Three-dimensional model of DEMO-FNS facility considering neutronics and radiation shield problems

Recent neutronics studies of blankets for tokamak-based demonstration fusion neutron source (DEMO-FNS) showed a crucial influence of coolant composition on the transmutation rate of transuranic elements and tritium breeding in the system. The coolant choice varies with the neutron spectrum and shielding properties of the blanket. This paper presents a three-dimensional model developed for the Monte Carlo calculations of DEMO-FNS neutronics. The model was used for estimating the capability of the radiation shield to protect the superconducting electromagnetic system (EMS) from neutrons and gamma radiation for two types of coolants, namely water and supercritical carbon dioxide. The neutron balance, neutron energy spectra, and energy release of the neutrons and gamma radiation were evaluated in the shield, case, and superconductor at the inner and outer contours of the EMS. In comparison with the closed shielding option, the radiation heating power at the case and superconductor of the outer contour located between the injection port (IP) and the blanket maintenance port was 10 times higher than that in the area facing the injector. Thus, further improvement of the local shield design near the IP is needed.