Plutonium Bombs and Fallout

  • Thread starter robinson
  • Start date
  • #1
197
0

Main Question or Discussion Point

Having followed a few threads due to Fukushima, and having read a lot of media reports, pdfs beyond number, scoured the Wikipedia pages for days, even cracked a book or two, I just realized I don't know the answer to a simple question. I was looking for a thread to ask it in, then realized that was selfish and short sited. Much like this opening paragraph is becoming.

There may be more questions, other people may want to chime in, the whole thing could very well start a chain reaction. But enough of that.

The query is this: Why and how do hydrogen bombs create radioactive cesium, iodine, and other dangerous fallout particles?

For example

The unleashed isotopes of concern from the damaged Japanese reactors - Iodine-131, Cesium-137, Strontium-90 and Plutonium-239 - are well known to the Marshall Islanders living downwind of the testing sites at Bikini and Enewetak atolls in the central Pacific, following sixty-seven A- and H-bombs exploded between 1946-58. In fact, it is precisely these isotopes that continue to haunt the 80,000 Marshallese fifty-three years after the last thermonuclear test in the megaton range shook their pristine coral atolls and contaminated their fragile marine ecosystems.

In fact, it was the irradiated downwind Marshallese on Rongelap and Utrik in 1954 caught in the Bravo fallout - and I-131 - that taught the world about the thyroid effect from the uptake of radioactive iodine.

The U.S.' largest [fusion] hydrogen bomb - Bravo - was 1,000 times the Hiroshima atomic [fission] bomb, and deposited a liberal sprinkling of these and a potent potpourri of 300 other radionuclides over a wide swath of the Central Pacific and the inhabited atolls in the Marshalls archipelago in March 1954 during "Operation Castle."
I've read from multiple sources that the world is already lightly dusted with all the isotopes that come from a leaking reactor, or burning fuel pond. But why would a bomb that contains just plutonium create all the same radionuclides?
The CDC report examined 18 additional isotopes that were spewed by the bomb tests, including strontium-90 and cesium-137, which are dangerous for between 280 and 300 years. Moreover, cesium-137 makes up 40 percent of total fallout in a given test. Together, a test’s cesium, zirconium-95, carbon-14 and strontium-90 make up 76 percent of the total radioactive fallout from most tests.
http://alethonews.wordpress.com/2011/03/16/80000-u-s-cancers-caused-by-bomb-test-fallout-15000-of-them-fatal/
And why so much of them? I thought a small part of the plutonium was turned into energy, thus the boom. Why and how and where did all the dangerous fallout come from?
 

Answers and Replies

  • #3
197
0
I understand that, I read that article.

"The lasting radiation from a nuclear weapon is in part due to the neutron activation of the bomb itself and the surrounding material, in addition to fission products."

How does that millisecond that the plutonium goes critical create all the long lived isotopes? The ones that take a long time to build up inside a reactor?
 
  • #4
1,045
2
I understand that, I read that article.

"The lasting radiation from a nuclear weapon is in part due to the neutron activation of the bomb itself and the surrounding material, in addition to fission products."

How does that millisecond that the plutonium goes critical create all the long lived isotopes? The ones that take a long time to build up inside a reactor?
In reactor fuel (which is low-enriched anyway) there is not much to activate. The isotopes you speak of are fission fragments, which subsequently decay. As only a few percent of the fissile Uranium or Plutonium actually fissions over the useful lifetime of a fuel element, there are not very many produced. Neutron activation makes radioactive isotopes in the walls of the reactor and the control rods and the water (tritium) and whatever else is inside.

In a bomb, most of the material (which is mostly fissile (read: highly enriched) to begin with) does break up into fission fragments. So from the start it is much more efficient at making both fission fragments and neutrons. Add LiD (fusion!) and possibly a tamper made of uranium and suddenly you have oodles more neutrons and lots more fission products already, per unit mass, than in a reactor.

And this is before the neutrons hit whatever is around the bomb!
 
  • #5
Astronuc
Staff Emeritus
Science Advisor
18,704
1,718
An atomic bomb uses a fissile core, and the U-235 or Pu-239 fissions under a fast (prompt) neutron spectrum. The fission products include Te, I, Xe, Cs, Ba and Se, Br, Kr, Rb, Sr, . . .

A hydrogen bomb uses a fissile trigger, so that produces fission products, and some configurations can use a tamper of depleted or natural U, and the U-238 fissions from fast neutrons, also producing fission products.

One concept - http://en.wikipedia.org/wiki/Teller–Ulam_design
 
  • #6
QuantumPion
Science Advisor
Gold Member
902
42
I understand that, I read that article.

"The lasting radiation from a nuclear weapon is in part due to the neutron activation of the bomb itself and the surrounding material, in addition to fission products."

How does that millisecond that the plutonium goes critical create all the long lived isotopes? The ones that take a long time to build up inside a reactor?
It doesn't. There are much fewer fission products created by a bomb than a reactor. A typical power reactor generates one kiloton TNT of energy every twenty minutes. However a bomb widely disperses all of the fission products into the environment, via the enormous explosion.
 
  • #7
NUCENG
Science Advisor
914
0
An atomic bomb uses a fissile core, and the U-235 or Pu-239 fissions under a fast (prompt) neutron spectrum. The fission products include Te, I, Xe, Cs, Ba and Se, Br, Kr, Rb, Sr, . . .

A hydrogen bomb uses a fissile trigger, so that produces fission products, and some configurations can use a tamper of depleted or natural U, and the U-238 fissions from fast neutrons, also producing fission products.

One concept - http://en.wikipedia.org/wiki/Teller–Ulam_design
The state of the art in 1945 required a massive overdesign of the fission weapons used on Hiroshima (U235) and Nagasaki (Pu239). So the deposition of unfissioned U and Pu from those weapons would have been much greater than from a modern design optimized for fusion efficiency. Since the early designs were fission only they would also have generated relatively higher fission product yields in a smaller frallout footprint. The higher explosive level of a fussion weapon also scatters the fission products from the trigger more widely.
 
  • #8
88
2
The query is this: Why and how do hydrogen bombs create radioactive cesium, iodine, and other dangerous fallout particles?
In a thermonuclear (hydrogen) bomb, the only fission products (eg. 137Cs, 131I) come from (a) the fission of 239Pu in the bomb's primary (the fission "trigger" of a hydrogen bomb) and possibly from (b) the fast-neutron fission (with ~14 MeV fusion neutrons) of 238U in the "tertiary" stage of the bomb, the bomb's radiation case which can be made from 238U in order to add a whole bunch of nuclear yield (but it's relatively "dirty" fission yield as opposed to relatively clean fusion yield.)

Neutron activation of environmental stuff doesn't create fission products. It might create other radionuclides, like 14C, 36Cl, radioactive Fe, etc, but not fission products.

I've read from multiple sources that the world is already lightly dusted with all the isotopes that come from a leaking reactor, or burning fuel pond. But why would a bomb that contains just plutonium create all the same radionuclides?

239Pu fission in a bomb creates fission products just like 239Pu fission in a reactor does. The distribution of fission products is a little bit different because the neutron spectrum is a bit different, but the general facts are the same.

http://alethonews.wordpress.com/2011/03/16/80000-u-s-cancers-caused-by-bomb-test-fallout-15000-of-them-fatal/
And why so much of them? I thought a small part of the plutonium was turned into energy, thus the boom. Why and how and where did all the dangerous fallout come from?
Well, be careful when reading and evaluating dubious anti-nuclear scientifically illiterate screed on the Internet. Keep your science and skepticism and critical thinking close at hand. Maybe - you know - it's not actually true at all. Can the source material be reviewed, verified or investigated further,

There were a lot of bomb tests across the world over the last 70 years. They did release a good bit of radioactivity. We've stopped atmospheric testing, and that was a sensible decision.
 
  • #9
197
0
It's funny, because I don't read anti-nuke sites or literature. I guess I should investigate those arenas as these issues may have been discussed there before. But I don't enjoy discussions if they are not fact based.
 

Related Threads for: Plutonium Bombs and Fallout

  • Last Post
Replies
2
Views
3K
Replies
11
Views
6K
  • Last Post
Replies
2
Views
4K
  • Last Post
Replies
9
Views
27K
  • Last Post
Replies
13
Views
13K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
3
Views
2K
Replies
9
Views
6K
Top