Difference between revisions of "ML20023C176"

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Advises That Inservice Insp of Low Pressure Turbine,Required by License Condition,Revealed Cracks in Discs at Governor & Generator End for Low Pressure Turbine 1 & 2.Low Pressure Turbine Rotors Replaced.Investigation Underway
Person / Time
Site: North Anna Dominion icon.png
Issue date: 05/06/1983
From: Stewart W
To: Clark R, Denton H
Office of Nuclear Reactor Regulation
Download: ML20023C176 (2)



VIHOINIA EIACTHIC AND Powint COMI*ANY R ic u noxu, VI HO INI A 232G1 W. I.. srumur May 6, 1983 Vars Passinawr NecLEAu Orsaatrons

!!r. Harold R. Denton, Directot Serial No. 256 Office of Nuclear Reactor Regulation N0/JHL:acm Attn: Mr. Robert A. Clark, Chief Docket No. 50-339 Operating Reactors Branch No. 3 License No. NPF-7 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT NO. 2 LOW PRESSURE TURBINE INSERVICE INSPECTION North Anna Unit 2 License Condition 2.C(17) states, in part, " Prior to resuming power operation following the second refueling outage, VEPCO shall subject the low pressure turbines to an inservice innpection. The inspection shall consist of visual and volumetric examinations. The visual examination shall be applied to 100 percent of all accessible surface of the rotors, discs and blading. The volumetric examination shall use an ultrasonic technique to

, fully examine the bore and keyway region of the discs in each low pressure l turbine."

North Anna Unit 2 is in the prccess of completing its second refueling outage.

During this outage, the low pressure turbines were inspected by visual and

, volumetric examination. The inspection revealed that low pressure turbine number 1 had cracks in the number I and 2 dices at the governor and generator I

end. The inspection of low pressure turbine number 2 revealed that the number I discs had cracks at the governor and generator end. The number 2 discs on low pressure turbine number 2 was not examined. VEPCO then decided to replace the number 1 and 2 low pressure turbine retors. The new low pressure turbine rotors are of a universal design with a heavy hub and keyplate. The universal l

design of the new low pressure turbine rotors is designed to impede cracking.

l VEPCO and Westinghouse will pursue the cause of the low pressure turbine disc cracking. A report will be submitted in the future to identify the cause of low pressure turbine disc ciacking.

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e-Vinoixta EtzcTaic Axp Powra COMPAW 70arold R. Denton Since the low pressure turbine rotors have been replaced, preventative measures have been taken to prevent possible turbine missiles. Since VEPCO has taken ceasures to prevent possible turbine missiles, VEPCO intends to startup North Anna Unit 2 at the end of the current refueling outage which is currently scheduled for May 13, 1983. Very truly yours, i CL

                                                                  . L , ShT

W. L. Stewart cc: Mr. James P. O'Reilly Regional Administrator Region II Mr. M. B. Shymlock NRC Resident Inspector North Anna Ocwer Station l l l l l}}