ML20053C610
| ML20053C610 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 05/26/1982 |
| From: | Lentine F COMMONWEALTH EDISON CO. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| 4206N, NUDOCS 8206020377 | |
| Download: ML20053C610 (15) | |
Text
.
'^N Commonwealth Edison
) one First Nition",1 Pt:ra Chicigo. tilinois O
(j} Address Reply to: Post Office Box 767
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4 Chicago, Illinois 60690 May 2 6, 1982 Mr. Darrell G.
Eisenhut, Director Division of Licensing U.S.
Nuclear Regulatory Commission Washington, DC 20555
Subject:
Zion Station Unit 1 Steam Generator Inspection and Repair NRC Docket No. 50-295 Reference (a):
May 17, 1982, letter from F.
G.
Lentine to D. G.
Eisenhut.
Dear Mr. Eisenhut:
By letter of reference (a), Commonwealth Idison provided a report on the completion of the repair of the Zion 1D steam genera-tor tube ends.
That report described how a set o f high-resolution photographs had been taken following completion of the repair for evaluation by Commonwealth Edison and Westinghouse.
Also, a set o f test photographs had bee' taken in order to establish the resolving capability of the photographs.
This is to provide copies of those photographs and our related evaluations.
Enclosed are a complete set of photographs of the 1D tube-sheet and the resolution test photographs taken at Westinghouse.
Attachment A provides a description and evaluation of the resolution test photographs.
The test photographs demonstrate that the photo-graphic technique used on the ID tubesheet is capable of resolving tube-to-tubesheet weld indications larger than those allowed by the ASME Code Section XI.
The 1D tubesheet photographs have been evaluated by Westinghouse and Commonwealth Edison engineers, with the conclusion that all repairs have been successfully completed.
Mr.
W.
J. Key o f the NRC's Region III of fice has also examined the photographs.
The photographs revealed no relevant indications in the tube-to-tubesheet welds.
Also provided as Attachment B is the " Babcock and Wilcox Loose Part Noise Investigation Report," dated May 18, 1981, which was referenced in Appendix A to reference (a).
Please address any questions regarding this matter to this office.
Very truly yours, fk
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8206020377 820526 PDR ADOCK 05000295 F.
G.
Lentine G
PDR Nuclear Licensing Administrator g
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ATTACHMENT A Westinghouse Report on the Photographic Technique for Visual Examination o f Tube-to-Tubesheet Welds.
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INTRODUCTI'N O
Due to the complicity of the P.T. test for examining the defects on the
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welding area around the repaired tube ends, the possibility of the visual examination by using photography had been investigated.
According to ASME Code Section III, Division 1, Appendices XVI 3700, this test is to demonstrate the visual examination per preset photo equipment and technique is adequate to resolve a black line 1/32" wide on an 18% neutral gray card placed on the surface similar to the area to be visually examined.
Also in this test, a mockup of tube end with some manufactured defects on the welding area had been examined per procedure to indicate that the photography is adaquate to resolve the defects.
EXAMINATION PROCEDURE 1.
Photography conditions as established by CWE.
a.
Hasselblad camera b.
Lens:
60m mm Hasselblad c.
Lighting:
METZ 202 (Light center located at 61/2" off the lens center line) d.
Film:
KODAK +X120 e.
Focus Distance:
23" from the surface to be examined to the film surface 2.
Samples to be examined:
a.
A black line 1/32" wide on an 18% neutral gray card with the size of 1 15/16" wide by 4 3/4" LG.
b.
Tube end mockup with following manufactured defects on the welding area:
EDM Notch:
(1) 1/32" WIOTH x 1/16" LG x 1/32" DEPTH in radial direction (2) 1/32" WIDTH x 1/8" LG x 1/32" DEPTH in hoop direction (3).010" WIDTH x 1/32" LG x 1/32" DEPTH in radial direction AE644P/44P8205 2
a
Hole :
(1) 1/64" DIA x 1/64" DEPTH (2) 1/32" DIA x 1/16" DEPTH (3) 1/32" DIA x 1/32" DEPTH Scratch:
(1) 0.010" WIDTH x 1/32" LG in radial direction (2) 0.005" WIDTH x 1/32" LG in radial direction (3) 0.005" WIDTH x 1/32" LG in h oop direction 3.
The samples were installed in the steam generator channel head mockup to simulate the situation to be visually examined, the pre-described photo-graphy conditions were applied to take the pictures in the channel head.
4.
Three sizes of magnification with 1.2 X, 2.7X and 4.6X were applied to print the pictures for visual examination.
RESULTS The results shown in the pictures indicated that 2.7X magnii ation can clearly resolve the 1/32" wide black line on the 18% neutral gray card and the defects on the welding area in the channel head.
The preset photography conditions is adequate to be applied for the visual examination.
a AE644P/44P8205 3
ATTACHMENT B Babcock and Wilcox Loose Part Noise Investigation Report.
May 18, 1981 4206N
This report documents the loose part investigation at Zion-l.
Mr. J.
R.
Johnsen and Mr. H. J.
Braul were deployed by Babcock and Wilcox at the request of Mr. Alen Krawzak and Mr. Joe Reiss of Commonwealth Edison on April 26 and 28, 1981.
DESCRIPTION OF EVENTS Upon arrival, we were briefed on the situation and ex-plained that impacts were heard predominately on the L.P.
Monitor from the sensors on the steam generator "D" primary side.
Before our arrfval, impacts disappeared once for about two hours but then commenced again.
Recordings of the impacts were made which we analyzed at the site.
After we were analyzing data in real time for about hour, the impacts abruptly stopped and did not re-occur.
A reactor trip occurred at about 4:00 a.m.
in the morning after startup.
No impacts were heard again.
Following this brief initial investigation, the impacts stopped for approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
.Mr.
J.
R.
Johnsen was recalled to the site once the loose part returned for further investigation.
OBSERVATION AND INVESTIGATION (During first site visit) 1.
Plant Conditions:
Temperature 555.7 F.
Pressure 2235 PSIG Power 75%
M Hatts 745 Pumps 4 running 2.
The impacts were localized to the two sensors on the pri-mary side of the steam generator "D", which is on the bottom of the steam generator.
3.
The impacts were also observed on the secondary side of the steam generator.
The sensor is located on the tap line about 3/4 up the steam generator.
4.
Impacts were observed on R.C.P. and R.V. head.
5.
The impacts on the secondary, R.C.P.
and R.V.
head were less in magnitude.
See data below:
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Sensor:
1 and 2 on the primary i.64 vp-p to about 4.85 vp-p a.
on F.S.
range of 1, which corresponds to 1.64 g and 4.85 g.
background noise:
320 mvp-p to 606 mvp-p b.
On the secondary side approximatley 0.85 vp-p (0.85 g).
On F.S.
range of 1.
Not enough data was collected on this sensor because impacts stopped.
c.
On the R.C.p.:
284 mvp-p on F.S.
range of 1 (0.284 g).
background noise:
197.5 mvp-p J.
On the R.V. head 1.27 vp-p to 1.44 vp-p on F.S. range of 1 (1.27 g to 1.44 g) background noise:
950 avp-p 6.
Waveshape from the primary sensors displays steep leading edge - the waveshape of impacts was consistently displayed as a very fast rise time and fast ' decay.
OBSERVATION AND INVESTIGATION (During second site visit)
At approximately 10:30 on~ April 28, 1981, we were notified that the losse part had returned and Mr. J.
R. Johnsen returned to the site.
All the signals from sensors in the "D" Steam Generator loop were analyzed.
It appeared the part was on the primary side.
- However, it was possible that the part was on the secondary side impacting the tube sheet.
A fourth sensor was installed on the generator on the secondary side near the tube sheet, however, the accelerometer had failed some time before.
Zion personnel made the decision to bring Unit 1 down to 40%
power and to go inside and replace the failed accelerometer.
No spares were available, so one from another generator was selected.
The unit was at 40% power just af ter midnight and the accelero-meter was replaced.
During the replacement of the accelerometer, impacts to the steam generator were recorded and delay times were computed.
The delay _ time between primary and lower secondary side is approximately 1.7 ms, while the delay time between lower and upper secondary was approximately 6.5 ms.
The loose part was not present at this time.
j.
IL.__._._._._.
A meeting to discuss the loose part and possible low power outout was held at the site on Wednesday, April 29, 1981.
B&W was represented by J.
R.
Johnson.
Westinghouse was also represented (Raj Capal).
The general conclusions were:
(1) that the loose part and loss of power were not related; (2) that the loose part and loss of power were not related; (2) while the exact location of the part was not known (above or below the tube sheet), that it is most probably small and on the primary side.
No action items for B&W resulted from the meeting.
The question of the exact location of the part still remained open at this time.
Zion agreed to record 8 channels of data once the part returned and that Zion would send copies of the data to Lynchburg.
The noise returned lat'e Wednesday evening and tapes were sent to B&W for analysis.
Delay times were computed between the primary side and lower secondary side accelerometers.
Delay times bet ween each of the sensors were computed.
The two accelerometers mounted on the primary side are located near each other with essentially no delay time.
Delay times between the two primary and lower secondary are approximately 1.7 ms.
(Between' channel LPM-12 and LPM-24).
Delay times between the primary and upper secondary sensors are approximately 6.5 ms-8 ms.
These delay times are not always constant due to the part moving around.
Impacts near the tube sheet give shorter times while those near the lower primary would give longer times.
Figure 1:
Shows a typical comparison between the two primary side accelerometers.
LPD-12 appears to be somewhat more sensitive than LPD-ll, possibly due to the mounting techniques used.
Figure 2:
Shows a 6.2 ms time delay between primary and secondary.
The broad response and relatively low delay time suggest the part is between the two sensors, possibly near the tube sheet.
Figure 3:
Shows a typical delay time between the secondary upper and lower accelerometers.
Figure 4 Shows comparisons between the primary and lower secondary and accelerometers.
These two figures show the part is moving Figure 5:
around between the two sensors.
It is believed the loose part is on the primary side of the generator for several reasons.
1.
Figure 4 shows the impact nearer LPD-24 (secondary side) with a sharp rise time.
This case is possible with the impact near the tube sheet.
This case is not conclusive in that the impact could be on either side of the tube sheet.
2.
Figure 5 shows the primary side leading the secondary side by 2.4 ms.
This figure is significant since it shows the primary side leading by a fairly large valua.
If the part were in the secondary side, the time delay between the two sensors t'
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would be very small.
The 2.4 ms time delay indicates the part is nuch closer to the primary side accelerometer than secondary side.
CONCLUSIONS 1.
While the results varied due to the part moving around, a delay of 2.4 ms with the primary side leading indicates the part is on the primary side.
2.
Based on the data, the impact noises observed are of low energy content.
Estimated to be 0.50 ft-lbs.
3.
A very high probability it is a loose part, sometimes captured.
RECOMMENDATIONS 1.
Monitor LPM channels for any reoccurrences of the loose part and its subsequent changes.
2.
If impact levels remain as they are (2.0 to 5.0 g's or larger),
there is a potential for damage.
3.
AT the best opportunity, the loose part should be removed.
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Shows a typical delay time between the SG primary and upper secondary.
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Shows a small. time delay between the primary and secondary lower.
The short response of the secondary indicates the impact is,ncar~the
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Shows a 2.4 ms time delay between primary and secondary responses.
This large time delay indicates the part is most probably on the primary side with this impact near the primary accelerometer.
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