Neutron and gamma flux distributions and their implications for radiation damage in the shielded superconducting core of a fusion power plant
Neutron and gamma flux distributions and their implications for radiation damage in the shielded superconducting core of a fusion power plant
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中子和伽马通量分布及其对聚变发电厂屏蔽超导核心辐射损伤的影响
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发表时间：
2017
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通讯作者：
J. Morgan
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作者：
C. Windsor;J. Morgan
已使用 MCNP 蒙特卡罗程序研究了拟议的球形托卡马克发电厂的屏蔽高温超导中心柱内的中子和伽马射线通量。计算屏蔽和超导核心上通量的空间、能量和角度变化，并用于指定与辐射损伤和激活相关的实验研究。平均中子和伽马通量在能量和角度上平均，显示出通过屏蔽呈指数衰减，然后在核心区域保持大致恒定。中子的平均能量比通过屏蔽的中子通量衰减得更慢，而伽马能量几乎恒定在 2 MeV 左右。研究了作为能量函数的微分中子和伽马通量。中子能谱显示出 1 MeV 左右的聚变峰，在较低能量下变为超热 E−0.85 变化，在热能下变为麦克斯韦分布。中子和伽马能谱是针对超导芯外表面定义的，与损伤研究相关。屏蔽中包含硼化钨被证明可以减少能量沉积。考虑了等离子体主半径在 0.6 至 2.5 m 之间的一系列等离子体场景。中子和伽马通量随等离子体半径呈指数衰减，除非屏蔽厚度较低。使用当前已知的高温超导体实验注量限制，达到注量限制之前的连续运行时间已计算为 1.4 m 主半径处的天数增加到 2.2 m 处的年数。这项工作通过证明长寿命聚变发电所需的中子屏蔽可以容纳在紧凑的设备中，有助于验证球形托卡马克聚变发电路线的概念。
The neutron and gamma ray fluxes within the shielded high-temperature superconducting central columns of proposed spherical tokamak power plants have been studied using the MCNP Monte-Carlo code. The spatial, energy and angular variations of the fluxes over the shield and superconducting core are computed and used to specify experimental studies relevant to radiation damage and activation. The mean neutron and gamma fluxes, averaged over energy and angle, are shown to decay exponentially through the shield and then to remain roughly constant in the core region. The mean energy of neutrons is shown to decay more slowly than the neutron flux through the shield while the gamma energy is almost constant around 2 MeV. The differential neutron and gamma fluxes as a function of energy are examined. The neutron spectrum shows a fusion peak around 1 MeV changing at lower energies into an epithermal E−0.85 variation and at thermal energies to a Maxwellian distribution. The neutron and gamma energy spectra are defined for the outer surface of the superconducting core, relevant to damage studies. The inclusion of tungsten boride in the shield is shown to reduce energy deposition. A series of plasma scenarios with varying plasma major radii between 0.6 and 2.5 m was considered. Neutron and gamma fluxes are shown to decay exponentially with plasma radius, except at low shield thickness. Using the currently known experimental fluence limitations for high temperature superconductors, the continuous running time before the fluence limit is reached has been calculated to be days at 1.4 m major radius increasing to years at 2.2 m. This work helps validate the concept of the spherical tokamak route to fusion power by demonstrating that the neutron shielding required for long lifetime fusion power generation can be accommodated in a compact device.