A first-of-a-kind reactor system has been set up in Belgium by coupling a subcritical assembly with a particle accelerator. The work is a major step in a program to research advanced waste management.
|A cutaway of Myrrha.
The equipment, known as Guinevere, is a demonstration model that supports the project for a larger version that will be called Myrrha (Multipurpose Hybrid Research Reactor for High-tech Applications). It was assembled by France's National Centre for Scientific Research and is managed by the Belgian Nuclear Research Centre (SCK-CEN) at Mol, about 50 kilometres east of Antwerp. The overall project is supported by 12 other European laboratories and the European Commission.
Nuclear terminology classifies an item of equipment as in a critical state if the chain fission reaction is self-sustaining and each reaction leads on average to one more. The term supercritical means the number of fissions is increasing, while subcritical means it is decreasing and will therefore dwindle to nothing.
Guinevere is designed to be subcritical if it were not for an accelerator system that sends a constant stream of protons to a target that emits neutrons to trigger fission. SCK-CEN said, "This type of reactor is very safe because the reactor section relies on a particle accelerator: when it is turned off, the reactor will stop immediately."
As well as this kind of accelerator-driven operation, Guinevere is also capable of 'classic' criticality triggered by a neutron source in the reactor core and maintained by the reactor geometry and operation of its lead cooling system. This mode of operation was 'inaugurated' in February 2011.
Guinevere has "very limited power" and is being used to learn more about the operation and control of this kind of reactor arrangement. The knowledge will be put to use at Guinevere's larger relation, Myhrra, which should begin operation in 2023.
Myrrha will be able to produce radioisotopes and doped silicon, but its research functions would be particularly well suited to investigating transmutation. This is when certain radioactive isotopes with long half lives are made to 'catch' a neutron and thereby change into a different isotope that will decay more quickly to a stable form with no radioactivity. If achievable on an industrial scale, transmutation could greatly simplify the permanent geologic disposal of radioactive waste. Myrrha can also be used to test the feasibility of lead fast reactor technology and is seen as complimentary to the Jules Horowitz Reactor, a thermal spectrum reactor under construction in Cadarache, France.
The total cost of Myrrha has been put at €960 million ($1.2 billion), with 40% of this coming from the Belgian government. SCK-CEN is looking to set up an international consortium to ensure additional financing and has completed a memorandum of understanding with the Chinese Academy of Sciences focusing on Myrrha.
Researched and written
by World Nuclear News