I understand that PWR type reactors are ubiquitous because they are submarine reactors at a fundamental level. Shippingport was derived from submarine PWRs in 1957. However, there is another more simple type of fission reactor known as the Boiling Water Reactor. It is the second most common type of energy producing reactor around the world. It is too big for naval use, however. PWR and BWR dominate global nuclear energy production, with any other reactor types accounting for a much smaller sliver of the nuke pie. Is there a better way of fissioning atoms to make heat to boil water for steam? Are there better generation III+, or generation IV reactors that could be built that outperform current PWR and BWR plants? If so, what is preventing their construction? Also, would it ever be possible to skip the Carnot/Rankine cycles and utilize direct nuclear to make electricity?
A fission fragment reactor is a theoretical type of reactor that basically passes the exhaust from a fission fragment rocket through a magnetohydrodynamic generator, bypassing the Carnot cycle.
A gas-cooled or metal-cooled fast reactor can operate at much higher temperatures than a water-cooled reactor.
Nothing? A bunch are operational, and more are under construction.
We can already do that in a number of ways.
It’s generally used with physically small nuclear energy sources, partly since non-thermal methods are generally just as efficient at a small size*. “Heat engines” like your standard nuclear/fossil fuel power plant however generally become more efficient with size, encouraging large, centralized power plants.
- For an example from nature, the world is full of plants that rely on leaves of all shapes and sizes for energy because all that matters is the aggregate exposed surface area, not how massive the leaf is.
What’s ideal depends on a lot of factors. What are your constraints, what are your needs, what are your resources, what is your figure of merit?
There are ways to turn radioactivity directly into electrical energy, but I think they’re all based on natural radioactivity, not fusion, which puts pretty sharp limits on the power you can get out of them. The difficulty with fusion is that most of the energy is released in electrically-neutral neutrons. They can still be a good choice if you want a compact power supply that can provide a trickle of power for a very long time without refuelling: For instance, some pacemakers are powered this way.
Canada designed a small nuclear reactor once upon a time (Slowpoke, I think it was called) - ideal size for example for heating a large aprtment building with hot-water heat. The obvious question is - would you want to have to train the average building superintendant (Some guy named Simpson?) in managing a nuclear reactor? Should you leave decent quantities of nuclear fuel in random apartment buildings? There are ways around these problems, but the more obvious solution is to replace monstrously large reactors with a scalable array of modular small reactors, such that a problem with one unit does not significantly impact total output. But… still uses the Carnot cycle.
Oh, and you can also skip the Carnot or Rankin cycle by using some other sort of heat engine, like a Peltier junction. A lot of space missions use this (called an RTG, or Radioisotope Thermoelectric Generator): You have a lump of plutonium, that’s so radioactive that it gets red-hot, and then use the temperature difference between that and a radiator to drive a Peltier junction, which turns the heat directly into electricity. You still have the same inefficiencies as in any heat engine (in fact, I think they’re rather less efficient than steam engines), but the benefits are that the device is extremely simple and reliable, with no moving parts, and relatively compact and lightweight, all of which is good for something that you can’t realistically do any maintenance on.
My understanding is either sodium or lead cooled fast reactors were superior in many ways to the current Gen II technology. I have no idea beyond that.
My understanding is both sodium or lead cooled fast reactors were superior in many ways to the current Gen II technology but they had to keep running without interruption. If sodium or metal solidifies, it can not be melted again. It is like a glass producing facility. It is impossible to re-heat it evenly, it can only be kept hot and circulating.
Don’t ask me how they started them the first time.