ML19322B456
| ML19322B456 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 03/27/1975 |
| From: | Thies A DUKE POWER CO. |
| To: | Anthony Giambusso Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7912030295 | |
| Download: ML19322B456 (2) | |
Text
p.
aunn Duxz POWER GOMPANY Powan Bett.nzwo 4ae Sourn Caumen SrazzT, CnAntorrz, N. C. asso A c. THIES P, Q, Box 3378 Sthsom V'CE Patsectest PRODUCTION ANC TR AN$telSS60m March 27, 1975 Mr. Angelo Giambusso, Director 4
Division of Reactor Licensing U. S. Nuclear Regulatory Commission Washington, D. C.
20555 Re: Oconee Unit 1 Docket No. 50-269
Dear Mr. Giambusso:
During the first refueling outage of Oconee Unit 1, both once-through steam generators (OTSG) were inspected.
The examination was performed during November and December, 1974, using visual inspection and eddy-current techniques.
The eddy-current inspection utilized equipment, procedure, sample selection, and acceptance criteria consistent with the regulatory position of Regulatory Guide 1.83, " Inservice Inspection of Pressurized Water Reactor Steam Generator Tubes."
The eddy-current testing was performed by Conam Inspection, Inc., under subcontract to the Babcock & Wilcox Company and was stw e ised by B&W Construction Company. During this inspection, 503 (3,F
.ercent) of the tubes in the A OTSG and 493 (3.17 percent) of the tub w in the B OTSG were examined.
Tubes examined were randomly selected in all four quadrants of each steam generator.
The inspection was performed by personnel qualified in accordance with American Society for Non-Destructive Testing Stendard STN-TC-1A and supplements. The inspection was conducted in accordance with written, approved procedures.
Of the 996 steam generator tubes examined using the eddy-current technique, none of the tubes had a detectable wall penetration greater than 20 percent of the min 4== e:-manufactured tube wall thickness. The inspection equipment provided a sensitivity that will detect defects with a pene-tration of 20 percent or more of the tube wall thickness.
The visual inspection consisted of examination of four areas in the A OTSG and two locations in the B OTSG. Manways and handholds at various levels were selected te permit siewing potential problem areas.
Fiber optics were used to parmit viewing locations where access openings 3538 19120302fg
o a
o Mr. Angelo Giambusso Page 2 l
March 27, 1975 were small and to examine the tubes and tube support plates at points that would otherwise be inaccessible.
Generally, the tubes and tube support plates were covered with a greenish-black deposit.
The deposit was very light, with much of the original reflectiveness of the tubes still in evidence.
There was no evidence of tube-to-support plate interaction.
Fv==4 nation of the tube sheet and feedwater annulus showed essentially no accumulation of oxides in either area. Part of the inspection program included obtaining samples of oxide that may have accumulated in the generator. Attempts to collect oxide samples using a knife-edge, stainless steel spatula were futile due to the minimal amount of oxide present.
The reddish-brown oxide was easily removed by wiping with filter paper for oxide analysis.
The results of the wipe sample and scale analyses showed that the samples contained predominantly corrosion-product iron with lesser quantities of nickel and chromium.
None of these materials will be detrimental to the steam generators in the quantities found.
It is important to note that Oconee Unit 1 was involved in an extended j
startup program. The time from initial hot functional testing to shutdown for the first refueling exceeded 32 months. During that time, cleanup of the feedwater-condensate system was accomplished, and numerous starcups were experienced, including recovery from 37 un-scheduled trips. The period before the first steam generator inspection represents the worst service conditions expected to be encountered during the service life of the steam generators.
In spite of this, the steam generators were found free of detectable defects using eddy-current techniques.
Furthermore, there has been no deposition of solids which has been the arena for chemical attack.
It is also important to note that no conditions were found which are indicative of the tube wall thinning and stress corrosion problems which have been encountered recently in recirculation-type steam generators.
Very truly yours,
,Iv f y.s; A. C. Thies ACT:vr
~
_,.