ML19323J016
| ML19323J016 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 06/10/1980 |
| From: | Widner W GEORGIA POWER CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| TAC-41019, TAC-41020, NUDOCS 8006170640 | |
| Download: ML19323J016 (4) | |
Text
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Gecra,a Acaer Ccraca y DO : wmree street Fcst C+ce Era 4545 hta Georg a 30302 Tercce 404 5224C00 L
- w. A. Widner June 10, 1980 GeorgiaPower (c',';, ';l,,*lvG"'* *
- a n swwn e'ecmc sisem Director of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555 NRC 00CKETS 50-321, 50-366 OPERATING LICENSES DPR-57, NPF-5 EDWIN I. HATCH NUCLEAR PLANT UNITS 1, 2 TURBINE ROTOR ~ DISC CRACKING INFORMATION REQUEST Gentlemen:
Georgia Power Company hereby submits the following information in resoonse to Enclosure 3 to your letter dated May 13, 1980, concerning Tur-bine Rotor Disc Cracking.
Response to Site Specific General Questions 1.A. Both turbines for the Hatch units are General Electric (GE) type TC4F-43; 1800 RPM, tandem-compound, double flow, reheat.
B. Neither unit has been inspected to date for rotor disc cracking.
The postulated hours of generation until inspection are as follows:
Unit 1 Low Pressure Turbine A 17,544 hours0.0063 days <br />0.151 hours <br />8.994709e-4 weeks <br />2.06992e-4 months <br /> Low Pressure Turbine B 35,122 hours0.00141 days <br />0.0339 hours <br />2.017196e-4 weeks <br />4.6421e-5 months <br /> Unit 2 Low Pressure Turbine A 23,264 hours0.00306 days <br />0.0733 hours <br />4.365079e-4 weeks <br />1.00452e-4 months <br /> Low Pressure Turbine B 36,392 hours0.00454 days <br />0.109 hours <br />6.481481e-4 weeks <br />1.49156e-4 months <br /> C. Unit 1 has experienced approximately 81 turbine trips and approximately 5 overspeeds. Unit 2 has experienced approximately 52 turbine i
trips and approximately 2 overspeeds.
For both units there may i
have been more overspeeds following scrams; however, this information
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is not recorded.
D. Answers to these questions involve data which are proprietary to the General Electric Company.
Information was provided directly to the NRC during a meeting between GE and NRC representatives on
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April 21, 1980.
Per GE representative comments, the NRC has in-5 fomed them that the information supplied by GE during the afore f/o mentioned meeting is an acceptable reply to this question.
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o-o Georgia Power A Director of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission June 10, 1980 Page Two II. No inspections have been performed to date for either unit.
III. The normal water chemistry for both units has been good with <50 ppb of chlorides. The only significant change in water chemistry was an in-leakage of oil into the primary coolant on Unit 2.
IV. Unit 1 Low Pressure Turbine A and Low Pressure Turbine B are scheduled for inspection in 1982 and 1983, respectively. Unit 2 Low Pressure Turbine A and Low Pressure Turbine B are scheduled for inspection in 1985 and 1986, respectively. The inspection schedule for the two units, per GE representative comments, is in accordance with the inspection time recommendations as specified in GE TIL 857, " Inservice Inspection of 1500 and 1800 RPM Nuclear Turbine Rotors".
V.
This item is not applicable as there have not been any inspections performed to date.
VI. An analysis and evaluation regarding turbine missiles does not appear to have been performed for Unit 1.
Consideration will be i
given to scheduling an analysis and evaluation, if, in fact, this analysis has not already been performed. Site engineering services personnel are in the process of researching plant records for documentation of any such analysis. An analysis and evaluation has been performed for the Unit 2 turbine and is documented in Section 10.2.3 of the Unit 2 Final Safety Analysis Report (FSAR).
Response to Generic Questions I.
. After the rough machined wheel / disc forging has been tempered, material is removed from surface locations to measure mechanical properties. The forging is then subjected to a 100% volumetric ultrasonic inspection.
If the test results meet stringent acceptance standards, the forging is released for final machining. During final machining, attention is continually paid to the finish, contour and dimensions of every surface.
For instance, the keyway depth, width, location, radii, and surface finish for every wheel is checked for conformance to drawings. Quality control personnel assure that tolerances are maintained. Any deviation from accepted tolerances are reported to engineering for disposition.
o Georgia Power d Director of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission June 10, 1980 Page Three f
Only coolants and lubricants approved by engineering are used in the manufacturing and assembly process. These coolants and lubricants have undergone extensive laboratory corrosion testing to ensure their acceptability prior to their approval for use in manufacturing. Periodic sampling is done on all such fluids to verify that their chemistry is within acceptable limits.
If required, corrective actions are taken to maintain the chemistry within limits.
After finish machining, each wheel is thoroughly cleaned and given a magnetic particle inspection of all surfaces.
If acceptable, the buckets are assembled and the wheel is static balanced. After assembly on the shaft, each wheel is inspected and measurements are made to assure its proper location. The assembled rotor is then spun to 20% overspeed following a high speed balance.
- Finally, after a magnetic particle inspection of the buckets, the rotor is cleaned to prepare 'or shipment.
II. Stress corrosion cracks have not been observed to date in nuclear wheels manufactured by GE, and they do not anticipate that removal or replacement of wheels will be required because of this phenomenon.
The water erosion which has been observed in the keyways of wheels on several non-reheat machines is being studied intensively. GE currently believes that the erosion process is self limiting and should not require the replacement of any wheels.
III. No imediate actions are required to minimize water erosion because of the apparent self-limiting nature of the phenomenon. However, if future inspections show an unexpected progression of the water erosion, appropriate operating restrictions and/or modifications will be recommended.
IV. The wheel / disc forgings are heat treated in the rough machined condition. The heat treatment consists of soaking at a temperature above the upper critical temperature with the time and temperature sufficient to ensure complete austenitization throughout the forging, followed by a quench in cold, vigorously circulated water for a sufficient time to ensure complete transfomation throughout the section. The forg6 are he,'ted uniformly to a tempering temperature below the w. _ c critical temperature and held for a sufficient time to soften to the desired tensile range.
After tempering, the forgings are still-air cooled to room temperature.
After final machining, the wheels (discs) are uniformly heated in an electric furnace to a temperature below the embrittling range, but sufficiently high to increase the wheel diameter enough to assemble on the shaft with the required shrink fit.
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GeorgiaPowerd Director of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission June 10,1980 Page Four If you have any questions in this regard, please contact my office.
Sincerely yours, i
7D.IVJ n W. A. Widner Vice President and General Manager Nuclear Generation JAE/mb xt:
Ruble A. Thomas George F. Trowbridge, Esquire R. F. Rogers, III
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