Low Part Count
A solid fuel reactor requires thousands of highly engineered, highly stressed fuel pins. Some fast breeder designs require more than 50,000. Failure of a single fuel pin will shut the reactor down and force a difficult decontamination process.
ThorCon is a liquid fuel reactor. In a liquid fuel reactor’s primary containment there are a few dozen components and only one major moving part, a pump impeller. And if something does break, you can drain the principle source of radioactivity, the fuel, in order to fix things.
Move Fuel Around With a Pump
Anyone visiting a solid fuel nuclear plant will be amazed and perhaps appalled by the refueling systems. Some such as Candu are remarkably ingenious. Some are horrible kluges. Some employ complicated robotic fuel element shuffling devices that are supposed to operate for decades in a highly radioactive environment with nil maintenance. All are complex, failure prone headaches that drive the design.
All this disappears with liquid fuel. Moreover, we can adjust the fuel composition on the fly. There is no need for excess reactivity to account for the fact that in a solid fuel reactor the quality of the fuel deteriorates over time. Nor need you worry much about variations in the fuel makeup. Solid fuel reactors, especially fast breeders, require a very even isotopic fuel composition to avoid hot spots. In a liquid fuel reactor, any variation in the fuelsalt is quickly mixed away.
Pressurized Water Reactors operate at 160 bar (2300 psi) pressure. High operating pressure means 9 inch thick reactor vessels and piping. Some of these forgings can only be done by a few specialized foundries. Worse, if there is a big piping failure, the pressurized water explodes into steam spraying radioactivity all over the place. A very large and strong containment structure in needed. In the event of a loss of coolant, this gigantic structure must somehow be kept cool despite all the decay heat in the core.
Now the reactor, heat exchangers and all sorts of plumbing are entombed in this mausoleum where they are extremely difficult to repair or replace. Therefore, we pretend that they will need essentially no maintenance for the life of the plant.
But it gets still worse. These colossal structures must be made out of reinforced concrete. The rebar is as thick as a man’s wrist and so dense that special concrete is formulated to allow it to flow into place. Reinforced concrete construction has four major characteristics:
- It cannot be done on a panel line using block construction.
- It is nearly impossible to automate.
- It cannot be done in parallel. The containment done becomes the critical path. Even the Chinese cannot build a PWR in less than 4 years.
- It is difficult to inspect and extremely difficult to repair.
ThorCon’s low operating pressure and lack of phase change allows us to use a simple steel containment structure that can be manufactured as blocks on a panel line using less than 5 man-hours per ton of steel and assembled in months if not weeks.