Innovative Accelerator Technology for Accelerator Driven Subcritical Reactors

核电目前占英国发电量的20%，但在15年内，英国大部分核电站都将关闭。ADS系统有可能用一种更安全、更便宜、更可持续的核电形式来填补无碳核电站的空白，从而造福于消费者和环境。Ns-FFAG加速器可能是使ADS反应堆可行的关键因素。在2007年能源白皮书中，英国政府表示，忽视核能--目前更具成本效益的低碳选择之一--将增加无法实现我们的长期碳减排目标的风险。然而，尽管核能的碳足迹为零，但它的公众认知受到安全问题、核废料的辐射毒性及其与核扩散的联系的影响。与传统的以铀或钚为燃料的关键核反应堆相比，一个安全得多的替代方案是加速器驱动的次临界(ADS)反应堆。这样的反应堆不仅可以使用比铀多4倍的非浓缩钍作为燃料，而且它既可以繁殖和燃烧自己的燃料，也不会在燃料循环中产生钚。最重要的是，因为反应堆是亚临界的，所以核连锁反应必须来自外部的中子源，在这种情况下，提供的中子源是加速的质子或重离子，这些离子从反应堆内部的散裂目标中剥离(或剥落)中子。因此，加速器在常规反应堆中扮演控制棒的角色，其显著不同之处在于，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的数量比传统反应堆少得多。此外，散裂过程产生的过剩中子可以被用来燃烧、转化传统反应堆产生的废物，并使其安全。因此，ADS反应堆为常规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。它必须极其安全可靠，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，从而造成工程负荷)。目前的回旋加速器、同步加速器和直线加速器并不完全适合或足够强大地完成这项任务。然而，作为英国加速器科学和辐射肿瘤学联盟(BASROC)CONFORM项目的一部分，我们正在开发和制作一种全新类型的加速器--所谓的无比例固定场交变梯度(ns-FFAG)加速器--它比传统加速器更简单、更可靠、功耗更低。ns-FFAG很可能被证明是ADS反应堆的理想、紧凑和经济有效的驱动器，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巴斯罗克Conform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原型测试这些参数。最终，我们希望得到一种可以计算成本的功能设计。我们将利用这一点让核工业对进一步开发该项目感兴趣。尽管欧洲、美国、日本、中国、印度和澳大利亚的ADS反应堆目前正在接受调查，但英国几乎没有或根本没有ADS努力。我们的项目不仅将帮助英国加快ADS技术的发展，如果成功，它还将使一种更安全的核动力形式更接近实现。

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.