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DIY heavy water reactor

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69 pointsstenl21 comments

I don't believe him.

1kg of uranium spread into 10x ingots, suspended in a pool of heavy water ... I don't think this is sufficient to actually maintain criticality, even if he had a startup neutron source. There isn't nearly enough mass. A commonly cited figure for a CANDU reactor is ~8 kg, in a well-designed geometry, with a properly designed reflector in addition to the moderator.

He used metallic uranium instead of uranium oxide. Therefore, I don't think he had a sufficient neutron source to get the chain reaction started. For example, modern power reactors rely on (alpha + oxygen -> neon + neutron) reaction, with the alpha decay of the fuel as the alpha source.

"Should the reactor run away" Water-moderated reactors have a negative temperature coefficient of reactivity. So if he actually achieved criticality and generated enough power to produce heat, the reactor would be self-regulating.

Ditto - there's quite a bit here that suggests it's a fabrication, as had someone done this they'd want to talk about the gritty technical challenges they overcame, not gloss over them.

That said, if you want to play nuclear physicist, there are plenty of fun home projects. Farnsworth fusors can be built cheaply by a dedicated amateur, and you can build your own particle accelerator (cyclotron or synchrotron, take your pick) if the fancy takes you. Easier yet is making a cloud or bubble chamber, and you can use all sorts as a particle source.

Me too. Looks like a 4chan story.

> even if he had a startup neutron source

In the words of my [nuclear engineering] professor: "criticality is a property of the system and is independent of any external source." 1kg of uranium isn't enough to form a critical mass, period. Nothing else really matters and adding a source doesn't change that. It's possible this person built something that experienced induced fissions, but a self-sustaining chain reaction (i.e., a reactor) is not.

The bullshit-o-meter is off the scale on this one. So this individual left centrifuges for two years separating heavy water, and went around the countryside, geiger counter on hand, picking up uranium ore?

And then, after the experiment was done, he just filled the room (which had to be built by himself, no contractors here) with concrete, casually picked up with a truck and dumped far offshore?

That's something you would do in Minecraft, not real life.

Regarding heavy water separation, the BS article says:

> All the water in the world contains light water H20, heavy water D20 and very heavy water T20. ... The thing we need to know is that in every 5 liters of tap water there is 1 cc (cubic centimeter) of heavy water. Now heavy water is 17% heavier that light water. ..

That leaves out HDO, or semi-heavy water. Quoting now from https://en.wikipedia.org/wiki/Heavy_water#Semiheavy_water:

> In normal water, about 1 molecule in 3,200 is HDO (one hydrogen in 6,400 is in the form of D), and heavy water molecules (D2O) only occur in a proportion of about 1 molecule in 41 million (i.e. one in 6,4002). Thus semiheavy water molecules are far more common than "pure" (homoisotopic) heavy water molecules.

The 1:5000 ratio (1cc in 5L) is much closer to the 1:3200 ratio for semi-heavy water, not the 1:41 million for D20.

The BS article also says:

> [Heavy water] is considered a munition so you can not just go and and buy some without all kinds of legal documentation and permits

United Nuclear says there are no restriction. See http://unitednuclear.com/index.php?main_page=product_info&cP... . Also, a kilo costs $725.

Sigma-Aldrich sells it at http://www.sigmaaldrich.com/catalog/product/aldrich/151882?l... . 4 kilos @ 99+% pure costs about $4,000.

I was thinking the same. I remember looking when considering building a Fusor and found that deuterium gas was relatively affordable. Why not simply react high purity deuterium gas and oxygen to form the heavy water? Or just buy heavy water directly as you have noted.

Wasn't there a graduate student who wrote thesis about building an atomic bomb from readily available resources. I don't remember if his work was ever published, but I certainly remember reading about this.

Update: https://en.m.wikipedia.org/wiki/John_Aristotle_Phillips

If this is phony, then it shouldn't be on the front page of HN. And if it's true, it should not be on the front page of HN. Humanity as a whole doesn't need more people building reactors in their garage... Svetlana Alexievich's book "Voices of Chernobyl" is an excellent explanation why.

This is really impressive and shows that the basics of nuclear technology aren't all that complicated in small scale. Just like fire requires a spark and oxygen, a fission reaction really only requires a fissionable metal and an appropriate moderator.

Interestingly, given the right conditions, chain reactions can take place with very little effort. There is one known example of a natural nuclear reactor that was in operation for a few hundred thousand years (2 billion years ago). https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto...

This just has to be a hoax. It's too conveniently packaged to be true. Bad spelling and grammar make it less believable.

Horrifying. Hope this is a joke.

If this sort of thing isn't going on or hasn't gone on, I'd be surprised.

It's completely believable. See: https://en.wikipedia.org/wiki/David_Hahn

That doesn't make it any less terrifying. This kind of thing is how you end up with a superfund site on your hands.

Maybe, I'm more worried about local industry's contribution than some science nerd's overly-ambitious projects.

It would be preferable if the suddenly-wealthy tinkerer was inspired to build a solar farm instead, yes. Or even a thorium reactor. I would think that refining your own uranium would be fairly hazardous to your own health, even if it wasn't enough to leave much of dangerous cleanup site.

I remember reading that and it's much more believable.

I really wanted to try it butnof course didn't but the smoke detector americium and aluminum pie plates always makes me laugh.

And "they were sawing up the shed with electric saws and a uffing the pieces in barrels".

We need to get that German lady BioNerd here to verify these stories.

This feels more like "I read the Wikipedia article about CANDU and wrote a story from it."

That's what I was thinking. The author glosses over years and years worth of tricky engineering problems, particularly regarding heavy water production.

Sheldon? Is that you?

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