ML19320B985

Forwards Response to Re Discovery of Cracks in Keyway & Bore Sections in Westinghouse Low Pressure Turbines

ML19320B985
Person / Time
Site:	Crane
Issue date:	07/11/1980
From:	Herbein J METROPOLITAN EDISON CO.
To:	Reid R Office of Nuclear Reactor Regulation
References
TLL-299, NUDOCS 8007150589
Download: ML19320B985 (25)

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Metropolitan Edison Company

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Post O'fice Box 480 Middletown, Pennsylvania 17057 717 9444041 Writer's D; rect Oial Numtaer July 11, 1980 TLL 299 Office of Nuclear Reactor Regulation Attn:

R. W. Reid, Chief Operating Reactors Branch No. 4 U. S. Nuclear Regulatory Commission Washin gen, D.C.

10555

Dear Sir:

Three Mile Island Nuclear Station, Unit ' (TMI-1)

Operating License No. DPR-50 Docket No. 50-289 Low-Pressure Turbine Disc Cracking Enclosed please find a response to your letter of May 19, 1980, concerning the discovery of cracks in the keyway and bore sections of discs in Westinghouse lo.:-pressure turbines.

c'icerely, sp

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vs J. G. Herbein Vice President TMI-I JCH:DGM: hah Enclosure

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RESPONSE TO NRC REQUEST FOR INFORMATION TURSDE DISC CRACKING NRC DOCKET No. 50-289 QUESTICN IA: TURSINE TYPE?

ANSWER: Three Mile Island Unit #1 (TMI-1) Turbine-Generator is a General Electric Co. tandem compound non-reheat unit with three low pressure double flow sections.

The General Electric turbine type designation is TC6F-38. Nameplate electrical rating is 837 MW.

Turbine serial number is 170X399.

QUESTION IB: NUMBER OF HOURS OF OPERATION FOR EACH LP TURBINE AT TIME OF LAST IURSINE INSPECTION OR IF NOT INSPECTED, POSTULATED TO TURBINE INSPECTION.

ANSWER: The A-LP Turbine was last inspected 3/18/78 and total operating hours on the machine at that time were 24,421.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.

The "B" and "C"-LP turbines were last inspr ced 2/15/76 and total operating hours at that eine were 10,938., hours.

Postulated operating hours at eine of next inspaction for each LP turbine are:

A-LP Turbine - 38,181 hours0.00209 days <br />0.0503 hours <br />2.992725e-4 weeks <br />6.88705e-5 months <br /> 3-LP Turbine - 45,131 hours0.00152 days <br />0.0364 hours <br />2.166005e-4 weeks <br />4.98455e-5 months <br /> C-LP Turbine - 45,131 hours0.00152 days <br />0.0364 hours <br />2.166005e-4 weeks <br />4.98455e-5 months <br /> Please note that the A-LP turbine is being inspected again af ter 14,000 additional run hours while the B, C-LP's will have 35,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> between inspections r The nornal reinspection interval based on our 5

~

year cycle schedu1e is 35,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> and the 3, C-LP's are still on that schedule. The A-LP however is being reinspected early to allow repair of water erosion discovered during the 1978 inspection. This erosion is unrelated to the subject of this NRC information request.

i See enclosure #5 for a brief history of operating hours versus inspection dates.

QUESTION IC: NUMBER OF TURBINE TRIPS AND OVERSPEEDS ANSWER: The total number of turbine overspeeds experienced since initial operation on 6/20/74 is 17.

All of these were the result of planned testing.

Six (6) of these were at % 112 (2016 RPM) and eleven (11) were at % 108" (1944 RPM) overspeed.

The total number of turbine trips experienced since initial operation is 4_0. - This number is composed of:

0 A. Trips from greater than 20% reactor power - planned 5 unplanned 13

3. ' Trips from less than 20% reactor power - planned 20 unplanned 2

Page 1

~.

Enclosurss #3 and #4 contain a detailed lischg of trips and overspeeds both after commercial operation and prior to commercial operation.

QUESTION ID: 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.

KETWAY TEMPERATURES 5.

CRITICAL CRACK SIZE AND BASIS FOR THE CALCULATION 6.

CALCULATED BORE AND KEYWAY STRESS AT OPERATING DESIGN OVERSPEED 7.

CALCULATED K DATA lc 8.

MINIMUM YIELD STRENGTH SPECIFIED FOR EACH DISC ANSWER: The General Electric Co. has provided this information to the NRC i

subsequent to the meeting between G.E. and the NRC on January 9, 1980.

Enclosure #6 is the G.E. Co.'s response to our request for this information.

The G.E. Co. considers this information propriel:ary in nature and has declined to provide it directly to us.

QUESTION II: PROVIDE DETAILS OF THE RESULTS OF ANY COMPLETED INSERVICE INSPECTION OF LP TURBINE ROTORS, INCLUDING AREAS EXAMINED, SINCE ISSUANCE OF AN i

OPERATING LICENSE. FOR EACH INDICATION DETECTED, PROVIDE DETAILS OF THE LOCATION OF THE INDICATION, ITS ORIENTATION, SIZE, AND POSTULATED CAUSE.

ANSWER: Details of all inservice inspections done on the A,B,C-LP rotors are included in enclosure #1. The LP disc sonic inspection addressed in the subject NRC memo was preformed on the A-LP rotor in March 1978. Details of this inspection are included as enclosure #2.

QUESTION 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.

ANSWER: Very little empirical data is available to verify actual chemical conditions in the steam to the LP turbines at TMI. As a boundary condition, chemical contaminents could not exceed the levels observed in the HP steam. These values are described in Table 1.

Measurements performed on moisture separator drains demonstrate that ame contaminents tend to concentrate in this stream.

It may therefore be Luferred from mass balance calculations that the actual concentratioc d sodium and some anions are significantly lower in.the LP steam than the values observed in the feedwater and,HP.sceam. A sampling of LP steam was performed on January 26, 1979 by Westinghouse. Many of the values observed were less than detectable by the methods employed. A few very high values were also observed. Since some of these high values were observed-on sample streams which were monitored by continuous on-line indicate the absolute values or show any fluct-l analyzers which did not l

untions, the high grab-sample num5ers may be attriuted to contamination l

of the grab samples. A copy of the Westinghouse analytical results is included as Table Two and a typical Moisture Separator Drain analysis is included as Table Three.

Page 2

During the operating history of Unit I, there have been several chemistry excursions due to both main and auxiliarf condenser tube leaks. Also, in September of 1977 an inadvertant sulfuric acid centamination of the secondary system occurred. This was caused by various failures in the cycle =akeup damineralizer system which allowed regenerant acid to be injected into the condenser.hotwell. The highest sodium concentration measured in the HP steam dur'ng this excursion was 0.47 ppm. The duration of the incident as measured from the time when on-line feedwater chemistry analyzers indicated a problem to turbine trip was % 58 minutes. The lowest pH as measured at the secondary side of the OTSGs was 3.6.

Some of the main and auxiliary condenser tube leaks have been minor and have required only that we increase our frequency of Powdex vessel resin precoating to maintain proper feed-water and steam quality. Others - two in 1974, three in 1976 and one in 1975 required power reduction and cire -ater isolation from the portion of

-the condenser with the leaking tube (s), and subsequent plugging of the tube (s)- The highest sodium concentration 2.n the OTSG feedwater during any of the cbove mentioned leaks as measured by AA was 27 ppb. The highest cation conductivity was 0.55 umho.

l Page 3

TABLE I TYPICAL HP STEAM CHEMISTRY - TMI UNIT I PARAMETER TYPICAL VALUE_

pH 9.3 Cat *.on Conductivity (umho/cm) 0.20 f.a (ppb) 2-3 i

i Dissolved Oxygen (ppb)

<2 i

SiOz (pph)

<5 C1 (ppb)

<5 l

l Fe (ppb)

< 10 1

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i TAlti.F. 2 1/26/79 Metropolitan Edison, Three Illie island #1 (PWR, AVT, 870 MW )

Ani ns/ ppb Cations /pple Spec. Cond.

Time pH tis /cm p

Time Cl-PO ~ NO 0

Time I.Na

[ NH 4

3 4

4 LP Steam 11:09

<10 11:00

<1

<1

<1 41 11:04 58

<1 540 (at crossover)

'11:31 8.8

[11:11 1

<1

<1 6

11:11

<l

<l 6001 (160 psig, 11:36 4.9 (20*C) 11:13 6

<1 x1

<1 1I:18

<1

<I 540 370*F) 12:19 0-5 11:21

<1

<1

<1

<1 11:24 19 6 550 Feedwater 11:18

<10 11:05 3

<1

<1 43 11:10

<1 8 590 (at steam 11:25 8.6

[11:19 2

<1

<1 6

11:19 4

<1 570]

generator 12:25 0-5 11:38 3

<1

<1 19 11:43 181

<1 570 header)

%13:00 8.2 (44.5*C) 12:50 9.0 Holsture 11:35 8.4 2 ",

11:20 4

<1

<1 6

11:26 326

<1 290 Separator 11:37

[11:36 6

<1

<1 5

11:36 6

<1 290]

Drain 12:46 0-5 11:46 7

<1

<1 6

11:50 40

<l 300

%13:00 2.3 (23.5'C) 12:55 8.8 Once-through steam generator Data in brackets were ion chromatographically determined 1n samples that had been stored in polystyrene bott les.

Pane 5 e

4 TABLE 3 TYPICAL MOISTURE SEPARATOR DRAINS CHEMISTRY - TMI UNIT I L

t 1

- PARAMETER TYPICAL VAL"E pH ~

8.5 - 9.1 i

Cation Conductivity (umho/un) 0.5 - 1.5 SiO; (ppb) 60 Na (ppb) 15

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F Page-6

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. QUESTION IV:

IF YOUR PLANT HAS NOT BEEN INSPECTED, DESCRIBE YOUR PROPOSED SCHEDULE AND APPROACE TO ENSURE THAT TURBEIE CMCKING DOES NOT EXIST IN YOUR TUR3INE.

ANSWER: - The A-LP Turbine rotor has been sonically tested as detailed in question II.

j.

The B,C-LP rotors are scheduled for inspection within the next two fuel cycles.

4

.The testing recommendations contained in g.a. co. til 857 have been incorporated into the cyclic 5 year-maintenance schedule of TMI-1 to ensure rotor cracking does not go undetected for extended periods.

QUESTTON V:

IF YOUR PLANT HAS BEEN INSPECTED AN PLANS TO RETURN OR HAS RETURNED TO PO'4R WITH CRACKS OR OTHER DEFECTS, PROVIDE YOUR PROPOSED SCHEDULE FOR THE NEXT TURBEE INSPECTION AND THE -BASIS FOR TdIS INSPECTION SCHEDULE, ETCLUDUiG POSTULATED DEFECT GRC'aTd RATE.

ANSWER: TMI-l has not returned to power with cracks' or defects of the kind l

[

addressed in the subject NRC memo.

The A,3,C-L? rotors have been returned to service at various times with known. cracked dovetail pins in the last stage (L-0) buckets.

In all instances these crack indications were evaluated by the G.E. Co. and the rotors were judged satisfactory for continued service until the next regularly scheduled inspection (5 years).

OUESTION VI:

E!DICATE '4HETHER AN ANALYSIS AND EVALUATION RECARDING TUR3ETE MISSILES HAVE EEEN PERFORMED POR YCU2 PLMr" rid PROVIDED TO THE STAFF.

IF SUCH AN ANALYSIS AND EVALUATION EA3 3EEN PERFORMED AND REPORTED, PLEASE PROVIDE APPROPRIATE REFERENCES TO TdE AVAILABLE DOCUMENTATION.

IN THE EVENT THAT SUCH STULIES HAVE NOT BEEN MADE, CONSIDERATION SHOULD BE GIVEN TO SCHEDULING SUCH AN ACTION.

ANSWER: An analysis and evaluation of turbine missiles was done by the Turbine-Generator supplier (GE) and is described in the final safety analysis report (FSAR) docket No. 50-289, Volume 2, page 5068, para. 5.4.3.2.4,

" Main Steam Turbine Missiles".

Missile pfbtection'.has been. provided for various systems by means of shielding and7or separation of. redundant components. Missiles from sources, in_ addition to the turbine, have been postulated.

Refer to FSAR Volume 1, page 1-31, para. 1.4.40.

I 1

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.Page 7

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GENERIC QUESTIONS:

I Describe what quality control and inspection procedures are used for the disc boro and keyway areas.

II Provida details of the General Electric repair / replacement procedures for faulty discs.

III What irmediate and long ter:a actions are being taken by General Electric to : minimize future " Water cutting" problems with turbine discs?

IV Describe fabrication and heat treatment sequence for discs, including thermal exposure during shrinking operations.

ANSWERS: Answers to these questions have been provided by the General Electric Co.

as per enclosure #6.

i i

Page 8

3

.__. 3 ENCLOSURE 1 1 INSERVICE INSPECTION HISTORY TMI-1 A,B,C-LP TURBINE ROTORS 1.

The first major inspection of the A,B,C-LP rotors was performed during the period of Feb. 20, 1976 thru April 14, 1976.

All three LP rotors were given a complete visual and magnetic particle inspec-tion over all peripheral surfaces (wheels, buckets, covers, tenons). There were no cracks or indications found on any of the rotors using these nethods.

No UT inspection of the Disc bore and keyway areas was perfor=ed since the inspection technique wasn't developed until 1978.

The last stage (L-0) bucket erosion shields on all three rotors were dye-e penetrant inspected and no indications were found.

The last stage (L-0) and next to last stage (L-1) bucket dovetail pins on all three rotors were UT inspected for cracks. There were no crackad pins in the L+0 stage pins on any of the rotors. All three rotors did have cracked pins in the L-1 stage however. The nunber and locatio_ns are listed below. All cracked pins were replaced prior to Re-start.

l Rotor 4 of cracked L-1 dovetail eins A-LP 10 Turbine End (TE) 31 Generator End (CE)

B-LP 21 TE 71 GE C-LP 42 TE 30 GE All of the cracked L-1 dovetail pins were 0.343 inches in diameter by 5 inches long. The cracks occurred at various locations along the length of the pins but always away from the shear planes of the pins. The cause of the cracking is postulated by General Electric to be intergranular stress corrosion cracking.

Additional discussion of L-0 and L-1 stage pin cracking is contained in General Electric TIL 689 dated October 30, 1973.

2.

During the period of March 18, 1977 thru April 20, 1977 the last stage bucket areas of all three rotors were inspected visually. None of the LP turbines were disassembled.

The L-0 stage buckac erosion shields of all three rotors were dye-penetrant inspected with no indications being found.

The L-0 stage dovetail pins of all three rotors were UT inspected with no cracked

's pins being found.

Enclosura 11 pas: 0 3.

During the period of March 18, 1978 thru May 2,1978 the A-LP turbine was disassembled for inspection. The "B" and "C" LP turbines were not disasse=blad but their L-0 stage areas were inspected.

The L-0 stage bucket erosion shields of all three rotors vera dye-penetrant inspected with no indications being found.

The L-0 stage bucket dovetail pins of the "B" and "C" LP rotors were UT inspected.

No cracked pins were found on the B-LP rotor. The C-LP had 4 cracked pins - 2 TE and 2 GE.

The General Electric Co. evaluated the number and location of the cracked pins and approved the rotor for re-start without replacing the pins. The cause of these cracks was the same as discussed under the first year inspection.

The A-LP rotor was given a complete visual and magnetic particle inspection over all peripheral surfaces. There were no cracks or indications found using these methods.

The A-LP rotor L-0 and L-1 stage bucket dovetail pins were UT inspected. The L-1 stage had 13 (12 GE and 1 TE) cracked pins - all were replaced. The L-0 stage had 2 TE pins cracked - all were replaced.

The newly developed rolling sonic inspection of LP disc bore and key way areas was performed on the A-LP during this inspection. No indications were found.

A copy of General Electric's report on this inspection is attached.

4.

During the period of February 16, 1979 thru March 9, 1979 the last stage bucket areas of all three LP rotors were inspected visually. None of the LP turbines were disassembled.

The L-0 stage bucket erosion shields of all three rotors were dye-penetrant inspected with no indications being found.

The L-0 stage dovetail pins of all three rotors were UT inspected.

The A-LP had one GE pin cracked. The B-LP had no cracked pins. The C-LP had 2 GE and 4 TE pins cracked. All of the cracked pins were evaluated by General Electric and approval for re-start was given without replacing the pins.

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SERVICE ENGINEERING GENER AL ELECT 4fC CcMPANY 3 PENN CENTER ALAZA DIVISIO N AHILACELPHI A.

P ENpSYLVANI A 13102 l'

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June 27, 1973

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Re:

Metroc.olitan Edisen ccmo.any

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Three Mile Island Unit #1

' f, Turbine $170X399

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'?-A Wheel Ultrasonic Inspection Metropolitan Edison Company Three Mile Island Middlancwn, Pennsylv=

d=

7057 Attention:

.Mr. J.?. O'Hanlon, Superintendent

aar Sir:

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The ic11cwing are the results of the inspection.

An ultrasonic examinaticn of the shrunk-on wheels en the *?-A ro cr of the abcve uni was ccnducted en March 22, - 31, 1973.

The bcre regicn of all 14 wheels was examined with the wheels in place on the shaft.

The inspection revealed ne indications of cracks on or near the bore or keyway surfaces.

The wheel dovetails of the first 5 stages en both ends of the roter were inspected u'::asenically with the buckets in place.

All three hooks were examined en wheels 1 and 4, hcwever, due to geccetry limitations, che icwer and middle hecks only were exa.u.ned on wheels 1,3, and 3.

c indicatiens were fcund.

The' bucket devenail pins in the 'ast :wo stages were ultrascnic-1*'.y tested in acceriance Vith !!~. 539.

Indicati:ns ci

• • ~.cks tere 5:und in ' 3 ci.s.

It is Our understanc.-- -.2:

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.n s w'.:n _nc.:2:.:ns were raciacec.

The distric: repcr ed that i magnetic particle :ss was cen-ducted en the. peripheral surfaces of the rc:Or 2.nd no indica-

acns were found.

EtJCLcSudz *~

G E tl E A A L >Jd iLiC T R I C Mr. J.P. O'Hanlen wune 2 <,

19.,,2 Page No. I The reter was #~md satisfacterv for continued service in accer-dance with cur current starting and icadang recc==endations.

It was recem= ended that the roter be reinspected in accordance with TIL 857 which prescribes a nagnetic particia test of external surfaces during subsequent cutages and an ultrasenic inspection of the wheels at about 6 year intervals of service.

In evaluating the above reccmmendations, the cwner should recog-nice that there are many cpo. rating practices and conditions in-cluding, but nc: li=ited sc, these mentioned above which af fect centinued sa isfactcry operatien Of which General Electric has no knowledge and over which General Electric has no contrel.

It is the cwner's respcnsibility te deter =ine whether or no: the rc:c:

shculd continue to be used in light cf the infor=ation furnished abcVe and his cwn cperating.practicas and conditions. General Electric's responsibility in connecticn with furnishing this re-port is as set ferth in the epneract under which this reper is furnished.

5 If you have any questions, please centac: me.

very truly yours, OkW 7

/ O 772k D.3.

Pceter ISSE M&N Field Engineer Fer: C.L. Heyd Service Superv scr Mechanical and Nuclear Serrica O SP / 3=n-

THI-1 TURBINE TRIPS & OVERSPEEDS (Af ter Commercial Date of 9-2-74)

Enclosure #3 j_

Trips Overspeeda l

Date of Planned Initial Planned

1. at

1. at trip or Rx Power cause or 108%

112%

-Unplanned llaplanned 10/20/74 P

15%

Repair H2 seal and pzr relief P

1 0

valves 11/16/74 P

15%

Dropped Rod 1/23/75 UP 100%

liigh moisture sep. level.

3/30/75 UP 100%

Loss of EllC DC power 4/4/75 P

15%

Dropped Rod 5/9/75 UP 100%

Hofsture sep. level switch 5/23/75 P

15%

112 seal repair and control rod interchange 6/18/75 UP 100%

Voltage spike in EllC Sys.

6/25/75 P

15%

Control rod drop 6/26/75 t!P 15%

Water inductioa 9/26/75 P

15%

Repair RC-P-1A 10/1'./75 P

15%

Repair CR7 stator 11/12/75 P

?5%

Repair CRD stator and #3 CV linkage 12/16/75 P

15%

Repair HU-V-94

~

Enclosura 73 pags 2 t

DatC of Planned Initial

' Planned.

'f at

'I at trip or

- Rx Power Caime or 108%

112%

Unplanned Unplanned

1/16/76 P

15%

Repair Clun stator 2/15/76 P

100%

1st year outage 5/27/76 UP 26%

Rx scram during restart P

3 1

11/5/76 P

15%

Repair Dil-V-1 2/4/77 P

15%

Repair oiltrip device P

1 3/18/77 P

15%

2nd year outage P

2 1

9/16/77 P

15%

liigh conductivity in 0TSG 11/14/77 UP 100%

ICS co.nponent failed 3/14/77 P

15%

3rd year outar.e P

1 1

6/21/78 P

15%

Repair 1 C--P seal 11/15/78 UP 99%

Loss of Elle 14: iwwer 2/17/80 15%

4th year.natase p

1 1

l 4

THI-1 nlRBINE TRIPS ANI) OVERSPEEDS (Prior to Comunercial date of 9/2/74)

Enclosure #4 Trips j

overspeeds

1) ate of -

Planned or Initial Planned or i at I at trip Unplanned' Rx Power Cause Unplanned 108%

112%

6/20/74 P

15%

Initial Start-up P

1 1

6/24/74 P

15%

Test Procedure for start-up 6/25/74 P

20%

Test Procedure 7/7/74 P

40%

Test Procedure 7/12/74

.UP 65%

Unknown 7/13/74 UP 15%

Loss of Feedwater 7/14/74 UP 76%

Crounded Tave.

7/17/74 P

30%

Test Procedure 7/20/74 P

15%

overspeed Test P

1 1

7/25/74 UP

>20%

1. 11 Bearing Vibration 8/3/74 UP 100%

Rx Trip 8/13/74 P

98%

Full Load Cen. Trip 8/30/74 UP 75%

1. 11 Bearing Vibration

TMI-1 LP TURBINE OPERATING HOURS Enclosure #5 Total Cumulative Operating Hours Since Initial Data Event Installatica 1..

6/20/74 Initial Operation 0 hrs.

2.

9/2/74 Start Commercial 1090.6 hrs.

Operscion 3.

2/15/76 End of First Cycle-10,938.4 hrs.

A,3,C-LP Turbines Inspected 4.

3/18/77 End of Second Cycle-17,348.3 hrs.

no LP Turbines Inspected 5.

3/18/78 End of Third Cycla-24,421.5 hrs.

A-LP arbine Inspected 5.

2/17/80 End of Fourth Cycle-31,180.9 hrs.

no LP Turbines Inspected

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SERVICE ENGINEERING GENERAL ELECTRIC c0MPANY 3 PENN CENTER PLAZA DIVISION P HILA o ELPHI A.

P E N N SY LVA NI A 19102 June 13, 1980 Re: Metropolitan Edison Company Three Mile Island - Unit #1 Turbine # 170X399

.IRC Request for Infomation on Low Pressure Ro:ce Disk Metropolitan Edison Company Three Mile Island P. O. Box 40

-Middletcwn, Pennsylvania 17057 Attention: Mr. C. Seit:

Turbine Engineer

Dear Sir:

This letter is the resconse to your letter of 30 May 1980 requesting data for the NRC on your number 1 unit's low pressure rotor and wheels.

SITE SPECIFIC OUESTIONS:

Ouestion I-0:

For each turoine disk, please provide the following:

a). Type of material including material specifications b) Tensile properties data c) Toughness properties data including' fracture aptaarance, j

transition temperature, and charpy upper steel energy and temperature d)

Keyway temoeratures e) Critical crack size and basis for tne calculation

')

Calculated bore and keyway stress at ocerating design overspeed

) Calculated X r data h)

Minimum yield ~ strength s:ecified for eacn disk

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'l ' e W d gn cloSailE %! ft. 1 Mr. C. Seitz Page 2 June 13,1980 Ref anse I-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 General Electric and NRC recresentatives on Acril 21, 1980. The NRC has informed us that this information is an acceptable reply to this question. Ouestien II: Provide details of the results of any completed in-service inscection 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. Resconse II: In March, 1978 an in-service wheel bore ultrasonic inscection was c mpleted on ne LP "Ad rotor of the Three Mile Island Unit #1. The results were described in a letter on this subject dated June 27, 1978. A copy of this letter is attached for your ready reference. GENERIC OUESTIONS: Question r: Describe wnat'ouality control and inspection procedures are used for the disk bore and keyway areas. Rescansa I: After the rougn macninec whesi/ disk forging has been emaered, material is removed from surface locations to measure meenanical crecerties. The forging is then sucjectec to a 100% volumetric ui:rasonic insaection. If :he est results meet stringent ac-cactance stancarcs, the forging is released for #inal macnining. During final machining, attention is c:ntinually : aid :o :ne finisn, c:nt ur and :imensions of every surface. For instance, the '<eyway depth, width, location, radii, anc surface finisn for every wheel is ' checked for conformance to drawings. Cuality EnscloSudE % P3 GEN ER AL fo$ ELECT 3IC. Mr. C. Seitz Page 3 June 13, 1980 control personnel assure that tolerances are maintained. Any deviation frem accepted tolerances are reported to engineering for disposition. Only coolants and lubricants approved by engineering are used in the manufacturing and assembly orocess. 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 reouired, 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 ac-captable, the buckets are assembled and the wneel is static balanced. Aftar assemoly on the shaft, each wheel is inscectad and measure-ments are made to assure its proper location. The assemoled rotor is : hen scun to 20% overspeed following a hign sceed balance. Finally, after a magnetic particle inspecticn of :ne cuckets, the rotor is cleaned to prepare for shipment. Question II: Provide details of the General Electric repair /reolacement crocedures for faulty disks. Resconse II: Stress-corrosion cracks have not been observed to date in nuclear wheels manufactured by General Electric, and we do not anticipate that removal or replacement of wneels will be reouired because of this.phencmenon. The water erosion wnich has ceen ooserved in the keyways of wheels on several non-reheat machines is being studied intensively. We currently believe : hat :he erosion crecess is self-limiting and should not recuire :ne reolacement of any wnesis. Cuestion III: What immediata and long : arm actions are being :3 ken by General Electric to minimi:e future " water cutting" arcolems with turbine disks? What actions are being recommended to utilities :o minimize 'watar cutting" of disks? I- EN cl. o.rd E

• G P+

.... 2 1.i;?.1:0-Mr. C. Seitz Page 4 June 13, 1980 Resconse III: No immediate actions are required to minimize water erosion because of the apparent self-limiting nature of the phenomenen. However, if future inscections show an unexpected progression of the water erosion, appropriate operating restrictions and/or modifications will be recommended. Question IV: 4 Describe fabrication and heat treatment sequence for disks, including thermal exposure during shrinking ocerations. Resconse IV-The wheel / disk forgings are heat treated in the rcugh machined condi tion. The heat treatment consists of soaking at a. temperature above the upper critical temperature with the time and temperature sufficient to ensure ecmplete austenitization througnout the forging, 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 temcerature 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 temcerature below the embrittling range, but sufficiently hign to increase the wheel diameter enough to assemole on the shaft with the required shrink fit. Please let me know if you have any further questions on this subject. Very truly yours, s (?: -

c. 3. Pc:ter Service Sucervisor Mechanical and Nuclear OSP/mdk Enclosures cc: Mr. R. Teole

u Lu.) EAJC L OEM E t.' '2 f.5-G E N E R A L h E l.E CT R I C. S ERVICE ENGIN SERING GEN ER AL ELEc'lAlc. COMP ANY 3 PENN CENTEA P t.A ZA C1VISICN PHILACELPHf A. P E N NSYLV A NI A 19102 June 27, 1978 Re: Met==pcli"*" Edisen Cc pany Three Mila Is1d Unit tL T" W "a $170X399 LP st Wheel Ultrascric Inspectics. utE1~* STY <333133,,3 Met:cyc'4" 'discn Ccmpany ovor.s ,,o.. m .s...e._4 1 a ..s5. a. 4 cyv7 cc :.,a v n yac w Middletcwn, Pen =sviva:ia 17057 "O c-#C.,,,,g s.!3 C TSP' y.4.:s s C., 2e4S+ 30*- Superintendent O sti;# A :enti n: .Nir. J.P C ' '"len, u DTS C q.her is 4 W ;c p,;.L G rM.- y eer :_.rr

J.3 Cur _

g the Spring inspec-ica c: usi: ti, Schenectady.:ersc=nel en a _ a_ _.

a_

v. -,

.o. ,e_ = ec. a. - 2 4-. .- r "ha fellcwisy ara ""a --anits c' -"* ' spectic= A: citrascric ex* d aticn of the sh:: k-c= wheels en de ~J-A. .e a c a. _. 4..aas - e.,ctos u,

a. 2.,,

.u. -,.i.n. i s. w -- c. "a wheels The-bcre repicn;;f all 14 wheels was ex=~d ed w" in place en the shaft. The inspection ravealed ac indicati:ns cf cracks c: cr near the bcra c: keyway surfaces. The wheel deve-'ils cd ha fi:s 5 stages en bc-2 ends ed -la

=r were inspec ed ci rasc=ic zy v'

-"a buckets is place. .i t ' -- ee hecks vere av'~4 ed. en wheels. I and 4, hcwever, due te gec=e:r-I 1.4 ~4 =atic s, -le icwer and =iddle hecks.==17 were ex d ed := wheels 1,2, and.E. Ne indicati::s were feu=d. '..a ' u %a - '. e., *._- '~s '._ -.= 'as ~.~c a-- c.=s

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'. ~ ~ - ~ ~ '.. - y 2 --- in - - _... 3 .s_ 4..,, _a,--, 2 w.

a..

.. ; 4 ., 2.... 2 z 2..3 4.. ; ,e u. ..,a. -a wi-2. indicati::s were :eplaced. ,4t. -.. -..a.3 m.s O '; 4.. 2. =. .C. 4h.,.. y C.- 9 '3 a E.=s. Css, A. ~"a .. =. =. ' '. - 2 ** A =.=.*..'.=.dA.*._w A..C-. A_ ks e.. 4 r ;. a..==s '

• -**==

r - s. -icus we:a 2:c:6. I b ta Q gnclosage CQ ^* i' O GENERAL $El.ICiala Mr. J.P. O'Ea:1ca i 91. 1 o e -u,....-.i Page Nc. 2 "".a :=t:r was fcund satisfacto:I f== cen 4 -ned servica in accc - dance wi d cur==: rent s** ~d g and leading =ac-enda: ices. It was rec =mmanded dat tha =cter be. reinspected. is. ac== dance w-d TIL 357 which prescribes a.nagnetic par-dcle test of external surfaces d :ing sesequent cutages and an ultrasenic inspectice ofdthe wheels at ahcut 6 year intervals cf servics-I=. evalta 4 g de aheve rec =:cmendations, de cwner shouli rec =g-ni=a dat dare are manv. cpera d - s ::arcices and ccnditiens in-ted to, thcse =entiened aheve whid addecc. cit-di~7, but not T 4 "4 cen~4-ned.sa*d efact==I eperatica of which General Electric has ac k=cwledge and ever which General Electric has no cent:01. It :.s the cwner's respcnsibility t= deter-d e whether er non de ::::: shculd cen-4 -ne to be used is. light cd de info-=rien ft :ished aheve and his cwn cperating practices and ccndia.icns. General Electris's sspc=sibilirl in cc =ectica w ~~ 'shing dis ra-d pc:t is as set f :d is.the centrac under which --*s

spc:: is fn==ished.

If vec have an't cuestic=s! please centact ca. e e 7='? t:11'I ? A=s I cA/ M D.3. ?cteer !&S?. MSN ?ield E:gizeer I::: C.~.. Heydt 5ervice Super-riscr Me@ =~' cal and Nu '==- *e_rica 03F/ *- O ,_ic; ~ w. .~.s v Ov closat g. & fo 1:. a ULTRA 5ONIC TESTING OF COVETAIL PINS f r7 Cus :mer: /ry:7 & lt7J.l. ,C. /h,y ~~ s h -llT 5C1;i=n; $ /r-// '~ ~.~-C///d' Naner ._ A Scr. No.: /.//' /c'V/ Test Date:.5-2 -7,f' Location Distance To I Ind Fre::t l 5 5 Adjacent Bucket s Stage Serial Numbers or 3 Disch. Rcw Number j j l= c[ Ad=. Side = c = 51:e 44' 6' / I / l1-/ I44 -z<a l l I v'l 4-/ 7mrEssi / A" 4 / 1-/ ei-es. l / /4' +2 .fz +'s' / .4-/ 84-ir,- + v / L-/ !27.jed

/

(d/ " +9y ' 4 /6 " /6 ' / i / i z-/ lSz-zasi l l / e " l / l 1-/ l 5/-ley / I6 " /t ' / if 97/' / 1-/ fo-ts:o' l / 1 -/ .!//-m / .//4 ' f' /H /oe -resa h/ A* 4 / L -/ /22-72di V ?6' 4' l i !!-/ l??-Jeal l / /' l. / *' / f ! L-l 20-7mLl /

4 //

/// I / i i i i I l 4 i 'lI 14-0 l //, l / I l / d & JV l i i i I $5. /b$ f b$ l l l l l l l w. l l { I I I I i l l ~l l l f~ l .?....- c =:,.o._.% /7 ., ~ m e se i.... k. General Electric C =pa.y, Scha:.ectady, N. 2. [; ULTRASCNIC TIST OF *riE-- OCVITC .=u' : i o totor ser:.al: _/f y 77 Rotor Type:,i p ,q" 5 hee: / 0; / l, .arbine Mc.: j 7,g g79 gg g-g, Station: e! l 5 l$f720 Mi 7#tt (OIhoit - STG & 'd? ' Tested. (one/two) Eccks of Eccks Results i 1 "- Ef4 W - ?2. 3 ucoes e r.9 AGm-1

• A ocus e 3

Alom~ l J'" Gen W -91 ? 6ft1 U - b S*~ 0 Pcces e 5:- $ ( $8rin u 2 Nt00 W ) Non<? n"m W-66 3 uocer er 3 Nour I f (i& W~W Q !.tcoks c.:- S [ 8077on s Mtoou-) // cue-l ~ I"ren Lu - H. 3 ace es m: ? /k w 2 10&2 W ~~ T 3. S HC0 Vh Q.* ] ( ?C 7 tom i ib (0 $r.? ) bfC/h" / !YtCol<?) f?"!!F as 2 T.!29 IU ~ b $~ S !.:Qbn e G-A '. d C rica r 7 2'tfdli W~b$ 3 Nc C d s c2."- 3 .AlC.</ f 4=hd t3 U-W e2 NCC V 3 A A-S $C??cru 9 l$ toy t./ Calf-i l ~ i NOTI: Si=ple shape "cre - drawing mus-he altered to match the wha =1 w' I dove **#T "=sted. I Liftine Test Results STC-Ad=. Side l Oisch. Side 0 NC bMNT YSTO / Eh1. 5 Tutt lYO t 5ilkf* /YCh: f,0 // (t it l /e ft /r c' C%t. 1 TU46. I te 1, i le it U

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