There ain't no rules around here! We're trying to accomplish something!

Nuclear Power: How it Works, What’s Next

In Physics on March 7, 2009 at 9:56 pm

Going back to Peter’s post on nuclear energy, I’d just like to link to Jonathan Golub’s great six-part series on nuclear power at his blog Dear Science.

What is radioactive waste, exactly? Well, nuclear fission works by knocking neutrons off the nuclei of uranium atoms, which releases energy in a chain reaction. In a nuclear reactor, the uranium rods are the fuel. Once the chain reaction has taken place, the rods are still radioactive — new elements have been created, which keep on undergoing radioactive decay. But these new reactions release neutrons too slowly to sustain a chain reaction, so they’re useless as fuel. These are called “spent” rods, and they’re what we mean when we talk about nuclear waste. We have to put them somewhere: we’ll next build some metal and concrete casks outside of the reactor building, next to the plant and store the rods there, at least for a few years. In the long term, you want them far underground and away from people — and that’s where Yucca Mountain comes in. How much risk remains, and how we evaluate costs and benefits, I honestly don’t know.

But we have another option: we can build better reactors. Normally nuclear power plants use lightly enriched uranium. Heavily enriched fuels (that release more neutrons) are typically used for bombs in the world’s nuclear arsenals. With better fuel, we can build a fast neutron reactor — no need for a moderator to slow down the neutrons and sustain the chain reaction. All those extra neutrons can smash up the radioactive decay products. This both boosts efficiency and burns off the radioactive waste.

Golub says:

Nuclear waste is the overwhelmingly major problem with nuclear power plants today. There is no plan, no strategy beyond burying it someplace for at least a million years. No technology exists that matches the problem. Fast neutron plants, that eat their own waste and potentially the waste of others, are an overwhelmingly better solution than Yucca mountain.

Where are these plants? The ideas here aren’t new ones. A pilot project, the Integral Fast Reactor (IFR) was to build a liquid sodium metal cooled, plutonium and U-235 fueled fast neutron reactor with an on-site waste processing center. The project’s budget was cut in 1994 by President Clinton’s energy secretary and thus languished before the project could be completed. The ideas from this project have been rejuvenated, with plans for a liquid sodium, liquid lead and gas cooled reactor variants based around the same general principles, called generation IV reactors, to be ready for commercial operation in 2030.

2030 is too far away. If we were smart, we would throw resources at these fourth generation technologies, pushing to have the pilot reactors and designs finalized within ten years. None of these are perfect. No source of power is without risk or environmental injury. None. Our planet hosts nearly seven billion people. Fossil fuel reserves are dwindling. The atmosphere and oceans are buckling under the carbon strain. Nuclear power, particularly responsibly applied with standardized plant designs and a real plan for dealing with the waste, remains our best hope. The physics and technology is available. We just need to do it. Now.


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