ML19224D264
| ML19224D264 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 05/30/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19224D263 | List: |
| References | |
| NUDOCS 7907110210 | |
| Download: ML19224D264 (5) | |
Text
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SAFETY EVALUATION OF THE ELECTRICAL, INSTRUMENT AND CONTROL ASPECTS OF THE PROPOSED ECCS MODIFICATION F0P. SMALL BREAK LOCA FOR CRYSTAL RIVER UNIT 3 INTRODUCTION In the sutaittal of July 21, 1978, Florida Power Corporation (FPC) described the permanent solution to the ECCS Small Breaks Analysis problem at Crystal River, Unit 3.
A July 28.1978 letter by FPC correcced a minor error in the July 21, 1978 submittal.
By letters dated November 17, 1978, January 12, 1979, and February 28, 1979, the licensee provided certain additional detailed information regarding the High Pressure Injection (HPI) system of Crystal River, Unit 3.
The existing High Pressure Injection system is designed to have two make-up and purification pumps (MUP's) provide HPI flow with a third pump as a standby. All three pumps are automatically started when the Emergency Safeguards (ES) signal is actuated. The discharge of these pumps is directed through four injection lines to the primary loops to maintain core cooling following a LOCA (see Figure 1). To mitigate the accident resulting from a small break at the reactor coolant pump discharge, that initiates the HPI system (but not the low pressure injection system), the licensee has determined that the HPI system should achieve at least the equivalent of 70% of the flow of one pump to the reactor.
It was also determined that the following injection line pump configuration will result in at least the required flow:
4 lines with 2 HPI pumps 4 lines with 1 HPI pump 3 lines with 2 HPI pumps 2 lines with 2 HPI pumps The proposed modification of the HPI system is intended to assure one of these configurations with the worst case single failure for the small break LOCA (assuming the loss of offsite power).
For certain single failures (i.e., loss of a diesel generator, a d-c battery or an ES actuation signal),
this will require operator action by 10 minutes into the accident. The licensee has stated that the modifications proposed are consistent wit.'
the staff positions regarding allcwable operator actions for which credit may be taken following a small break LOCA (this has been reviewed by the Reactor Safety Branch).
- 7907339g, 332 iN
The proposed modification consists of keeping the HPI pump crM s-connect valves normally open and providing means of supplying electrical power to the motor operators of the high pressure injection valves (MUV-23, 24, 25 and 26) frcm the Engineering Safeguards electrical buses of both channels through appropriate transfer switches and circuit breakers (see Figure 2).
The present electrical distrubition system has MUV 23 and MU" 24 supplied frc:i ES-Al-MCC and MUV 25 and MUV 26 supplies from ES-B1-MCC.
? e proposed modirication will provide new motor control center uections with motor-operated molded case circuit breakers and electrical transfer switches arranged such that MUV-23, i
-24, MUV-25 and MUV-26 each can be supplied power from ES-Al-MCC and ES-MCC.
Selector switches are provided in the main control room to enable.
operator to select the MCC to whicn each motor-operated valve can be connected. The proposed modification of the transfer switcning scheme is designed in accordance with Regulatory Guide 1.6 and Regulatory Guids 1.75.
The licensee has stated that the equipment required for the proposed modification will be designed, manufactured and qualified in conformance to the applicable standards and codes that apply to the present HPI system (as documented in Crystal River, Unit 3 FSAR Sections 6.1 and 8).
DISCUSSION The proposed modification requires an operator to perfonn the action of positioning the selector switches of two injection valves to transfer the electrical power source to the valves from one electrical bus to another, in the event of a small break LOCA and loss of power to one of the buses which causes the inoperability of HPI injection valves and one HPI pump.
The operator will take this action based upon annunciation of initiation of the Enginaered Safeguards Actuation System and verification of no HPI flow in one train.
The proposed modification, by providing manual selector switches to initiate transfer of MOV loads between redundant power supplies assures that no automatic connection is provided between redundant load groups. Thus, this design conforms to the requirements of Regulatory Guide 1.6.
The design is stated to be in conformance with Regulatory Guide 1.75, " Physical Independence of Electrical System".
Further, our review of the control schematics of the transfer switches has shown that no single failure in the transfer circuits will compromise redundant load groups of the plant.
Florida Power Corporation by its letter dated January 12, 1979, submitted the Single Failure Analysis of Proposed ECCS Mcdification for Small P eak LCCA.
Based on its analysis the licensee has shown that the modified HPI system, with the allowed operator actions, adequately satisfies the ECCS flow requirements of a small break LOCA.
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CONCLUSION Based on our review, we find that:
1.
The proposed ECCS modification for a small break LOCA will assure that for all postulated single failure conditions the HPI system will be capable of supplying sufficient flow to the reactor to mitigate the accident.
2.
The propcsed modification will not affect the performance of other systems important to safety.
3.
The proposed modification requires operator action to switch electrical power to two inoperable HPI valves from the operable ES electrical bus.
4.
The equipment required to implement the proposed modification will be designed, manufactured, qualified and tested to the applicable codes and standards that apply to the ECCS system.
Accordingly, we conclude that the proposed design modification is acceptable.
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