ADS is the abbreviation for Accelerator Driven Sub-critical System, which works under the principle that spallation reaction is carried out between high-energy protons accelerated by accelerators and heavy target nuclei (for instance, Plumbum), during which dozens of neutrons can be generated by every proton, and these neutrons then serve as neutron sources to drive the sub-critical blanket system, so as to obtain energy through maintaining chain reactions of the sub-critical blanket system; meanwhile, the remained neutrons can be applied to nuclear material proliferation and nuclear waste transmutation.
The main purpose of developing ADS lies in separating and transmuting irradiated nuclear fuel. Three major units constitute the separation and transmutation system driven by accelerators, i.e., the accelerator unit, target unit, and the separation unit. The accelerator produces high-energy (approximately 1GeV) charged particles (like protons), and these particles bombard the heavy material target, which brings about super-strong neutron sources (we call this process the spallation).When the neutrons come into the sub-critical nucleus (called outer shell), they actualize the proliferation there. In the core of sub-critical nucleus, the actinide elements conduct transmutation reaction with fission products. After a while, the nuclei already transmuted have to be dissolved from the fuel, in order to avoid any undesirable activation. So the long-lived fission products and actinide elements return from the separation unit to the shell; and the short-lived and stable isotopes and fission poisons will be dissolved and disposed for storage.
At the very beginning, accelerator driven system was developed for the purpose of producing fission materials. Later on, accelerator technology development aroused people’s interest in the use of accelerator driven system. In the past decade, people have come up with various combined accelerator driven systems aiming at different applications.
For instance, the CERN proposed the adoption of a combined system based on the cyclotron years ago, which generates nuclear power circularly in the use of thorium material. This is an attractive conception, which involves in decreasing high active actinide elements contents, and in generating energy with thorium, which is a cheap and abundant natural resource.