how to restart a fusion reactor in space?

[Kozak]

any ship that massive will be carrying enough fuel to make multiple attempts.

and the Tu-199's reactor was heavier than 10-tonnes IIRC. and the shielding was a bit crap.

Hard to argue with someone who forgets what you've said a minute ago...

 

[the.punk]

But the problem of an fission reactor is the "waste" that is produce. And this waste is radioactive. And a fusion reactor don't has this waste. The only thing that is produced is helium. But you're right that the fusion reactor itself is very very radioactive because of the high energetic neutrons and for this reason very dangerous.
The sun uses the same way to produce energy and I don't want to stand nearby it.
The big problem of a fusion reactor is the heat. But maybe we can handle this in any way.

 

[insane_alien]

DW, where exactly did i do that? i can't see anything that suggests that.

 

[RisingFury]

But the problem of an fission reactor is the "waste" that is produce. And this waste is radioactive.

Exactly, so why would you wanna have a fission reactor on board?

Even if you "stop" the reactor, the fuel is still radioactive and the reaction isn't completely stopped.

 

[the.punk]

Exactly, so why would you wanna have a fission reactor on board?

Even if you "stop" the reactor, the fuel is still radioactive and the reaction isn't completely stopped.

Exactly that I mean. That's why I don't like those fission reactors.
The "waste" is the big problem of fission reactors.
Fusion reactors don't have this "waste. They are radioactive when they are on.

 

[RisingFury]

When you say fusion reactor are only good when they are big than I think it would be good to have a fission reactor as backup to star the main fusion.

^^ then why all this?

 

[willy88]

I think we need a guide or something...

 

[the.punk]

^^ then why all this?

I don't like those reactors. But maybe one for the emergany that the fusion reactor stops. And then to restart is. I meant that this fission reactor is offline the whole flight and only when this emergany happens it will be started.
But I still think that it is an old technology and that they are not so good.
This was just an quick idea I had. Nothing that changes my opinion.
I don't like them.

 

[jedidia]

I meant that this fission reactor is offline the whole flight and only when this emergany happens it will be started.

Well, that is just one of the big problems of a fission reactor: once you start it, you cannot really shut it down anymore. Not without throwing your plutonium rods out of the window, anyways...

 

[RisingFury]

Well, that is just one of the big problems of a fission reactor: once you start it, you cannot really shut it down anymore. Not without throwing your plutonium rods out of the window, anyways...

It's not like you can *ever* stop it. Nuclear decay occurs weather or not your control rods are all the way in or all the way out.

 

[the.punk]

Well, that is just one of the big problems of a fission reactor: once you start it, you cannot really shut it down anymore. Not without throwing your plutonium rods out of the window, anyways...

Yes. I know that. That's why I don't like those. This was just a quick thought.

 

[jedidia]

It's not like you can *ever* stop it. Nuclear decay occurs weather or not your control rods are all the way in or all the way out.

Well, of course. But when you through the rods out the window of a spaceship, you can consider the reactor as pretty much shut down...

 

[RisingFury]

Well, of course. But when you through the rods out the window of a spaceship, you can consider the reactor as pretty much shut down...

Fuel rods, yea... I meant the control rods that control the speed of the reaction.

 

[jedidia]

errr... the plutonium rods are the control rods? seems I got some misconceptions about a nuke reactor, then. appart from most completely sucseeding in misspelling "throw" in the las post. I wonder how I managed that... :embarrassed:

 

[RisingFury]

Fuel rods are made out of fissile nuclear material that can sustain a reaction. When a nucleus falls apart, it usually releases two large chunks and 2 or 3 neutrons. Those excess neutrons then fly into other nuclei, turning them into unstable isotopes, which then fall apart rapidly and the process continues.

Control rods are a way to control the reaction and extract heat. They're inserted partially into the core to capture free flying neutrons, thus inhibiting the reaction. They're made out of stuff that produces stable isotopes even when neutrons hit it, therefore it effectively breaks the chain. Boron and graphite I can recall off the top of my head... The massive kinetic energy neutrons have, as well as the act of adding a neutron to the nucleus, releases energy.

If the control rods are pulled out of the reactor, the nuclear reaction will speed up because there are more free flying neutrons available to continue the chain. If you push the rods all the way into the reactor, most free neutrons will be captured, thus effectively bringing the reactor to a halt. It won't stop the nuclear reaction completely and it won't prevent nuclear decay from happening by itself... but it will inhibit the reaction enough for no meaningful power to be extracted from the reactor.

 

[the.punk]

Fuel rods are made out of fissile nuclear material that can sustain a reaction. When a nucleus falls apart, it usually releases two large chunks and 2 or 3 neutrons. Those excess neutrons then fly into other nuclei, turning them into unstable isotopes, which then fall apart rapidly and the process continues.

Control rods are a way to control the reaction and extract heat. They're inserted partially into the core to capture free flying neutrons, thus inhibiting the reaction. They're made out of stuff that produces stable isotopes even when neutrons hit it, therefore it effectively breaks the chain. Boron and graphite I can recall off the top of my head... The massive kinetic energy neutrons have, as well as the act of adding a neutron to the nucleus, releases energy.

If the control rods are pulled out of the reactor, the nuclear reaction will speed up because there are more free flying neutrons available to continue the chain. If you push the rods all the way into the reactor, most free neutrons will be captured, thus effectively bringing the reactor to a halt. It won't stop the nuclear reaction completely and it won't prevent nuclear decay from happening by itself... but it will inhibit the reaction enough for no meaningful power to be extracted from the reactor.

Nice explanation. After the fuel rods are burhed down - even then the reaction isn't stoped. Maybe for thousands of years it is radioactive and dangerous.

 

[RisingFury]

Which is why you don't wanna have two types of reactors on board - you have to deal with the disadvantages of both, but you have no major advantage from it.


I agree that fission reactors should become the power source in the short term (next ~10 - 20 years) and I agree that when we gain the capability to put a fusion reactor in space that we should, but there are other, more effective ways of restarting a nuclear fusion reactor.

 

[the.punk]

Which is why you don't wanna have two types of reactors on board - you have to deal with the disadvantages of both, but you have no major advantage from it.


I agree that fission reactors should become the power source in the short term (next ~10 - 20 years) and I agree that when we gain the capability to put a fusion reactor in space that we should, but there are other, more effective ways of restarting a nuclear fusion reactor.

This with the restart with a fission reactor wasn't meant as my opinion. It was was just a quick thought.
And I have changed this, because when I think of it again it isn't so nice to have such fission reactor. Because I think it is an old technology.

 

[TSPenguin]

And let's not forget that fuel for fission reactors is very limited. That makes it at least in the long term not really an option.

 

[the.punk]

And let's not forget that fuel for fission reactors is very limited. That makes it at least in the long term not really an option.

Exactly. Fission reactors are nothing new.
And also the transport and storage of the waste that is still radioactive is very expensive.