ML15071A343
| ML15071A343 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 03/16/2015 |
| From: | Correia C NRC/RES/DRA |
| To: | |
| Dale Yeilding 301-251-7577 | |
| Shared Package | |
| ML15070A232 | List: |
| References | |
| LER 373-2013-001-02 | |
| Download: ML15071A343 (52) | |
Text
The switchyard arrangement is such that offsite power to both units cannot be lost due to any single failure.The design of the protective relay circuits for the 345-kV oil circuit breakers and the 345-kV transmission lines is such that the loss of either battery or the loss of both batteries and associated feeder cables will not cause the loss of offsite power sources.
Two utility reports identify another failure mechanism in which circuit breaker protective devices lock out the circuit breaker to protect it from potential damage resulting from repeated opening and closing (referred to as "pumping"). The operator actions required to reset the circuit breakers may be quite complicated and could result in a high probability of failure to recover.
times ten raised to the power ofa ba b"axb
if SRV[1] + SRV[2] then event tree(LOOPSC) = Flag(ETF-SORV); endif
Operator Fails to Recover Offsite Power in 30 Minutes Operator Fails to Recover Offsite Power in 1 Hour Operator Fails to Recove r Offsite Power in 4 HoursOperator Fails to Recove r Offsite Power in 7 HoursOperator Fails to Recover Offsite Power in 12 Hours
One SRV Fails to CloseBWR ADS/SRV Fails to RecloseTwo or more SRVs Fails to CloseThree or more SRVs Fails to Close
Criterion 17-Electric power systems. An onsite electric power system and an offsite electric power system shall be provided to permit functioning of structures, systems, and components important to safety. The safety function for each system (assuming the other system is not functioning) shall be to provide sufficient capacity and capability to assure that (1) specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded as a result of anticipated operational occurrences and (2) the core is cooled and containment integrity and other vital functions are maintained in the event of postulated accidents. The onsite electric power supplies, including the batteries, and the onsite electric distribution system, shall have sufficient independence, redundancy, and testability to perform their safety functions assuming a single failure. Electric power from the transmission network to the onsite electric distribution system shall be supplied by two physically independent circuits (not necessarily on separate rights of way) designed and located so as to minimize to the extent practical the likelihood of their
simultaneous failure under operating and postulated accident and environmental conditions. A switchyard common to both circuits is acceptable. Each of these circuits shall be designed to be available in sufficient time following a loss of all onsite alternating current power supplies and the other offsite electric power circuit, to assure that specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded. One of these circuits shall be designed to be available within a few seconds following a loss-of-coolant accident to assure that core cooling, containment integrity, and other vital safety functions are maintained. Provisions shall be included to minimize the probability of losing electric power from any of the remaining supplies as a result of, or coincident with, the loss of power generated by the nuclear power unit, the loss of power from the transmission network, or the loss of power from the onsite electric power supplies.
()+=composite composite PSF NHEP PSF NHEP HEP
()+=composite composite PSF NHEP PSF NHEP HEP