ML17252A490
| ML17252A490 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 10/24/1974 |
| From: | Stephenson B Commonwealth Edison Co |
| To: | James Keppler US Atomic Energy Commission (AEC) |
| References | |
| Download: ML17252A490 (2) | |
Text
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.Regulatory D ~...
OC'/let Fi/~
Dresden Nuclear Power R. R. #1 Morris, Illinois October 24, 1974 Mr. James G. Keppler, Regional Direct<;>r Directorate of Regulatory Operations-Region III
- u. s. Atomic Energy Commission 799 Roo~evelt Road Glen EllYn, Illinois 60137
SUBJECT:
LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT #3.
SUPPLEMENTARY INFORMATION TO REPORT OF UNUSUAL EVENT PER S~TION
. 6.6.B.2 OF THE T~HNICAL SP~IFICATIONS.
PRlNARY CONTAINMENT ISOLATION VALVE LEAKAGE.
References:
- 1) Letter from Mr. W. P. Worden to Dr. P. A. Morris dated May 18, 1972.
- 2) Letter from Mr. W. P. Worden to Mr. J. F. O'Le~y dated December 19, 1973.
- 3) Drawing P&ID M-356
Dear Mr. Keppler:
In the letter sent to you from Mr. w. P. Worden dated December 19, 1973, concerning primary containment isolation valve leakage, it was stated that leakage through the rubber seated butterfly valves had been a recurring problem. At that time, it was not known whether the leakage was associated with the rubber seats or another problem; Since that time ;the manufacturer.of the valves, the Henry Pratt Co., was asked to investigate this problem. They concluded that the cause. of the leakage was due to improper assembling of the valve operator. They had checked the valves with the operators off and found them to be bubble-tight, and leakage did.not occur until af'ter the operators were assembled to the valves and. installed in line.
The valves had been sent to the manufacturer to be rerubbered with an Ethylene-Propylene Terpolymer rubber, a high temperature radiation resistance rubber seat material af'ter the original seats failed because 9f heat deterioration.
However, the operators remained at the station. According to the company, when the operators were reassembled at the station~ clearances existed between the operator plate bearings and the shaf't lever, and some set screws in the operator lever that lock it against the valve shaf't were missing. These components help to position the valve disc. Therefore, the clearances between the operator plate bearings and the loading caused by the assembly of the operator to the valve allowed the disc to move along the axial center line of the valve shaft. This movement resulted in leakage at the hub area.
OCT
- 5 1974
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Mr. James G. Keppl~r
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October 24, 1974
. ---1 The Henry--Pratt Co. has sent the. station drawings on the.assembly of the valve and operator, and these drawings have beeri submitted to the mainten-
-ance,_ department._
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