ML20042E947
| ML20042E947 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 04/27/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20042E946 | List: |
| References | |
| NUDOCS 9005040314 | |
| Download: ML20042E947 (3) | |
Text
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[p u y*'g UNITED STATES
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NUCLEAR REGULATORY COMMISSION
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'f WASHINGTON. D. C. 20555 yj SAFETY EVALUATION BY THE OFFICE NUCLEAR REACTOR REGULATION RELATED TO THE ACCEPTABILITY OF THE AS-BUILT ALTERNATE ROD INJECTION AND REACTOR TRIP SYSTEM POWER SUPPLY CAROLINA POWR & LIGHT COMPANY BRUNSWICK STEAM ELECTRIC PLANT. UNITS 1 AND 2 DOCKET NOS. 50-325 AND 50-324
- 1. 0 INTRODUCTION In early February 1989, the NRC resident inspector performed an inspection 1
on the "as-built" Anticipated Transient Without Scram (ATWS) Alternate Rod Injection and Recirculation Pump Trip (ARI/RPT) systems at the Brunswick Steam Electric Plant (BSEP), Units 1 and 2, and noted that the ARI logic and solenoid valves were powered from the same distributi'on panel which was also used to supply power to the reactor trip system (RTS) analog transmitter trip units (ATTU).
This raised NRC concern regarding the independence of the ARI system power supply from that of the RTS, The staff in its letter to the licensee dated August 21, 1989 provided two options by which the licensee can clarify the acceptability of the BSEP, Units 1 and 2, "as-built" ATWS ARI/RPT system power supply.
The options were:
1.
Provide an independent non-class IE de power supply with non-class IE battery backup that provides power to the ARI system logic and ARI solenoid valves.
l 2.
Upgrade the ARI system to a class IE system that is powered by RTS power sources and show through a failure modes and effects analysis that common mode failures will not propages through the power supplies and disable both the RTS and the ARI/RPT system.
By letters dated October 23, 1989 and March 13, 1990, the licensee provided additional information to demonstrate the reliability of the power supplies and a failure modes and effects analysis to show that common mode failures will not propagate through the power supplies and disable both the RTS and the ARI/RPT system.
2.
EVALUATION The Brunswick ARI/RPT system has redundant channels and uses the two-out-two actuation logic based on high reactor pressure or low reactor water level.
The sensors and the trip units are located on safety related racks and cabinets, respectively.
Relay coil to contact isolation devices are provided between the ARI/RPT circuitries upstream of the isolation devices and are considered as part of the safety related system.
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e 2
The RTS logic and actuation devices are su aplied with ac control power from motor-generator sets.
Control power for t1e ARI logic and actuation devices is supplied f rom the battery backed Class IE de sources.
The sensors and the trip units which supply trip signals to the RTS are powered through the l
125 y de distribution panels which are part of the battery backed Class IE de sources.
The staff's safety evaluation of tcpical report NEDE-31096 " Anticipated Transient Without Scram:
Response to ATWS Rule,10 CFR 50.62" stated that if the ARI system has to use a safety-related power supply through " proper isolation," then bvo qualified Class IE brea kers in series with proper relay coordination should be provided for the isolation function.
In t he Ma rch 13, 1990 submittal, the licensee provided the circuit breaker coordination curves which denonstrated that the branch circuit breaker will tri) before its associated main feeder circuit breaker, thereby isolating t1e equipment served by that particular branch circuit breaker from the rest of the system.
l The licensee provided additional infornation.in the March 13, 1990 sW)mittal which analyzed the effects of degraded voltage conditions.
Analy si s s hows that power related common node failure pechanisms between the RTS and the ARI/RpT systems will not propagate through the power supply and disable both the RTS and the ARI/Rpi systems.
3.
CONCL USION Dased on the infornation provided by the licensee, we conclude that the Brunswick design satisfies the option 2 condition, as stated in our August 21, 1989 letter.
Therefore, this issue is resolved.
Principal Contributor:
H. Li Dated:
April 27, 1990
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