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

On Sun, 1 Dec 2024 19:49:12 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:

On 12/1/24 18:46, Joe Gwinn wrote:

On Sat, 30 Nov 2024 23:54:54 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
 

On 11/30/24 22:59, john larkin wrote:

On Sat, 30 Nov 2024 21:12:23 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
>

On 11/30/24 18:19, john larkin wrote:

On Sat, 30 Nov 2024 11:57:50 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
>

On 11/30/24 10:34, Liz Tuddenham wrote:

Jeroen Belleman <jeroen@nospam.please> wrote:
>

On 11/29/24 23:03, Liz Tuddenham wrote:

Jeroen Belleman <jeroen@nospam.please> wrote:
>

On 11/29/24 21:04, Liz Tuddenham wrote:

Jeroen Belleman <jeroen@nospam.please> wrote:
>
[...]

It would be lovely to have 50kWTh or so of PU238 in the basement,
if it could be made cheaply enough. Power for a lifetime for the
whole house and then some.

>
...but the lifetime might not be very long if any got out.
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>

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If, if. Such arguments can be used to prove anything.
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I've got a diesel-powered car in the basement garage. Fully tanked,
it contains 60kg of fuel, good for 2.4GJ or so. Imagine the havoc
that could cause, if it got loose. For reference, a stick of dynamite
is about 1MJ.

>
I've seen what happened when builders accidentally set fire to a tank of
diesel far bigger than that.  It burned slowly and steadily until it set
fire to the roof of the house - then the house burned down.  Nobody was
injured or killed, the mess was easily cleaned up and a new house built
on the site.
>
It wasn't like the sudden release of energy you would get in a fuel-air
explosion (quite difficult to initiate with diesel without specialist
knowledge) and there wasn't a lot of residual toxic contamination.
>
>

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OK. Now back to small 238Pu fuelled units. Why would you expect
anything to go wrong if the Pu was contained in a hermetic canister?

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There's always an idiot (or a terrorist) who would challenge themself to
open it.
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>

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Yes, probably. There have been similar incidents in the past.
I'm convinced it can be made safe enough for widespread normal
use, but there will always be some fool somewhere. If we let
that stop us, no technology is safe enough.
>
Jeroen Belleman

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A kilogram, properly distributed, would make a city uninhabitable for
centuries. Imagine such an active alpha emitter in a water supply.

>
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.
>

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It would make some cool glow-in-the-dark gadgets.
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Critical mass is around 10 Kg. Kids could make nukes.
>

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238Pu doesn't sustain a chain reaction, at least not in the quantities
we talk about. Nukes use 239Pu, the fissionable isotope. That's the
isotope that has a critical mass in the 10kg ballpark. Even then, it's
*very* hard to keep it together for long enough to create a sizable
explosion. No kid is going to pull that off, even if he could get his
hands on 239Pu in sufficient amounts.
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Jeroen Belleman

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Wiki claims
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https://en.wikipedia.org/wiki/Plutonium-238
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10 Kg critical mass. Are they wrong?
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I think so.
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Jeroen Belleman

 
More sophisticated bomb design likely requires less plutonium.
 
Joe Gwinn

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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.

I think people are mixing Pu238 and Pu239 up.

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
238Pu, that is, if anything can be called straight-forward in this
area. Even if it could be provoked to fission, it shouldn't be
too hard to distribute it such that that doesn't get supercritical.
Alloy it with 50% of Al and shape it into long rods, dope it with
boron, or something else yet, I haven't really looked into that
much detail.
>
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.

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