ML20084D506
| ML20084D506 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 01/29/1971 |
| From: | Hoyt H COMMONWEALTH EDISON CO. |
| To: | Morris P US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084D510 | List: |
| References | |
| 10580, NUDOCS 8304120065 | |
| Download: ML20084D506 (2) | |
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Commonwealth Edison Company ONE FI R S T NATIONAL PLAZA
- CHICAGO. I L LI N Ol e Address teel fe:
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- CHICAGO, ILLINOl5 60690 Dresden Nuc1(.ar Power Station R. R.
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_SUBJ ECT: LICENSE DPR-19 DRESDEN NUCLEAR POWER STATION UNIT #2 SECTION 6.6.B.3 OF THE TECHNICAL SPECIFICATIONS
Dear Dr. Morris:
z This is to report a ecndition relating to the operation of the
'1 station in which on January 22, 1971, Main Steam Isolation Valve 2D failed to close on receipt of an isolation signal.
Problem, Investigation and Corrective Action At 9:21 p.m. on January 22, 1971, a primary containment isola-tion signal from the " < 850 psig in Run mode" signal caused closure of seven (7) of the eight (8) Main Steam Isolation Valves (MSIV's).
The low pressure was caused by normal pressure decay following a turbine trip and reactor scram with the mode switch in "Run".
MSIV 2D did not close on the automatic isolation signal nor would it close when the manual switch was placed in the "close" position. At about 10:00 p.m., MSIV 2D was closed by operating the " test" button until the valve went closed.
The manual switch was then placed in the "close" position to hold the valve shut.
Prior to the scram and subsequent failures of MSIV-2D, one of the operating personnel had noted that the pressure drop across the recently installed air filters appeared normal.
Subsequent to the scram, the filters were inspected, noted to be cican ani dry, and reinstalled without further cleaning.
The pressure drop across the air filters was again checked and found to be the same as before the scram.
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b The seven MSIV's that operated normally were timed at 1:00 a.m.
, on January 23,\\1971, and found to be within the Technical Specificatica limits.
The MSIV pilot valve temperatures were checked at 11:30 p.m. on January 22, 1971, and found to be within their operating limits.
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.a o-v s-Dr. Peter A. Morris Page 2 January 29, 1971 Corrective action involved cleaning all outboard MSIV pilot valves, the air lines leading to the pilots and the air accumulators for the outboard pilots with a solvent followed by a dry nitrogen purge.
A very slight film of oil was found on the pilot valve from IdSIV-2 D.
As previously stated, the filters in the air line had been inspected and found to be clean and it was concluded that the oil film was the result of inadequate cleaning of the air lines at the time that the filters were installed.
During the subsequent startup all eight MSIV's were functionally checked and MSIV-2D was timed.
All checke were satisfactory.
A program of increased surveillance will oe initiated as soon as possible which will require both the partial and full closure tests to be performed on all MSIV's twice a week.
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- 11. K. Iloyt Superintendent ilKil:dmc
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