Professor Jörg Starflinger, a nuclear energy expert from the University of Stuttgart in Germany, is also working on sC02-HeRo and says that its compact system means it can ’be tailored for old power plants’ and ‘new ones too’.Īnother technology that could prevent a meltdown is a Molten Salt Fast Reactor (MSFR), which uses molten salt combined with thorium and uranium to simultaneously act as a fuel and coolant. ‘The system kicks in automatically and no operator action is required,’ said Prof. In a reactor’s case, it can rapidly remove heat from the core’s surface and release it through steam. Its strength rests in the fact that supercritical CO2 is able to transport huge amounts of heat in a low-cost, non-toxic and non-flammable way. In theory, the system designed by sCO2-HeRo would stop a meltdown before it begins, opening a window for power plant operators to identify, and address, the potential overheating of the core by, for example, alternative mobile cooling systems. ‘By removing the heat, it prevents a potential core meltdown and buys time to react,’ said Professor Dieter Brillert from the University of Duisburg-Essen in Germany, who is the project coordinator of sCO2-HeRo, an EU-funded project developing the technology. The supercritical CO2 approach effectively removes heat build-up from a core without the requirement of external power sources, meaning it could work if the power is somehow cut, for example, during a natural disaster. They are working towards different ways to eliminate the risk of nuclear meltdowns, with automatic methods such as a heat removal system using so-called supercritical CO2, a state where the chemical has properties of both a gas and a liquid, and the use of molten salt. However, if the threat of a meltdown can be removed, some scientists think we should reconsider tapping into this carbon-free source of energy. Over the last few decades, public fears in some countries have prevented more nuclear power from entering the grid. The core - where the nuclear reactions take place - can’t withstand the rising temperature and begins to melt, allowing radioactive materials to possibly escape into the environment. Within one year after having been unloaded from the reactor, the activity contained in the irradiated fuel decreases to about 1/100 of the original level and slowly decreases further in the following years.A nuclear meltdown happens when the reactor's residual power exceeds the heat that can be removed by the cooling systems. The water largely shields the radiation and at the same time absorbs the generated residual heat. Therefore the spent fuel elements are initially stored in a water-filled pool inside the nuclear power plant ( spent fuel pool). If the heat would not be removed, this so-called residual heat would increase the temperature far beyond the melting point of the fuel elements. The fission products generating inside the fuel elements are radioactive and generate large amounts of heat, even after the reactor has been shut down. In the case of a pressurised water reactor, water with added boron is additionally fed into the reactor for permanent subcriticality. The control rods catch the neutrons generated in the reactor and thus end the nuclear chain reaction. Subcriticality is achieved by lowering the neutron-absorbing control rods between the fuel elements in the reactor core. To shut down a nuclear power plant, the reactor must be brought into a permanently uncritical state (subcriticality) and the heat that continuous to generate must be discharged safely. This chain reaction is maintained by the fact that more neutrons are produced in the fission process than are used in the absorption process.

During the power operation of a nuclear power plant, a self-sustaining chain reaction occurs in the reactor core.

Inside nuclear reactor meltdown