ML20039G865
| ML20039G865 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 01/07/1982 |
| From: | Dale L MISSISSIPPI POWER & LIGHT CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| AECM-82-20, NUDOCS 8201190240 | |
| Download: ML20039G865 (3) | |
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MISSISSIPPI POWER & LIGHT COMPANY Helping Build Mississippi P. O. B O X 164 0, J AC K S O N. MI S SIS SIP P 9205 JS
,' N January 7, 1982
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NUCL E AR PHoOUCTioN DE PAR TMENT
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%-JA[J7g7f02hh' U. S. Nuclear Regulatory Commission l
Office of Nuclear Reactor Regulation
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20555 m
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Attention:
Mr. Harold R. Denton, Director
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Dear Mr. Denton:
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SUBJECT:
Grand Gulf Nuclear Station Units 1 and 2 Docket Nos. 50-416 and 50-417 File 0260/L-334.0/L-350.0 MTEB Concerns on Turbine Disc Integrity, SSER 1.11(27)
AECM-82/20 In accordance with your request for additional information in support of the Grand Gulf Nuclear Station Safety Evaluation Report, NUREG-083' (SER),
Mississippi Power & Light Company is submitting the enclosed information pertaining to Turbine Disc Integrity, SSER 1.11(27).
Answers to informal MTEB questions are provided in the attachment.
If you have any questions or tequire additional information please contact this office.
Yours truly, Jr
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L. F. Dale Manager of Nuclear Services RFP/JCC/JDR:ph i
Attwhment cc:
Mr. N. L. Stampley Mr. R. B. McGehee Mr. T. B. Conner Mr. G. B. Taylor Mr. Richard C. DeYoung, Director g
Office of Inspection & Enforcement 60i U.S. Nuclear Regulatory Cor: mission y
Washington, D.C.
20555 II 8201190240 020107
{DRADOCK 05000416 PDR Memoer Midcle South Utilities System
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r Attachmint to AECM-81/507 Page 1 of 2 ADDITIONAL INFORMATION REQUEST MATERIALS ENGINEERING BRANCH
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DIVISION OF ENGINEERING I
j We have reviewed Section 10.2.3 of the Final Safety Analysis Report submitted by the applicant. Our evaluation cannot be completed without additional information from the applicant relating to the design, assembly and operating conditions of the low pressure turbine discs. Past experience with similar equipment in the United Kingdom and more recently with Westinghouse turbines in the United States has revealed a propensity for stress corrosion cracking in discs which was not predictable.
In order for the staff to assess the potential for stress corrosion cracking in the applicant's plant, the following information will be required.
A - What lubricant was used in the hub area of the discs for assembly.
B - What are the similarities / differences between the discs in the Grand Gulf turbines and those used by Westinghouse.
C - What are the operating temperatures in the bore area of the discs.
D - Which disc or discs are exposed to a moisture level during operation that approximates the level of moisture present in cases of cracking.
E - What are the calculated critical crack sizes and what is the method used to calculate that size.
F - What capability for volumetric inspection of the disc hub areas is available to Grand Gulf.
Response
Grand Gulf utilizes the Allis-Chalmers Power System, Inc. (ACPSI) low pressure turbine.
A.
The lubricant used in the hub area for disc assembly is MITTAL DAG 156.
This is a lubricant acceptable for nuclear systems containing a graphite base with an isopropyl-alcohol binder.
B.
Westinghouse turbines have revealed propensity for keyway cracking at the point where the discs attach to the turbine shaft. For the Allis-Chalmers turbine, the highest stressed location in the shrunk on disc is the locking pin dead end hole. The Allis-Chalmers design includes a radial groove to minimize local stress concentrations in this area. A more detailed comparison cannot be performed since the j
Westinghouse turbine information is not available to Grand Gulf. Refer to FSAR, Volume 16, Section 10A.
In Section 10A, ER 504 gives details of shrink fit assembly of the disc to the rotor. Allis-Chalmers j
drawings NM4.02 and MA4.05 give detail on the locking pins and the last stage disc, respectively.
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..... a Attachment to AECM-81/507 Page 2 of 2 i
C.
At rated conditions, the following disc metal temperatures can be expected:
DISK ADMISSION SIDE (*F)
EXHAUST SIDE (*F) 1 333 257 2
257 210 3
210 176 4
176 145 5
145 156 D.
ACPSI has not experienced any disc cracking on nuclear steam turbine low pressure rotors. Based on the experience of other suppliers, Allis-Chalmers would consider discs 2 and 3 as the discs operating under the worst corrosion conditions.
E.
ACPSI is currently preparing a critical crack report for the Grand Gulf Nuclear Station turbine discs. The estimated completion date for this report is January,1982. A summary of this report will be provided for review following report completion.
F.
ACPSI is presently developing a technique to perform ultrasonic testing inspection of the hub area and disc without removing the disc from the shaft. This procedure is currently under development by ACPSI.
Implementation of that procedure will be based on the recommendations and guidance provided by ACPSI and on the MP&L evaluation of that procedure.
Additional information will be provided regarding this issue following the MP&L avaluation of this procedure. We expect this evaluation to be completed prior to the first regularly scheduled refueling outage.
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