Novel method accelerates neutron transport calculation

Recently, Dr. ZHENG Yu from Institute of Plasma Physics, Hefei Institutes of Chinese Academy of Sciences, proposed a new method to accelerate Monte Carlo large-scale shielding simulation, in cooperation with the Institute of Neutron Physics and Reactor Technology (INR) of Karlsruhe Institute of Technology (KIT), Germany.

The new global variance reduction method, which is also called On The Fly (OTF), made the Monte Carlo (MC) codes applicable for shielding analysis of large-scale and complex fusion reactor.

The relevant results have been published in Nuclear Fusion.

MC is one of the most accurate methods in the field of nuclear analysis for fusion and fission reactor. However, the shielding calculation of fusion device by using of Monte Carlo transport codes is still challenging due to the complexity and heavy shielding of a fusion reactor. The slow convergence rate of MC method rendering in analogue simulations is prohibitively costly in computational time.

This method introduced a new idea of timely updating the weight window along the transport process.

Also, it proposed an innovative solution based on automatic dynamic adjustment of the upper bounds of weight window, which addressed the problem that has plagued the neutronics particle transport calculation of MC for a long time.

When scientists applied OTF method to the nuclear analysis of international thermonuclear experimental reactor (ITER), the International Fusion Materials Irradiation Facility-DEMO-oriented neutron source IFMIF-DONES accelerator, they achieved remarkable acceleration effects. Compared with the automated variance reduction generator (ADVANTG) variance reduction method developed by Oak Ridge National Laboratory (ORNL), the acceleration effect of OTF method is 13 to 20 times that of ADVANTG.

Aside from that, OTF was serving the global radiation field calculation of Chinese fusion engineering testing reactor (CFETR), and provided an important basis for evaluating the safe operation of key components such as magnets and vacuum vessel under nuclear irradiation conditions.