Creationism is a mental illness (Page 280)

The water that is inside the nuclear reactor facility to cool it becomes Heavy Water and as such is not mixed with the cooling water that is in a heat exchange system.

Confirming what I said "Now the cooling system is (nowadays) 𝐚𝐥𝐰𝐚𝐲𝐬 𝐚 𝐝𝐨𝐮𝐛𝐥𝐞 𝐬𝐞𝐩𝐚𝐫𝐚𝐭𝐞𝐝 𝐬𝐲𝐬𝐭𝐞𝐦!"

The first cooling system is the steam cirquitry and is the primary cooling system of the reactor; the secondary cooling system is the one that cools down the "primary cooling system" and is completely "separated" from the other.
The primary cooling system is always a closed cirquit, the secondary mostly an open cirquit. What means "cold"water is pumped up from a water source and the "heated" water is (mostly) "dumped" back where it came from ...
It is, technically (till now) , the most efficient thermal exchanging method.

I understand Canada uses a less refined Uranium reactors that do not melt down should the water pumps fail.

You mean less enriched Uranium I suppose: it is possible. I have no knowledge about what type of enriched Uranium used in Canadian Nuclear powerplants (also the type of powerplant)
Anyway as far I can understand the used Uranium needs a minimal enrichment to be functional.

https://www.nuclear-power.com/nuclear-power-plant/nuclear-fuel/nuclear-fuel-cycle/uranium-enrichment/#:~:text=Uranium%20enrichment%20is%20a%20process%20in%20which%20the,the%20nuclear%20power%20plant%20operator%20%28e.g.%2C%20cycle%20length%29.

Isotopic decay produce heat: the more and faster decay "needed", the more heat has to be dissipated!
The technical best heat dissipation is by producing high-pressure steam that can activate high-pressure turbines. After that: the presure is lowered and the steam condensed in those big condensation towers to be used again.
That's the basically explained type of system that is used.

Right, I was talking to a nuclear engineer that worked on Canadian power plants, their design is for less enriched, so that if it gets shut down, it doesn't take outside power to keep the rods cool.

Possible: I have again no knowledge and the engineer will know it better than me
There are also two methods to control the "chain reaction": adding carbon rods between the Uranium or removing Uranium rods. The fission stops normally when the total mass of U is either under the critical mass or enough neutrons are absorbed by i.e. carbon. You need electrical power to do that.

Belgian,, true, but what I was thinking about was the situation of Fukashima, where they lost power and melted down even though the reactors were shut down.

If I recall my history well; Fukushima is not the first meltdown.

As long enriched U is above its critical mass fission occurs with the consequent of "heat production" that has to be be dissipated - evacuated in some way.

To bad Zeff isn't here to answer all our nuclear engineering questions...lol

yup; he might have used it to get his He or H² balloon above the "von Karman" line

the foresight you created isn't mental. police investigate themselves come to the same conclusions.

The only lessons we can have from all those meldowns are : you cannot have 100 % safe enginered constructions and nothing is perfect

Presupposing to teach Hakuna Matata. Same mental illness, opposite side of the expert coin.

That has always been the crux of the issue, they see the bible as the holy work of God, and as such has to be believed verbatim