03 Nuclear Fission & Fusion

Micro-reactor concepts like this one from the company HolosGen could be used in a variety of settings to provide emissions-free power. / Image courtesy HolosGen

Nuclear Fusion

In theory there is nuclear fusion in which hydrogen isotopes Deuterium (which is extracted from salt water) and Tritium (also created during fusion reaction) are fed to the reactor and pressed / forced together to merge, theoretically creating 4 times more thermal energy than fission. Unfortunately, as yet, there hasn't been a nuclear fusion reactor that is net positive ie creates more power than is put in it to get it started. As nuclear fusion isn't available yet and we thus can't know how scalable it is going to be we are going to talk about nuclear fission.

Nuclear Fission

In fission, neutrons are blasted at unstable uranium-235 to split it and start a chain reaction of atom explosions to create heat that run steam turbines. Traditional fission reactors however are expensive and take a long time to build. They tend to cost 11-15 billion US dollars to build, take up a lot of space from about 4.2km² upward, require a lot of water for cooling and are usually placed at great distances from civilization for safety reasons (thus needing expensive infrastructure to connect them to the grid).  They can take up to 10+ years to build due to building delays (because of their complexity), design revisions and changes in the political landscape.

The first nuclear fission power plant was completed in the mid to late 1950s. Traditional fission power plants can generate electrical power ranging from 100's of MW to as much as 1600MW or 1.6GW of power. They have been the dominant size of fission power ever since they were first built. However lately quite a lot of research has been put in Smaller Modular Reactors (SMR) meant to be scaled according to a regions needs. SMR's are defined as producing up to 300MW or less. One developed by Nuscale is 22m tall and can produce between 50-77MW. However up to 12 of them can be combined, to create an array that could give a power output as high as 600-924MW.

There are a further two categories currently being developed VSMR (Very Small Modular Reactors) up to 50MW and mSMR (micro Small Modular Reactors) up to 1.5MW.

There are two types of fission reactors Thermal Reactors and Fast Reactors. Thermal Reactors need a moderating fluid (water or a molten salt) to slow down the neutrons in order to increase the probability of them colliding and creating energy. In Fast Reactors the problem of getting the neutrons to collide with one an other is solved by having more enriched fuel added to the mixture whose extra neutrons have a greater chance of being collided with thus starting the nuclear reaction. These Fast Reactors have the added bonus of using up nuclear waste.