It is one of those AW! things and it's not shucks.
I short definition I've seen is that it is the loss of all distributed power within the battery limits of the plant.
I've been involved in 3 total blackouts not in a Nuclear Plant but in a chemical plant that makes synthetic fiber. From the ammount of chaos this caused in our plant I can imagine what it would be like in a Nuclear Plant. In our plant we also have a time constraint to get polymer processes back on line. If this doesn't happen within 45 minutes a unit has to be overhauled at considerable cost.
Now in the case of a multi-unit station that has non environmentally qualified stand -by generators (SG)and 2 environmentally qualified emergency power generators (EPG).
A black out would mean to loose all reactors and the ability to transfer power between them and the SG's would be down and the EPG's would be unavailable. And the outside grid would be unavailable.
That would leave only the power from the batteries and AC power given from the inverters from the batteries.
Is that right?
By the way it is for CANDU plant and with regards to WANO
You've described the "function" of a station blackout adequately in a legal sense -> But, big "but" this is a nuclear station where the "regulation" terms used by the nation's agencies define policy and requirements. Then designs and procedures must be made based on the "definition" chosen, not by reality or the effects of three or four mutual "unforeseen" common catastrophes.
A station blackout happens when there is no electrical power available inside the transformer yard. A station brownout happens when there is insufficient reliable power of the right voltage at the right capacity capable of running for the right amount of time inside the fence.
Make sense?
You can write elaborate definitions of a station blackout all you want, but if you didn't anticipate an earthquake wiping out the regional power, a tsunami wiping out the plant's backup power, backup fuel, and backup power distribution network to pumps and equipment; and the plant itself is automatically being shutdown by a Cat 9 earthquake, then your plant still has no power.
If the pump you need to run needs 4180 volts, but you have only a generator trailer putting out 440 volts, you still have a station power problem - regardless of whether you call it a station blackout or a station screwup or a station problem.
as Racookpe1978 said: If the 4160 Volt motors of the pumps you need to run were flooded out by Tsunami seawater right up to the top bearings, it is irrelevant whatever auxiliary power generators are brought in- The motors are effectively unserviceable, until removed and replaced totally. Each weighs in at several tons.
That was the fate of the Megawatt class seawater pumps on the outdoor platform at Fukushima, affecting all the reactors, simeltaneously.
Call it a blackout if you like, it was the seawater flooding of the electrical auxiliary plant, including the Diesel Generators (each several MW) that sealed the fate at Fukushima.
I can't answer your question for CANDU and WANO, but here's the definition from Title 10 of the US Code of Federal Regulations, Section 50.2:
Station blackout means the complete loss of alternating current (ac) electric power to the essential and nonessential switchgear buses in a nuclear power plant (i.e., loss of offsite electric power system concurrent with turbine trip and unavailability of the onsite emergency ac power system). Station blackout does not include the loss of available ac power to buses fed by station batteries through inverters or by alternate ac sources as defined in this section, nor does it assume a concurrent single failure or design basis accident. At single unit sites, any emergency ac power source(s) in excess of the number required to meet minimum redundancy requirements (i.e., single failure) for safe shutdown (non-DBA) is assumed to be available and may be designated as an alternate power source(s) provided the applicable requirements are met. At multi-unit sites, where the combination of emergency ac power sources exceeds the minimum redundancy requirements for safe shutdown (non-DBA) of all units, the remaining emergency ac power sources may be used as alternate ac power sources provided they meet the applicable requirements. If these criteria are not met, station blackout must be assumed on all the units.
You might find something similar at the Canadian Nuclear Safety Commission's website:
