The Shanghai Institute of Applied Physics - part of the Chinese Academy of Sciences - has been given approval by the Ministry of Ecology and Environment to commission an experimental thorium-powered molten-salt reactor, construction of which started in Wuwei city, Gansu province, in September 2018.
The molten salts mixture is multi-purpose, it serves both as the coolant and contains the molten radioactive fuel in this type of reactor, compared to more conventional reactors that use solid uranium rods as fuel, and regular water as coolant.
Most of the dangers with conventional reactors stem from the high pressures of the coolant steam, as well as the build up of high pressure gases next to the fuel, which in the case of an unattended runaway reaction tend to break things and cause radioactive juices to splatter all over the place, in the ground and in the atmosphere. And then the uncooled fuel also melts through the protective barriers, with the same effects.
Salts, on the other hand, don’t evaporate at 100 degree Celsius, one atmospheric pressure, like water does, so they can get heated to much much higher temperatures at normal pressure. And considering they contain the fuel too, if they expand a bit, they pour out of the core into a safety container, and therefore separate most of the fuel away from itself, and therefore stop the radioactive runaway reaction.
The fact that the fuel is liquid also makes the fuel reprocessing and refueling easier (can even be done while it’s turned on), which is very important when dealing with all the radioactive intricacies. It even lets us use a different more abundant and in some ways cleaner fuel, thorium, instead of direct uranium, because it being liquid lets us turn it into uranium “on the fly” inside of the reactor itself, this is called “breeding” uranium, which simplifies the entire process immensely.
The big downside is, well, hot molten salts are extremely corrosive, as you can imagine. And that’s why we haven’t had reactors like this so far. This one is also experimental.
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There are many reasons for and advantages to it!
The molten salts mixture is multi-purpose, it serves both as the coolant and contains the molten radioactive fuel in this type of reactor, compared to more conventional reactors that use solid uranium rods as fuel, and regular water as coolant.
Most of the dangers with conventional reactors stem from the high pressures of the coolant steam, as well as the build up of high pressure gases next to the fuel, which in the case of an unattended runaway reaction tend to break things and cause radioactive juices to splatter all over the place, in the ground and in the atmosphere. And then the uncooled fuel also melts through the protective barriers, with the same effects.
Salts, on the other hand, don’t evaporate at 100 degree Celsius, one atmospheric pressure, like water does, so they can get heated to much much higher temperatures at normal pressure. And considering they contain the fuel too, if they expand a bit, they pour out of the core into a safety container, and therefore separate most of the fuel away from itself, and therefore stop the radioactive runaway reaction.
The fact that the fuel is liquid also makes the fuel reprocessing and refueling easier (can even be done while it’s turned on), which is very important when dealing with all the radioactive intricacies. It even lets us use a different more abundant and in some ways cleaner fuel, thorium, instead of direct uranium, because it being liquid lets us turn it into uranium “on the fly” inside of the reactor itself, this is called “breeding” uranium, which simplifies the entire process immensely.
The big downside is, well, hot molten salts are extremely corrosive, as you can imagine. And that’s why we haven’t had reactors like this so far. This one is also experimental.
For more fun reading: 1, 2
Molten salt is used as coolant instead of water.