ML20038B181
| ML20038B181 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 11/10/1981 |
| From: | Tramm T COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8111240812 | |
| Download: ML20038B181 (5) | |
Text
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D Commonwealth Edison
) one First National Plaza. Chicago, Illinois O
O' Address Reply to: Post Office Box 767 Chicago Illinois 60690 L
l November.10, 1981
\\'
'As Mr. James G. Keppler, Director
(-(y]\\
d Directorate of Inspection and N[(,' "( p 7 *,, '
Enforcement - Region III h
U.S. Nuclear Regulatory Commission 799 Roosevelt Road T
9 NOV ~q o gg.i.
ao Glen Ellyn, IL 60137 u
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Subject:
Byron Station Units 1 and 2 k
/-
l Braidwood Station Units 1 and 2 Q,f 50.55(e) Deficlecy Report No. 81-
'A s fS /
i NRC Docket Nos. 50-454/455/456/457 Reference (a):
July 24, 1981, letter from T. R. Tramm to J. G.
Keppler.
Dear Mr. Keppler:
i Reference (a) provided the preliminary report on an apparent deficiency in the Byron /Braidwood Volume Control Tank level control system.
The significance of this deficiency has been reviewed and this is the final report.
q.
The Byron /Braidwood Volume Control Tank level control system incorporates information from two analogue level instruments:
LT-ll2 and LT-185.
Attachment A to this letter tabulates the various control and alarm functions associated with each channel.
It shows the setpoints established by Westinghcuse for the various control and alarm functions.
It also indicates the information l-which is provided to the operator in the event of the f ailure of either level instrument and the amount of time which is available for protective action.
This information demonstrates that there is sufficient time for the operator to take action in the event of a level control sys-tem malfunction to preclude loss of suction to the charging pumps.
No plant changes are required but appropriate precautions and instructions will be incorporated into plant procedures to assure correct operator response in the event of level instrument failure.
r Please contact this of fice if there are further questions regarding this matter.
Very truly yours, hp D^ ^ ^ ^ 4 T. R.
Tramm Nuclear Licensing Administrator S
1m f
2850N 8111240812 811110' Mh)V j g gg8{
PDR ADOCK 05000454 S
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ATTACHMENT A VCT LEVEL INSTRUMENTATION FUNCTIONS, CHANNEL ASSIGNMENTS & SETPOINTS LT-ll2 LT-185 Function Setpoint Setpoint Fully Divert Valve LCV-ll2A N/A(2) 95%
High Level Alarm 95%
95%
Modulate Divert Control Setpoints for Valve LCV ll2A 73%
N/A Auto Makeup Stop 55%
N/A f.uto Makeup Start 37% C3)
N/A Low Level Alarm 20%
20%
Emergency Makeup RWST(1) 5%
5%
Level Indication Control Board Local NOTE:
(1)
Coincident 2/2 logic requires signals from both level channels in order to transfer the pump suction to the RWST.
(2)
N/A:
Not Applicable (3)
Alarm if control switch is not in the " auto" position.
2850N
ATTACHMENT A (cont'd)
VCT LEVEL INSTRUMENTATION FAILURE MODES AND EFFECTS (Refer to Attached Diagram) 1.
Level Transmitter LT-185 generates an incorrect high level signal resulting in complete diversion of letdown to the Recycle Holdup Tanks via VCT level control valve LCV-112A.
The emergency makeup function is defeated.
A high le el alarm is generated.
Decreasing level in the Volume Control Tank will be indicated in the control room by LT-112.
LT-ll2 will also initiate automatic makeup if the makeup system has been pre-set for automatic operation or generate an alarm if the makeup control switch is not in automatic.
A low VCT level alarm will sound if the makeup control system does not maintain level within the normal operating band.
2.
Level Transmitted LT-ll2 generates an incorrect high level signal which diverts all or a portion of the letdown to the Recycle Holdup Tanks.
LT-112 will provide misleading high level indication in the control room and may (or may not) generate an erroneous high level alarm.
The same failure simultaneously defeats the refueling water transfer and the automatic makeup function associated with LT-ll2.
Decreasing level in the Volume Control Tank would subsequently be alarmed in the control room by LT-185.
2850N
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ATTACHMENT A (cont'd)
VCT LEVEL INSTRUMENTATION OPERATOR ACTION TIME TIME TO EMPTY VCT IN MINUTES At 120 At 75 Level Setpoints GPM GPM Modulate Divert Setpoint 73%
16 26 Auto Makeup Stop 55%
13 21 Auto Makeup Start 37%
10-1/2 16-1/2 Low Level Alarm 20%
7-1/2 12-1/2 Emergency Makeup 5%
5-1/4 8-1/2 2850N
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