ML20215C616
| ML20215C616 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 12/10/1986 |
| From: | Bailey J GEORGIA POWER CO. |
| To: | Youngblood B Office of Nuclear Reactor Regulation |
| References | |
| GN-1218, NUDOCS 8612150282 | |
| Download: ML20215C616 (3) | |
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4 Georgi: Power Company
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Post Offic3 Box 282 Waynesboro, Georgia 30830 Telephone 404 554 9961 404 724-8114 Southern Company Services,Inc Fbst Office Box 2625 Birmingham, Alabama 35202 Teiepnone 205 87u0u VOglle Project December 10, 1986 Director of Nuclear Reactor Regulation File: X7N16 Attention:
Mr. B. J. Youngblood Log:
GN-1218 PWR Project Directorate #4 Division of PWR Licensing A U. S. Nuclear Regulatory Commission Washington, D.C.
20555 NRC DOCKET NUMBER 50-424 CONSTRUCTION PERMIT NUMBER CPPR-108 V0GTLE ELECTRIC GENERATING PIANT - UNIT 1 TECHNICAL SPECIFICATIONS
Dear Mr. Denton:
By letter dated November 14,1986 (GN-1183) we submitted marked-up pages from the Proof and Review Copy of the VEGP Unit 1 Technical Specifications and Section 15.4.6 of the VEGP FSAR reflecting the current boron dilution analysis. During a December 4,1986, telecon with your staff concerning this submittal, we were asked to provide additional information concerning reactor coolant system volumes and dilution flow rates assumed in the analysis and this information is provided as an enclosure to this letter.
If your staff requires any additional information, please do not hesitate to contact me.
.cerely,
'. t. f J. A. Bailey Project Licensing Manager JAB /caa Enclosure xc:
R. E. Conway NRC Regional Administrator R. A. Thomas NRC Resident Inspector J. E. Joiner, Esquire D. Feig B. W. Churchill, Esquire R. A. McManus (W/o Encl.)
M. A. Miller (2)
L. T. Gucwa B. Jones, Esquire (W/o Encl.)
Vogtle Project File G. Bockhold, Jr.
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C 8612150282 861210 PDFs ADOCK 05000424 g
PDR g
A
o Dilution Flowrates For the four initiators analyzed in the original analysis, the dilution flowrates ranged from a minimum of 3.5 gpm to a maximum of 186 gpm.
Since the maximum flowrate always yields the most limiting times for operator response, the response time calculation done for the initiator with the maximum flowrate always bounds the calculations done for the other initiators. The initiator which yields the maximum flowrate is the failure closed of flow control valve FV-110A on the Boric Acid transfer line in Reactor Makeup. In order for this initiator to introduce a flowrate of 186 gpm of unborated water into the charging pump suction, the following failures in the Reactor Makeup Control system and the Chemical and Volume Control System must occur.
Failure closed of flow control valve FV-110A on the Boric Acid transfer line, Failure of the Boric Acid Flow Deviation alarm with a setpoint of +/-0.8 gpm, Failure open of flow control valve FV-0111A on the Reacter Makeup water line (which may only allow a maximum of 130 gpm total depending on the internal caging),
Failure of the Reactor Makeup Water flow deviation alarm with a setpoint of +/- 8 gpm),
Failure open of both charging flow control valves (HV-0190a and HV-8116) which have a high setpoint of 130 gpm, Failure of the operator in putting a second cenirifugal charging pump on line in shutdown modes (maximum capacity of a single centrifugal charging pump is approximately 140 gpm),
Failure of the Total Charging Flow alarm with a high setpoint of 150 gpm.
Therefore a total of seven independent, simultaneous failures of equipment, operators, and alarms are required in order to achieve dilution at this flowrate from this initiator. The first two failures listed above would initiate the dilution event at a maximum flowrate of 120 gpm (the maximum Reactor Makeup Water flow through valve HV-111A is set to match maximum letdown of 120 gpm), while the last five failures are necessary to achieve the dilution flowrate of 186 gpm. The frequency of obtaining these seven simultaneous, independent failures is so low that it would not cause an inadvertent boron dilution event of moderate frequency. Therefore for the reanalysis only the more plausible case of the failure of valve FV-110A and the Boric Acid Flow Deviation alarm were considered for this initiator with a maximum dilution flowrate of 130 gpm (10 gpm were added to account for the Reactor Makeup Water Flow Deviation alarm setpoint and instrument error).
Since none of the dilution flowrates from the other three initiatots exceed 130 gpm, this flowrate became the new bounding flowrate for limiting response time calculations.
- i Revised Boron Dilution Parameters For Vogtle Analysis When the boron dilution analysis methodology was modified to take into account new findings, the parameters used in the initial probabilistic analysis were reviewed. - Some of the parameters used in the original analysis were detected to be in error as compared to the parameters used in subsequent analyses on other plants. These parameters were changed to reflect a more realistic analysis model in the revised analysis. The new values for the parameters and their derivation are provided herein.
Volumes The volumes for vessel and piping included herein are taken from Westinghouse general reactor coolant system information. The four loop data is used for the Vogtle plants.
1 For the shutdown modes, when at least one reactor coolant pump is running (always in Mode 3 and sometimes in Mode 4), it was revealed as the result of loop system hydraulic analysis that lower loop system pressure differentials exist when inactive loops are compared with the operating active loop. Thus, l
the operation of an RCP will cause reverse flow in the inactive loops, and the j
existence of the reverse flow will assure mixing of the reactor coolant aucng the loops. Therefore, the volume considered for this condition is:
i 4 Loop Piping
= 1130.4 cubic feet 4 S/G Volumes
= 3894.4 cubic feet 4 RC Pump Volumes = 344. cubic feet Volume 4 RC Loops = 5368.8 cubic feet Vessel Volume
= 4603.5 cubic feet Total Volume 9972.3 cubic feet = 74,532.8 gallons For the shutdown moder, when only the Residual Heat Removal system is running (Mode 5 and sometimes in Mode 4), Westinghouse confirmed that reverse flow from the operation of the RHR system will mix the reactor coolant in the loop on which the RHRS operates. Therefore only the volume of one loop, the vessel volume, and the volume of the RHR piping are considered in the response time calculations. Thus, the volume considered for this condition is:
Volume 1 RC Loop = 5368.8 cubic feet /4 = 1342.2 cubic feet Volume 1 RC Loop = 1342.2 cubic feet Vessel Volume
= 4603.5 cubic feet RHR Piping Volume = 400. cubic feet Total Volume 6345.7 cubic feet = 47,465.8 gallons This Mode 5 volume does not take into account that situation in which the pressurizer and steam generators are drained down (Mode 5b).
The total volume considered is so small in this situation that all boron dilution initiators will need to be administratively controlled as they are in the refueling mode (Mode 6).
Therefore, Mode 5b was not analyzed in the revised analysis and only that situation where the pressurizer is filled (Mode Sa) was analyzed.
0915V
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