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Specular reflection of neutrons?
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Peter Fairbrother
Dec 31, 2011, 2:09:39 PM12/31/11
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Does anyone know anything about this? I's probably getting a bit
star-wars, but what I have in mind is a power application.
A central reactor acts as a source of neutrons, which are fed into
several just-sub-critical outer reactors. The neutron amplification in
the outer reactors is sufficient to produce most of the power.
Why? Well first of all you only have to control one reactor using
traditional methods. The outer reactors can be controlled much more
easily. This reduces problems related to loss of control.
Specular reflection would be a good way to control the outer reactors,
plus it means the reactors can be physically further apart, and thus
much bigger overall - think tens of megawatts per reactor suite.
Second, the outer reactors can be dirty (by which I mean you can chuck
almost any old radioactive junk in there, especially spent rods and
unwanted nuclear weapons) very high temperature molten salt fuelled fast
reactors.
Imagine that, people paying to give you most of your fuel :)
I'm not thinking of the traditional molten salt reactor here, but of a
much simpler one where the fuel is dissolved in ordinary salt, sodium
chloride, mixed with potassium chloride. Operates at up to 1380 K.
The chlorine is not isotopically purified - there is no fluorine present
to form sulphur hexafluoride from the sulphur formed from Cl-35 - though
enrichment in Cl-37 (which is much cheaper than purifying out the Cl-35)
might be useful for better neutron ratios, especially if the reactor is
being used to dispose of even-numbered transuranic wastes.
Hydrogen/dueterium/tritium is removed by sparging, but that's about all
the continuous reprocessing done, though exact details depend on the
actual fuel used. [a redacted bit goes in here]
To get a little adventurous, perhaps the central reactor could be
another subcritical molten salt reactor, but fed with a continuous
neutron gun-type source.
Control then becomes very easy and very reliable and almost entirely
fail-safe - and the few non-safe "spectacular" failure modes do not
involve the release of any nuclear material if very simple precautions
are used. Ordinary everyday leaks are of course still possible, but are
inherently likely to be less than those from a BWR or PWR complex.
Oh, and of course these reactors don't melt down. :)
They are already molten. If they get too hot through a loss of control
or a criticality incursion (which is almost impossible, their action is
inherently opposed to such incursions), the molten salt melts a safety
plug and the salt runs down into air-cooled tubes, where it can safely
stay forever without cooling or other attention.
You'd probably want to keep people out so they didn't pinch anything,
and in the first few days people right next to the tubes would get
fried. but that's about all.
It isn't like a meltdown in an ordinary reactor where the molten core
("corium") can undergo further incursions, or where active cooling is
needed - the rate of heat production is much lower for the corium
produced in a PWR/BWR meltdown.
Anyway, if useful specular reflection could be used, even at low angles,
it would make things simpler and better. So, any experts out there?
Thanks,
-- Peter Fairbrother
star-wars, but what I have in mind is a power application.
A central reactor acts as a source of neutrons, which are fed into
several just-sub-critical outer reactors. The neutron amplification in
the outer reactors is sufficient to produce most of the power.
Why? Well first of all you only have to control one reactor using
traditional methods. The outer reactors can be controlled much more
easily. This reduces problems related to loss of control.
Specular reflection would be a good way to control the outer reactors,
plus it means the reactors can be physically further apart, and thus
much bigger overall - think tens of megawatts per reactor suite.
Second, the outer reactors can be dirty (by which I mean you can chuck
almost any old radioactive junk in there, especially spent rods and
unwanted nuclear weapons) very high temperature molten salt fuelled fast
reactors.
Imagine that, people paying to give you most of your fuel :)
I'm not thinking of the traditional molten salt reactor here, but of a
much simpler one where the fuel is dissolved in ordinary salt, sodium
chloride, mixed with potassium chloride. Operates at up to 1380 K.
The chlorine is not isotopically purified - there is no fluorine present
to form sulphur hexafluoride from the sulphur formed from Cl-35 - though
enrichment in Cl-37 (which is much cheaper than purifying out the Cl-35)
might be useful for better neutron ratios, especially if the reactor is
being used to dispose of even-numbered transuranic wastes.
Hydrogen/dueterium/tritium is removed by sparging, but that's about all
the continuous reprocessing done, though exact details depend on the
actual fuel used. [a redacted bit goes in here]
To get a little adventurous, perhaps the central reactor could be
another subcritical molten salt reactor, but fed with a continuous
neutron gun-type source.
Control then becomes very easy and very reliable and almost entirely
fail-safe - and the few non-safe "spectacular" failure modes do not
involve the release of any nuclear material if very simple precautions
are used. Ordinary everyday leaks are of course still possible, but are
inherently likely to be less than those from a BWR or PWR complex.
Oh, and of course these reactors don't melt down. :)
They are already molten. If they get too hot through a loss of control
or a criticality incursion (which is almost impossible, their action is
inherently opposed to such incursions), the molten salt melts a safety
plug and the salt runs down into air-cooled tubes, where it can safely
stay forever without cooling or other attention.
You'd probably want to keep people out so they didn't pinch anything,
and in the first few days people right next to the tubes would get
fried. but that's about all.
It isn't like a meltdown in an ordinary reactor where the molten core
("corium") can undergo further incursions, or where active cooling is
needed - the rate of heat production is much lower for the corium
produced in a PWR/BWR meltdown.
Anyway, if useful specular reflection could be used, even at low angles,
it would make things simpler and better. So, any experts out there?
Thanks,
-- Peter Fairbrother
Norm X
Jan 1, 2012, 3:30:29 PM1/1/12
to
As far as I know, specular reflection of neutrons works best (i.e. 100%
efficiency) with beryllium coated quartz at 0.004 Kelvin. The interesting
thing is that under those conditions any minuscule quantity of fissile
material is such a container would become instantly supercritical!
efficiency) with beryllium coated quartz at 0.004 Kelvin. The interesting
thing is that under those conditions any minuscule quantity of fissile
material is such a container would become instantly supercritical!
Norm X
Jan 1, 2012, 3:44:17 PM1/1/12
to
can recall the second best material for specular reflection of neutrons is
Thorium (IV) carbide, ThC at any temperature. Check the open source
literature for more fun ideas.
Peter Fairbrother
Jan 1, 2012, 9:30:01 PM1/1/12
to
Reminds me of what was originally thought of Vinge's "bobbles", though
they didn't turn out this way - an impenetrable bubble of force, often
formed around an about-to-explode nuclear bomb.
So, bomb goes of in impenetrable bubble - what happens? The bomb
reactions probably go okay, though reflection might mess then up a
little, but then any fission reactions are going to completion and the
resulting thermal landscape should be enough for any fusion reactions,
or any unlikely fission reactions in an outer fission shell, to go to
completion too.
I reckon that's going to be about 2 or 3 times the nominal yield for a
medium bomb. It's going to be very hot in there. It can't expand, or
lose energy to the outside - so, for 20 points, will it stay hot?
> I remember doing some research on this rather naughty topic. As best
> as I can recall the second best material for specular reflection of
> neutrons is Thorium (IV) carbide, ThC at any temperature. Check the
> open source literature for more fun ideas.
Thx,
-- Peter Fairbrother
Norm X
Jan 1, 2012, 10:59:37 PM1/1/12
to
"Peter Fairbrother" <zenad...@zen.co.uk> wrote
> Any literature suggestions?
Literature suggestions are hard to come by but in case you are an agent for
a wanna be nuclear power, I've stashed some pictures of the internals of the
Tsar Bomba:
https://sites.google.com/site/tsarbombapics/
I've not yet completed an engineering analysis but you might want to
complete the work for me. Thanks.
> Any literature suggestions?
Literature suggestions are hard to come by but in case you are an agent for
a wanna be nuclear power, I've stashed some pictures of the internals of the
Tsar Bomba:
https://sites.google.com/site/tsarbombapics/
I've not yet completed an engineering analysis but you might want to
complete the work for me. Thanks.
Peter Fairbrother
Jan 2, 2012, 12:02:11 AM1/2/12
to
http://groups.google.com/group/alt.war.nuclear/msg/cf4009f93814462d
but the whole thread may be of interest
http://groups.google.com/group/alt.war.nuclear/browse_thread/thread/85570a11e5a72952/cf4009f93814462d?#cf4009f93814462d
An approximately-to-scale interior view might be something like:
http://www.zenadsl6186.zen.co.uk/rect3925.png . Sadly, I don't remember
where I put the numbers I calculated and used in the design, but they
were all open-literature.
I do remember thinking later that the tertiaries were a little on the
small side, and redid the drawing more accurately to scale, but the
redone drawing didn't get posted and is probably lost now. It wasn't
that different.
Though I don't know whether that does anything to prove or disprove my
agent-for-a-wanna-be-nuclear-power status. :)
BTW, any comments on the reactor suite design? It works better with
specular neutron reflection, but it would still work without it.
I particularly like the inherently safe, low pressure, cheap, fast
neutron (like a breeder, but it destroys transuranics rather than making
them), and high temperature aspects.
-- Peter Fairbrother
Norm X
Jan 2, 2012, 3:37:18 PM1/2/12
to
Sorry, I should not have brushed you off so quickly.
A little bit of Googling turns up the following catalog from The China
Tungsten Company:
http://www.chinatungsten.com/dictionary-of-tungsten/dictionary-of-industrial-nuclear.pdf
You might want to correlate the Chinese characters for "thorium carbide"
with those for "neutron shield" or "neutron reflector". Both thorium-232 and
carbon-12 have desirable neutron scattering properties. However, pure carbon
is amorphous and neutrons diffuse into it. Likewise, all metals occur as
assemblies of disordered microcrystals and so neutrons would diffuse into
thorium. However, Thorium (IV) carbide, ThC can be prepared in a rock salt
crystal form. What you want to do is to prepare a giant crystal of ThC. This
is done routinely for silicon. It is only a matter of money and technology.
Maybe The China Tungsten Company would do the work for you. Then slice the
giant crystal into many thin slices each of which has an ordered crystal
structure.
When neutrons impinge on an ordered crystal structure they refract at
several angles depending on energy and at low angles they reflect. Pure
crystalline Thorium (IV) carbide, though expensive, should comes as close as
possible to 100% efficiency for the specular reflections of neutrons that
you want.
I hope this helps.
A little bit of Googling turns up the following catalog from The China
Tungsten Company:
http://www.chinatungsten.com/dictionary-of-tungsten/dictionary-of-industrial-nuclear.pdf
You might want to correlate the Chinese characters for "thorium carbide"
with those for "neutron shield" or "neutron reflector". Both thorium-232 and
carbon-12 have desirable neutron scattering properties. However, pure carbon
is amorphous and neutrons diffuse into it. Likewise, all metals occur as
assemblies of disordered microcrystals and so neutrons would diffuse into
thorium. However, Thorium (IV) carbide, ThC can be prepared in a rock salt
crystal form. What you want to do is to prepare a giant crystal of ThC. This
is done routinely for silicon. It is only a matter of money and technology.
Maybe The China Tungsten Company would do the work for you. Then slice the
giant crystal into many thin slices each of which has an ordered crystal
structure.
When neutrons impinge on an ordered crystal structure they refract at
several angles depending on energy and at low angles they reflect. Pure
crystalline Thorium (IV) carbide, though expensive, should comes as close as
possible to 100% efficiency for the specular reflections of neutrons that
you want.
I hope this helps.
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