Technology development to evaluate dose rate distribution in PCV and to search for fuel debris submerged in water

开发技术来评估 PCV 中的剂量率分布并寻找淹没在水中的燃料碎片

基本信息

批准号：
EP/N017749/1
负责人：
Malcolm Joyce
金额：
$ 51.67万
依托单位：
Lancaster University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2015
资助国家：
英国
起止时间：
2015 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FN017749%2F1
关键词：
Technology development evaluate dose rate

项目摘要

The Great East Japan earthquake off the pacific coast of Tohoku was the most powerful recorded earthquake ever to hit Japan and triggered powerful tsunami waves. These inundated the coast including the area of the Fukushima Daiichi nuclear power plant. The flooding that followed disabled the auxiliary cooling systems at the power plant which, although being shut down, caused the reactors to overheat as a result of the effect of decay heat. This resulted in core damage to 3 of the 6 reactors on the Fukushima site. The damage is strongly suspected to have resulted in fragmentation of the nuclear fuel inside the reactors themselves and thus they are inoperable and need to be decommissioned. A key task is the removal of the nuclear fuel from the reactors. Once this is removed and stored safely elsewhere, radiation levels will fall significantly rendering the plant much safer than at present which will enable the remaining decommissioning requirements of the plant to continue more quickly, easily and with reduced cost.However, the fuel debris cannot be removed until we know how much there is and the form it has adopted after the accident i.e. is it a molten lump confined to the reactor or a mixture of damaged fuel elements with some egress beyond the primary containment? The reason we need to know this information is that it is essential that the likelihood of re-criticality is assessed (the chance that the nuclear fission reaction could start up inadvertently when the debris is disturbed) and also that we know of the extent of radioactivity and the form it is in in order to plan disposal routes. This information is very difficult to obtain because the type of reactor affected at Fukushima operated in what is known as a primary containment vessel or PCV. This is a large, thick-sided steel tank that is bolted shut very securely. A PCV has only a few, narrow access routes by which it is possible to get inside. There is no light inside and in order to set the reactor into a safe state and maintain its cooling, each reactor at Fukushima has been flooded with sea water. As a result of the radioactivity from the fuel there are very high levels of radiation exposure which prevent human beings from getting near to the PCV, whilst access to the PCV would result in serious injury to people and could damage untested instrumentation. The water filling the PCVs further complicates matters but, for the timebeing, cannot be removed as it acts to cool the fuel debris and to shield the surrounding area from radiation emitted by the reactor.In this project we combine two world-leading research activities in the United Kingdom associated with the portable detection of radioactivity (Lancaster University) and the development of small, submersible remote-operated vehicles (Manchester) in collaboration with the Japan Atomic Energy Agency, the National Maritime Research Institute of Japan, BeamSeiko Instrument Co. Ltd (Tokyo) and the Nagaoka University of Technology. The key objective of the research is to determine whether we can combine these capabilities to produce a remote-operated submersible vehicle with a radiation detection payload to detect neutrons and gamma rays. This device will be either mobile in the PCV, and thus able to inform us of the distribution of fuel debris in the reactor, or tethered in place in order to provide a continual indication of the core state; neither capability currently exists and clean-up of the reactors cannot continue without an assessment of this type. The distinction of the neutron and gamma-ray detection recommended for the payload on the submersible in this project is that the combination of the information provided by these two radiation types can tell us about the resident radioactivity, the risk of re-criticality and also provide a means for comparison with severe accident calculations to determine what happened to the reactor fuel in the accident.

东日本的大东日地震是托霍库（Toohoku）的太平洋海岸，是有史以来最强大的地震袭击日本，并引发了强大的海啸浪潮。这些淹没了沿海，包括福岛大道核电站的地区。随后残疾的洪水使电厂的辅助冷却系统虽然被关闭，但由于衰减热量的影响，反应堆导致反应堆过热。这导致了福岛站点上6个反应堆中3个中的3个核心损坏。强烈怀疑损坏导致反应堆本身内部的核燃料破裂，因此无法承受，需要退役。一个关键的任务是从反应堆中去除核燃料。一旦将其删除并安全地在其他地方安全存储，辐射水平将显着使植物比目前更安全，这将使植物的剩余退役要求更加快速，轻松，轻松，降低成本降低，否则才能将燃料碎屑除去。出口超出了主要遏制？我们需要知道这些信息的原因是，必须评估重新批判性的可能性（核裂变反应在碎片受到干扰时可能会无意间启动的机会），并且我们也知道放射性的程度及其形式的程度，其形式是为了计划处置路线。这些信息很难获得，因为在福岛（Fukushima）上受到影响的反应堆类型在所谓的主要围护容器或PCV中运行。这是一个大型厚的钢罐，非常安全地关闭螺栓。 PCV只有几个狭窄的访问路线，可以通过这些路线进入内部。内部没有光，为了将反应堆设置为安全状态并保持冷却状态，福岛的每个反应堆都充满了海水。由于燃料的放射性，辐射暴露水平很高，可防止人类靠近PCV，而使用PCV会导致严重伤害人，并可能损坏未经测试的仪器。填充PCV的水进一步使事情变得复杂，但是在时间到处是，不能去除燃料碎屑，以冷却燃料碎屑并保护周围区域免受反应堆发出的辐射。在这个项目中，我们结合了英国在英国的两项世界领导的研究活动，与可移植的远程（Lancaster University）与小型远程（lancaster University）相关联（Lancaster University）（lancaster University）的远程（lancaster）的遥远遥控器（lancaster）的遥远遥控器（能源局，日本国家海事研究所，Beamseiko Instrument Co. Ltd（东京）和Nagaoka技术大学。该研究的主要目的是确定我们是否可以将这些功能结合起来，以生产远程操纵的潜水车辆和辐射检测有效载荷以检测中子和伽玛射线。该设备要么是PCV中的移动设备，因此能够告知我们反应堆中燃料碎屑的分布，或者将其束缚在适当的位置以提供核心状态的持续指示；目前两种能力都不存在，如果没有对此类评估进行评估，反应器的清理就无法继续。建议在该项目中潜水的有效载荷的中子和伽马射线检测的区别是，这两种辐射类型提供的信息的组合可以告诉我们居民放射性，重新临界性的风险，还提供了一种与严重事故计算相比的手段，以确定事故中反应堆燃料发生的情况。