Are nuclear batteries possible?

[Pseudo Epsilon]

is it possible to make a nuclear "battery" which works off nuclear not electrochemical reactions using berylium/graphite shielding?

 

[mfb]

It is
Please try to look up those things yourself first. It takes you less time than posting here.

 

[Pseudo Epsilon]

i meant fission or something more powerful?

 

[mfb]

That would be a nuclear reactor. Fission is just one type of nuclear reactions.

 

[Pseudo Epsilon]

i know that but what I am asking is:theoreticly can you make a nuclear reactor 50cm by 50cm asuming the u-235 was dense enough to reach critical mass?

 

[mfb]

Without shielding and heat sinks... yes.

The reactor measured 39.62 cm (15.6 in) long, 22.4 cm (8.8 in) diameter and held 37 fuel rods containing ²³⁵U as uranium-zirconium-hydride fuel.

 

[QuantumPion]

i know that but what I am asking is:theoreticly can you make a nuclear reactor 50cm by 50cm asuming the u-235 was dense enough to reach critical mass?

You can make one even smaller than that. For Pu-239 with a reflector it can be as small as a sphere with radius ~5 cm.

 

[mfb]

Well, a sphere of plutonium is not a reactor. You need moderation, control mechanisms, cooling cycles, power generation and so on.

 

[Pseudo Epsilon]

if it got to 5cm couldn't you just use thermionic methods of power generation instead of steam?

 

[QuantumPion]

Well, a sphere of plutonium is not a reactor. You need moderation, control mechanisms, cooling cycles, power generation and so on.

Well you don't need a moderator for a reflected plutonium sphere. And it can be designed to be self-regulating. But you're right that it would still need a coolant system, heat exchanger, and thermoelectric converter to actually produce electricity. I imagine the SNAP-10 reactor, at about the size of a microwave oven, is about as small as one could be practically made.

 

[Pseudo Epsilon]

assuming break even fusion was achieved how big do you think the smallest fusion reactor could be?

 

[QuantumPion]

assuming break even fusion was achieved how big do you think the smallest fusion reactor could be?

Enormous. The ability of a magnetic confinement fusion reactor to produce power is proportional to its volume. ITER will hopefully be the first reactor to achieve better than break-even, I think it has a diameter of something like 20 meters.

 

[Pseudo Epsilon]

out of the hypothetical methods of fusion (inertial, z-pinch, laser ect..) what would be the smallest?

 

[QuantumPion]

out of the hypothetical methods of fusion (inertial, z-pinch, laser ect..) what would be the smallest?

There are no laser confinement fusion methods close to achieving breakeven, and even if they were they are even more massive machines than the tokamak. There is no compact way to producing fusion power, as all of the various methods require enormous power inputs in either magnetic fields or lasers to produce the conditions required for fusion to occur. These simply cannot me miniaturized.

 

[mfb]

Well, there is a method to use fusion power within the size of a vehicle. It is a very destructive method, however ;).

 

[Pseudo Epsilon]

lol, what is the energy needed to initiate fusion?

 

[mfb]

In weapons? You need a fission bomb to start fusion, conventional explosives are not powerful enough.