What is the function of heavy water in the production of a nuclear bomb?

[shadu]

I am just looking for a brief explanation.
We hear about it all the time - would be nice
to know what it means.

[madrchsod]

1. since you asked such a question

i will have to inform mr asscrap of your post..other than that -i can`t spell chemisry let alone know anything about it-i got an f in chem101....

[shadu]

3. i suspect the answer can be stated simply, by someone

we shall wait and see. Chemistry and Physics never
liked me so much, either

[shadu]

6. you're a math guy, aren't you?

I always thought you were a math and computer guy

[Endangered Specie]

2. Its used in converting Uranium to Plutonium...

it makes the process relatively easy, so, people who make it are heavily monitored.

D20 is like H20 expect the H atoms have an extra neutron, making them an isotope of Hydrogen (Deuterium, or D)

Hydrogen is the only element to have different names used for its isotopes.

[shadu]

4. O boy, that's not so easy :)

So, how does it make the conversion from Uranium to Plutonium
easier? Is Plutonium more radio active than Uranium?

[Endangered Specie]

12. ok...

Uranium-235 is fissionable, and can be used in bombs and reactors... however, it is very rare, makes up a fraction of all the uranium (most is U-238).

Plutonium is VERY fissionable (much more than uranium), but it is an artificially made (not naturally occuring) element. It is much better suited for shall we say, bigger bombs.

Uranium was used in Little Boy
Plutonium was used in Fat man (the two bombs had very different design, based on the 'fuel' used)

Plutonium is also used as a trigger for Fusion (thermonuclear bombs)

Radioactivity has nothing to do with how 'big' bombs are, but plutonium is much more deadly to be around than uranium.

[shadu]

19. Thank You, Mr. Spock. I did not know any of that.

Those are good-to-know facts.

[Endangered Specie]

5. Oh, and it also works as a reaction moderator in fission power reactors.

It can also be used to detect neutrinos in the Sudbury Neutrino Detector... neutrinos are a form of elementary particle... very hard to detect... extraordinarily light (compared to the mass of other fundamental particles) and are uncharged... yet they make up a significant % of the mass of the universe, so they are important.

[qazplm]

7. when we get to fusion

heavy water will likely be the ideal candidate as an energy source.

[shadu]

9. So, does the denseness of heavy water make the conversion from

Uranium to Plutonium easier by providing a stable
(nonreactive)medium

[Donkeyboy75]

8. You actually don't need heavy water to make a bomb,

but it makes it much easier. As endangeredspecie said, the hydrogen isotope present in heavy water contains a neutron. This allows the conversion of unenriched uranium to be converted into plutonium, which is used in the bomb. All plutonium used in bombs is made from uranium. The mechanism involves uranium reacting with a neutron, then beta decay to form plutonium. Heavy water, unlike light water, doesn't react with neutrons, so the effective concentration of neutrons at any one time is higher. Ergo, a lower-grade uranium can be used.

If "light" or normal water is used in the reactor, one must use enriched uranium, which is much harder to come by for "rogue nations." Uranium, on the other hand, isn't.
Big concern...

[shadu]

11. Fascinating, Mr. Spock

Where does heavy water come from?

[Donkeyboy75]

14. It is distilled from normal water.

Heavy water weighs 20 grams per mole, while light water weighs 18. This weight differential allows the two to be separated by distillation (deuterium naturally exists...on earth approximately .1% of all hydrogen is deuterium).

Heavy water is common in chemistry labs, but it is VERY expensive compared to water. This is due to the cost of purification. Separating heavy from light and semi-heavy (HDO) water is tedious and expensive.

On edit: I think there are other ways to isolate heavy water, but I'm not too familiar with them

[Endangered Specie]

30. here are some other ways

http://www.fas.org/nuke/intro/nuke/heavy.htm

[Endangered Specie]

21. Heavy water is 'made' in heavy water plants...

D20 is present in nature, albeit in small amounts... usually its H2O but sometimes you get DHO or D2O, they are chemically identical, you drink all 3 everyday.

These plants 'seperate' the D20 from the rest of the other waters. There are many ways to do this, since they have different physical properties.

edit: its not really made, technically

[Endangered Specie]

13. Actually, that is 2 beta decays...

[Donkeyboy75]

16. I left that out for simplicity, which is why I didn't say "a" beta decay,

but you're right. :thumbsup:

[elvisbear]

10. Here's a brief definition and a few interesting facts.

http://en.wikipedia.org/wiki/Heavy_water

[gpandas]

15. wish there were more threads like this on du. n/t

[Endangered Specie]

24. start them and I will answer them

:) we have these from time to time, id like there to be more too.

[papau]

17. bomb-usable plutonium without requiring enrichment facilities is produced

Heavy water is a neutron moderator - slows down neutrons so that they can react with the uranium in the reactor - so with just natural uranium, the reaction to create heat with the nuclear material (called criticality) is obtained with the natural uranium converted to bomb ready plutonium.

Other reactors use light water, but the fuel must be more powerful enriched uranium rather than natural uranium if you want to achieve criticality and the conversion to bomb ready plutonium.

A nation with a sufficiently powerful heavy water reactor can use it to turn uranium into bomb-usable plutonium without requiring enrichment facilities.

[DrWeird]

18. Alright, I'm an organic chemist, not a nuclear chemist, but...

if I'm not mistaken, heavy water acts as a nuclear moderator. That is, in the course of nuclear reaction, "fast neutrons" are produced. These don't participate in nuclear reactions, as they go zooming right out of the reactor. With deuterium, the nuclei in the medium are essentially twice as large as in regular water. It is much more likely for neutrons to hit the deuterium nuclei, and they are then slowed down into what are called "thermal neutrons." Thermal neutrons, while still quite fast and energetic, are slow enough to use in chain reactions.

So you can kind of think of the heavy water molecules as pins and bumpers in a game of pinball. They slow down the ball in just the right way to chalk up a bunch of points.

[Donkeyboy75]

20. I'm also an organic chemist, but I have had

some exposure to nuclear chemistry. I think one other advantage of heavy water is that the hydrogen atoms in light water will absorb these neutrons, whereas the deuterium atoms are much less likely to.

[papau]

22. That was my understanding of the math - criticality is not possible

with natural uranium using normal water as the moderator.

[Endangered Specie]

23. It can also be used to make tritium, in a D20 moderated reactor...

[shadu]

25. I'm catching on. So when 'critical mass' is reached, what has happened?

[Endangered Specie]

29. ...

Critical mass it the minimum amount of a given fuel required to produce a sustained nuclear reaction. In a bomb, you must go from sub critical (not enough for reaction) to super critical (beyond sustained, more like, out of control) mass in a VERY short amount of time to produce an explosion.

Alot of this is probability,
fissionable uranium and plutonium will fission on its own spontaniously (it 'wants' to), WHEN is purely up to chance.

sub critical: even though this stuff spontaneously fissions, there isnt enough mass for there to be, probability speaking, enough to start a chain, (self-sustaining) reaction/

Critical mass: you have enough mass, so that, according to probablility there will be enough fuel atoms spontaneously fissing to start a SUSTAINED chain reaction... and you get this chain reaction when, according to probability (again), out of the 3 neutrons released by each fissioned atom, on average, 1 neutron will go on to cause fission in another atom, and then, that one will have 1 of 3 neutrons start another fission and so on...

Supercritical is when more than one of the neutrons will (from the view of probability) go on to cause fission, and hence the reaction is not only sustained but increasing in rate.

For a bomb to work, it must reach supercritical (from sub) Almost instintaniously.

[shadu]

31. Now I know something about heavy water/critical mass.Thank You All

[Endangered Specie]

33. no problem...

I always love science question threads.

[ChavezSpeakstheTruth]

26. isn't this a better question for General Discussion?

Just thinking that you might get more responses there.

[shadu]

27. I'll bet you are correct

Some people think Coltrane originated
the Lydian Chromatic Concept, what do you think
about that? (oops, here we go again ; )

[ChavezSpeakstheTruth]

34. I thought George Russell originated the concept?

D'oh!!!

:)

[shadu]

28. When I come to DU I review the Forum listings

Other than LBN I never review specific forums.
I come here to see all the news I can use.

[Endangered Specie]

32. actually, it belongs in the Envir/Energy/Science forum.