Nuclear physics anyone?

[diddi]

So what you're saying is that we are probably not hearing a very true assessment of the likely degree of damage and lack of containment of radioactive material. No wonder their foods and water are being affected as is being reported...

 

[chuckchuckit]

I think it is much worse than they are saying which we will find out more about as time goes on.

But worse than that is the potential for escallation of radiation is far beyond what most people even suspect. I think they are just gambling that it will not get out of control. Enough time has past to where maybe it won't from here on, but I think it was way more dangerous there in the beginning than was ever even hinted to.

They may have been afraid of starting a mass panic (39 million people in the Tokyo area), but I think that is not the main reason for such down playing. It is rather a sweeping under the rug approach and even corruption without concern for the possible consequences that has always happened with their nuclear facilities.

They may have averted a massive tragedy with this nuclear facility, but doubt they are fully out of the woods yet. Many people there are undoubtably sacraficing their lives (literally) to try and avoid the worst case. If it weren't for them I think there for sure would have been a massive tragedy perhaps beyond the effects from the earthqauke and Tsunami combined.

 

[B0Z0]

Can anyone shed some light on a bit of a grey area for me...

The terrible events in Japan have prompted me to ponder: if there is a 'meltdown' in a reactor core, which presumably means that all the fuel accumulates at the bottom of the vessle before burning its way through, why does the fuel not exceed its critical mass and a undergo nuclear fission explosion?

Once again, I am just a layperson but this is my understanding of the reason why the meltdown won't cause a nuclear explosion:
In a nuclear bomb, there are three explosions. The initial catalyst is a chemical explosion around the plutonium that compresses the plutonium to a point that starts the fission explosion, the fission explosion then triggers the third part of the bomb which a fusion fuel and this third explosion is what gives the bomb its power as it uses the surrounding environment as its fuel ie fusing two hydrogen atoms into helium and releasing excess energy.

In a meltdown there is no catalyst to make the plutonium start the fission process (plus the plutonium is not as enriched as in a nuclear weapon) and if there was then there would have to be a fusion fuel that requires the fission process as its catalyst for the meltdown to resemble a nuclear explosion.

The problem with a meltdown is the invisible-to-the-eye radioactive material that can escape into the environment if it is not contained. There won't be a destructive force emanating from ground zero but there will be unstable atoms released into the air that can affect those atoms around it until it has enough half lives to become stable.

 

[diddi]

the typical U-235 or Pu-239 bomb does not require hydrogen to be self sustaining. for plutonium, even a weakly enriched sample with say, 15% Pu-239 has a critical mass well under 20kg. this corresponds to a cube less the 10cm wide.

in certain fission bomb designs a small H-fusion reaction is the SECOND stage of triggering, not the third. this increases the initial bombardment of neutrons on the fissionable fuel to reduce wastage.

 

[diddi]

i hear in todays news, evidence of major containment problems in Japan, with the discovery of plutonium outside the reactor along with highly deuterated water puddles. makes one wonder what the true extent of the problem is...

 

[Expiry]

I know nothing about Nuclear power, which will become apparant with this question, I'm sure.

Is radiation a byproduct of nuclear power, or is it the radiation that produces the energy?

Basically, what I'm asking is, why can't we use ALL of the power (radiation) that is created which would therefore mean there's no such thing as nuclear waste?

I have a feeling this is a stupid question.

 

[diddi]

the uranium in the nuclear fuel is a mixture of 2 different types. one is U-235, and the other U-238. if you have been following the thread, you will have noted that both are discussed. U-235 is the highly reactive part of the fuel and is responsible for all of the nuclear energy production.

in a normal reactor there might be about 4% U-235; all the rest, at least initially, is U-238. enery is produced when the U-235 atoms split into parts. a large atom of uramium can break up into 2 smaller atoms...

eg uranium-235 -> barium + krypton + lots of energy (as radiation)

this reaction is caused by smashing the U-235 with a neutron. one of the byproducts of the reaction is more neutrons, which flood into the fuel and cause the reaction to continue without re-triggering.

many of the neutrons don't hit another atom of U-235 since there is anly a small percentage present. the rest is U-238. when U-238 is hit by a nuetron, the neutron is absorbed and so U-239 is produced, but nothing else. this slowly turns into plutonium over a period of weeks.

so to answer your question... after a period of years, there are the following materials in the reactor:

U-235 (still to be used)
U-238 (still to be used)
U-239, Np-239 (intermediate steps towards plutonium)
Pu-239 (material identical to that used in Nagasaki bomb 1945)
Ba, Kr, Cs, Rb, I, etc (all radioactive products from U-235 splits)

there is a huge amount of left over material, virtually all of which is radioactive (ie it can undergo another nuclear reaction), and that is what the anti nuclear proponents complain about. also, every country with nuclear reactors for electricity generation is breeding plutonium as a by-product which can used in nuclear weapons.

 

[chuckchuckit]

It sounds like any one of those materials from a reactor could do serious harm (as we are starting to see with the reactors in Japan).

The unfolding accident in Japan is a serious concern worldwide. Water, soil, food chain contamination etc. It is unfortunate most people do not see the true danger of these materials getting into the hands of terrorists, and what they will do with it.

Not to mention the enriching of plutonium by terrorist supporters. Perhaps the Japan accident will give a reason to not keep overlooking this event that some say is just a matter of time. At some point it will be too late.

"Why" this does not concern people "before it is too late", is a valid question...

 

[diddi]

yes, it now appears that in Japan the exclusion radius is to be expanded and that the sea water is becoming considerably more contaminated.

the notion of terrorist access to fissile material is quite real. that is why there is so much concern about 'rogue nations' with terrorist sympathetic tendencies having ANY forms of nuclear development because the ever peaceful nuclear power plant is also a plutonium breeder, and whilst Pu bombs are more difficult to make over U-235, 'where there's a will...' to coin a cliche.

 

[chuckchuckit]

And terrorists have proven many times that they like to wait until they can “set them all off at once” for maximum effect. Perhaps 19 will be their goal?
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Even if only one dirty radiation bomb or plutonium device is detonated in a city or port (hidden in an incoming ship), it would start a mass panic of living and dying “contaminated people and vehicles” spreading radiation as they flee in all directions. Detecting more hidden nuclear bombs or radiation devices not detonated yet in other cities might be difficult as radiation would already be spread everywhere.
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Perhaps people are not concerned enough to actually do something about stopping this real threat that would likely destroy civilization as we know it, because it does not seem real (yet). Instead of a person “taking the time” to think things through for themselves, it is easier to just let “the media experts” tell us.
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I would say that our decades and generations of “media entertainment absorption” have blurred the lines between fantasy and reality. Hollywood can even turn nuking one of our cities into “entertainment”. If “everything” becomes entertainment, we can lose the capacity to know the difference between reality and fantasy, and truth or lies. Including losing the capacity to be able to fear true danger, when it is right before us. Because it all seems like entertainment. If we do not like what is entertaining us, we just change the channel.
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Very slowly it has taken decades and generations to get to this point. We are headed for big trouble, and it seems we may have lost the capacity to even know it. “Instead” of looking the other way and pretending it is not real, it will instead take courage, and speaking out about it. Perhaps even the “combined courage” of the people of many nations. And then actually do something about it, by literally putting a stop to it. Before one day very soon, it will “most certainly” be too late.