ML19296D956
| ML19296D956 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 02/21/1980 |
| From: | Hazelton W Office of Nuclear Reactor Regulation |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| TASK-03-04.B, TASK-3-4.B, TASK-RR NUDOCS 8003130641 | |
| Download: ML19296D956 (2) | |
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%% y FEB 2 : !$8C MEMORANDUM FOR:
D. G. Eisenhut, Acting Director Division of Operating Reactors L. C. Shao, Acting Assistant Director for Engineering Programs, DOR FROM:
W. S. Hazelton, Section A Leader, Engineering Branch Division of Operating Reactors THRU:
V. S. Noonan, Chief, Engineering Branch Division of Operating Reactors
SUBJECT:
YANKEE R0WE TURBINE FAILURE At about 9:30 am on February 15, 1980, the Engineering Branch was notified by the Yankee Rowe project manager, A. Burger, that he had just heard via telecon from Region I that the Yankee Rowe turbine had experienced some kind of major feilure. A call was put through to Mr. Autic, the plant superintendent, and the following preliminary information was obtained.
The Engineering Branch also contacted I&E Headquarters (J. Collins) and found that they had not yet heard of the incident.
DSS personnel were also no-tified, and this preliminary information was also given to them (M. Boyle).
The plant had been shutdown since January 19, 1980, to implement the Lessons Learned Category A items. All work was completed and on February 14, 1980, operations to return tha unit to power were underway. All turbine testing was completed showing all conditions to be normal. The reactor was at 2-3%
power to provide sufficient steam for turbine startup.
The turbine was rolled, brought up to 1800 rpm full speed and put on governor control. At 11:35 am conditions were achieved to synchronize the generator and load the turbine.
Before synchronizing, a thump was heard from an apparent severe jarring of the turbine.
The t~urbine coasted down for about 25 minutes compared to the normal coastdown time of 45-60 minutes.
It is believed that the turbine tripped automatically on thrust bearing float. But the manual trip was also immediately activated, so it is not known which action actually caused the trip. There are no vibration trip devices on this unit.
There was severe turbine vibration.
The vibration meters on No. 3 and No. 4 bearing read off scale (10 mils upper scale limit).
The other bearings read between 6 and 7 mils.
Normal vibration is 1 mil or less. Attempts to put the turbine on turning gear failed to turn the turbine. Observation at the inspection ports indicated no apparent damage to the last stage. With the cover removed at the 3rd point extraction line some debris was seen, and a section of disc about I ft. long was removed, containing one blade sheared at its dovetail, another blade twisted.
The reactor did not experie'nce a transient as a result of the turbine failure.
There was negligible decay heat in the core because of the long period of B 00313 0
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Ftc 380 D. Eisenhut L. Shao shutdown and no condition to cause a reactor trip. The reactor was left critical for about 1/2 to 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> then was shutdown normally and was placed in a cold shutdown condition. There was no loss of condenser vacuum.
Conditions in the reactor cooling systen and the secondary system aopeared normal.
Yankee Atomic Electric Company (the licensee) contracted Westinghouse to perform an investigation of the turbine failure and to do the repairs.
The licensee anticipated a prolonged shutdown of the facility.
Since February 15, members of the Engineering Branch (D0R) (Sellers, Noonan) have visited the site, and Consultants to the Engineering Branch from Lawrence Livermore Laboratory and Brookhaven National Laboratory were also sent to the site to help evaluate the primary cause of the failure. Addi-tional information available to us as of 10:00 am February 21, is as follows.
The turbine outer and inner casings have been removed and an initial visual inspection was performed.
It was found that both first stage discs in the low pressure rotor are completely failed. They are broken in several major pieces and many smaller fragments. Major damage was also observed at several adjacent rows of blades and stators.
Preliminary information indicates extensive cracking in the bore of the first stage disc at the generator end.
The mechanism of cracking is not known at this time, but is consiaered most likely to be primarily stress corrosion.
It appears that one large piece of a first stage disc got wedged against the shaft during turbine coastdown and may have caused sicnificant damage to the shaft. The inner housing was severely cracked and distorted, and cracks were found in the outer hous-ing at the centering pin area.
'c Warren S. Hazelton, Section A Leader Engineering Branch Division of Operating Reactors cc:
H. R. Denton K. M. Kampe E. G. Case W. J. Collins V. Stello S. A. Treby D. F. Ross D. T. Swanson D. B. Vassallo E. S. Christenbury L. R. Nichols J. F. Stol z R. C. DeYoung R. L. Baer H. D. Thornburg
- 0. D. Parr T. F. Engelhardt L. S. Rubenstein M. C. Moseley A. Schwencer B. K. Grimes W. J. Ross J. P. Knight D. L. Ziemann W. E. Kreger T. A. Ippoli to S. S. Pawlicki R. W. Reid R. M. Gamble S. Varga H. F. Conrad M. Boyle R. A. Hermann R. W. Klecker C. D. Sellers G. W. Knighton