ML19330B542

Forwards Responses to NRC 800516 Request for Info Info Re Turbine Disc Integrity

ML19330B542
Person / Time
Site:	FitzPatrick
Issue date:	07/29/1980
From:	Bayne J POWER AUTHORITY OF THE STATE OF NEW YORK (NEW YORK
To:	Ippolito T Office of Nuclear Reactor Regulation
References
JPN-80-37, NUDOCS 8008050005
Download: ML19330B542 (6)

Text

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POWER AUTHORITY OF THE STATE OF NEW YORK to CoLUMaus CIRCLE NEW YORK. N. Y 1o019 v

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Trustees JOHN W sCSTCN JoMN s.DYsON Er p*[ sn oes'n"a'r[o s GEORGE L. INGALLs

. JOSEPH R. SC IEDER WIC E CMalAMAN ,

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• caiu ROSERT t. MILLO N Z1 LERQY W. SINCLAIR ss% ion vict passicsNT

,REoERiCx R. CLaR,c July 29, 1980 . c- u n ~*~ cia' JPN-80-37 THOM AS R. FR EY l'20."'*U",".'au'"'

Director of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Mr. Thomas A. Ippolito, Chief Operating Reactors Branch No. 3 Division of Operating Reactors

Subject:

James A. Fit: Patrick Nuclear Power Plant Docket No. 50-333 LP Turbine

Reference:

Letter, T.A. Ippolito (NRC) to G.T. Berry (PASNY) dated May 16, 1910

Dear Sir:

Attached are responses to the NRC requests for information in Enclosure 3 to the referenced letter related to LP turbine disc integrity.

Very truly yours, O .N-:lb&*'  ; cul_

J/. P. B5'yne

' Senior Vice President Nuclear Generation 00/

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RESPONSE TO REQUEST __FOR INFORMATION RELATED TO TURBINE DISCS SITE SPECIFIC GENERAL QUESTIONS

.QUESTION I:

Provide the following information for each LP turbine:

A. Turbine type B. Number of hours of operation for each LP turbine at tite 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 Appear-ance 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 i

7. Calculated Klc data

8. Minimum yield strength specific for each disc i

RESPONSE TO I: l I.A. Turbine Generator Type; GE 170X504, tandem-compound with

'four-flow low pressure s ages. The turbine consists of I

3. sections, a double flow high pressure and 2 double flow H low pressure sections. -

1.B. The last low pressure turbine ultrasonic inspection of key-

-ways was during fabrication of the unit. Ultrasonic examina-tion to detect possible cracks at keyways is scheduled for the next refueling outage at the end of fuel cycle 4.

Since initial operation, the turbine generator has been in service (generator online) for 30,309 hours0.00358 days <br />0.0858 hours <br />5.109127e-4 weeks <br />1.175745e-4 months <br />. Based on a

!- fuel-cycle 4' target burnup of 7362 Mwd /t and a unit capacity factor of 80%, it is estimated that the turbine generato.

L wi11' operate an -additional 10,517 hours0.00598 days <br />0.144 hours <br />8.54828e-4 weeks <br />1.967185e-4 months <br /> before the next-inspection.

1.C. Since initial start-up, overspeed test of the turbine has been conducted five times. No additional overspeed events have occurred. Since initial start-up, 13 turbine

-trips have occurred.

1 1

c _

, -RESPONSE (cont).

I.D. AnswersLto these-questions involve data'which are proprietary

'to the General-Electric Company. Information was provided directly to the NRC during a meeting between General Ele 0- ,

.tric and MRC representatives on April 21, 1980. The NRC hastinfornod GE that this'information is an acceptable reply to this - question.

QUESTION _II:

ProvideLdetails of'the-results of any completed inservice inspec--

tion 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 TO II:

As noted in item I.B.above, the inservice inspection of the low pressure turbine rotors which have been conducted since initial

!: start-up, have not included ultrasonic examination for the purpose of detecting keyway cracks. Consequently, the existence of any 1

possible cracks is an unknown factor.

.. . QUESTION III:

. Provide the nominal water chemistry conditions for each LP.

i Describe any condenser inleakages or other significant changes in water chemistry-to this point in its operating life.

RESPONSE TO III:

i

+ Two steam. carryover tests were performed at JAF during the initial Estart-up chemistry testing program. The results of the tests are as follows:

' Test Date %Na-24 Carryover  % Iodine Carryover-5/19/75 0.004 0.51 (I 133)

, 11/8/75 0.0011 0.88 (I-133) a Iodine-131.was not used in-the first test because it could not

.be detected in-the' steam sample. With regard to turbine discs this data is' considered the most relevant since it is a measure

of steam quality. Samples of steam are not routinely taken be-cause ' of the dif ficulty. in obtaining representative samples due to the, amount of sample cooling with respect to required flow and flowEtime necessary. 'However,.there-is no reason'to believe

.that the carryover values have changed because the results ob-tained from the start-up samples were representative' of- other BWR U carryover tests.

i

- -. . -. ,, . -,--s r -----,~ ~ ,-

GENERZC QUESTIONS'

. QUESTION I:

- Describe what quality control' and inspection procedures are used' for,the disc bore and keyway areas.

RESPONSE TO I:

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 accept-ance 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.

Only' coolants and lubricants approved by engineering are used in the manufacturing.and assembly' process. These coolants and lubri-cants'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 madeito 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.

QUESTION II: I

~

-Prov'ide details of.the General Electric repair / replacement pro--

lcedures for' faulty disks.

, RESPONSE'TO-II:

Stress corrosion cracks -have not been observed to date in ' nuclear

-wheels manufactured by~ General Electric, and we do not anticipate thatiremovalfortreplacement of wheels will be required because of

this phenomenon. The water erosion ~which has been observed in'the

4_4 - - -

RESPONSE TO II (cont):

~ 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.

QUESTION 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 TO III:

No immediate actions are required to minimize water erosion because of the apparent self-limiting nature of the phenomenen.

However, if future inspections show an unexpected progression of the water erosion, appropriate operating restrictions and/or modifications will be recommended.

QUESTION IV:

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

RESPONSE TO IV:

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 through-out-the forging, followed by a quench in cold, vigorously circu-4 lated 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 r

y.

3-RESPONSE ' (cont) :

In a review of.'the routine reactor water samples for 1979 and 1980, i- it:was found that silica? concentrations averaged approximately 50 ppb and that'three weekly samples showed highs of 400 to 600 ppb.

QUESTION 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.

-QUESTION V:

If your plant has been inspected and plans to return or has 1 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.-

4 ~ RESPONSE TO IV AND V:

) No keyway cracks are known to exist and no inspection for the pur-pose of detecting such cracks'is planned until during the refuel-ing outage at the end of fuel cycle 4. Bases on the-inspection of other~ turbine generators with a similar operating history and' age,-

General Electric does not consider it likely that any cracks exist i in . the FitzPatrick ' unit at this time, j j- QUESTION VI:

" Indicate 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 had been-performed and ~

reported,'please provideLappropriate. references to the available

documentation. In the event that such studies have not been made,

consideration should be given to scheduling such an action.

1 I

< RESPONSE TO VI:

A discussion of turbine missile analysis for JAF was provided in

-response to the NRC-letter of November 29,-1971, Question 10.1.

_This' response.is provided.in the FSAR.

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