nuclear fission

[apples]

hey everyone im doing this thing on nuclear fission and the more i read the more confused im getting lol, some questions:

 

Are there any other decay reactions insides a nuclear core besides ‘236U – Ba + Kr + 3n’

 

How are slow moving neutrons injected into the reactor core of a nuclear power plant

 

If fast moving neutrons from a fission reaction cannot effectively enter a nucleus and initiate fission more fission (too fast), how does it work in a fission bomb? Is there a moderator present?

 

ty

[vincent]

This is the wrong forum for your question. You should have it reposted in the quantum theory forum.

[swansont]

hey everyone im doing this thing on nuclear fission and the more i read the more confused im getting lol, some questions:

 

Are there any other decay reactions insides a nuclear core besides ‘236U – Ba + Kr + 3n’

 

How are slow moving neutrons injected into the reactor core of a nuclear power plant

 

If fast moving neutrons from a fission reaction cannot effectively enter a nucleus and initiate fission more fission (too fast), how does it work in a fission bomb? Is there a moderator present?

 

ty

 

 

There are lots more reactions, but they all start with the U-236 compound nucleus you have after U-235 absorbs a neutron. Technically they are not decays, since they are induced rather than being spontaneous.

 

The fission yield curve shows what the range of products are by mass; you'll get one large and one small one, plus a few neutrons.

 

The slow neutrons are produced by slowing doen the fast neutrons emitted in fission. They aren't really "injected" into the core; they are already there. There isn't a moderator present in a bomb. Fast neutrons can initiate fission, but they generally have a smaller cross-section for doing so. You just have to engineer things accordingly (e.g. the critical mass will be different if you are relying on fast fissions)

[thedarkshade]

There are lots more reactions, but they all start with the U-236 compound nucleus you have after U-235 absorbs a neutron. Technically they are not decays, since they are induced rather than being spontaneous.

 

The fission yield curve shows what the range of products are by mass; you'll get one large and one small one, plus a few neutrons.

 

The slow neutrons are produced by slowing doen the fast neutrons emitted in fission. They aren't really "injected" into the core; they are already there. There isn't a moderator present in a bomb. Fast neutrons can initiate fission, but they generally have a smaller cross-section for doing so. You just have to engineer things accordingly (e.g. the critical mass will be different if you are relying on fast fissions)

 

Yeah, they all do start with U-235. And this link provides quiet good explanation about these things.

 

http://youtube.com/watch?v=fnY_Ug0DabM

 

The Hiroshima Atomic Bomb was build based on these principles. U-235 has the ability to absorb neutron, so you need a neutron to break it into two "smaller pieces". There are some methods of getting neutron, like the Be one. All you got to do is act with alfa rays to a berillium and automatically a neutron shoots out. And when that neutron hits the nucleus of the U-235, it breaks the balance proton-neutron and the nucles breaks into two (Ba-142 and Kr-91, called F-fragments) and releases three neutrons. The probability that the neutron released from Be to hit the nucleus U-235 is quit astronomical, and critical mass in necessary for this to happen. Critical mass is usually spheric so the neutron cannot leak out. And then three other neutron released form U-235 hit the other nucleus' and so it always keeps on doubling. The key thing about uranium bomb is neutron. Super-fast moving neutrons double the other U-235 while the explosion is still in progress, releasing so the largest energy existing (nuclear energy). And it was the energy (heat) that killed all those people in Hiroshima.

 

Another "bad" effect of the nuclear explosion is also radiation. Except the released energy there is also released radiation, which consequences show up gradually. Still today, the level of the radiation on Hiroshima is 10 times higher than normal.

[swansont]

Yeah, they all do start with U-235. And this link provides quiet good explanation about these things.

 

http://youtube.com/watch?v=fnY_Ug0DabM

 

The Hiroshima Atomic Bomb was build based on these principles. U-235 has the ability to absorb neutron, so you need a neutron to break it into two "smaller pieces". There are some methods of getting neutron, like the Be one. All you got to do is act with alfa rays to a berillium and automatically a neutron shoots out. And when that neutron hits the nucleus of the U-235, it breaks the balance proton-neutron and the nucles breaks into two (Ba-142 and Kr-91, called F-fragments) and releases three neutrons. The probability that the neutron released from Be to hit the nucleus U-235 is quit astronomical, and critical mass in necessary for this to happen. Critical mass is usually spheric so the neutron cannot leak out. And then three other neutron released form U-235 hit the other nucleus' and so it always keeps on doubling. The key thing about uranium bomb is neutron. Super-fast moving neutrons double the other U-235 while the explosion is still in progress, releasing so the largest energy existing (nuclear energy). And it was the energy (heat) that killed all those people in Hiroshima.

 

Another "bad" effect of the nuclear explosion is also radiation. Except the released energy there is also released radiation, which consequences show up gradually. Still today, the level of the radiation on Hiroshima is 10 times higher than normal.

 

 

Actually the critical mass in the Hiroshima bomb wasn't spherical. Since they used a gun topology rather than implosion, it was cylindrical. Simpler and more robust, so it had a smaller chance of failure (they never fully tested this design — the Trinity test was an implosion device). The cylinder means a slightly higher critical mass, because of increased neutron leakage. (Leakage never goes to zero)

 

Do you have a cite for the radiation level? All the sources I've seen claim that it's no higher than normal background.

http://www.pcf.city.hiroshima.jp/kids/KPSH_E/question_box/question12.html

[Riogho]

A fission reaction works by bombarding an unstable nucleus with a particle causing it to split in two(or more) smaller more stable nuclei, also it emits a few neutrons. The neutrons then hit another atom, etc etc, causing a chain reaction.

[ydoaPs]

Swansont, the streets were lined in cobalt.

[swansont]

A fission reaction works by bombarding an unstable nucleus with a particle causing it to split in two(or more) smaller more stable nuclei, also it emits a few neutrons. The neutrons then hit another atom, etc etc, causing a chain reaction.

 

The fission fragments are often unstable, which is why nuclear waste is such an issue.

 

Swansont, the streets were lined in cobalt.

 

 

Lol. That would make for a "fun" time for several years, but probably not 60 years later. Both Co-60 (from thermal neutron absorption) and especially Fe-59 (from a proton ejection) have short enough half-lives to be imperceptible above background in that time. (5.25 years and 44 days, respectively)

 

 

Actually, one of the things I ran across was a study from a few years ago where they measured the fast neutron dose by looking at copper samples from the blast area. They didn't have the ability to do this in the WWII era, so they really weren't sure what that exposure was. For fast neutrons you can get ⁶³Cu(n,p)⁶³Ni, and the Ni has a 100 year half-life. The ability to measure the small amount of Ni wasn't acquired until well after the war, so they couldn't have done the measurement back then.

[thedarkshade]

Sorry swansont, I mixed it up with the place where the first atomic test took place. I'm very very sure that it was said "10 time higher than normal", and it was Brian Greene who said that on a collection of videos of his Elegant Universe in youtube.

[Riogho]

I played with Cobalt-60 the other day...

 

YEA CHEM~

[ydoaPs]

I played with Cobalt-60 the other day...

 

YEA CHEM~

How much? Got an activity estimate? And, the obvious one...why?

[YT2095]

Co-60 isn`t that the isotope they use to irradiate some Foods with?

 

still, it`s probably cheaper and less painful than a vasectomy.

[swansont]

Sorry swansont, I mixed it up with the place where the first atomic test took place. I'm very very sure that it was said "10 time higher than normal", and it was Brian Greene who said that on a collection of videos of his Elegant Universe in youtube.

 

Ah, yes. I've read that about the trinity test site as well, though I can't find what particular isotopes are responsible for the radiation.

 

And, as far as Co-60 goes, it's a good gamma source, so it's used for sterilization (as YT surmised) and for medical treatments, and other uses.

[Riogho]

How much? Got an activity estimate? And, the obvious one...why?

 

We were doing a pathetically simple lab, it had to do with radiation shielding, we got radioactive samples, and shielded them with different materials and used a geiger counter to count... geigers

 

Then we derived what was the best, why, etc etc

 

edit:

 

we had just a little bit, i think the radiation i was picking up from it from... 4 inches was 2000 'hits' on the geiger counter...

 

But it is used to cure cancer

[ydoaPs]

We were doing a pathetically simple lab, it had to do with radiation shielding, we got radioactive samples, and shielded them with different materials and used a geiger counter to count... geigers

Why doesn't Mueller ever get any credit?

[Riogho]

Because his name blows.

[iNow]

Why doesn't Mueller ever get any credit?

 

Geiger probably takes the majority of the credit since he invented it long before Mueller's involvement, and even when Mueller improved the device it was with Geiger's help.

[ydoaPs]

Because his name blows.

 

Fair enough. I wonder if people just call it the Geiger region as well.