What are we learning? Why are we learning this?
content, procedures, skills
Tier II: High frequency words used across content areas. Key to understanding directions, understanding relationships, and for making inferences.
Tier III: Low frequency, domain specific terms
Building on what we already know
What vocabulary & concepts were learned in earlier grades?
Make connections to prior lessons from this year.
This is where we start building from.
Here we see the glow of Cherenkov radiation as a nuclear fission reactor starts up.
In principle there are many ways that we can generate nuclear power
1. nuclear fission of uranium
The largest metal atoms are not stable. They spontaneously break apart (“fission”) into smaller pieces. But the fascinating thing is that when you add up the mass of the smaller parts, they almost – but don’t quite – equal the mass of the parent atom!
Where did the massing mass go? We think mass could never “just disappear” – that violates the law of conservation of mass. Isn’t that a “law of nature”?”
Turns out that there is no law of conservation of mass. Sure, mass is usually conserved in everyday life, but it isn’t always conserved. So what’s the real deal?
Any missing mass has been converted into photons (particles of light) with high energy.
Under very specific conditions, mass can turn into energy, and vice-versa. So there’s no absolute ‘law of conservation of mass’ or ‘law of conservation of energy’. Rather, these are just two aspects of a higher order law of nature: ‘the law of conservation of mass & energy.’
Scientists have discovered how to use isotopes of uranium to create large amounts of power, which we use to create electricity.
2. nuclear fission of thorium
The general idea here is the same as for uranium. Nuclear fission of a radioactive metal to produce power. Thorium is far more abundant, easier to process, and much safer to use. It doesn’t sustain the kind of reactions that occur in an atomic or nuclear bomb. Thorium reactors can’t blow up. It makes very little radioactive waste, and the little that it makes degrades safely, in a shorter period of time. And it’s waste can’t be used to make nuclear weapons, so there is no fear of nuclear weapons proliferation. It has always been recognized as safer, cheaper, and better all around. So why aren’t we using it?
… research into the mechanization of nuclear reactions was initially driven not by the desire to make energy, but by the desire to make [atomic] bombs. The $2 billion Manhattan Project that produced the atomic bomb sparked a worldwide surge in nuclear research, most of it funded by governments embroiled in the Cold War. And here we come to it: Thorium reactors do not produce plutonium, which is what you need to make a nuke. How ironic. The fact that thorium reactors could not produce fuel for nuclear weapons meant the better reactor fuel got short shrift, yet today we would love to be able to clearly differentiate a country’s nuclear reactors from its weapons program.
… Thorium’s advantages start from the moment it is mined and purified, in that all but a trace of naturally occurring thorium is Th232, the isotope useful in nuclear reactors. That’s a heck of a lot better than the 3% to 5% of uranium that comes in the form we need.
Then there’s the safety side of thorium reactions. Unlike U235, thorium is not fissile. That means no matter how many thorium nuclei you pack together, they will not on their own start splitting apart and exploding. If you want to make thorium nuclei split apart, though, it’s easy: you simply start throwing neutrons at them. Then, when you need the reaction to stop, simply turn off the source of neutrons and the whole process shuts down, simple as pie….
… There are at least seven types of reactors that can use thorium as a nuclear fuel, five of which have entered into operation at some point. Several were abandoned not for technical reasons but because of a lack of interest or research funding (blame the Cold War again). So proven designs for thorium-based reactors exist and need but for some support.
– The Thing About Thorium: Why The Better Nuclear Fuel May Not Get A Chance, by Marin Katusa , Forbes, 2/16/2012
Here we see the difference between a uranium fission and a thorium fission nuclear power plant.
3. nuclear fusion (several types)
in the sun
Inside a star, gravity pulls billions of tons of matter towards the center. Atoms are pushed very close together. So close that sometimes two atoms will fuse into one, heavier atom.
The mass of this new atom is slightly less than the mass of the pieces that it was made of in the first place? Where the did missing go? It effectively becomes energy – which we see as photons, or as the heat/motion energy of other particles.
As an example, here we see deuterium fusing with tritium. The resulting product has less mass than the parts going in to the collision. That missing mass we see becomes 3.5 mega electron-volts of energy,
For more details see Stars are powered by nuclear fusion.
How can we possibly replicate the energy of stars here on Earth? For the last 70 years people have been steadily working on creating and sustaining nuclear fission in the laboratory, and the process actually works! Not surprisingly it has been extremely challenging to do this.
In this device, called a torus, engineers have designed extremely powerful electromagnets. These create a super-powerful magnetic field, strong enough to contain the hot plasma. We see the plasma contained inside as a glowing blue gas.
At the present time we can not use nuclear fusion as a practical way to produce energy, but research is continuing at a steady rate.
In practice we are only using nuclear fission of uranium. Research on thorium fission reactors is slowly proceeding, and we expect to see such reactors operating within the next 20 years. (We could do it much sooner if governments sustainably funded more reserach.) Research on fusion reactors is slowly proceeding, but we don’t expect to see such reactors operating soon. It is unclear at the moment when such reactors will be practical.
How does nuclear fission power work?
What are the benefits of nuclear power?
What are the risks of nuclear power?
What about the nuclear power plant disasters?
What about the radiation release from not using nuclear power?