ML17249A505
| ML17249A505 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 12/02/1979 |
| From: | Noonan V Office of Nuclear Reactor Regulation |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML17249A502 | List: |
| References | |
| NUDOCS 8001280116 | |
| Download: ML17249A505 (5) | |
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+yg*4 UNlTED STATES NUCLEAR REGULATORY COMMISSIOlv WASHINGTON, D. C. 20555 NEMORANDUM FOR:
D. L. Ziemann, Chief; Operating Reactors Branch
..2 Division of Operating Reactors FROM:
SUBJECT:
V. Noonan, Chief, Engineering Branch Division of Operating Reactors SUMtARY OF MATERIALS AND STEAM GENERATOR PROBLEMS ENCOUNTERED AT R, E,
GINNA DURING DECEYiBER 2, 1979 OUTAGE Plant Name:
R, E. Ginna Licensee:
Rochester Gas 8 Electric Company NSSS/AE:
Westinghouse/Gilbert Docket Number:
50-244 Project Manager:
J.
J.
Shea The Engineering Branch, Division of Operating
- Reactors, has reviewed the actions taken by the licensee regarding the leakage in Steam Generator "B" and the flaw located in the 4" diameter pressurizer nozzle to safe end weld.
The staff evaluation of the problems stated above are enclosec Me concur with the actions taken by the licensee to evaluate the source of and eliainate the steam generator leakage and to evaluate and repair the pressurizer nozzle safe end weld.
Based on the above, the staff does not object to the return of the unit to service.
Enclosure:
As stated Yincent S,
- Noonan, Chief Engineering Branch.
Division of Operating Reactors cc:
D, G. Eisenhut R,
Tedesco L,
C.
Shao W. Hazelton B.
D. Liaw R.
Hermann R.
LaGrange 8001880
STAFF EVALUATION OF PROBL YiS ENCOUNTERED AT R.
E.
GINNA OURING DEC. 2, 1979 OUTAGE St G ~iti The Ginna Unit 1 pressurized water reactor (PWR) is a Westinghouse designed two-loop plant that uses two Model-44 recirculating typ steam generators.
The unit started-up in July, 1979 with phosphate treatmont for the secondary
- water, and was converted to AYT in April 1975.
The plant commenced normal shutdown on December 2.due to the detection of a leak in steam generator B on December 1.
The leak rate was calculated to be 0.007 gpm and did not exceed the technical specification limit of O.l gpm.
This leak rate limit was established back in Apri1, 1975, when the unit was converted to AVT and corresponds to a crack length that precludes tube burst when subjected to a pressure differential associated with a postulated main steam or feedwater line break accident.
This leak rate limit was conservatively calculated and is less than the current Westinghouse standard technical specification limit of 500 gpd Three conference calls with the licensee, one each on December 11, 12, and 13, were held in order to get more information.
The licensee stated that the majority of leakage was from a tube in the No.
4 wedge area, located at R43C54.
The ele-vation of the thru-wall crack was at the top of th tube sheet.
An 80Ã thru-wall large volume defect was also found in the sam.
wedge area, location R43C57.
Both tubes were plugged.
There is no indication oi denting.
Activity in this area is consistent with previous inspection results at Ginna and the licensee states that the approximately 20 tubes in this area have been =plugged.
A total of 27~ of the tubes in steam.generator B wore inspected with Zetech 3300 eddy current inspection equipment using a single frequency with a differential coil probe.
Ten tubes had multiple indications of 20% to 50% thru-wall cracks from 3" to 15" inside the tube sheet.
On
- tube, location RI5C37, indicate a thru-wall crack 4" below the top of the tubesh.e.
and w s found to be "weeping."
All ll tubes were located between rows 15-18 and col u~s 37-41 and have been
- plugged, No inspections of steam generator A tubes were performed since crevice cracking has only been found in generator B and the leakages cave from generator B.
Since the 0.1 gpm limit was not exceeded, a specific sample size was not required to be inspected.
However, the licensee expanded the inspection in generator B to 275 of the tubes rather than only inspecting the area around the leakers, A total of 78 tubes in generator B and 121 tubes in generator A have been plugged to date for various
- reasons, but the majori.y of tubes plugged were for wastage degradation in tho past.
The licensee believes they are able to detect 20~1." 50'hru wall cracks wi'thin the tube sheet because of a testing program initiated by them to characterize the eddy current indica.ions expec-ec from deep crevice cracking.
They perform their own inspections and interpret the results t:"emselves.
They also believe that the extensive sludge lancing perfor, d when :he unit was converted to AVT has somewhat minim-',zed the poten-.ial for crevice racking at Ginna, as compared to the deep crevice cracking experienced a-other plants.
'he staff 'has reviewed the above information and concurred with the licensee's position that no further inspection or plugging is necessary at this time.
We believe the integrity of the steam generator tubes can be maintained during the full range of normal operating and accident conditions.
This conclusion is based on 1) the 13 degraded tubes hgve been plugged,
- 2) all tubes in wedge area 4 have been
- plugged,
- 3) the licensee's ability to detect degradation of tubes within the tubesheet.
2.
4" Diameter Pressurizer Nozzle Safe End Weld Flaw
- During,this outage, the licensee elected to perform routine inservice inspection
~ in accordance wi th their ASME BEPV Section XI program of the pressurizer pi ping.
Liquid penetrant inspection of the 4" diameter pressurizer nozzle to safe end
~ weld revealed a circumferential indication approximately 1 inch long.
After further surface preparation, liquid penetrant examination was repeated and a
circumferential flaw approximately 6 inches long was observed.
The licensee performed volumetric inspections by X-ray and ultrasonic methods.
The X-ray and ASME Section XI inspections revealed no unacceptable defects.
Special ultrasonic examinations located five reflectors at the inside diameter pipe, The reflectors were evaluated as geometric indications associated with a seal weld of a corrosion resistant sleeve in the nozzle.
The flaw was evaluat-ed by in place metallography and determi ned to be in the 309 stainless steel weld butter.
The flaw was removed by grinding and repaired by gas tungsten arc welding (GTAW),
The depth of the flaw was 1/8 inch.
The repair was subse-quently inspected in accordance with ASME Section XI and deemei acceptable.
The licensee has performed liquid penetrant insoections of all the nozzle safe ends on the pressurizer top as well as 24 additional welds in the piping.
No other relevant indications were found.
The licensee has committed to inspect the affected weld at the next refueling outag The staff concurs with these actions and feel they are sufficient to insure the piping integrity will be maintained.
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