Modelling the electron anti-neutrino flux from nuclear reactors

模拟核反应堆的电子反中微子通量

• 批准号: 2435526
• 金额: --
• 依托单位: University of Liverpool
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2435526
• 关键词: Modelling; electron; anti; neutrino; flux

Since the first experimental detection of the neutrino, with the Cowan-Reines experiment in the 1950s,nuclear test reactors have played a central role within the field of neutrino physics as a source of electronanti-neutrinos. These electron anti-neutrinos can be detected through an inverse beta decay reaction:[1] and arise from the beta decay of neutron rich nuclei formed by the fission of majoractinides within the core. As a result, this electron anti-neutrino flux is inherently tied to the operation ofa reactor, and related to the power of the reactor and the fissile inventory of its core [2].Given the dependence on the operational parameters and fissile inventory of a reactor, the concept of utilisingneutrinos to monitor reactors has existed for some time, but it is only recently that the understanding of thehas made such prospects feasible [3]. In contrast to current IAEA procedures, anti-neutrino based safeguardsallow for bulk accountancy of nuclear fuel, yielding an estimate of the masses of fissile material producedwithout necessitating assumptions regarding the mass of items. Additionally, anti-neutrino methods arenon-invasive, being carried out through use of a detector at a standoff distance from the reactor and allowfor real time measurement of the core.In the near future, the most reasonable expectation for the utilisation of this technology is through thedeployment of tonne-scale portable anti-neutrino detectors at a standoff distance of the order of 10 metres.At these distances, neutrino oscillation experiments have demonstrated the vastly reduced effects of neutrinodisappearance on the flux compared to detectors operating at far greater standoff distances, such as in theKamland experiment [4] [5]. Whilst far field monitoring of nuclear reactors through neutrino detection is adesirable prospect, the contributions of neutrino mixing and the increased background of the spectra greatlyincrease the complexity of modelling required.Use of the electron anti-neutrino spectra for the purposes of reactor monitoring is reliant on deviationsfrom an expected flux and energy spectra. Thus, models of an expected flux and energy spectra are neededin comparison with the measured rate, where through statistical methods, a threshold for a significant deviationfrom the model, and the time frame needed to detect this deviation, can be established [6].This anti-neutrino modelling is likely to form the main underpinning of a thesis in anti-neutrino physics.This will include generation of anti-neutrino source terms for reactors based on operational data providedfrom nuclear reactors, such as Hartlepool, along with spent fuel inventories. These source terms will bequantified to include to provide an estimation of the flux incident to a detector at varying distances, consid-1ering phenomena such the neutrino mixing of this flux along with the expected evolution of a nuclear core ona real time basis, something that existing applications, such as geo-neutrinos [7], do not consider and mighttherefore be used to inform such software.Beyond this, several avenues exist for further pursuit. These include phenomena such as the unexpectedexcess of anti-neutrinos detected at around 5 MeV with an unknown cause, speculated by some to be due topossibilities such as neutrino induced deuteron disintegration or coherent elastic neutrino-nucleus scattering[8]. Another, further, anomaly that may lend itself to investigation is that of the drop in expected reactoranti-neutrino events in short baseline experiments [9].2 References[1] Cowan, C., Reines, F., Harrison, F., Kruse, H. and McGuire, A., 1956. Detection of the Free Neutrino:a Confirmation. Science, 124(3212), pp.103- 104.[2]Bemporad, C., Gratta, G. and Vogel, P., 2002. Reactor-based neutrino oscillation experiments. Reviewsof Modern Physics, 74(2), pp.297-328.[3] Bowden, N., 2008. Reactor monitori

自从 20 世纪 50 年代首次通过实验检测到中微子以来，核试验反应堆作为电子反中微子的来源，在中微子物理领域发挥了核心作用。这些电子反中微子可以通过逆β衰变反应来检测：[1]并且由堆芯内大锕系元素裂变形成的富中子核的β衰变产生。因此，这种电子反中微子通量本质上与反应堆的运行有关，并且与反应堆的功率及其堆芯的裂变库存有关[2]。考虑到对运行参数和裂变库存的依赖性反应堆中，利用中微子来监测反应堆的概念已经存在了一段时间，但直到最近，人们对这一概念的理解才使这种前景变得可行[3]。与国际原子能机构现行程序相反，基于反中微子的保障措施允许对核燃料进行大量核算，从而对所产生的裂变材料的质量进行估计，而无需对物品的质量进行假设。此外，反中微子方法是非侵入性的，通过使用距反应堆一定距离的探测器进行，并允许对堆芯进行实时测量。在不久的将来，对该技术的利用最合理的期望是通过在10米量级的相距距离上部署吨级便携式反中微子探测器。在这些距离上，中微子振荡实验已经证明，中微子振荡的影响大大降低与在远距离运行的探测器相比，通量上的中微子消失，例如卡姆兰实验 [4] [5]。虽然通过中微子检测对核反应堆进行远场监测是一个理想的前景，但中微子混合的贡献和光谱背景的增加大大增加了所需建模的复杂性。使用电子反中微子光谱进行反应堆监测依赖于与预期通量和能谱的偏差。因此，需要与测量的速率进行比较的预期通量和能谱的模型，其中通过统计方法，可以建立与模型的显着偏差的阈值以及检测这种偏差所需的时间范围[6]。反中微子建模很可能成为反中微子物理学论文的主要基础。这将包括根据哈特尔普尔等核反应堆提供的运行数据以及乏燃料生成反应堆的反中微子源项库存。这些源项将被量化，包括提供对在不同距离处入射到探测器的通量的估计，考虑到中微子混合等现象以及实时核芯的预期演化，这是现有的应用程序，例如地球中微子[7]，不考虑并且可能因此被用来通知此类软件。除此之外，还存在一些进一步追求的途径。这些现象包括在 5 MeV 左右检测到意外过量的反中微子，原因不明，一些人推测这是由于中微子引起的氘核分裂或相干弹性中微子核散射等可能性造成的[8]。另一个可能需要调查的异常现象是短基线实验中预期反应堆反中微子事件的下降[9]。2 参考文献[1] Cowan, C.、Reines, F.、Harrison, F., Kruse, H. 和 McGuire, A.，1956。游离中微子的检测：确认。 Science，124(3212)，第 103-104 页。[2]Bemporad, C.、Gratta, G. 和 Vogel, P.，2002。基于反应堆的中微子振荡实验。现代物理学评论，74(2)，第 297-328 页。[3] Bowden, N., 2008. 反应堆监测