空间推进用气冷反应堆技术的挑战和JANUS空间反应堆概念的发展
The challenges of gas-cooled reactor technology for space propulsion and the development of the JANUS space reactor concept
摘要：
有强烈的动机开发高功率输出核裂变反应堆（约1兆瓦）用于空间应用，如高有效载荷任务和火星以外的长期任务，其中太阳通量的减少使使用替代能源具有挑战性。许多已公布的用于空间应用的气冷反应堆设计在100 kWe范围内提供输出，典型功率密度约为4 MW/m $^3$。在这里，我们提出了一个气冷反应堆设计-称为JANUS -采用氦-氖冷却剂和直接布雷顿循环，可以实现高功率输出（约0.8 MWe）和更高的功率密度（24 MW/m $^3$）比以前公布的设计。堆芯采用包覆颗粒燃料形式，在石墨基质中具有氮化铀内核，并具有高填充率（45%）。从CEA公布的OPUS空间反应堆设计开始，考虑了各种方法来实现气冷反应堆的高功率密度，包括改变堆芯纵横比。我们的JANUS设计采用减小的冷却剂通道直径和燃料元件间距，同时增加燃料元件的数量并采用径向浓缩分区。该设计实现了功率密度的显著增加，同时遵守2000有效全功率日的堆芯寿命限制和1900 K的峰值燃料工作温度。堆芯已经用ERANOS和SERPENT代码进行了中子建模，并使用我们开发的简单而强大的热尺寸工具来研究峰值燃料温度，以确保燃料在其设计限制范围内运行并帮助优化。
英文摘要：
There is a strong motivation to develop high-power output nuclear fission reactors (around 1 MWe) for space applications, such as high-payload missions and long-duration missions beyond Mars, where the reduced solar flux makes using alternative energy sources challenging. Many published gas-cooled reactor designs for space applications deliver outputs in the 100 kWe regime, with typical power densities of around 4 MW/m$^3$. Here we present a gas-cooled reactor design - referred to as JANUS - employing He-Xe coolant and operating on a direct Brayton cycle, that can achieve a high power output (around 0.8 MWe) and higher power density (24 MW/m$^3$) than previously published designs. The core employs a coated particle fuel form with uranium nitride kernels in a graphite matrix and with a high packing fraction (45%). Starting from the CEA's published OPUS space reactor design, a variety of approaches were considered for achieving high power densities in a gas-cooled reactor, including changing the core aspect ratio. Our JANUS design uses a decreased coolant channel diameter and fuel element pitch, whilst increasing the number of fuel elements and employing radial enrichment zoning. The design achieves a significant increase in power density whilst obeying core-life limits of 2000 Effective Full Power Days and a peak fuel operating temperature of 1900 K. The core has been modelled neutronically with the ERANOS and SERPENT codes, with a simple yet robust thermal dimensioning tool developed by us to study peak fuel temperatures, to ensure the fuel operates within its design limitations and to aid optimisation.
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