ML19343C345
| ML19343C345 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 03/02/1973 |
| From: | Hartley F CONNECTICUT YANKEE ATOMIC POWER CO. |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| AO-73-02, AO-73-2, CYH-2323, NUDOCS 8103100459 | |
| Download: ML19343C345 (2) | |
Text
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Wgulatory CONNECTICUT YANKEE ATOMIC POWER COMPANY
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HADDAM NECK PLANT RR = 1. BOX 127E, EAST HAMPTON, CONN. 06424 March 2, 1973 CYli-2323 t-c6 %
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Washington, D. C. 20545 h.f;s"J 4,\\
U. S. Atomic Energy Commission
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ATTENTION: Director, Directorate of Licensing tr a m;; m:t L
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REFERENCE:
Provisional License No. DPR-14
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[lyji Docket No. 50-213 m
Abnormal Occurrence 73-2
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Dear Sir:
As defined by Technical Specifications for Connecticut Yankee Atomic Power Station Section 5.3, the following incident involving an unacceptable set point in one of three pressurizer low pressure / core cooling trip units, is reported as Abnormal Occurrence No. 73-2.
In accordance with the surveillance requirements of Technical 5pecification 4.12, Connecticut Yankee tests pressur-izer pressure setpoints and alarms every six weeks. The test involves injection of a simulated signal into the channel to verify its proper response, including alarms and trip initiation points. The required pressurizer pressure setpoint check was performed February 22, 1973 and the 1700 psig low pressure / core cooling set point for one of three channels was found to be s 75 psig below the 1700 psig required setpoint. The other two press-urizer pressure channels were verified to be functioning as required. The protective instr; mentation logic required for m
full power operation was satisfied by inserting a high pressure S
trip signal, a low pressure / core cooling signal, and a low g
pressurizer level trip signal.
- g The signal for pressurizer pressure channel 2 passes
'lE MAR 7 1973 >
through a thermovolt optical meter relay for high pressure g
reactor trip and low pressure core cooling. This meter relay My@ff U g
was removed, inspected and an erratic / light sensitive photo-ECW cuu i
g diode was replaced. With installation of the new photo-diode g
the thermovolt optical meter relay operated as required. All a
m three pressure channels were then returned to service in a normal 2/3 logic.
Operation of the core cooling system is initiated auto-matically by an actuation signal generated as a result of two out of three low pressurizer water level signals coincident with two
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U. S. Atomic Energy Commission March 2,.1973 out of three low pressurizer pressure signals. These signals are backed up by a high containment pressure signal which will also initiate core cooling. The system may also be actuated manually from the control room.
In evaluating the safety implications of the lower than required low pressure / core cooling trip signal it is quite apparent that the many redundant features of the core cooling actuation circuitry would have Lctuated core cooling as required, even though one low pressure /
core cooling trip unit set point was below the required value. There-fore it is concluded that the safety of the reactor and the public was not compromised with a lower than required pressurizer pressure / core cooling setpoint.
The Plant Operations Review Committee reviewed the incident and concluded that the cause of the malfunction was a faulty light sensitive photo-diode. f.s was stated in A0 73-1, these optical meter relays are being replaced on a systematic basis with relays of improved design.
Very truly yours, f
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'F. W.
artley Plant Superintendent RHG/bn cc: Mr. James P. O'Reiily, Director Region 1, Directorate of Regulatory Operations 1
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