and upper bounds for Y axis values.
Figure 5.2 P scan axis presentation in this presentation, colors are assigned to images. Iml has a red block beside it, indicating that Image 1 is represented by red areas on the image; Im2 is yellow; Im3 is green; and Im4 is dark blue. Any image portion in which the signal amplitude is below the "lewer" value 5.3 Imaging Modes indicated in the ECHO VIEW (see below)is shown in background color (gray in this image). In this file, Imag-Dere are two types ofimaging: P-scan and T-scan. P-es 14 represent time gates 1-4, which were set at four scan is an amplitude presentation and T scan is a thick-ntervals through the block, gate I staning slightly below ness presentation. For either type, there are two modes:
the near surface and continuing to a depth of about 1.5 in.
Imaging and A scan. Imaging mode provides projected (4 cm), gates 2 and 3 following at greater depths, and data, whereas A scan provides full RF or vidso data.
gate 4 ending just past the far surface. The gate settings Most images for weld inspection are P.scati Imaging; are shown diagramma:ically in Figure 5.4 (the Prebes and erosion / corrosion inspection uses T-scan Imaging. A-scan Gates diagram is further explained in Section 5.5); the mode is used only for evaluation, as it generates large exact settings are given in Table 4.31, as determined by a data sets.
data print-out of the scan parameters (scan parameter printouts are detailed and explained in Section 15.2).
)
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NUREG/CR 5985, Suppl. I s1,33
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7 Pscan i
15.0 Review Checklist 15.1 Before and During Inspection How the following uhrasonic parameters bem properly set and noted?
How reference standards been scanned to assure proper system operation and required sensitivity?
Probe frequency Refracted angle Have scanner parameters been correctly recorded, either Skew angle on the computer, or by color photograph, or in writing?
X ed Y o# sets Assure the correct recordmg of the followmg parameters Delay of shoe X MOTION Matenal velocity (sheer or longitudmal m appro-STEP (ON/OFF)
Priate)
STEP SIZE (mm)
Part thicimess, width, and length CORRECTION FACTOR (+/-percent)
A-scan start and range CONT (ON/OFF)
Gate starts and lengths SPEED (+/-mm/s)
Auenuation, if used DIRECTION (CW/CCW)
Probe reference levels, if used Y MOTION NEAR END (+/-mm)
For any parameters recorded in writing, have the corre-SPEED (mm/s) sponding sections of the computer record been left blank FAR END (+/-mm) or made identical to the wrmen record, so that there can be no confusion? Particularly, step siae and speed?
Have positioning conventions been observed and clearly noted, and photographed if appropriate? ' Assure that the Has full coverage been assured? If any C-scan view is following have been noted:
examined at fbil gain, there should be no areas of missmg l
l Zero angle reference marks or interminst data. Areas of missing data indicate lack Weld centerline of coverage. Areas of intermment dass indicate either Positioning of the scanner unit relative to the part Poor couplant or excessive speed relative to the repetition Clockwise / counterclockwise rate.
Scanner arm relative to flow direction Orientation of probe (s) la areas of muhiple overlapping indications, has A-scan Channel number for each probe data (which allows image manipulation) been taken or real-time evaluation been performed?
Is scanner arm aero position correctly calibrated or noted?
In the unusual case of multiple indicatie= sned up along if a curved Y-arm was used, has it been fbily described?
both X rsd Y axes, have A-scans or subvolurne scans Has the correction factor been set and recorded?
been made?
If scanner is mounted on a pipe of diNerent diameter than If RF or Rectified data were used to evaluate indications, the one being inspected, have both diameters been record-has an appropnate A-scan data set been recorded and ed and the appropriate correction factors entered (both on Prmted?
the scanner control unit and in the software)?
Have all scanner arm screws been checked for tightness at Was the scanner mounted on a track? If not, the final intervals dunng the inspection? If found loose, has area position should be very carefbily checked to ensure that been recanned?
the scanner has not become unduly skewed dunng the Has final scanner position been verified to a.#d to scan.
expected travel?
$1.91 NUREG/CR 5985, Suppl. I
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P-scan i
is each image clearly marked to indicate its position relative to the entire part meanned?
15.2 After Inspection
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If Image Processing has been used, have the original as Have prmted images been made of all areas containing l
well as the pra-nad files been saved?
indications (at least for reportable indications; preferably for all indications evaluated)7 If welds longer than about I foot 00 cm) were scanned, were they scanned as separate sections (called " parts")?
Have printed copies been made of all inspection param-mers set in the software?
nis is important because the files can than be merged to 1
view the entire weld, or viewed separately to achieve I
manmum resolution.
Have backup copies been made of all data diskettes?
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If blank lines appear between the scans, verify that the Have printed images been carefully annotated? In combination of beam width and scan increment indicates partialar, have Winning w eding h values full coverage.
been noted for Y and Z axes (the vertical axes in the primM We)?
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Are image interpretations consistent with the length, width, and height scales?
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NUREG/CR 5985, Suppl. I St.92 l
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