ML20084G086
| ML20084G086 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 01/13/1975 |
| From: | Schmit A FLORIDA POWER & LIGHT CO. |
| To: | Case E US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084G080 | List: |
| References | |
| AO-251-75-1, NUDOCS 8304210408 | |
| Download: ML20084G086 (3) | |
Text
P.O. LOX SICQ MIAMI, HoniDA 33101 f'!!,
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m January 13, 1975
({ID6 Mr. 1;dson G. Case, Acting Director J'\\
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Directorate of Licensing
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U.S.
Atomic Energy Commission Qge,,,
Washington, D.
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Dear Mr. Case:
5-k.;. s Abnormal Occurrence No. 251-75-1
'Q, January 13, 1975 q,,
Occurrence Date:
January 3, 1975 Pressurizer Pressure Protection Channel II - Lead / Lag Controller Failure A.
Conditions Prior to Occurrence The reactor was in steady-state power operation at 99.8%
reactor power.
Pressurizer Pressure Protection Channel II was in t-h e t ripped modo to perform a f u n c t-i n n a l_
t o s t-on this channel.
B.
Description of Occurrence During the performance of a functional test on Channel II of the Pressurizer Pressure and Level Protection System, it was noted that the output signal from the pressurizer low pressure lead / lag controller (PM-456A) was higher than the signal from the pressure transmitter simulator.
Under these test conditions tbc output of the lead / lag controller should have been equal to the input test signal.
When the test signal was decreased to a value equivalent to a pressurizer pressure of 1701 psig, the output of the lead / lag controller corresponded to a pressurizer pressure of 1715 psig.
C.
Cause of Occurrence A zero-shift in the pressurizer low pressure lead / lag con-troller on Protection Channel II was the cause of this occurrence.
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Mr. Edson G. Case, Acting Director Page 2 January 13, 1975 When the pressurizer pressure signal is steady, the lead / lag controller output is equal to the input signal.
- However, when the signal falls rapidly, the lead / lag controller output signal becomes lower than the input signal.
This will cause the low pressurizer pressure reactor trip to occur at a higher pressure because the pressurizer pressure is falling rapidly.
D.
Analysis of Occurrence The incidents analyzed and presented in the Turkey Point Unit Nos. 3 and 4 Final Safety Analysis Report assume conservative values for instrument error in measuring pressure, time delays associated with tripping functions, and maximum trip points assumed for analysis.
A value of 30 psi was assumed for steady state fluctations in primary pressure and measuring A maximum trip point value of 1685 psig was assumed error.
for the low pressurizer pressure reactor trip.
A low pressurizer pressure reactor trip is assumed to be actuated from any two out of three pressurizer low pressure channels.
Functional tests of low pressurizer pressure protection Channel Nos. I and III demonstrated that both of these protection cnannels were operable.
If pressurizer pressure had dropped to a value of 1701 psig, low pressurizer pressure protection Channel II would have operated.
A rapid drop in pressurizer pressure would have caused these protection channels to operate at a higher pressure than shown by the functional test.
Review, analysis, and evaluation of the reactor operating con-ditions during this occurrence concludes that the reactor would have been protected by the two operable channels.
The error caused by the zero-drift in the Channel II lead / lag controller (PM-456A) was equal to 14 psi allowance used in the safety analysis.
The maximum trip point pressure of 1701 psig deter-mined by the functioaal test is higher than the value of 1685 psig assumed in the safety analysis.
Therefore, neither reactor safety nor the health and safety of the public were jeopardized by this occurrence.
E.
Corrective Action Pressurizer low pressure lead / lag controller (PM-456h) was adjusted to correct for zero-shift.
Functional test performed after the controller was calibrated demonstrated that the lead /
lag controller performed satisfactorily.
There was no evidence of generic failure.
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Mr. Edson G. Case, Acting Director Page 3 January 13, 1975 F.
Failure Data Review of the operating and failure reports show this is the first abnormal occurrence due to malfunction of a low pressurizer pressure lead / lag controller.
This lead / lag controller ( PM -4 56A) was manufactured by IIagan Controls Corporation.
Model No. 198125-2206 Optimac Lead / Lag Controller.
Serial No. 80150.
Very truly yours, hl[
sm k A.
D.
Sclunidt Vice President Power Resources VTC/mld cc:
Norttan C. Moseley Jack C.
Newman, Esquire 1
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