Innovative Accelerator Technology for Accelerator Driven Subcritical Reactors

核能目前提供了我们20%的电力，但在15年内，英国的大多数核电站将关闭。ADS系统有潜力以一种更安全、更便宜、更可持续的核电形式填补无碳核电站的空白，对消费者和环境都有好处。ns-FFAG加速器可能是使ADS反应堆可行的关键因素。在2007年的《能源白皮书》中，英国政府建议，忽视核能——目前成本效益更高的低碳选择之一——将增加无法实现长期碳减排目标的风险。然而，尽管核电的碳足迹为零，但公众对其的看法却受到安全问题、核废料的放射性毒性以及与核扩散的联系等问题的影响。与传统的铀或钚燃料临界核反应堆相比，一个安全得多的替代方案是加速器驱动的亚临界（ADS）反应堆。这样的反应堆不仅可以使用比铀丰富4倍的非浓缩钍作为燃料，而且它既可以自己生产和燃烧燃料，也不会在燃料循环中产生钚。最重要的是，由于反应堆是亚临界的，核链式反应必须由外部中子源提供，在这种情况下，由加速的质子或重离子从反应堆内部的散裂靶上切碎（或剥落）中子提供。因此，加速器在传统反应堆中扮演着控制棒的角色，其显著区别在于，加速器和反应堆可以瞬间关闭，从而使反应堆完全安全。此外，ADS产生的长寿命核废料比传统反应堆产生的要少得多。此外，由散裂过程产生的剩余中子可用于燃烧、转化和使传统反应堆的废物变得安全。因此，ADS反应堆为传统核能提供了一种安全、环保和可持续的选择。加速器本身就是这种反应堆的关键。运行它的功率不能超过产生的功率。它必须非常安全可靠，易于操作，并且不容易受到束流跳闸的影响（这会给反应堆堆芯带来不必要的热负荷和工程负荷）。目前的回旋加速器、同步加速器和线性加速器都不完全适合或不够强大。然而，作为英国加速器科学和放射肿瘤学联盟（BASROC）的“一致性”项目的一部分，我们正在开发一种全新类型的加速器，即所谓的无缩放固定场交替梯度（ns-FFAG）加速器，它比传统加速器更简单，更可靠，能耗更低。ns-FFAG很可能被证明是ADS反应堆的理想、紧凑和成本效益高的驱动因素，我们在这里提出的计划将着手探索这种可能性。我们将聘请一名博士后研究助理与BASROC confirm团队一起工作。PDRA将评估使ns-FFAG驱动ADS系统所需的操作参数，并将有机会使用我们的ns-FFAG原型测试参数。最终，我们希望达到一个功能设计，可以成本。我们将利用这一点让核工业对进一步开发该项目感兴趣。尽管目前欧洲、美国、日本、中国、印度和澳大利亚都在调查ADS反应堆，但英国几乎没有ADS反应堆。我们的项目不仅将帮助英国加快ADS技术的发展速度，如果成功，还将使一种更安全的核电形式更接近实现。

Nuclear power currently produces 20% of our electricity, yet within 15 years most of the UK's nuclear powerstations will have closed. The ADS system has the potential to fill the gap of carbon-free nuclear power stations with a safer, cheaper, more sustainable form of nuclear power, for the benefit of the consumer and the environment. The ns-FFAG accelerator could be a key factor in making ADS reactors viable.In the 2007 Energy White Paper the UK government suggested that to ignore nuclear power, one of the currently more cost effective low-carbon options , would be to increase the risk of failing to meet our long term carbon reduction goal. However although nuclear power has a zero carbon footprint, its public perception is coloured by issues of safety, the radiotoxicity of its waste, and its links to proliferation.A far safer alternative to conventional uranium or plutonium fuelled critical nuclear reactors is the accelerator driven sub-critical (ADS) reactor. Not only can such a reactor be fuelled by non-enriched thorium, which is 4 times more plentiful than uranium, it both breeds and burns its own fuel and does not produce plutonium as part of the fuel cycle. Most importantly, because the reactor is subcritical the nuclear chain reaction must be fed from an outside source of neutrons, in this case provided by accelerated protons or heavying ions chipping (or spalling) neutrons from a spallation target inside the reactor itself. The accelerator therefore plays the part of the control rods in a conventional reactor with the significant difference that the accelerator, and hence the reactor, can be switched off instantaneously rendering the reactor entirely safe. In addition the amount of long-lived nuclear waste from an ADS is considerably less than that from a conventional reactor. Moreover, the surplus neutrons produced by the spallation process can be utilised to burn, transmute and render safe the waste from conventional reactors. ADS reactors therefore provide a safe, environmentally friendly and sustainable option to conventional nuclear power.The accelerator itself is a key to such a reactor. The power to run it must not outweigh the power generated. It must be extremely safe and reliable, easily operated and not be susceptible to beam trips (which place unnecessary thermal and therefore engineering loads on the reactor core). Current cyclotron, synchrotron and linear accelerators are not entirely suitable or sufficently powerful for the task. However as part of the CONFORM project of the British Accelerator Science and Radiation Oncology Consortium (BASROC) we are developing and prototyping an entirely new type of accelerator - the so called non-scaling fixed field alternating gradient (ns-FFAG) accelerator- which is simpler, more reliable, and consumes less power than conventional accelerators.The ns-FFAG may well prove to be an ideal, compact and cost effective driver for an ADS reactor, and the programme we propose here will set out to explore this possibility. We will employ a postdoctoral research assistant to work along side the BASROC CONFORM team. The PDRA will evaluate the operational parameters necesssary to enable a ns-FFAG to drive an ADS system, and will also have the opportunity of testing the parameters using our ns-FFAG prototype. Ultimately we hope to arrive at a functional design that can be costed. We will use this to get the nuclear industry interested in developing the project further. Although ADS reactors are currently under investigation in Europe, US, Japan, China, India and Australia, there is little or no ADS effort in the UK. Our project will not only help to bring the UK up to speed in ADS technology, if successful it will also bring a far safer form of nucler power much closer to realisation.