ML19242A652
| ML19242A652 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 06/20/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19242A648 | List: |
| References | |
| NUDOCS 7908030315 | |
| Download: ML19242A652 (5) | |
Text
SAFETY EVALUATION REPORT OVERPRESSURE MITIGATING SYSTEM CRYSTAL RIVER UNIT 3
1.0 INTRODUCTION
By letter dated Deuember 2,1976, (Reference 1) Florida Power Corporation (FPC) submitted to the NRC a plant-specific analysis in support of the reactor vessel ',verpressure mitigating system (CMS) for Crystal River Unit 3 Nuclear Powr.r Station (CR-3). The analysis was supplemented by letter dated Februar.r 17, 1979 (Reference 2) and other documentation submitted by FPC (Refertnces 3, 4, 5).
FPC has installed the equipment and incorporated the procedure! described in this report.
Our review of :he information submitted by FPC in support of the proposed overpressure mitigating system is complete and has found that the system provides adequate protection from overpressure transients. A safety evaluation follows.
2.0 EVALUATION The enclosed Technical Evaluation Report was prepared for us by EG&G, Idaho, Inc., as part of our DOR technical assistance program.
3.0 SYSTEM DESCRIPTION The CMS consists of both active and passive subsystems.
The active subsystem is simply the modification of the actuation circuitry of the existinc, electrical pilot actuated relief valve (PARV) to provide dual setpoints, a nor al operation setpoint of 2255 psig and a low pressure setpoint of 550 psig. The low pressure set;oint is employed when the reactor coolant system is below 2800F. This system is manually enabled. An alarm will function should the operator fail to enable the system when the temperature drops below 230 F.
An alarm has also been installed to monitor the position of the 0
pressurizer relief block valve, RC-V2.
This alarn indicates over-pressuriza-tion mitigating system not enabled.
The passive subsystem consists of the introduction of a nitrogen blanket in the pressurizer. The reactor is o;erated during heatuo and cooldown with a steam or nitrogen bubble. The bubble functions as a pressure damperer. This subsystem is actually the original B&W design.
In addition to the existing design and the above design features, we reccmmend tnat the licensee implement the cnanges described in Section 5 of this evaluation.
2.0 PRCCE::URES A number of provisions for prevention of pressure transients are incoroorned in the plant ocer ating procedures. These are discussed in the RSB safety eval uation report. However, those procedures that affect the instrument and pcwer systems are describec below:
$ds bio 7 9 08 030 3 I f (a) The CMS is to be manually enabled when the reactor coolant system 0
temperature is less than 280 F.
An alarm will sound if the operator fails to enable the system at this temperature. This requirement is to be incorporated in the plant Technical Specifi cations. An alarm will also be actuated if the operator fails to open or close the PARV isolation valve and the RCS temperature is below 2800F.
(b) The plant is to be operated with a steam or nitrogen blanket in the pressurizer during plant cooldowns and heatups. The initial pressurizer water level is to be less than or equal to the high level alam at system pressures above 100 psig and less than the high level alam for pressures less than or equal to 100 psig.
At least two channels of level instrumentation will be required to be operable when overpressure protection is required.
(c) The makeup tank water level is to be less than the hign level alam. Level instrumentation as required for (b) above.
(d) A Core Flood Tank is provided. Discharge valves are to be closed and circuit breakers for the notor operators " racked out" during plant cooldown prior to reaching 280cF system temperature.
Pcwer to these valves is also alarmed.
(e ) Testing of HPI pumps during shutdown will only be performed with the vessel head removed.
Each of the items, (a) through (e) above, where operator dependence upon instrumentation and alam indicatlons to assure the overpressurization analysis assumptions have been complied with will be tested and calibrated in accordance with the recairements of the technical specification.
We find that the procedural and administrative controls described are acceptable.
5.0 CONCLUSION
S The Florida Power Corporation's proposal for a icw temperature overpressure mitigation system for Crystal River Unit 3 does not fully meet all of cur criteria in the areas of electrical, instrumentation, and controls.
It fails to meet the criteria on the basis that (a) operator action will be recuired within ten minutes after detection of one specific transient (HP saiecy injection), (b) the system does not have redundant cnannels and may te susceptable to a single failure, and (c) tne system dces not satisfy the IEEE Std-279 and seismic requirements.
t.
,Il j 9 _I
()~t Although the CR-3 plant does not comply witn all of our overpressure criteria, there are other factors wnich we considered to be compensatory.
The criteria for an CMS wera originated for PWR's that mcy be operated with the RCS in a water solid condition during cooldown and startup.
The B&W designed plant never operates with a water solid condition. A steam or nitrogen bubble is maintained in the reactor pressurizer at all times.
Of the 44 overpressure transient to date, there has been only one low temperature overpressure transient at B&W designed plants.
In order that the OMS be found acceptable in the areas of EI&C, it is reconrended that the following additional changes be made by the licensees at the next refueling outage.
1.
Pressure alams should be installed to give the operator direct indication that a low temperature pressure transient is in progress and that the RCS pressure is on a trend to exceeding the 550 psig relief setooint.
2.
The RCS pressure and temcerature should be continuously recorded to provide a per anent record of all icw temperature pressure transients. The recorder should have the capability to record 100 psig per second overpressure transients.
Based on the above, we find the Crystal River Unit 3 overpressure mitigating system acceptable in the EI&C area as a long term solution to the problem of overpressure transients.
6.0 REFERENCES
1.
J. T. Rodgers " Interim Response to Overcressurization at Shutdown Conditions," December 2,1976, FPC letter.
2.
J. T. Rodgers, " Response to NRC Request for Additional Information,"
Februa ry 17, 1977, FPC letter.
3.
J. T. Rodgers, Status re:: ort to John Stolz, NRC, June 3,1977, FPC letter.
4 W. P. Stuart, "Res;:onse to NRC Request for Acditional Infor-ation,"
January 5,1978, FPC letter.
5.
W. P. Stuart, " Technical Specification Change Recuest No. 17,"
Janua ry 23, 1973, FPC letter.
$gj di-
_4_
6.
" Staff Discussion of Fifteen Technical Issues Listed in Attachment G, November 3,1976 Memorandum from Director NRR to NRR Staff.
NUREG-0138, November 1976.
7.
J. F. Stolz, " Verification for Compliance with Appendix G Pressure-Temperature Limits During Startup and Shutdown," NRC lettar, October 1,1976.
8.
J. F. Stolz, NRC letter to FPC in regard to overpressure protection system, NRC letter, November 19, 1976.
9.
J. F. Stolz, " Verification for Compliance with Appendix G Pressure-Temcerature Limits During Startup an.' Jhutdown" (Crystal River Unit 3 Nuclear Generating Plant), NRC letter, January 7,1977.
10.
R. W. Reid, NRC letter to FPC in regard to overpressure protection system, November 11, 1977.
11.
J. 3. Herbein, " Overpressure Protection System," January 13, 1978, Met-Ed letter GQL 0048.
h
-