ML20003C402
| ML20003C402 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 02/14/1974 |
| From: | JERSEY CENTRAL POWER & LIGHT CO. |
| To: | |
| References | |
| AO-50-219-74-10, NUDOCS 8103030624 | |
| Download: ML20003C402 (3) | |
Text
s OYSTER CREEK NUCLEAR GENERATING STATION FORKED RIVER, NEW JERSEY 08731 Abnormal Occurrence Peport No. 50-219/74/10 Report Date Feb ruary 14, 1974 Occurrence Date February 8,1974 Identification of Occurrence Violation of the Technical Specifications, paragraph 2.3.7, low pressure main steam line pressure switches RE23A, C,. and D were found to trip at pressures less than minimum required value oL 860 psig.
This event is considered to be an abnormal occurrence as defined in the Technical Specifications, paragraph 1.15A.
Conditions Prior to Occurrence The plant was operating at steady-state power.
The major plant parameters at the time of the occurrence were:
Power:
Peactor: 1908 MNt Electric: 672 MNe 6 lb/hr Flow:
Recire. 60.2 x 10 Feed:
7.13 x 106 lb/hr Reactor Pressure:
1020 psig Stack Gas:
28,357 pei/sec Description of Occurrence On Friday, February 8,1974, at 1030, while performing a surveillance test on the four main steam line low pressure switches, it was discovered that RE23A, C, and D tripped at 850, 856, and 855 psig, respectively.
These values are below the minimum required trip point of 860 psig, which is derived by adding to the Technical Specification limit of 850 psig head correction factor.
The as-found switch settings were:
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Abnormal Occurrence No. 50-219/74-10 Page 2 Test Results RE23A 850 psig RE23B 860 psig RE23C 856 psig RE23D 855 psig The pressure switches were then recalibrated and checked to actuate as follows:
Test Results RE23A 860 psig PE23C 860 psig RE23D 860 psig Apparent Cause of Occurrence Design is considered to be the major factor contributing to this event.
Sensor drift is a recognized problem and work is in progress to formulate a final solution. The steps required to achieve this end were delineated in Abnormal Occurrence Report No. 50-219/74/1.
Analysis of Occurrence
- As indicated in the bases of the Technical Specification, "The low pressure
~ isolation of the main steam lines at 850 psig was provided to give protection
- against fast reactor depressurization and the resultant rapid cooldown of the vessel. Advantage was taken of the scram feature which occurs when the main steam isolation valves are closed to provide for reactor shutdown so that high power operation at low reactor pressure does not occur, thus providing protection for the fuel cladding integrity safety limit."
ne adverse consequences of reactor isolation occurring at reactor pressure approximately 10 psig below the specified minimum value of 860 psig is limited to those effects attendant to a greater than normal reactor cooldown rate. The-fuel cladding integrity safety limit only comes into effect for power operation at reactor pressures less than 600 psig or for power operation greater than 354 >Mt with less than 10% recirculation flow. D erefore, the consequences of a 10 psig lower than normal reactor isolation and scram setpoint has no threatening effect whatsoever on the fuel cladding integrity.
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Abnormal Occurrence No. 50-219/74/10 Page 3 The effects of a too rapid cooldown due to the lower isolation pressure are inconsequential since there is approximately a 10F difference between the saturation temperature for 860 psig and 850 psig.
Corrective Action Centinuing corrective actions being taken at this time are as follows:
1.
Investigation is being conducted into the basis for the steam line low pressure setting of 850 psig.
Development of a Technical Specification change to lower the setpoint will follow if results of transient analyses indicate this possibility.
2.
Recommendations to possibly reduce or eliminate the sensor setpoint change problem have been received.
It was reported that General Electric tests on a pulsating line to simulate plant conditions show that precycled Barksdale switches show improvement but that the. switches still do not meet 1% repeatability.
General Electric, therefore, recommended an Ashcroft switch as it is more accurate.
The Ashcroft catalog number is 61 S 6080 BN20-06L-1028.
As a result,one switch of each type (precycled Barksdale and Ashcroft) are being purchased for test and evaluation at Oyster Creek.
Failure Data Manufacturer data pertinent to these switches are as follows:
heletron Corp. (subsidiary of Barksdale)
Los Angeles, California Pressure Actuated Switch Model 372 Catalog No. 372-6SS49A-293 Range 20-1400 psig Proof Psi.1750 G Previous Abnormal Occurrence Reports involving these switches are:
1.
Letter to Mr. A. Giambusso from bh. D. A. Ross, dated December 24, 1973.
2.~ Abnormal Occurrence Report No. 50-219/74/1.
3.
Abnormal Occurrence Report No. 50-219/74/9.