ML20084R973
| ML20084R973 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 09/16/1974 |
| From: | Stephenson B COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML20084R976 | List: |
| References | |
| 665-74, AO-50-249-74-28, NUDOCS 8306160092 | |
| Download: ML20084R973 (3) | |
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September 16, 197 A y ~ ~~~ 'G4
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Directorate of Regulatory Operations-Region III D[
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U. S. Atomic Energy Cc:nnission y). g,, _,
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Glen Ellyn, Illinois 60137
SUBJECT:
REPORT OF AB?!OR'tAL OCCURRENCE PER SECTION 6.6.B 0F THE TECD!ICAL SPECIFICATICNS.
TIP 1&CHII!E EALL VALVE FAILURE, U'!IT TEREE.
References:
- 1) Regulatory Guide 1.16, Rev.1, Appendix A
- 2) Notification of Region III of AEC Regulatcry Operations Telephone: Fr. F. Maura, 1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br /> on September 9, 1974 Telegram: 10. J. Keppler,1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br /> on September 9,1974 Report Number: 50-249/1974-28 Report Date: September 16, 1974 Occurrence Date: September 8, 1974 Pacility: 'Dresden Nuclear Power Station, Morris, Illinois IDD!TIFICATION OF OCCURRENCE TIP machine ball valve failure, unit three.
CONDITIONS PRIOR TO OCCURRE!CE Unit three was in the run mode, at a thermal power of 1459 IGt 'and an electrical load _ of 447 IGo, at the time of the occurrence.
DESCRIPPION OF OCCURRE1?CE At about 2030 hours0.0235 days <br />0.564 hours <br />0.00336 weeks <br />7.72415e-4 months <br /> on September 8, 1974, transversing incore probe (TIP) scans of the unit three core were initiated.
Following the scans, the probes were withdrawn into their shicids as normal, and the ball isolation valves were given a signal to close.
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Ssptember 16, 1974 i
The ball isolation valve on 3E TIP machine failed to elose, as indicated by 7
a light on the TIP machine control panel DESIGNATION OF APPARE!iP CAUSE OF OCCURRENCE (Design Deficiency)
The valve apparently became stuck due to a weak closure spring, because a tap given to the' casing caused the valve to spring closed. Weak closure springs are a known design deficiency in these valves (See Deviation Reports U-2-72-32, D-12-2-73-91, and D-12-3-74-33 plus supplement).
ANALYSIS OF OCOURRENCE No abnormal reactor conditions resulted from the occurrence. The TIP ball valve is a part of the primary containment isolation, and as such, its failure to close represents a potential breach of primary containment, until the isolation shear valve in series with the ball valve is verified as operable.
As long as this backup system (shear valve) is operable, no safety threat exists to plant personnel or to the public by having a TIP ball valve fail open during operation.
If the shear valve is inoperable, accident conditions could pose a safety threat, due to possible blowdown through the TIP tube to a point outside
.the drywell.
CORRECTIVE ACTION The ball valvo casing was tapped on, causing the valve to snap closed.
A work request (S8126) was issued on September 8,1974 to deternine the cause of the failure.
The cause was verified to be insufficient tension on.the closure spring, which was readjusted.
Past failures of a similar i
nature (sce above) have been attributed to design deficiencies in the
-ball valves. A new type of ball' valve is' presently available that elbninates these design deficiencies. A plant modification package, number M12-2-73-187, i
which is pending completion at this time, calls for the replacement of all of the TIP ball valves with this new type.
Until the completion of the modification, operating procedures are in offcet which are intended to increase the reliability of the ball valves now in service. The ball valves are cycled weekly, to loosen them up and to demonstrate their. operability. Also, during each refueling' outage, the valves are completely overhauled.
FAILURE DATA For similar failures in the past,. see Deviation Reports U-2-72-32, D-12-2-73-91, '
D-12-3-74-33 and D-12-3-74 h6.
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k) 3';pt:mber 16, 1974 Mr. James G. K cr
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EQUIRE.'T IDEiTIFICATIO:7 580A56 valve, Ituelear Instrumentation, General Electric Company filD Ball' for Trancversing Incora Probe.
Sincerel t :pum B.1. $"' ephenson Superir cndent EBC:do l
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