There is another use for nuclear energy. Back when I was a roofer, our company had for Troxler nuclear moisture gauges. It had a tiny core of americium that emitted a pulse of fast neutrons into the roof membrane. Depending on how much of the pulse bounced back into the collector, we could determine how wet the roof insulation had become without having to physically cut a core sample.

 

Ok. That makes sense, so a "spent" rod is radioactive because there is still some fission going on?

 

It is both radioactive and generates heat. When uranium fissions, the left over parts are unstable and rapidly decay to other, unstable isotopes. Also, the high neutron flux 'transmutes' non-uranium atoms into unstable isotopes. These all have a 'half-life' and decay to other isotopes. But over time, the rapidly decaying ones 'transmute' into longer half-life time isotopes. This reduces the radiation rate.

Also, radiation tends to come in at least these 'flavors':

• Alpha - helium nucleus w/o electrons
• Beta - electrons
• Gamma - high frequency Xrays
• Neutrons - same thing

Each has different penetration abilities and leave behind them a wake of ionized atoms. These ions can damage cells. However, they have many useful purposes too.

BTW, some of the radioactive isotopes are a gasses. This means they can be breathed in.

I read one story about the first Fermi reactor. They got it started and were quite pleased when is shut itself down. Upon further analysis, it turns out the fission by-products 'poisoned' the initial reaction. The solution was to pull the control rods out a little further and the fission reaction resumed.

Bob Wilson

 

Back to my list: I did leave out one section of uses for nuclear reactors and nuclear power (purposefully): weapons. However, on a related note, I recently read an article about the strategies that a certain group of astronomers are putting together to deal with the potential problem of large meteors hitting the earth. The main strategies involve gravity tugs and so on to deflect the meteors out of the path of our planet, but the more drastic ones call for the use of nuclear bombs to deflect or impact the meteors. This one is only a half-serious addition to my list, though.

 

I always thought an Alpha particle was essentially a helium nucleus stripped of its electrons. This would give is a +2 positive charge, but would also make it heavy and slow when compared to other forms of radiation.

An Alpha particle can be stopped by a piece of paper and cannot penetrate skin (except through an open wound). From what I understand, Alphas can be breathed into the body. Once inside a living organism, it is incredibly harmful (mainly because it sticks around instrad of just passing through the way a single electron or a gamma ray would).

I'm not sure how a fast neutron compares to an Alpha particle in terms of the potential to damage life. But isn't there a kind of nuclear weapon called a neutron bomb, in which the blast vaporizes human flesh but leaves buildings standing? Or is that a Star Trek weapon? I can never remember...

As I recall, an ion has a charge imbalance (too mant or too few electrons), while an isotope has a weight imbalance (too many or too few neutrons.)

 

Oh... And don't forget the oft overlooked non-ionizing radiation. This would include infrared (for heating food), and radio waves (like in a cell phone). Both kinds have the ability to heat tissue (which is why some people get headaches from extended cell phone use), but neither is powerful to push atoms around or strip electrons (thus they do not create ions).

 

Ashen- No, I don't think the neutron bomb is a Star Trek weapon. They exist, though to my knowledge no one has ever used one against anybody. And yes, the principle is that the atom bomb destroys both buildings and people, but a neutron bomb, more advanced technology, would destroy the people and preserve the buildings. I know someone who used to joke that the next step in advanced bomb technology would be to develop the neutrino bomb, because it would preserve both the buildings and the people. (just kidding)

 

There seems to be a couple of general misconceptions about nuclear power.

1. Waste is deadly, and lasts for thousands of years.

True and false. The waste is indeed deadly, but the reason it's so deadly is because there is so much material left in the waste that's actually useful fuel.

Basically, "full" fuel rods contain a fair amount of fissionable material. As the fuel is "burnt", non-fissionable material builds up, reducing the useability of the rod. Eventually, build-up occurs to the point as to make the rod useless in our current reactors.

The waste is whatever is left in the rod. However, there is plenty of useable material left. The rods would need to be reprocessed. Doing so greatly extends the useable life a a fuel rod. There are also other materials in a spent rod that can be fed into "breeder" reactors to get even more useful fuel out of them.

The bonus is, the end waste is far less deadly and has a dangerous period of about 300 years as opposed to 10,000 years for standard nuclear waste. There would also be a whole lot less of it since more of the fuel fission into non-radiological materials.


2. Nuclear plants are risky, and an accident can wreck major havoc.

Modern designs such as pebble bed reactors can't melt down. Worst case scenario, the core becomes hot but the design prevents it from becoming the next Chernobyl.

However, an even better source of nuclear power is to use thorium. More on this later.

3. Nuclear fuel is a limited resource as well, so we'll hit yet another peak fuel situation.

While it is true that like oil there is a limited supply of fuel, we deadline is much farther into the future. Using a combination of breeder reactors and thorium based fuel, there is enough fuel to last around 10,000 years.

Thorium (unlike uranium) is quite plentiful. It's also safer than uranium as a fuel since thorium reactors require a neutron pump (cut off the pump and the reactions stop on their own).


Nuclear power is the most likely candidate for (mostly) clean power at least in the near term. You can only build so many hydroelectric dams (ecological impacts an all that). Solar cell efficiency is still too low to be practical (though there are some advancements that may help there) and the manufacturing process is rather nasty. Geothermal would be good if only it was more easily obtainable.

Our ultimate solution is fusion, but that still is at least a couple decades away unless some major breakthrough occurs.

In the meantime, both ecologically and practically, nuclear power is the best.

~X~

 

That's because neutron bombs are completely impractical, and do not work as advertised.

Neutron bombs are basically small fusion devices designed to disperse high energy neutrons into the surrounding area. However, there were several major problems with the concept. Clicky the Wiki http://en.wikipedia.org/wiki/Neutron_bomb

~X~

 

In the early 70s -if I recall properly- there were some ads in the National Geographic magazine by the Caterpillar Co.
They would pose some challenging question in one page (i.e. logging) and on the next they would answer on how the Caterpillar Co. was helping in solving the dilemma. The ads always ended with the motto: "There are no simple answers, only intelligent choices" (or something along those lines, my memory fails me).

That motto was true 35 years ago, it is far truer today, specially in all matters related to energy.

No matter how much one fears it, despises it, or hates it, neither nuclear, fossil fuels, hydro or whatever can be removed from the overall energy equation without disrupting the balance.

Every energy source has its pros and cons, and the future will hold a mix of technologies. What percentage to allocate to each technology should actually be the subject of discussion, since we won't be able to do without the contribution of each.