Re: New fusion power system test creates 300,000 degrees C plasma

It's like electronic design. Splatter your brain all over the solution space and invent things.

There are myriad ways to create havoc, if we wanted to. I have castor plants in the garden. They are very decorative. Properly distributed, there is enough ricin in them to kill tens of thousands of people. Nobody cares. Weaponizing noxious substances isn't so easy.

Jeroen Belleman

Wiki claims

I think so.

Jeroen Belleman

John Larkin hasn't invented anything - based on his patent count - and it shows.

The process doesn't involve splattering your brain across the solution space but rather tracking down initially implausible trains of thought.

You are exploring the solution space, as opposed to sampling it at random.

Perhaps. It's a calculated critical mass. Nobody seems to have assembled a marginally sub-critical mass and done experiments on it, probably because it would be very radioactive and quite hot. The wikipedia page does say that it is unsuited to making nuclear weapons. They don't spell out why.

Googling has many references and some papers, all around 10 Kg unshielded, half that with a good neutron reflector.

I suppose something that doesn't normally emit neutrons can still fission, from a cosmic ray or something.

All 5 plutonium isotopes have a critical mass, at which point I assume that Something Bad happens.

Quite a lot is known, if not by you.

It's temperature rather than pressure that makes the difference.

Of course it has to. Gravitational compression created the pressure and the heat that eventually started the nuclear reaction. It takes about

That's a relief. You mostly ventilate your idiocies non-stop.

Not really. We wouldn't understand them.

Most species last about 10 million years. We might completely wreck the earth and kill ourselves off in the process, but we've survived several ice-age to interglacial transitions.

Just a bit bigger than ants, with rather more technology.

Another one of your mindless assertions.

There is plenty you can "know" that isn't known to other people.

You produce more nonsense than most, and most of what you think you know strikes other people as largely unoriginal nonsense.

"It does not have to be break even or positive at all."

You don't have to assume anything. Critical mass is the point where some neutron showing up anywhere in the critical mass is likely to hit another atom and produce enough neutron that one of them will hit another atom somewhere in the mass before it escapes.

If the atom it hits immediately produces a batch of prompt neutrons, you may get a lot of energy released before the critical mass melts and dribble away.

Nuclear reactors are controllable because U-235 doesn't seem to emit all it's neutrons all at once and the ones that show up late give you time to push in the control rods before the process runs away.

You haven't been paying attention, or perhaps you can't plug the text version of an LTSpice .asc file into LTSpice.

It was a perfectly okay fridge, for some unusual applications. Theoreticians don't do experiments, and the Pauli Effect suggests that they stop experiments from working. Wolfgang Pauli and Pqul Dirac didn't do any experiments either, and that didn't stop them from being almost as famous as Einstein.

Don't be silly. His letter - with Leo Silzard - to Roosevelt didn't have anything to say about using the atom bomb. It just pointed out that such a bomb was possible, and that Germany might be working on it.

In your demented opinion.

Looking up during the day confirms something rather different.

ITER hasn't done anything yet. The Joint European Torus in England worked well enough to demonstrate that ITER was worth doing.

It seems the most likely outcome. We wouldn't have invested in it if it wasn't. Of course if they found a reason why a bigger torus won't actually deliver the goods, they would report that too. That's why people do scientific experiments.

Not my tax money. I live in Australia and pay my taxes to the Australian government

Evolution does produce a lot more duds than successes. You seem to be one of them.

More sophisticated bomb design likely requires less plutonium.

Joe Gwinn

Making bombs with plutonium is complicated. Anyway, that was not our interest. The subject was using 238Pu to generate heat to provide enough energy for a single, or a small number of households.

Some sources claim that 238Pu has a critical mass of about 10kg, which is odd, because it's not listed as fissile. It's predominantly an alpha emitter.

As a rule, only isotopes with odd mass numbers are fissile. Of course Pu has an exception: 240Pu fissions even without being provoked. Oh well. Incidentally, that's what makes Pu difficult to use for bombs.

Anyway, it's relatively straight-forward to get isotopically pure

So, in summary, the problem is producing enough 238Pu cheaply, containing it safely for widespread use, and combining it with a compact device to produce electricity and domestic heating.

I don't truly believe this has any chance of happening, except maybe for a few special cases, like lighthouses in remote Siberia, or deep space probes, or something.

Jeroen Belleman

Reflectors and tampers reduce critical mass, as does explosive supercompression.

A bit of tritium in the pit helps too. I think the minimal nuke used about 1 Kg of p239.

p238 would be a terrible bomb material. Might work, though, in an implosion bomb with a neutron injector to kick-start things.

p238 isn't "fissile", namely doesn't capture slow neutrons well.

That is my understanding as well.

The US Many B61 warheads are small and/or have adjustable yield.

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There was an 8-inch nuclear artillery shell that would be fired from a big gun.

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Yes.

Joe Gwinn

I think people are mixing Pu238 and Pu239 up.

Yes.

It's the same problem as using Thorium in a nuclear power reactor: It needs a very strong neutron source to keep the Thorium fissioning, and it's hard to make enough neutrons cheaply enough absent a real nuclear reactor to make the neutrons.

In hydrogen bombs, the purpose of the hydrogen part is to make enough neutrons fast enough to make the U238 blanket fission wildly all at once.

Joe Gwinn