Do 2 Kilowatt Nuclear Reactor Still Exist

average guy

i was told that the smallest nuclear reactor power
station is 2 Kilowatts and they take up about
half a city block?
is that correct?
can they be built?

Have A Nice Day!

Simon Bridge

What makes you think there is a lower limit to the power output to a nuclear power plant?
If nothing else, you could just use a normal one to drive a really really inefficient generator :)

Even sub-critical masses of radioisotopes can produce enough heat to do useful work.

average guy

simon
your question/answer:
1 i don't know
2 doesn't sound like a good idea.
3 that went over my head.
can a 2 Kilowatt Nuclear Power Generator be
built the size of a city block?

Have A Nice Day!

Pengwuino

2 KW is extremely small in terms of power generation. They sell gasoline generators at the store that you can put in your trunk that will do that. I would be very surprised if you couldn't build a reactor of that size in a very small foot print. There would be considerations for shielding and a lot of other things, but I don't see any theoretical reason why it would not be possible. Hell, how big are nuclear reactors in submarines? They produce a couple dozen megawatts

Simon Bridge

[after a sleep and a cup of coffee]
I suppose I could break this into two parts:
1. is the historical 2kW plant still running? (which one?)
2. what is the minimum power from a supra-critical core? eg. how far can you damp a critical mass and still have a chain reaction?

close enough?

note: we usually think of a nuclear reactor as like the one in Fukushima and Chernobyl[1] - these exploit a nuclear chain reaction to produce heat to run a steam engine, which is hooked to an electric generator. To get a chain reaction, you need a minimum mass of fuel ... called a "critical mass".

However, the fuel gets warm before it goes critical.
You can get a few tens of grams of plutonium, for eg, and insulate it, and it can get red-hot quite quickly.
You can use this to drive, say, a stirling engine ... or a thermo-couple. These things are normally called nuclear "batteries" rather than reactors but I would argue that this is just spin. "Battery" sounds nicer than "reactor".

Now I could take a nuclear battery and just connect it to something that will glow - so it becomes a nuclear powered light.

One way of doing this, rather than go through a generator and wires and stuff, is to just surround the fissioning material with glass coated with phosphor (or whatever) so it glows when the fission fragments hit it. This is how beta-lights work... from beta-decay (a nuclear reaction). So if I am going to be really general by defining a nuclear power reactor as any machine which generates useful power from nuclear reactions, I'll have to include beta-lights as nuclear reactors. Which may be pushing the definition a tad :)

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[1] the building you see on the news are much much bigger than the actual reactor itself. Similarly, the "city block" sized plant would just be the building.
iirc the first atomic pile fit comfortably inside a squash court.

russ_watters

I suppose you could take a thousand megawatt reactor, pull 2 kW off it and dump the other 999,998 kW as waste heat...

Astronuc

I've not heard of a 2 kWe nuclear power plant. Would it be a simple thermal plant for district heating. A capacity of 2 kWe is an appropriate capacity for 1 home. Half a city block would be wasted on 2 kWe.

I'll have to check my records, but the smallest nuclear electrical plant of which I'm aware was Big Rock Point at about 60 MWe.

Simon Bridge

Yeah - the really really really inefficient generator idea.
Just cause you are producing the energy does not mean you have to use it ... but where's the fun in that?

It's been too long since I did any nuclear chain reaction stuff ... not actually being interested in nuclear power (being in NZ and all) at the time.
iirc the reaction rate broadly depends on the range of the fast neutrons v how diffuse the fuel is (and the kind of moderator)? Wasn't there a naturally occurring reactor in prehistory that was very slow?

average guy

simon
i may have the rating number wrong, it's been more than
8 years since i talked to this person.
what is the smallest true nuclear power plant that
can be built and it's power output?

Have A Nice Day!

Simon Bridge

define "nuclear power plant"
The Radioisotope thermoelectric generators in spacecraft are of order of 100s of Watts and about man-sized. Voyagers were 470W. Pic from Cassini probe:
... weighs 57kg and outputs 300W

Astronuc

The AGN-201M has a power of 5 W. It's nice for practicing reactor startup, or analyzing neutron source strength, differential rod worth, approach to criticality.

It would be impractical for any power generation.

average guy

simon
what most people would consider a nuclear power plant.
the guy said it can be built in less than a city block and
it generates electricity and is nuclear powered.

astro nuke
think bigger!

Have A Nice Day!

Schr0d1ng3r

Well, the research reactor at my school is rated at 5MW(t), and the reactor facility takes up MUCH less than half a block. I know there are SLOWPOKE reactors that run around 20kW(t), so there's no reason that I can see preventing one from making a 2kW(e) nuclear power station in half a block or less. There's just no point...

Pengwuino

I love it.

average guy

schroding
sure there is!
there's that 2!
20 kilowatt was probably what he was talking about!
the idea is to have people work at them and
get used to them.
the neighborhood GE Nuclear Power Plant!
sounds like a winner to me!
penguin
what do you love?

Have A Nice Day!

Simon Bridge

Oh yeah but there were already others chiming in who knew about the other kinds.
eg Astronuc was checking records...
I think these ones are cool.

Admittedly the AGN-201M probably takes the prize.

But mine is much cooler to look at xD
I mean it is black and shiny and has fins and it sits in a precision engineered clamp - not some old bits of 2x4... look, it's the porsche of nuclear technology - you don't see any women checking out the AGN in that pic do you? No! Case closed. ;)

Ryan_m_b

To put the 2KW figure into perspective; I'm sitting next to an electric heater that consumes so much. A "city block" sized reactor to fuel that would indicate a gargantuan waste. IIRC a normal nuclear reactor operates at 1 million times this.