ML20248G700
| ML20248G700 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 10/02/1989 |
| From: | Sieber J DUQUESNE LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TAC-62888, NUDOCS 8910100343 | |
| Download: ML20248G700 (6) | |
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.U. S. Nuclear Regulatory Commission Attn:. Document Control 1 Desk i
. Wash ngton,fDC. 20555
Reference:
- Beaver Valley Power Station, Unit No. 2 Docket.No. 50-412, License No.' NPF-73 Letter 2NRC-7-095 Dated April 24,.1987 TAC 62888f--Turbine Maintenance Program Gentlemen:
In: a letter. dated April 24, 1987, DLC responded,-in part, to
- confirmatory. issue 5
described in SER 3.5.1.3.
That response
- consistedi of a
proprietary probability analysis performed by the turbine.. manufacturer.which presented the' probability of missile generation as a'resultEof stress corrosion.
This information was acknowledged by SER Supplement 5
and-incorporated in UFSAR
'3.5.1.3.
The calculation results indicated the probability of 10-8.that
- missile generation is 'less than when over 10 years of accumulated-operating time-has elapsed since the last disc inspection.
10-ge substantial probability. margin, below'the NRC T
~ maximum.-of is due to the partially integral rotor design
- used at.BVPS-2.
providesadescriptionofturgineinspectionsto Attachment 1
be used. at BVPS-2 for ensuring that:the 10~
probability for a
' brittle failure is not exceeded.
It also provides a description of, valve. testing and inspection which is used to limit the possibility of overspeed.
Having reviewed the March 20, 1989 Perry submittal on this subj'ect,
we. believe that this submittal similarly provides the necessary information requested in SER Supplement 5.
Very truly yours, b
/,.
D.
Sieber Vice President Nuclear Group cc:
- Mr. J.
Beall, Sr. Resident Inspector Mr. W. T. Russell, NRC Region I Administrator Project Manager Mr. P. Tam, Sr.
del Ad: h/DW/"'" ge k H. M. Siegel i
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ATTACHMENT 1 u
E S-2 TURBINE MAINTENANCE PROGRAM Inservice inspection of. the steam. turbine assembly will be condu'cted to-provide assurance'against-brittle failure of a' disc at design overspeed.
The inservice inspection will be performed-
.approximately. eve'ry 10 -years, coincident with a plant shutdown..
The
~ inspection interval is based upon lthe' probability' of generating a.
turbine missile as a function of actual operating operating tine related probabilities associated gith-time.
The the. BVPS-2 low. pressure.' turbine rotor were less than 10~
as jpreviously presented in letter 2NRC-7-095 dated April'24, 1987.
The inservice.. inspection will consist of visual and surface examinations.of couplings, coupling bolts, high pressure turbine rotor and
- discs, and low pressure turbine blades.
Low pressure turbine. rotors and. discs will also be volumetrically examined using the inspection techniques described below.
Inspection Techniaues
' Westinghouse has developed two ultrasonic inspection techniques which'may. be employed for detecting cracks in keyways and bores without need for unshrinking. discs.
Cne technique, called the tangential aim technique, detects indications because of its high sensitivity and the
- other, called the radial aim technique, verifies indications and measures their depths.
Tanoential Aim Techniaue In the tangential aim technique, an ultrasonic transducer is mounted on a
_ plexiglas block that sits on the disc hub (Figure 1).
The plexiglas block is contoured so that it is in complete. contact with the disc hub.
The ultrasonic waves are directed tangentially towards the-bore / keyway so that any cracks above the bore / keyway area will be perpendicular to the sound beam and reflect the sound.
A careful analysis of the time differences between the echos from the keyway and cracks should allow discrimination of false indications.
Radial Aim Lechniaue Because stress corrosion cracks have been found to be branched, the radial aim technique has been successfully used to verify the presence and quantify the depth of cracks.
In this technique, the ultrasonic waves. are directed perpendicular to the keyway / bore (Figure 2).
The depth of the crack is estimated from the time difference between an echo from the crack and the echo from the keyway' crown or bore.
When. the turbine is disassembled, a visual and magnetic particle examination is made externally on accessible areas of the high pressure
- rotor, low pressure turbine
- blades, and low pressure discs.
The coupling and coupling bolts are visually examined.
D'.
lBVPS-2 TURBIME MAINTENANCE PROGRAM Page 2-The initial inspection program for. throttle, governor, reheat stop and
' interceptor valves is in accordance with the vendor's recommended interval. of. 1 5,.
27, and 39 months after initial start-up-of a' turbine.. In this program, some valves are inspected 12 to 15 months.'after start-up, others 24 to 27 months, and the-remainder 36 Lto 39 months so that all valves are inspected at least, once in. the 39 months of. operation following initial start-up.
Throttle and reheat stop valves are inspected twice in-this period.
After this. initial inspection program is completed,~ valves will be inspected periodically in accordance with Westinghouse recommendations.
Throttle and governor valves are inspected on a 36 month frequency,. with roughly half.being. inspected each 18 month period.
Reheat stop and interceptor valves are inspected on
'a staggered outage basis with a
54 month frequency.
.These frequencies are consistent with the Westinghouse recommendations of 39 and 60 months, respectively, found in their Steam Turbine Information Manual Section 13, CT-24038, Revision 1.
Functional testing of the turbine inlet. valves is performed on the monthly frequency recommended in the Steam Turbine Information.
- Manual, Section 13, CT-24039, Revision 1.
Any changes to this interval would require an amendment to the technical specifications.
This testing can. be done while the unit is carrying load.
The purpose of the test' is to ensure proper operation of the throttle, governor, reheat stop, and interceptor valves.
The operation of these valves will be observed during the test by an operator ' stationed at the valves.
Movements.of the valves should be smooth and free.
Jerky or intermittent motion may indicate a buildup of deposits on shafts.
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KEYWAY BORE FIGURE 1 TANGENTIAL AIM INSPECTION TECHNIQUE BEAVER VALLEY POWER STATION-UNIT 2 i
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COMMONWEALTH (OF PENNSYLVANIA).
-)L SS:
COUNTY:OF BEAVER
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LOn.this--
day of !
M d J 7 L l d d J
, 1989, lbefore me, I lad /2/
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a Notary'Public in and for said g
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- Commonwealth 'and County, personally appeared J.
D. Sieber, who being duly.
sworn,.' deposed,. and said that- (1) he-is Vice President of-
- Duquesne Light, -
(2) -he -'is duly authorized.to' execute and file the
. foregoing. Submittal on behalf of said Company, and (3) the statements.
set Lforth. in the Submittal are true and correct to the best of his' c,
information and belief.
- knowledge, I
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