ML20236E466
| ML20236E466 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 09/22/1987 |
| From: | Gieske J SANDIA NATIONAL LABORATORIES |
| To: | Hum M Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20236E423 | List: |
| References | |
| NUDOCS 8710290236 | |
| Download: ML20236E466 (3) | |
Text
1 Sandia National Laboratories
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September 22, 1987 4 1
1 Mr. M..R. Hum
'U. S. Nuclear Regulatory Commission i Materials Engineering Branch Washington, DC 20555
Subject:
Indian Point Unit 2 Vessel Indication Inspection Plan and Indian Point Unit 3 Flaw Indication of June 1987
Dear Mr. Hum:
Indian Point Unit 2 Inspection Plan A meeting was attended on September 15 and 16, 1987 at Westinghouse Waltz Mill Site in Pittsburgh to review the demonstration phase results of the inspection program plan. The inspection program plan now includes: (1) a repeat examination using the ASME Code Section XI ultrasonic testing techniques with the same flat transducers and transducer plate used in 1984; (2) an expanded- j examination using the. delta / pitch catch techniques employed in t 1984 with the flat transducers (3) a new examination using the ,
ASME code techniques with large 5'.5 inch diameter focused '
transducers; and, (4) a new examination of the delta / pitch catch techniques using the large diameter focused transducers. All four of the ultrasonic examinations will be conducted using the
. Sonic Mark VI ultrasonic instrument which was the same instrument used in 1984. All ultrasonic A-scans observed at 0.1 inch increments over the area of interest around the flaw indication ,
will be recorded, displayed, and analyzed using the NES/Dynacon Ultrasonic Data Becording and Erocessing System (UDRPS). (
At the meeting, general results obtained with the four techniques on the 9 inch thick IPP-2T-REV.1 demonstration block were pre- ('
sented. The block is cladded on the ID surface and contains notches of various depths and lengths at the OD surface.
Data comparing the sizing of the notches with the flat transducers and the focused transducers were presented using the 50% DAC criterion. All sizing parameters were obtained using the UDRPS software which can be performed on the raw A-scan data in a quick efficient manner. A demonstration of the UDRPS software capabilities for the raw A-scan data taken on the demonstration block was conducted showing color displays in "B-scan format" where the pulse-echo and tip-diffraction data was displayed for several of the techniques. The pulse echo signals from the root of the notch and the tip of the notch could be distinguished and l measured in depth from the B-scan plots of some but not all of l
the notches.
1 o ADO O D
P I
Mr. M. R. Hum Septemb3r 22, 1987 I
Besults of the Demonstration Phase of the Insoection Plan After calibrating by ASME code and sizing all notches in the j demonstration block by 50% DAC using UDRPS, the amplitude data showed the same oversizing characteristics of the notches as was i obtained in 1984. This demonstrated that the UDRPS data '
processing did not change the amplitude sizing characteristics of the slots. It is, therefore, expected that the data of the flaw indication in the vessel will be directly comparable with the )
data taken in 1984. If the flaw is unchanged the UDRPS data {
analysis will indicate that. l After a calibration by ASME code, 50% DAC sizing of the notches j in the demonstration block was also performed using the large i diameter focused transducers where the focal spot diameter at the !
OD surface of the block is estimated to be only 10 mm. Data was i presented where a large improvement in the sizing by 50% DAC levels was obtained from that of the flat transducers. The actual figures of the improvement are not available now since Consolidated Edison promised to send the tabulated data of the results to the consultants at a later date. ,
i' Data was also presented showing a further improvement in sizing accuracy using a successive dB drop technique developed by the French. Details of this technique will not be commented on now l until further study of it's applicability can be made.
Data was also presented on the sizing of the notches with the UDRPS software for the pulse echo root and tip diffracted signals using the longitudinal and shear wave beams of the focused transducers. The size calculation depends only on the delay time differenc'e between the respective peak amplitude of the echoes of
. interest and not on a given amplitude level. A very good agree-ment between the calculated depth size and the actual size was obtained for the notches above 0.18 inch depth. The 0.3 inch depth notch showed very distinct root and tip diffracted signals for the longitudinal waves so that a calculated depth was straight forward. The reason that the UDPRS displays make these calculations possible where they were not available before, due to the small tip diffracted signals being buried in the noise, is that both time averaging by trigger jittering and spatial averag-ing of the digitized ultrasonic signals is performed, and a great improvement in signal-to-noise ratio is obtained. The depth resolution of the pulse echo tip diffracted signal for the present system and transducers is approximately 0.2 inch.
The same kind of processing by the UDRPS system was demonstrated on toe raw A-scan data obtained with the delta technique for the 0.18 and 0.3 inch depth notches. Clear distinct echoes of the tip and base diffracted signals from the notch were shown for the focused transducer data of the 0.3 inch depth notch but the 0.18 inch depth notch was unresolved. However, one set of the delta l technique data using the flat transducers showed a distinct tip and root diffracted signal for the 0.18 inch depth notch; and, a very good agreement between the calculated value and the actual depth was obtained.
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Mr. M. R. Hum Septembnr 22, 1987 Conclusions RI Ih2 Demonstration Phase Results A comparison of the amplitude characteristics of the flaw indica-tion in the vessel between the 1984 data and the data to be taken in 1987 using UDRPS should be straight forward and should indicate whether the flaw is changed or unchanged in its size by the 50% DAC sizing criteria.
Sizing the flaw depth accurately by the pulse echo tip and base diffraction data, using the large diameter focused longitudinal wave transducer, should be accomplished by the UDRPS software if 1 the flaw is 0.2 inches deep or deeper. Sizing the flaw depth accurately by the tip and base diffracted signal with the flat-transducers using the delta technique and the UDRPS software, should be accomplished if the flaw is 0.18 deep or deeper. The length sizing of the flaw indication in the vessel should be greatly improved using the focused transducers where the maximum '
length exaggeration should be approximately 10 mm.
IA41AB Point Unit 2 Zlay Indication June 1987 e The ten year examination was conducted on Unit 3 in June 1987. I Three ultrasonic indications were detected in the intermediate ]
shell longitudinal weld at 300 degrees and eight inches above the 1 intermediate to lower shell circumferential weld. The three indications were observed with the 6 0 degree shear wave beam and ,
a single indication was observed with the o degree longitudinal- {
beam. Video replays of the CRT screen of the ultrasonic instru- i ment were shown while we were at the Waltz Mill site. The UDRPS {
processing of the longitudinal 0 degree raw A-scan data was also ;
demonstrated to us. From the video tape replays and the pulse j echo O degree calculations of the data by the UDRPS software, I j
, agree with the conclusion that the flaw is but one small slag j stringer of approximately 0.235 inches in depth and 4.5 inches ;
long; and, the' three indications observed with the 60 degree shear beam are due to mutiple path reflections from the same cylindrical shaped flaw.
Sincerely, J6h'n H. Gieske JHG:jk Copy to:
C. Poslusny, NRC 6442 D. S. Horschel 7552 W. W. Shurtleff I