What is fusion? Fusion reactors are a type of reactor that uses safe, cheap, non radioactive fuel. These reactors produce high ammounts of energy for a very cheap price. The ultimate free energy source. Fusion will be a very influential and powerful technology once we figure it out, but we're not there yet. Currently no fusion reactor has been able to sustain a positive energy output.
PROBLEM:
Many people think that the Authority should have the technology to make these reactors function effectively. This presents critical problems for making impactful and captivating stories. This is why…
The Authority as an unstopable übermensch:
The Authority is written as the powerful shadow government that protects the world from everything unusual. Already we have made ourselve into a force to be reckoned with. Giving free infinite energy to the most powerful entity on earth would virtually make the Authority into a god. The problem is that gods don't fear anything. Making the Authority into a god lobotomizes the most valuable asset of the site, the horror. Why worry about a sea monster eating London when you can just fire your fusion powered mega death ray at it. Making the Authority this powerful removes the threat and mystery of the story. If you don't believe me, try making it through every episode of Sherlock, or modern Doctor Who. They made the characters invincible übermensches that can't be stopped and always win. Everyone thinks thats what they want, but what you end up with is a boring, dull, and predictable story that always ends the same way with no consequences or out of the box ideas ever.
Fusion is flawed:
The technology is just too far away. Current fusion reactors are massive, complicated, and at least a decade from being feasable. Even if the Authority somehow has technology 20 years in advance of the public, fusion still wouldn't make sense for everything, especially mobile applications. All current designs require precision manufacturing and very heavy components to start.
The two major designs are the "magnetic bottle" and the "compression" types. Magnetic bottles require a large amount of energy to superheat plasma and maintain a strong enough magnetic field to contain that plasma. The equipment required is massive and can't be mobile for at least 50 years.
The other design uses lasers or pistons to compress the fuel into a plasma. The power and equipment reqired is also massive and couldn't be portable for at least 40 years.
Aside from the technical problems, there are plot problems. If the Authority developed the solution to free energy, why would they keep it to themselves. The world would benefit from free energy immensely. The problems it solves are endless. Clean water, abundant food, better medical care, ect.
SOLUTION:
Instead of using fusion, the Authority will use advanced fission reactors. These are the reactors we use today in nuclear powerplants. Fission is already compact and well understood, so we aren't reinventing the wheel. Fission reactors reuqire radioactive fuel, and are dangerous if you run out of coolant or break it. The Authority has technology to mitigate the dangers posed by fission, but its no silver bullet. This technology comes in the form of the "Edgar-Levitt Aspect Diffraction Field Generator."
About the size of a short bus and about six times as heavy, they prevent fallout by containing radiation within their area of influence. In the event of a catastophic failure, the generator stops fallout from escaping in a 5 meter sphere around itself. The ELAD generator is powered directly by the radiation emmitted by the fuel so it continues to function in the event of turbine failure or catastrophic breach. ELAD field generators shunt the radiation into an extra-dimensional zone and does not violate the laws of physics or thermodynamics.
Once powered on by a source of radiation, the generator will not effect radiation from other sources. You can't protect yourself from a gamma ray burst by standing in it's field, IT IS NOT A RADIATOIN SHIELD. All it does is contain whatever is in it's range once it's functional.
Edgar-Levitt Aspect Diffraction Field Generators can be loaded into a standard large shipping container with a small reactor to provide reasonably portable power for mobile sites.
Using ELAD generators to contain radioactive anomalies:
Please don't unless you have to. As a result of anomalous tech gone too far the Foundation had to invent entirely new fields of "science" to fight against. Thaumaturgy, pataphysics, ontokinetics. I haven't got a clue what these mean and the plot suffers from it. You need to be "in the know" to get most of the modern articles and thats terrible for new readers. In theory SRAs and telekil are good ideas, but the writing gets more convoluted as a result.
However, if I had to pick between abundant fusion power and a few anomalies contained with ELAD generators, I would pick the latter every time.