ML19321A055
| ML19321A055 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 07/18/1980 |
| From: | Sylvia B VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Harold Denton, Youngblood B Office of Nuclear Reactor Regulation |
| References | |
| 638, NUDOCS 8007220384 | |
| Download: ML19321A055 (2) | |
Text
VIItorxrA Er.ncrnrc Axx) Powniz CommNY HrcirMown VzmonarA 20e01 July 18, 1980 Mr. Harold R. Denton, Director Serial No. 638 Office of Nuclear Reactor Regulation LQA/WRM:ms Attn:
Mr. B. Joe Youngblood, Chief Docket No. 50-339 Licensing Branch No. 2 License No. NPF-7 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D. C.
20555
Dear Mr. Denton:
ADDITIONAL INFORMATION NORTH ANNA POWER STATION UNIT NO. 2 In our letter dated July 14, 1980, (Serial No. 620), we provided members of your staf f with additional information concerning the Residual Heat Removal (RHR) system for North Anna Unit No.
2.
Specifically, our letter discussed t
the possible use of t'
surizer power-operated relief valve (PORV) for depressurization of
-..cor coolant system.
This letter provides addi-tional information in response to questions from members of your staff concerning our submittal dated July 14, 1980.
On July 17, 1980, a simulation of the use of the pressurizer PORV to depres-surize the reactor coolant system was performed on the Surry Power Station Simulator.
The objective of the simulation was to demonstrate the ability to depressurize the reactor coolant system by discharging the pressurizer PORV to the pressurizer relief tank (PRT) without failing the PRT rupture disc and to establish the time required to accomplish the depressurization through this process.
1 The following is a description of the simulation sequence.
The initial conditions of the pressurizer relief tank were:
PRT Level 62%
PRT Pressure 3 psig PRT Temperature 80*F The accumulators were blocked and Safety Injection was defeated.
Following reactor trip from full power and stopping all Reactor Coolant Pumps, reactor coolant system cooldown was commenced using the atmospheric dump valves. The cooldown was halted at 350*F and the reactor coolant system was pressurized to 8 007sse M4 j7
Vaucim Etrcruic aw Powsw courov to Mr.
Harold R.
Denton 2
2235 psig.
These conditions would present a worst-case example by requiring the maximum amount of energy to be discharged to the PRT.
Depressurization was initiated by discharging the pressurizer PORV to the PRT.
The FORV was cycled twice and then Icft open.
The rate of depressurization was approxi-mately 300 psig/ minute and lasted approximately five minutes.
The RHR was placed in service and depressurization was terminated.
The final conditions were:
Primary Temperature 320*F Primary Pressure 425 psig PRT Level 78%
PRT Pressure 18 psig PRT Temperature 185'F The PRT IcVel can be reduced at a rate of one-half percent per minute.
Draining of the PRT and refill with primary grade water was verified successful.
We believe that this simulation demonstrates that reactor cosiant sys. ;M cooldown and depressurization can be accomplished by alterrate methode.
We hope this information will assist you fa concluding your review of this item.
Should you have any further questions, jlease contact us.
Very truly yours,
')
C B. R.
ylvia Manager - Nucles.r Operations and Maintenance l
cc:
Mr. James P. O'Reilly, Director Of fice of Inspection and Enforcement Region II i
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