Recently, Zheng Yu, a postdoctoral fellow in the Laboratory of Fusion Reactor Materials and Components at the Institute of Plasma Physics, Hefei Research Institute, Chinese Academy of Sciences, has made new progress in large-scale accelerated simulation research in Monte Carlo. The results were published in Nuclear Fusion.
In the field of nuclear energy, Monte Carlo simulation is one of the most accurate solution methods, and the fusion reactor geometry is complex, the size is large, the shield is thick, and there is a problem of deep penetration shielding in Monte Carlo’s large-scale calculation, resulting in low computational efficiency, high time cost, and difficult to converge, which has always been the technical bottleneck of fusion reactor nuclear analysis. In view of this problem, Zheng Yu cooperated with the German KIT Neutron Physics and Reactor Technology Institute to propose a new global subtractive variance method (on-the-fly, referred to as the OTF method) directly based on the Monca transport core. This method introduces the optimization idea of timely updating the power window in the transportation process, proposes an efficient and unbiased solution based on the automatic dynamic adjustment of the upper limit of the power window for a long time, and completes the development and testing of the corresponding software, which is applied to the international thermonuclear experimental reactor ITER, the international fusion material irradiation facility – the verification of the nuclear analysis example of the neutron source IFMIF-DONES accelerator for DEMO, and achieves significant acceleration effect (Figures 1 and 2).
Figure 1. ITER-C Neutron model (left), neutron flux distribution (middle), and statistical error distribution (right)
Figure 2. IFMIF-DONES T gate horizontal section view (left), neutron flux distribution (center), error distribution (right)
Figure 3. Distribution of neutron fluxes in the lateral section (left) and longitudinal slice (right) of the CFETR 360° model
The development of OTF acceleration methods has made the Monte Carlo method applied to the shielding analysis of large-scale and complex models a reality, and efficiently serves the fine full-reactor radiation field calculation of CFETR (Figure 3), supports the nuclear analysis and shielding design of CFETR cladding, bias filter, heating system, etc., and provides an important evaluation basis for the safe operation of key components such as magnets and vacuum chambers under nuclear irradiation conditions, and the relevant application results are also published in Nuclear Fusion. (Source: Hefei Institute of Physical Sciences, Chinese Academy of Sciences)
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