ML19318A403
| ML19318A403 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 06/13/1980 |
| From: | Daltroff S PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8006200487 | |
| Download: ML19318A403 (14) | |
Text
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PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. BOX 8699 PHILADELPHIA. PA.19101 S HIELDS L. D ALTROFP tbECTR C PR UCTION June 13, 1980 l
Docket Nos.:
50-277 50-278 1
)
Mr. Robert Reid, Chief Operating Reactors Branch #4 Division of Licensing i
U.S. Nuclear Regulatory Commission Washington, DC 20555
Reference:
Letter from R. W.
Reid to E.G.
Bauer, Jr.
dated May 13, 1980
)
Dear Mr. Reid:
This letter is in response to the letter referenced above which requested information related to low pressure turbine 1
disc cracking.
Our response concerning Peach Bottom Units 2 and 3 turbine disc information is included in Appendix A hereto.
Our response concerning generic information related to turbine disco is included in Appendix B hereto.
In accordance with 50.54(f) of the Commission's Regulations, an affidavit relating to the information provided in response to Mr. Reid's letter is attached.
If you have any questions or require additional information, please do not hesitate to contact us.
00l Very truly yours, S
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y j' App:
e3 g B;// ks Attachment 8 0062 0DYT9 p
I COMMONUEALTH OF PENNSYLVANIA :
ss.
COUNTY OF PHILADELPHIA S. L. Daltroff, being first duly sworn, deposes and says:
That he is Vice President of Philadelphia Electric Company; that he has read the response to the letter from R. U.
Reid to E.
G.
- Bauer, Jr.,
dated May 13, 1980, contained in a letter to Mr. Reid dated June 13, 1980, and Appendices A and 3 thereto, and knows'the contents thereof; and that the statements and matters set forth therein are true and correct to the best of his knowledge, information and belief.
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APPENDIX A Information Relating to Turbine Discs-Peach Bottom Atomic Power Station I.
Provide the following information for each LP turbine:
A.
Turbine type B.
Number of hours of operation for each LP turbine at time of last turbine inspection or if not inspected, postulated to turbine inspection C.
Number of turbine trips and overspeeds D.
For each disc:
1.
type of material including material specifications 2.
tensile properties data 3.
toughness properties data including Fracture Appearance Transition Temperature and Charpy upper steel energy and temperature 4..
keyway temperatures 5.
critical crack size and basis for the calculation 6.
calculated bore and keyway stress at operating design overspeed 7.
calculated KIC data 8.
minimum yield strength specified for each disc
Response
A.
Each main turbine is an 1800 rpm, tandem-compound, six-flow non-reheat steam turbine consisting of one double-flow high pressure (HP) turbine and three double-flow low pressure (LP) turbines. The HP turbine ex-haust is passed through moisture separators before entering the LP turbines. There are five stages of extraction for feedwater heating.
The turbine is rated at 1,098,305 KW at inlet conditions of 965 psia, 1191 BTU /lbm, 13,365,081 lbs/hr and 0.32% moisture content and a back pressure of 1.5 inch Hg Abs. The maximum expected capacity at valves wide open is 1,150,768 KW.
Each low pressure turbine has 43 inch last stage buckets.
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Page 2 Response - (continued)
B.-
Unit 2 began commercial operation on July 4, 1974. Since that time the unit has accumulated a total of 38,373 operating hours as of May 31, 1980. Unit 3, as 6f May 31,1980, has operated for 36,500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> since it began commercial operation on December 24, 1974. The number of operating hours prior to and following each LP rotor inspection are as follows:
Unit 2 - A LP rotor 18,881 hours0.0102 days <br />0.245 hours <br />0.00146 weeks <br />3.352205e-4 months <br /> before inspection 19,492 hours0.00569 days <br />0.137 hours <br />8.134921e-4 weeks <br />1.87206e-4 months <br /> after inspection as of May 31, 1980 Unit 2 - B LP rotor 18,881 hours0.0102 days <br />0.245 hours <br />0.00146 weeks <br />3.352205e-4 months <br /> before inspection 19,492 hours0.00569 days <br />0.137 hours <br />8.134921e-4 weeks <br />1.87206e-4 months <br /> after inspection as of May 31, 1980 Unit 2 - C LP rotor 12,569 hours0.00659 days <br />0.158 hours <br />9.408069e-4 weeks <br />2.165045e-4 months <br /> before inspection 25,804 hours0.00931 days <br />0.223 hours <br />0.00133 weeks <br />3.05922e-4 months <br /> after inspection as of >hy 31, 1980 Unit 3 - A LP rotor 22,149 hours0.00172 days <br />0.0414 hours <br />2.463624e-4 weeks <br />5.66945e-5 months <br /> before inspection 14,351 hours0.00406 days <br />0.0975 hours <br />5.803571e-4 weeks <br />1.335555e-4 months <br /> after inspection as of May 31, 1980 Unit 3
,C LP rotor 14,576 hours0.00667 days <br />0.16 hours <br />9.523809e-4 weeks <br />2.19168e-4 months <br /> before inspection 21,924 hours0.0107 days <br />0.257 hours <br />0.00153 weeks <br />3.51582e-4 months <br /> after inspection as of May 31, 1980 The Unit 3-B LP rotor is scheduled for inspection in the spring of 1981 at which time we estimate it will have operated for 43,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />.
C.
Units 2 and 3 have experienced 73 and 65 turbine trips, respectively, since beginning commercial operation. These trips include manual trips, automatic trips and controlled shutdowns. Neither of the units has experienced any overspeeds.
D.
The information requested for each dise has'been identified as proprietary by General Electric Company and was provided to the Materials and Qualif-ication Engineering Branch of the Nuclear Regulatory Commission during an April 21, 1980 meeting between General Electric and the NRC.
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Page 3 II.
Provide details of the results of any completed inservice inspection of LP turbine rotors, including areas examined, since issuance of an operating license. For each indication detected, provide details of the location of the indication, its orientation, size and postulated cause.
Response
The following inspections have been completed on the LP turbine rotors:
1.
Unit No. 2 "A" LP Rotor - Inspected during spring outage of 1977. All external surfaces were inspected using magnotic particle examination and no indications were found. The bucket dovetail pins on the L-0 and L-1 rows were inspected using ultrasonics. A total of 87 pins with indications was found. All pins with indications were removed and replaced with new material. The rotor discs were not inspected using ultrasonics.
2.
Unit No. 2 "B" LP Rotor - Inspected during spring outage of 1977. All external surfaces were. inspected using magnetic particle examination and no indications were found. The bucket dovetail pins on the L-0 and L-1 rows were inspected using ultrasonics.
251 pins were found with indications and were removed and replaced with new material. The rotor discs were not inspected using ultrasonics.
3.
Unit No. 2 "C" LP Rotor - Inspected during spring outage of 1976.
All external surfaces were inspected using magnetic particle examination and no indications were found. The bucket dovetail pins on the L-0 and L-1 rows were inspected using ultrasonics and a total of 105 pins were found with indications. These pins were removed and replaced with new material. The rotor discs were not inspected using ultrasonics.
4.
Unit No. 3 "A" LP Rotor - Inspected during spring 1978 outage. All external surfaces were inspected using magnetic particle examination and no indications were found. The buckot dovetail pins on the L-0 and L-1 rows were inspected using ultrasonics.
Indications were found on 284 pins.
The pins with indications were removed and replaced with new material. The rotor discs were not inspected using ultrasonics.
5.
Unit No. 3 "C" LP Rotor - Inspected during winter 1977 outage. All external surfaces were inspected using magnetic particle examination and no indications were found. The bucket dovetail pins on the L-0 and L-1 rows were inspected using ultrasonics. Pins (173) with indications were removed and replaced with new material. The rotor discs were not inspected ultrasonically.
Page 4 III. Provide the nominal water chemistry conditions for each !? turbine and describe any condenser inleakages or other significant changes in water chemistry to this point in its operating life.
Response
Peach Bottom Units 2 and 3 are boiling water reactors (BWR's).
There are no provisions to monitor the steam chemistry entering the LP turbines.
However, reactor water conductivity is closely monitored and is a good indication of steam quality. Table I contains the average monthly reactor water conductivity for Units 2 and 3 during power operation.
Because the reactor water quality of a BWR is essential, condenser inleakage is minimized by close monitoring of water chemistry and prompt repair of leaks. As a consequence, condenser inleakage is not a significant factor affecting steam quality.
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TABLE 1 AVERAGE CONDUCTIVITY FOR PBAPS UNITS 2 6 3
( fA mhos/cm 8 25'C)
Month' Average Conductivity
!ionth Average Conductivity Unit 2 Unit 3 Unit 2 Unit 3 7/74 0.72 6/77' unit off 1.00 8/74 0.49 7/77 unit off 0.96 9/74 0.52 3/77 unit off 0.62 10/74 0.50 9/77 0.63 0.52 11/74 0.25 10/77 0.32 0.58 12/74 0.31 11/77 0.31 0.36 1/75 0.29 12/77 0.45 0.66 2/75 0.21 1/78 0.32 0.23 3/75 0.19 0.21 2/78 0.58 0.27 4/75 0.18 0.21 3/78 0.35 0.36 5/75 0.57 0.29 4/78 0.26 unit off 6/75 0.76 0.44 5/78 0.24 0.41 7/75 0.59 0.35 6/78 0.30 0.56 8/75 0.57 0.82 7/78 0.39 0.30 9/75 0.58 1.18 8/78 0.43 0.47 10/75 0.15 0.40 9/78 0.44 0.53 11/75 unit off 0.46 10/78 0.59 0.56 12/75 0.69' O.62 11/78 0.45 0.41 1/76 0.26 unit off 12/78 0.35 0.25 2/76 0.28 0.59 1/79 0.23 0.33 3/76 0.26 0.70 2/79 0.50 0.18 4/76 unit off 0.96 3/79 0.24 0.25 5/76 unit off 1.91 4/79 0.17 0.31 6/76 unit off 1.61 5/79 0.56 0.37 7/76 0.87 1.39 6/79 0.62 0.51 8/76 0.75 0.62 7/79 1.28 -
0.41 9/76 0.43 0.72 8/79 0.52 0.44 10/76 0.60 0.75 9/79 0.33 0.38 11/76 0.61 0.85 10/79 0.19 unit off 12/76 0.36 0.63 11/79 0.20 0.48 1/77 0.82 unit off 12/79 0.24 0.53 2/77 2.03 unit off 1/80 0.43 0.52 3/77 0.53 unit off 2/80 0.56 0.71 4/77' O.66 0.74 3/80 0.72 0.48 5/77 unit off 0.85 4/80 unit off 0.43 J
Page 5 s
Page 6 IV If your plant has not been inspected, describe your proposed schedule
~
and approach to ensure that turbine cracking does not exist in your turbine.
Response-All LP rotors with the exception of the Unit No. 3 "B" LP rotor have been examined; however, none of these examinations have included ultra-sonic testing of the discs. Present plans are to inspect the "B" LP roter at the next Unit 3 outage scheduled for the spring of 1981 and the Unit 2 "C" LP rotor at an outage scheduled for the fall of 1981.
Bcth inspection p7ans include ultrasonic examination of the discs.
One turbine element is scheduled for inspection every 18 months con-current w :h the unit refueling outages, resulting in each LP rotor being examined on a 6 year cycle. Ultrasonic examination af the LP rotor discs is planned for each of these inspections.
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Page 7 V.
If your plant has been inspected and plans to return or has returned to power with cracks or other defects, provide your proposed schedule for the next turbine inspection and the basis for this inspection schedule, including postulated defect growth rate.
Response
Previous LP rotor inspections have not revealed any cracking of the rotor discs. Future inspection plans are provided in response to Question IV.
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Page 3 VI.
Indicate whether an analysis and evaluation regarding turbine missiles has been performed for your plant and provided to the staff.
If such an analysis and evaluation has been performed and reported, please provide appropriate' references to the available documentation.
In the event that such studies have not been made, consideration should be given to scheduling such an action'.
RESPONSE
An evaluation of turbine generated missiles and their impact on safety related components and structures has been conducted for Peach Bottom Atomic Power Station. The results of this evaluation were provided in the Peach Bottom Final Safety Analysis Report, Supplement No.1, Question 11.2 S
APPENDIX B Generic Information Related to Turbine Discs I.
Describe what quality control and inspection procedures are used for the disc bore and keyway areas.
Response
After the rough machined wheel / disk 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 persornel assure that tolerances are maintained. Any deviation from accepted tolerances are reported to engineering for disposition.
Only approved coolants and lubricants 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 for shipment.
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Page 10 II.
Provide details of the General Electric repair /replacament procedures for faulty discs.
Response
Stress corrosion cracks have not been observed to date in nuclear wheels manufactured by General Electric, and General Electric does 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.
General Electric currently advises us that the erosion process is self-limiting and should not require the replacement of any wheels.
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9 Page 11 III. What immediate and long term actions are being taken by General Electric to minimize future " water cutting" problems with turbine discs? What actions are being recommended to utilities to minimize
" water cutting" of discs?
Response
GE has informed us that no immediate 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 modifi-cations will be recommended.
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Page 12 IV.
Describe fabrication and heat treatment sequence for discs, including thermal exposure during shrinking operations.
Response
The wheel / disk forgings a:e 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 tsarerature sufficient to ensure complete austenitization throughout the ferging, followed by a quench in cold, vigorously circulated water for a sufficient time to ensure complete transformation throughout the section. The forgings are heated uniformly to a tempering temperature below the lower 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 (disks) 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.
1 s.