Maybe in one plant somewhere, but that's not common. Not unless you're talking about the plant using grid power that just happens to come from a Hydro plant.

No? Where do nuclear grids usually get black start capacity?

"To provide a black start, some power stations have small diesel generators, normally called the black start diesel generator (BSDG), which can be used to start larger generators (of several megawatts capacity), which in turn can be used to start the main power station generators."

i.e. you don't need someone else's power plant, you can have a small one dedicated to black start.

Yes, hydro works really well for this. But it's not the only option.

Sure, it's not the only option, but isn't it the most common option? I admit I don't know much about black start.

No it's rare, if it exists anywhere at all. (Other than via a distant grid connection)

I'm no expert, but you clearly have no idea what you're talking about. You're confidently making strong assertions that are wrong or in some cases not even wrong.

Isn't black start almost always provided via a distant grid connection? Do you work in transmission or generation?

As I understand it, in the US, the NRC prohibits nuclear power plants from providing black start, for safety reasons: https://www.energy.gov/sites/prod/files/2019/05/f62/Hydro-Bl...

From the same source: "Historically, power systems have relied heavily on hydropower plants for black start capability. ... About 40% of the units in the United States maintained and tested for providing black start are hydropower turbines, although hydropower makes up only about 10% of overall US generating capacity."

It also answers the question of what is usually used, namely, gas combustion turbines — in the US, that is. Gas turbines provide over 50% of both black start capability and black start events in the US.

Maybe nuclear plant black start diesel generators do provide black start in some other countries? Where? Bueller? Bueller?

That's in the context of bringing the entire grid back up- a grid black start, not a nuclear plant black start. The 40% number is not nuclear specific- it's all types power plants (and it appears to be based on a 1967 New York blackout.) It's also not historical in the sense of what's been done, but was a hypothetical asked of plant operators akin to "if you have multiple options, which power source are you bringing online first?"

But to suggest that nuclear is sited near hydro for that purpose is just wrong.

As I said, in the US the NRC prohibits you from attempting a nuclear plant black start — that is, starting the plant during an ongoing LOOP event. So, at least in the US context, it's nonsense to talk about "a nuclear plant black start". Black start is a grid event, not a power-plant event.

The 40% number is not based on the New York blackout, which was in 1965 and not in 1967 as you say, and it is not hypothetical; one number is based on the black start capacity system operators file and pay power plant operators for, and the other is based on actual black start events.

It is true that that is not why nuclear plants are sited near water.

Just because the nuclear plant is connected to an active grid (in the process of restarting or otherwise), doesn't mean the grid has capacity to supply power for the plant to start.

The 1967 study was conducted in the wake of the 1965 blackout.

The never finished first polish NPP had hydroelectric starter in the form of pumping water plant built with reservoir on nearby hill. But that kind of setup appears to be pretty rare.