One of the coolest sounding ideas is the "pebble bed" reactor where you have carbide coated spheres that are fed into the top of the reactor and get withdrawn from the bottom, taken up an elevator and replaced.
When they tested this out in air the spheres we well lubricated and slipped past each other. In hot helium the Germans found that there was a lot more friction and the spheres were sticking to each other, cracking, getting stuck, and releasing radiation.
"Prismatic" designs where the same material is in blocks seem a little more promising. Still the reactors haven't done that well and as lurid the stories around the plutonium economy have been, the ratio of progress to problems for the liquid metal fast breeder reactor has been better.
We know how to bury oxide fuels for the long term and we know how to reprocess them. If there is a "what to do about the waste" problem it's that we can't make up our minds. Carbide fuels can be encapsulated in concrete and stored for the medium term but the actual mass and volume of the fuel is dramatically more than the LWR fuel because of the low power density. The long term stability for burial is not established, and the amount of material is 10x more. Reprocessing is not developed and faces the problems of dealing with a large amount of 'filler' that is going to be somewhat radioactive and have to be dealt with.
China's HTR-PM pair of test reactors is now grid connected. We'll see how it performs over the next few years.
The demonstration High Temperature Gas-Cooled Reactor - Pebble-bed Module (HTR-PM) at the Shidaowan site in Shandong province of China has been connected to the grid, the partners in the consortium building the plant have announced.
One of the coolest sounding ideas is the "pebble bed" reactor where you have carbide coated spheres that are fed into the top of the reactor and get withdrawn from the bottom, taken up an elevator and replaced.
When they tested this out in air the spheres we well lubricated and slipped past each other. In hot helium the Germans found that there was a lot more friction and the spheres were sticking to each other, cracking, getting stuck, and releasing radiation.
"Prismatic" designs where the same material is in blocks seem a little more promising. Still the reactors haven't done that well and as lurid the stories around the plutonium economy have been, the ratio of progress to problems for the liquid metal fast breeder reactor has been better.
We know how to bury oxide fuels for the long term and we know how to reprocess them. If there is a "what to do about the waste" problem it's that we can't make up our minds. Carbide fuels can be encapsulated in concrete and stored for the medium term but the actual mass and volume of the fuel is dramatically more than the LWR fuel because of the low power density. The long term stability for burial is not established, and the amount of material is 10x more. Reprocessing is not developed and faces the problems of dealing with a large amount of 'filler' that is going to be somewhat radioactive and have to be dealt with.