Appendix I: ADSR Accelerator Requirements continued FFAGs The Fixed-Field Alternating-Gradient (FFAG) accelerator combines m<strong>an</strong>y of the adv<strong>an</strong>tages of the synchrotron <strong>an</strong>d cyclotron. Similar to cyclotrons, FFAGs have fixed dipole fields allowing high duty factors <strong>an</strong>d rapid accelerations, but provide a synchrotron-like focusing of the beam. The beam current is only limited by the accelerating radio-frequency power that c<strong>an</strong> be fed to the particle beam. To minimise the size <strong>an</strong>d complexity of a FFAG a so-called non-scaling design c<strong>an</strong> be used. The UK is uniquely placed in FFAG development since the world’s first non-scaling FFAG, EMMA, is presently under construction at Daresbury Laboratory as part of the CONFORM project. The provision of <strong>an</strong> experimental prototype, as a focus for UK accelerator experts to test the ns-FFAG principle will secure the expertise for the UK to develop ns-FFAG designs for nuclear, medical, <strong>an</strong>d scientific applications. Summary The characteristics of the potential accelerator technologies available for ADSR deployment is summarised in the following table. Cyclotron Clearly there are several options, with different consequences <strong>an</strong>d risks. Whilst the ns-FFAG holds the greatest potential in terms of current, energy, cost <strong>an</strong>d size, should it prove impossible to secure ns-FFAG technology on the appropriate time scale the other technologies provide a proven fallback. It should also be emphasised that the R&D work necessary to establish the necessary levels of accelerator reliability is independent of the type of accelerator. As a nuclear reactor fuel, thorium presents numerous adv<strong>an</strong>tages in terms of availability, proliferation resist<strong>an</strong>ce, nuclear waste m<strong>an</strong>agement <strong>an</strong>d reactor perform<strong>an</strong>ce. In a 2005 status report the IAEA concluded that “….in recent times, the need for proliferation-resist<strong>an</strong>ce, longer fuel cycles, higher burn up, improved waste form characteristics, reduction of plutonium inventories <strong>an</strong>d in situ use of bred-in fissile material has led to renewed interest in Thorium-based fuels <strong>an</strong>d fuel cycles in several developed countries…….” The following points briefly summarise the main adv<strong>an</strong>tages of thorium fuel. Linacs Linear accelerators (linacs) are a relatively straightforward <strong>an</strong>d well understood technology that c<strong>an</strong> deliver high currents at high energies – but at a high price. Rather th<strong>an</strong> recirculating particles through just a few accelerating cavities to provide the acceleration, a much longer sequence of cavities each accelerate the charged particles only once. Circular accelerators designed to accelerate protons to energies of the order of 1 GeV generally have diameters of a few tens of meters, the equivalent linac must be several hundred meters long containing a sequence of accelerating cavities each of which are much more expensive th<strong>an</strong> the simple magnets which constitute the bulk of the circular accelerator. In the absence of cheaper, viable alternatives Linear accelerators are deployed in one-of-a-kind major large scale scientific facilities such as the SNS or ESS, where high energy, high current beams are required. Without signific<strong>an</strong>t technological adv<strong>an</strong>ced it may not be cost effective to exploit such linear accelerator technology as drivers for a commercial fleet of ADSR power stations. Plus points High current High energy High current <strong>an</strong>d high energy High current <strong>an</strong>d high energy Minus points Energy limited Current limited Not yet proven Expense Examples PSI CERN PSB EMMA ESS, SNS Appendix II: Thorium as a nuclear fuel 50 <strong>Towards</strong> <strong>an</strong> <strong>Alternative</strong> <strong>Nuclear</strong> <strong>Future</strong> Synchrotron ns-FFAG Linac A2.1 Thorium: <strong>an</strong> abund<strong>an</strong>t resource Thorium is present in the Earth’s crust in large qu<strong>an</strong>tities (similarly abund<strong>an</strong>t as lead <strong>an</strong>d about three times more abund<strong>an</strong>t th<strong>an</strong> ur<strong>an</strong>ium) <strong>an</strong>d widely distributed, with <strong>an</strong> average concentration of 10 ppm. This resource has barely been exploited commercially. Present in m<strong>an</strong>y phosphates, silicates, carbonates <strong>an</strong>d oxide minerals, thorium generally occurs in association with ur<strong>an</strong>ium <strong>an</strong>d rare earth metals in diverse rock types. Monazite, a mixed thorium-rare-earthur<strong>an</strong>ium phosphate, is the most common source of thorium, available in m<strong>an</strong>y countries in beach <strong>an</strong>d river s<strong>an</strong>ds.
Estimated thorium resources by country Country Total Identified Thorium Resources (‘000 t TH)