ML20039B210
| ML20039B210 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 12/14/1981 |
| From: | Rausch T COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8112220425 | |
| Download: ML20039B210 (4) | |
Text
Commonwealth Edison N
one First N tionti Pizza, Chicago, liknois 1
C 'O _ Address Reply to: Post Office Box 767 Obicago, Illinois 60690 December 14, 1981 Mr. Harold R.
Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Quad Cities Station Units 1 and 2 G3 4
Supplementary Information Concernin #
Proposed Changes to Appendix A, ig N.
\\
Technical Specifications on the
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OE N
Containment Cooling Mode of the g" %g0.2 I
RHR System 50-254 and 50-265 $ %$. Ige /88 b ;2 NRC Docket Nos.
n ldpiey.,
Reference (a):
T.
J. Rausch letter to H. R. Dento e
.y dated December 3, 1981.
,/
Dear Mr. Denton:
In Reference (a), Commonwealth Edison Company proposed a temporary change to Appendix A, Technical Specifications to Facility Operating Licenses DPR-29 and DPR-30 for Quad Cities Units 1 and'2, respectively.
The purpose of this change is to allow the "A" loop of the Residual Heat Removal (RHR) heat exchangers on each unit to be fed from the RHR "A" and "B" Service Water pumps from Unit 2 via a cross-tie line.
This change has been discussed with your staff in several recent telephone conferences.
As a result of these discussions, the following additional information is provided:
Emergency Power Systems Loads in the Event of a Loss of Off-Site Power.
Adequate contair. ment cooling is availabl'e, even in the..
event of a design basis Loss of Coolant Accident (LOCA) concurrent with a loss of off-site power.and the worst single
- failure, if one RHR and one RHR Service Water pump is available.
If the Unit 1/2 or the Unit 2 diesel generator is postulated as the single failure (with a loss of of f-site power) this proposal results in no change to existing procedures or to the existing design basis.
If the Unit 1 diesel generator is postulated to fail, then the amount of equipment.available for containment cooling, even in the event of a Unit 1 LOCA, still meets the original design basis with this change.
For,this OCI case, however, minor procedure. changes are required to assure J
that adequate power is allocated te the necessary equipment
/
during a loss o f of f-site. power.
// O 8112220425 811214 PDR ADOCK 05000254 P
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R'. Denton December 14, 1981 A procedure will be implemented which will allow Buses 13-1 and 23-1 to both be energized by the Unit 1/2 diesel generator.
This will then make available one Unit 2 RHR Service Water' pump 1
and one Unit 1 RHR pump, both fed by the 1/2 diesel.
This procedure would require that the ECCS pumps on Bus 23-1 be pulled-to-lock prior to closing two locally mounted switches (see the modification descriptions below) which permit both buses to be energized by the diesel.
It should be noted that the use of RHR containment cooling for any reason always requires manual operator actions.
Thus for any scenario, including.the loss of o f f-site power concurrent with - the Unit I diesel generator failure, this change results in no reduction in the margin of safety.
Alternatives to the Bus 13-1 to Bus 23-1 Crosstie Alternate equipment line-ups were reviewed for the postulated accident conditions.
The only_ arrangement, which is achievable without major modification,11s to utilize the existing crosstie between Bus 14-1 and Bus 24-1.
In this situation, the initial equipment line-up would have the Unit 2 diesel generator feeding Bus 24-1 for the Unit 2 loads and the 1/2 diesel generator feeding Bus 13-1 for the Unit 1 loads.
Then,-starting with Bus 14-1 unloaded, the crosstie between Bus 24-1 and Bus 14-1 could be closed.
Sequentially, each load would be dropped of f of Bus 24-1 and its corresponding load would be picked up on Bus 14-1, requiring multiple. operator actions.
Once Bus 14-1 was loaded, the transfer of the 1/2 diesel generator from Unit 1 to Unit 2 could begin.
All loads on Bus 13-1 would be tripped.
Then the feed breaker to bus 13-1 could be opened and the feed breaker to Bus 23-1 would be closed.
The loads needed for Unit 2 could then De put on Bus 23-1.
The method for implementing this alternative is less desirable because of the many operator actions needed to unload one bus and load another bus when compared with-the minimal actions required to crosstie Bus 13-1 and 23-1.
Under the assumed conditions, the only load changes needed are to trip one RHR pump of f of Bus 13-1 prior to starting an RHR Service Water pump on Bus 23, which is the logical sequence of actions an operator would have taken without this amendment.
The only non-routine operator action required is to actuate the keylock switches at the breakers on Bus 13-1 and 23-1 to allow the simultaneous closing of both feed breakers from the 1/2 diesel generator.
Consequently, the use of the crosstie between Bus 13-1 and Bus 23-1 is concluded to be the most desirable alternative.
3
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0 H. R. Denton December 14, 1981 Description of Electrical Wiring and Bus Loads Modification The installation of this moolfication will consist of two keylock switches installed such that the emergency 1/2 diesel generator can be loaded to Bus 13-1 and Bus 23-1, simultaneously.
The switches will be located in Bus 13-1, cubicle 1 and Bus 23-1, cubicle 10.
It was decided to install the switches locally inside the breaker cubicles since this of fers the greatest protection to the wires and switches.
It is not desirable to place the new switches in the Control Room since it would be necessary to run new wire from the breakers to the Control Room.
Also, there is ample time for personnel to actuate these switches because containment cooling is not initiated until on the order of hours af ter the event starts.
The switches are located witnin two minutes of the control room.
At such time that it is deemed necessary to feed both buses from the 1/2 Diesel, the switches will be actuated and the operator will close the feedbreakers to bus 23-1 from the control room.
The newly installed switches defeat the closing interlocks on the main feed breakers from the 1/2 diesel generator, allowing closure of both breakers simultaneously.
At no time will any of the automatic trips on the buses be affected.
The wiring of the modification will be fully tested in accordance with the modification program.
The modification test will prcve that the 1/2 diesel generator can energize Bus 23-1 when it is already energizing Bus 13-1.
Likewise, it will be shown that the 1/2 diesel generator can energize Bus 13-1 when it is already energizing Bus 23-1.
It will also be demonstrated that none of the existing closing circuitry will be affected when the swtiches are in the OFF position.
As is the case with all modifications of this nature, prior to its implementation, operator personnel will be trained and informed of the new installation.
Procedures will be written to explain the use of the new switches.
To assist you in your review, one (1) copy of each of the following drawings is being provided:
4E-1328, 4E-1345, 4E-2345, 4E-1344, 4E-2344, 4E-1303, 4E-1304, and M-39 sheets 1 and 2.
Drawings 4E-1345 and 4E-2345 have been marked in red to illustrate the proposed keylock switch.
Please address any questions you may have concerning this matter to this office.
.~.
H.R. Denton December 14, 1961 One (1) signed original and thirty-nine (39) copies of this transmittal are provided for your use.
Very truly yours, jh
%4 Thomas J. Rausch Nuclear Licensing Administrator cc:
Region III Inspector - Dresden im 3039N
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