Radioactive Wolves.

[Gawdzilla Sama]

How many reactors? How many bombs?

[Schneibster]

Here is a paper that estimates the height of the cloud at 50,000 feet (16 km).

The stratosphere starts at 10 km according to Wikipedia.

You maybe noticed that the authors themselves say that it's in controversy to previous estimates (8 km), and that only one of their pictures yielded such a high estimate, while the others where more in line with previous estimates. Still an interesting article, though. If that result is correct, certainly parts of the debris would have gone through the tropopause.

The real question is how much heat there was in the cloud. That's what drove it up after the initial impetus of the explosion.

[Warren Dew]

There are very few if any operational reactors that use plutonium.

Actually, almost every commercial reactor uses plutonium. This is because commercial reactors generally start with low enriched uranium, which is typically only 2-3% fissionable U235. The rest of the uranium is largely U238, some of which absorbs neutrons and transmutes to fissionable Pu239 which then undergoes fission. Over the usage life of a typical commercial reactor core, approximately the same amount of power is extracted from plutonium fission as from uranium fission.

Honestly, your post makes it sounds like you know very little about nuclear engineering. You might want to do some research before posting on the topic.

[Gawdzilla Sama]

Give it up, WD, you're out of your depth. And I personally am clean out of life rings.

[Warren Dew]

Give it up, WD, you're out of your depth. And I personally am clean out of life rings.

Look it up and you'll find I'm the only one who has all his facts straight.

[Schneibster]

There are very few if any operational reactors that use plutonium.

Actually, almost every commercial reactor uses plutonium.

[JimC]

There are very few if any operational reactors that use plutonium.

Actually, almost every commercial reactor uses plutonium. This is because commercial reactors generally start with low enriched uranium, which is typically only 2-3% fissionable U235. The rest of the uranium is largely U238, some of which absorbs neutrons and transmutes to fissionable Pu239 which then undergoes fission. Over the usage life of a typical commercial reactor core, approximately the same amount of power is extracted from plutonium fission as from uranium fission.

Honestly, your post makes it sounds like you know very little about nuclear engineering. You might want to do some research before posting on the topic.

True, although I'm not sure it is quite a half - around one third was what I had heard. However, I took Schneibster's point to be about the use of Pu239 as a primary fuel, derived from fast breeder reactors. The fashion for those never really took off, given the travails of transporting highly radioactive Plutonium, which is also a perfect target for a terrorist group...

[Schneibster]

The US decided to dispose of fuel after one time through the reactor, rather than reprocessing it. Part of the decision was cost, part was supply being very high, and part was concern over proliferation.

France reprocesses; I don't know if they burn plutonium or not.

[MiM]

Give it up, WD, you're out of your depth. And I personally am clean out of life rings.

Look it up and you'll find I'm the only one who has all his facts straight.

Then you maybe want to clarify why you claim the enrichment level to typically 2-3%, while it is said to be 3-4% (or even 5, for never designs) almost everywhere? And, as Jim just pointed out 50% is a very high rate for Pu energy production. Technically, if you go above that you have a breeder, according to the definition that a breeder is something that produces more fissile material than it uses.

But this is unnecessary bickering, and of course your post is correct in essence. As was my previous post, where I already said the same thing.

[JimC]

Give it up, WD, you're out of your depth. And I personally am clean out of life rings.

Look it up and you'll find I'm the only one who has all his facts straight.

Then you maybe want to clarify why you claim the enrichment level to typically 2-3%, while it is said to be 3-4% (or even 5, for never designs) almost everywhere? And, as Jim just pointed out 50% is a very high rate for Pu energy production. Technically, if you go above that you have a breeder, according to the definition that a breeder is something that produces more fissile material than it uses.

But this is unnecessary bickering, and of course your post is correct in essence. As was my previous post, where I already said the same thing.

Fast breeders reactors surround the core with "jackets" of depleted Uraniuim, mostly U238, to capture neutrons and gradually transmute into Pu239. From what I understand, it is then easier to extract the Pu239 from this surrounding material than the actual fuel rods, with their witche's brew of fissile products and trans-uranics...

This is a topic I teach to my Year 11 Physics students. We luvs it!

[MiM]

Schneib, look up MOX fuel on Wikipedia (or anywhere on the internet).

[Schneibster]

So, about 2% of the nuclear fuel burned today is MOX.

[Warren Dew]

True, although I'm not sure it is quite a half - around one third was what I had heard.

It likely varies a lot by the specific design. In the specific cases of commercial reactors I worked on, it was actually slightly more than half, but those were cases where they were trying maximize energy extraction per load of fuel. The typical amount may be lower now, if as Mim says typical enrichments are increasing.

However, I took Schneibster's point to be about the use of Pu239 as a primary fuel, derived from fast breeder reactors.

Such an argument would make no sense: the radioactive fission products from Pu239 don't care whether they came from Pu239 that was generated earlier in the life cycle of the current core, or Pu239 that was generated in a previous cycle in another reactor.

The fashion for those never really took off, given the travails of transporting highly radioactive Plutonium, which is also a perfect target for a terrorist group...

Well, except in France, where they have an entire nuclear infrastructure based on breeder reactors and reprocessing.

Then you maybe want to clarify why you claim the enrichment level to typically 2-3%, while it is said to be 3-4% (or even 5, for never designs) almost everywhere?

It was 2-3% in the commercial core designs I worked on, which were typical of light water reactors at the time. The only place I've seen the 3-4% figure cited is wikipedia, which is not notoriously reliable for specific numbers on things like this. However, it is quite possible that typical enrichments have been increasing as new enrichment technologies drive down the cost of enriching the uranium.

Of course, the enrichment varies tremendously depending on the design. The CANDU design can use natural uranium, without any enrichment at all. At the other end of the spectrum, this U.S. government source says U.S. Navy reactors use "highly enriched" uranium, a term which ordinarily means something on the order of 90%:

http://www.epa.gov/radiation/radionuclides/uranium.html

Technically, if you go above that you have a breeder, according to the definition that a breeder is something that produces more fissile material than it uses.

According to that definition, yes, and by that definition many light water reactors are breeder reactors. However, I think a more practical definition is that a breeder reactor is one whose fuel is externally reprocessed after use to provide more new fuel than was originally loaded in the reactor. By that definition, only France has a substantial infrastructure of breeder reactors.

But this is unnecessary bickering, and of course your post is correct in essence. As was my previous post, where I already said the same thing.

As was your previous point that it doesn't really make all that much difference, as the general hazard from U235 fission products isn't that much different from that from Pu239 fission products. However, discussion of the details may be of interest to some.

[Drewish]

Just watched video. Very cool.

[MiM]

However, discussion of the details may be of interest to some.

So let's continue on details:

Just a couple of examples on enrichment levels for light water reactors: On their public websites, the Finnish power companies says "3-5%" (Fortum, PWR) and "generally minimum 3%" (TVO, BWR). Naturally there are many other designs out there.

"High enriched uranium" (HEU) is actually precisely defined, by IAEA, as uranium that is enriched to 20% U235 or more. This stems from that IAEA regards this material as "direct use material", which is defined as material that it is possible to make an explosive device of, without further enrichment (according to IAEA, don't know about practice).

Because of this many research reactors use enrichment levels just below 20%, so that they can escape the more stringent safeguards measures that is put on HEU. Submarine reactors certainly use higher enrichment levels than that, as they have to be small, your guess about 90% is probably a good one. And, no, I have never heard of a weapon or weapons test with a 20% enrichment level.