The success of the Accelerator Driven Subcritical Reactor (ADSR)
will depend on the progress of their Accelerator Programme
First in order to understand the significance of why the ADSR is so attractive in theory is that it can run without Uranium or Plutonium as a startup fuel. That’s where the word “subcritical” comes in. From my initial observations it appears to be very different from a molten salt reactor. I will leave it to other more qualified bloggers to comment.
It’s going to be an interesting year for accelerator technology. Some are hoping for fusion!. But the ADSR needs less ambitious results but still challenging. They need a steady high energy, high current proton energy beam.
One principal limiting technology is that of the proton accelerator driver (Appendix I):
- Cyclotrons can deliver appropriate continuous currents in the mA range, but cannot deliver sufficiently high proton energies.
- Synchrotrons can deliver appropriate proton energies, but only at lower, pulsed currents.
- Linear accelerators can deliver both the required currents and energies but are too large and expensive to be considered as a feasible commercial proposition.
Perhaps more significantly, no existing accelerator technology can meet the stringent reliability demands of a fully functioning ADSR power system. All accelerators are subject to numerous and frequent “trips” or loss of beam for periods extending from milliseconds to seconds, often many times an hour. As the spallation neutrons produced by the proton driver are responsible for the giga-Watt thermal power within the core, repeated loss of beam, even over such short periods, results in rapid thermal cycling and therefore intolerable thermal stress on the ADSR core sub- and super-structure.
It is significant that particle accelerators of a power appropriate for deployment as ADSR drivers (5-10MW) are at the forefront of accelerator technology and are generally developed individually for specific particle or nuclear physics experiments, or as drivers for major scientific facilities such as the planned European Spallation Source (5MW) and the recently commissioned Spallation Neutron Source (1.5MW) in the United States. Moreover, accelerator reliability on the scale demand by ADSR deployment remains a key performance issue and must be explored through appropriate R&D programmes.
The principal challenge of ADSR technology is thus to develop an appropriately powerful and sufficiently reliable accelerator. Fortunately the UK is able to draw upon its internationally recognised expertise in accelerator design and innovation, and is therefore well placed to meet this challenge.
Seems like quite a challenge but it does raise an interesting question. If the LFTR needs a fissile fuel source to kick start the thorium cycle why can’t it use an accelerator beam? Maybe one of the followers can help with that question.
Here’s the proposed plan for their own portable (my word choice) accelerator system
A phased accelerator development programme: AESIR The principal objective of the five year AESIR (Accelerator Energy Systems with Inbuilt Reliability) R&D programme is to design, build and demonstrate a robust and reliable prototype accelerator system which will be suitable for mass production and commercialisation as an ADSR proton driver. The AESIR programme must therefore, on the one hand, be coherent and focussed, whilst on the other undertake the task of comprehensively evaluating the suitability of all potential advanced accelerator architectures and components.
Yes in theory an accelerator can be used to provide the fissile makeup for a LFTR/MSR. In fact that is the proposed route of the Japanese efforts of Prof Furukawa. He does not agree with connecting an accelerator to the reactor but to simply use it is a fuel farm. However, in my opinion this is not a very good route. The electricity costs alone would amount to something like 240$ a gram (from a paper by Ralph Moir) and I don’t think governments would very much like a machine that can produce weapons material if misused. The capital costs per accelerator is also enormous.
As for using accelerators as control elements for any reactor, I try to keep an open mind but I still don’t see how they are much more than a hugely expensive control rod. I have yet to meet a practicing nuclear engineer that has had any real interest in the concept.
David LeBlanc
Is there any way that a magnetic field could help with the right fluoride or chloride salt mix so that a laser could get the maximium efficiency in a molten salt which might make the need for a steady flow laser less important? I know that’s very different from the ADSR and probably differs from the Japanese concept.
Sorry, No Comprendo. What is the laser for?
Sorry I am in my own fantasy world but I was imagining that an accelerator is a laser and since you said the FUJI uses an accelerator that it might be possible to improve the efficiency by using a magnetic field but if the contents don’t respond to a magnetic field then there would be no point. And maybe I’m in dreamland and should stop now.