ML19318D214
| ML19318D214 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 06/26/1980 |
| From: | Cavanaugh W ARKANSAS POWER & LIGHT CO. |
| To: | Clark R Office of Nuclear Reactor Regulation |
| References | |
| 2-060-28, 2-60-28, NUDOCS 8007080066 | |
| Download: ML19318D214 (8) | |
Text
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ARKANSAS POWER & LIGHT COMPANY POST OFFICE BOX 551 LITTLE ROCK, ARKANSAS 72203 L501) 371-4422 WILLIAM CAVANAUGH lli Vice President June 26, 1980 Generation & Construction 2-060-28 Director of Nuclear Reactor Regulation ATTN: Mr. Robert A. Clark, Chief Operating Reactors Branch #3 Division of Licensing U.S. Nuclear Regulatory Commission WLshington, D.C.
20555
Subject:
Arkansas Nuclear One-Unit 2 Docket No. 50-368 License No. NPF-6 Information Request for GE Turbine Discs (File: 2-1510.1, 2-0285)
Gentlemen:
In response to each item of your May 15, 1980 letter, the following is provided under the provisions of 10 CFR 50.54(f).
I.A. Turbine TyTe Response: The ANO-2 turbine is a General Electric impulse reaction, 1800 rpm, tandem-compound, four flow, two-stage reheat unit.
I.B. Number of hours of operation for each LP turbine at time of last turbine inspection or if not inspected, postulated to turbine inspection.
Response: The total number of hours of operation and the postulated hours of operation to end of the first fuel gcle are given in a
Table 1.
I.C. Number of turbine trips and overspeeds.
Response: This information is also given in Table 1.
I.D. Disc Information OO7080gg MEMBER MIDDLE SOUTH UTILITIES SYSTEM
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. Response:: General Electric would not supply this information to AP&L.
According to G.E., this information was supplied, by them, directly to the NRC.on April 21, 1980.
II.
Provide details of the results of any completed inservice in-spection 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: No inservice inspection has been performed on the turbine.
III. Provide.the nominal water chemistry conditions for each LP turbine and, describe any condenser inleakages or other significant changes in water chemistry to-this point in its operating life.
. Response: The water chemistry conditions and condenser tube failures which have occurred to date are included in Tables 2, 3, and 4.
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: -Per our response to Item VI below, no action is required as the probability of turbine missile damage (P4) is sufficiently low to preclude the need (from a plant safety standpoint) for turbine inspection.
Nevertheless, an inspection will be done during our first refueling outage, currently scl duled for March, 1980, in the interest of continued turbine reliability.
i V.
.If.your plant has been inspected and plans to return or has re-turned 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 growta rate.
Sesponse:-The ANO-2 turbine has not been inspected.
VI. -Indication whether an analysis and evaluation regarding turbine missiles'have 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: A turbine missile analysis has been performed for ANO-2.
.The results of this analysis are given in Section 3.5 of the ANO-2 FSAR. The analysis showed a very low annual probability of-30)urbine missile damaging a critical component (P4=6.3_x t
-10 g.
-9
- {J Generic Questions
- I.
Describe what quality control and inspection procedures are used for the' disk bore and keyway areas.
Response: 'After the rough machined wheel / disk forging has been tempered, material is removed from surface locations to measure mechan-ical 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 con-tinually paid to the finich, 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.
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 fluid, to verify that their chemistry is within accept-able limits.
If required, corrective actions are taken to maintain the chemistry within lieits.
Aft'er finish machining, each wheei is thoroughly cleaned and.
given a magnetic particle inspection of all surfaces. If acceptable,- the buckets are assembled and the wheel is static balanced.
Af ter 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 magneti: particle inspection of the buckets, the. rotor is cleaned to prepare for shipment.
II.
Provid'e details of the General Electric repair / replacement pro-cedure for-iaulty disks.
-Response: Stress corrosion crachs have not been observed to date in nuclear wheels manufactured by General Electric, and we 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.
We currently
.believe that the erosion process _is self-limiting'and should
.not require the replacement'of any wheels.
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III. What immediate'and long term actions are being taken by General Electric to minimize future " water cutting" problems with turbine disks? What actions are being recommended to utilities to minimize
" water cutting" of disks?
Response: No immediate actions are required to minimize water erosion
.because of the apparent self-limiting nature of the phenome-non. However, if future inspections show an unexpected pro-gression of the water erosion,' appropriate operating restric-tions and/or modifications will be recommended.
IV.
Describe fabrication and heat treatment sequence for disks, in-cluding thermal exposure during shrinking operations.
Response: The wheel / disk forgings are heat treated in the rough machined condition..The heat treatment' consists of soaking at a tempera-ture above.the upper critical temperature with the time and
' temperature sufficient to ensure complete austenitization throughout the forging, followed by a quench in cold, vig-orously circulated water for a sufficient time to ensure co:oplete 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 a-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.
Very truly yours,,
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William Ca augh, III WC: MAS:nak Attachments I
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a STATE OF ARXANSAS
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SS COUNTY OF PULASKI
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William Cavanaugh-III, being duly sworn, states that he is Vice President, Generation & Construction, for Arkansas Power & Light Company; that he is authorized on the part of said Company to sign and file with the Nuclear Regulatory Commission this Supplementary Infonnation; that he has reviewed or caused to have reviewed all of the statements contained in such infonntion, and that all such statements made and matters set forth therein are true and correct to the best of his knowledge, informa-tion and belief.
/'
A' William Cay (catigh III SUBSCRIBED AND SWORN T0 before me, a Notary Public in and for the County and State above named, this dday of h
1980.
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Notary Public/
t, My Commission Expires:
My commemon Expires 9/,1/,81
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TABLE 1 ANO-2 TURBINE DATA DATES GENERATOR ON LINE If0URS
- OF TURBINE TRIPS 12-26-78 thru 12-31-78 52.8 3
01-01-79 thru 01-31-79 602.0 5
02-01-79 thru 02-28-79 1.1 1
03-01-79 thru 03-31-79 0
0 04-01-79 thru 04-30-79 0
0 05-01-79 thru 05-31-79 0
0 06-01-79 thru 06-30-79 235.4 1
07-01-79 thru 07-31-79 656.0 3
08-01-79 thru 08-31-79 611.6 3
09-01-79 thru 09-30-79 262.9 0
10-01-79 thru 10-51-79 78.0 1
11-01-79 thru 11-30-79 0
0 12-01-79 thru 12-31-79 537.1 4
01-01-80 thru 01-31-80 628.1 4
02-01-80 thru 02-29-80 0
0 03-01-80 thru 03-31-80 224.4 4
04-01-80 thru 04-30-80 394.2 4
05-01-80 thru 05-31-80 744.0 0
06-01-80 thru 06-05-80 103.5 0
06-05-80 thru End of Cycle 4920.2 0
TOTAL 10051.3 31 In addition to the 31 turbine trips, there have been 3 overspeed trips that were performed as a turbine overspeed trip test.
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TABLE 2 - STEAM CHEMISTRY PPM SUSPEhTED PH CONDUCTIVITY SOLIDS Cl-Si0 Na 2
mmhos
~Before:
8-11-79 9.0 4.8
<.0.01
< 0.1
< 0.002
'< 0.005
~After:
8-12-79 9.9-25
< 0.01
< 0.1 0.002.
< 0.005
~ B'efore:
8-22-79 9.2 4.2
< 0.01
< 0.1
< 0.002
< 0.005
'After:
8-23-79 9.2.
3.6
< 0.01'
< 0.1
< 0.002
< 0.005 Before:
8-29-79 8.8 2.2
< 0.01
< 0.1
< 0.002
< 0.005 After:
8-30-79 9.0 4.0
< 0.01
< 0.1 0.002
< 0.005 Before:
9-7-79 9.2-5.5
< 0.01
< 0.1
< 0.002
< 0.005 After:
~9-8-79 9.8 24
< 0.01-
< 0.1 0.006
< 0.005 Before: 12-25-79 9.1 3.5
< 0.d1
< 0.1 0.003
<.005 After:
11-26-79 7.0 1.35
< 0.01
< 0.1
< 0.002 (No Read-ing) h t
2 -
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1 t-
'y -
-- h H
4
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1
C 4
TABLE 3 Nominal water chemistry for steam to main turbine:
pH
- 8. 0 --+ 9.6 Conductivity 0. 7 -+ 12.5 mmhos Suspended solids 0.01 ppm C1_
0.1 ppm F_
0.1 ppm Na 0.0005 ppm SiO 0.002 ppm 2
Table 4 Condenser Tube Failures occurred on the following dates:
Approx.
Time to Repair 12-20-78 50 Hrs.
12-23-78 80 Hrs.
6-13-79 120 Hrs.
8-11-79 120 Hrs.
8-22-79 48 Ers.
8-29-79 100 Hrs.
9-7-79 300 Hrs.
12-25-79 48 Hrs.
These tube failures are believed to be startup related; subsequent design changes have considerably improved condenser performance.
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