ML19347C795
| ML19347C795 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 01/29/1974 |
| From: | JERSEY CENTRAL POWER & LIGHT CO. |
| To: | |
| References | |
| AO-50-219-74-8, NUDOCS 8103040542 | |
| Download: ML19347C795 (3) | |
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Abnormal Occurrence Report No. 50-219/74/8 Report Date:
January 29, 1974 Occurrence D..te:
January 17, 1974 Identification of Occurrence:
Violation of the Technical Specifications, paragraph 2.3.5, which re-quires that isolation condenser system initiation occur with a time delay of <15 seconds after a specified high reactor pressure is reached.
This evenE is considered to be an abnormal occurrence as defined in the Technical Specifications, paragraph 1.15A.
Identification of this item as constituting a Technical Specification violation which required reporting occurred during a routine review of the surveillance test sheet prior to its being filed. The excessive time delay was recognized as not being in conformance with the applicable Technical Specification during performance of the test and was reset at that time.
Conditions Prior to Occurrence:
The plant was shut down with reactor coolant at <212*F.
Description of Occurrence:
While performing a routine surveillance test on the reactor high pressure-isolation condenser initiation switches, contacts on three out of the four associated time delay relays failed to close within the preset time delay of 15 seconds (after each pressure switch was tripped and the associ-ated relay deenergized). The delay times of these three relays were found to be as follows:
6K9 - 20 seconds 6K11 - 16.7 seconds 6K12 - 18 seconds Each of the involved time delay relays was immediately reset to less than l
15 seconds.
7/030/o5 9
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Abnormal Occurrence Report No. 50-219f/4/8 Page 2 Apparent Cause of Occurrence:
Instrument drift has been identified as the cause of these excessive time delays.
Analysis of Occurrence:
Four pressure switches in the reactor protection system (RPS) activate the isolation condenser system when there is a persistent 15 second condition with reactor pressure at or above 1060 psig. Two of these pressure switches with associated time delay relays 6K9 and 6K10 are in one RPS channel, and the other two pressure switches with associated time delay relays 6K11 and 6K12 are in the other RPS channel. Iligh pressure signals from two pressure switches, one in each RPS channel, are required to activate the isolation condenser system (coincidence of two RPS channels, each of which is tripped by one of two pressure sensors). Accordingly, the excessive time _ delays of these three time delay relays would have resulted in an isolation condenser system initiation delay time greater than 15 seconds had the isolation pressur'e been reached. As detailed in Attachment 65 to the FDSAR, at least one of the isolation condensers is required to act as a means of heat removal during a postulated loss of coolant accident.
There is no evidence to indicate that isolation condenser system initiation would not have taken place with the three time delay relays operating as found. There does not appear to be any technical basis for the 15 second setting of the time delay relay.
Corrective Action:
Further research will be done to clarify the requirements for the 15 second time delay.
In the interim, the time delay set point will be reduced to 10 seconds.
Failure Data:
Pertinent manufacturer data are listed below:
Manufacturer:
Agastat Model:
7022 PDT Range:
5 to 50 seconds Coll:
120V DC 4
Serial Numbers: 6K9 - 1712235 6K11 - 1712237 6K12 - 1712228 The ongoing review of past surveillance test records has revealed the following heretofore unreported discrepancies with respect to the 15 second time delay limit:
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Abnormal Occurrence Report No. 50-219/74/8 Page 3.
As Found Date.
S,cnsor/ Relay Time Delav 4/12/73-RE15A/6K9 15.5 sec.
6/19/73 RE15D/6K12 29 sec.
9/28/73 RE15C/6K11 36 sec.
11/21/73 RE153/6K10 15.5 sec.
i RE15C/6K11 16.9 sec.
RE15D/6K12 16 sec.
It is expected that increased awareness of Technical Specification limits on the part of individuals associated with the testing program will en-sure that future discrepancies will be promptly reported.
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