Investigation and Analysis on Tritium Accumulation Phenomenon Based on a Water-Cooled Blanket for CFETR at 1.5 GW

China Fusion Engineering Test Reactor (CFETR) is a major scientific project independently designed and developed by China, which will demonstrate the engineering feasibility of continuous large-scale fusion energy for safe and stable power generation. One of the most critical issues for fusion reactors is to achieve tritium self-sufficiency with a tritium breeding ratio (TBR) of no less than 1.0, as it relates to the ability of the fusion reactor to fulfill the fuel cycle and continue stable operation. Moreover, the release and inventory of tritium is also a significant factor affecting the operation of CFETR. The temperature distribution inside the breeder blanket is precisely related to the tritium release. Therefore, it is particularly important for CFETR to optimize the temperature field inside the breeding blanket. It is significant that to ensure that the temperature of the mixed pebble bed zone reaches the limit of 900 °C as much as possible, which could maximize the tritium release efficiency. Simultaneously, it must make sure that other structural materials meet the allowable value of temperature. Tritium accumulation close to the cooling pipe is investigation, which will be adverse to tritium release. Hence, in order to solve this difficulty, the Be12 Ti tube was sleeved on the cooling pipe to increase the temperature of the mixed pebble bed zone near the cooling pipe. In this work, a water-cooled solid breeder blanket was proposed and the nuclear heat was calculated based on the 1.5 GW fusion power. The nuclear heat was used as the preprocessing data for thermal calculation carried out by the Monte Carlo N-Particle Transport Code (MCNP). With the given conditions, the thermal hydraulic was simulated with the commercial CFD code, the ANSYS CFX. In this way, a breeding blanket structure with a uniform temperature field of mixed bed zone close to 900 °C can be obtained. In addition, the selection of Be12 Ti tubes with the thickness of 0.525 cm can ensure a high TBR and increase the temperature around the cooling tubes to improve the tritium release efficiency. This work provides an important reference for the subsequent engineering design of CFETR breeding blanket.