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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: New fusion power system test creates 300,000 degrees C plasma
Date: Sun, 1 Dec 2024 13:56:19 +1100
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On 1/12/2024 8:59 am, 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.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>> If, if. Such arguments can be used to prove anything.
>>>>>>>>
>>>>>>>> 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.
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> 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?
>>>>>
>>>>> There's always an idiot (or a terrorist) who would challenge themself to
>>>>> open it.
>>>>>
>>>>>
>>>>
>>>> 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
>>>
>>> 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.
>>
>>>
>>> It would make some cool glow-in-the-dark gadgets.
>>>
>>> Critical mass is around 10 Kg. Kids could make nukes.
>>>
>>
>> 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.
>>
>> Jeroen Belleman
> 
> Wiki claims
> 
> https://en.wikipedia.org/wiki/Plutonium-238
> 
> 10 Kg critical mass. Are they wrong?

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.

-- 
Bill Sloman, Sydney