In the country that does not have a nuclear power plant of its own, a new type of reactor with superlatives is being developed: Copenhagen Atomics has found a project partner for the construction in the renowned Swiss Paul Scherrer Institute. By Wolfgang Kempkens
The Paul Scherrer Institute in Switzerland.
picture alliance/KEYSTONE | CHRISTIAN BEUTLER
A new reactor is being built in Switzerland. It was developed by the company Copenhagen Atomics (Video). The fact that Denmark, of all countries, which does not have a single nuclear power plant, is presenting the concept for a plant that is inherently safe, i.e. cannot “go through” or even explode, and which also defuses nuclear waste and produces its own fuel through a process called breeding, could arouse suspicion in view of the superlatives.
But this is prevented by the partner that the Danes have won to realize the project: the renowned Swiss Paul Scherrer Institute (PSI) in Villigen and Würenlingen in the Swiss canton of Aargau. The plant is also to be built there and will go into operation as early as 2026. The partners agreed to the cooperation on July 1 of this year.
“Personally, I am very happy that Copenhagen Atomics has chosen PSI as a cooperation partner to prove the feasibility of its vision here at our institute,” says Marco Streit, head of the PSI Hot Laboratory, the only Swiss laboratory that is allowed to work with radioactive materials and is significantly involved in the construction of the reactor, which for the time being is only intended to serve to prove feasibility.
Unlike all previously built nuclear fission reactors, the so-called molten salt or liquid salt reactor does not have a core in which the fuel uranium and/or plutonium is permanently located. The fissile material is finely distributed in molten salt, which is pumped through the reactor in a circuit. When it reaches the interior, the fission process begins, in this case of uranium 235 – the number 235 indicates the number of neutrons and protons in the nucleus of the atom. (Animation of power plant with several molten salt reactors).
This produces heat that can be used for industrial processes or to generate electricity, as in Bontang, Indonesia. A large factory for the production of green ammonia is to be built there, which will draw its energy from several reactors from Copenhagen Atomics. The electricity production costs are to be an unbeatable two cents per kilowatt hour, according to the PSE.
The fuel is a mixture of salts with the metals lithium, thorium and slightly enriched uranium. At the heart of the reactor, through which the molten salt is pumped, there is heavy water, which acts as a moderator. Its job is to slow down the neutrons released when the uranium atoms split. Only then can they split further atoms, defuse radioactive waste contained in the melt and, last but not least, convert thorium into fissile uranium (uranium 233). The reactor thus produces its own fuel. Thorium is available in large quantities worldwide, unlike uranium.
The radioactive waste is removed from the molten salt in each cycle and identified. Long-lived waste, i.e. waste that is dangerous for thousands of years, is fed back in to be defused by neutron capture. What remains is waste that only emits radiation for a few hundred years instead of many thousands.
When uranium is split, heat is released that heats the salt. A temperature of up to 1400 degrees is possible without damaging the salt, according to the Society for Reactor Safety (GRS) in Cologne. Due to the high temperature, steam can be generated with properties that correspond to those in modern fossil thermal power plants. This means that turbo generators off the assembly line can be used to generate electricity, so extremely expensive custom-made products are not necessary. The heat can also be used for industrial processes, such as producing cement and glass or splitting water to produce green hydrogen.
Normally, the Danish reactor provides a thermal temperature of 560 degrees Celsius with a module output of 100 megawatts. Each system fits into a standard container. It is completely assembled in a factory and transported to its destination by rail, ship, truck or even plane. If the size of one module is not sufficient, several of them can be set up next to each other, as is planned for Indonesia, for example.
Wolfgang Kempkens studied electrical engineering at the Technical University of Aachen. After working for the “Aachener Volkszeitung” and the “Wirtschaftswoche”, he now works as a freelance journalist. His main focus is energy and the environment.
