Radiation Shielding Study For Fusion Reactor Based On Neutronics Analysis Of ITER

Fusion energy is a clean energy and recognized to be one of the most practical and potential ways to sustain the energy demands in the future. Up to now, research related to fusion science and technology has been started in many countries such as China, Japan, Korea, Europe, Russia, etc. A series of fusion reactor concepts covering the engineering testing stage, science and technology demonstration stage, commercial application stage have been proposed. Radiation shielding is a key subsystem for fusion reactors as well as the first defense line for radiological safety. However, because of the complex structure and special shielding requirements, tools and experience in fission and accelerator shielding design cannot be applied directly in fusion design. Specific studies on fusion shielding are extraordinarily necessary.The International Thermonuclear Experimental Reactor (ITER) is one of the world biggest scientific cooperation programs and plays an important role in the way of fusion energy application. As an important topic for safety demonstration, radiation shielding has great significance in ITER licencing. Considering these requirements, the dissertation present therotical studies on fusion reactor shielding on the basis of the International Thermonuclear Experimental Reactor ITER, including:(1) The characteristics of radiation source in fusion reactor were analyzed. Combined with the protection of person and components, the requirements and limitations for fusion shielding design were studied, including the radiation limits to magnets, components rewelding, electronic systems and occupational radiation protection, etc. The main issues and challenges in design, assessment, validation and verification were addressed.(2) Based on the current design of ITER, the shielding related issues for ITER Tokamak and buildings were further studies. The assessment of coolant activation for ITER plasma facing components was improved. The activation of a typical ITER blanket, which is one of the typical radiological sources was analyzed along with assessment of the induced shutdown dose. Typical shielding problems in Tokamak machine, such as the admissibility of rewelding in blanket, the effects on maintenance dose inside cryostat from port streaming, were analyzed and guidance for improvement was provided. For the shielding of building, the study focused on the shielding capability of port cell in Tokamak building and shielding doors in hot cell building. The weakness in current ITER shielding design was found out and optimized schemes were proposed. Besides, based on the relationship between ITER and high power fusion reactors, the shielding problems for fusion reactors were analyzed qualitatively, and the applicability of experience in ITER design and analysis for furture fusion reactors were predicted with suggestions.(3) The uncertainty analysis for shielding calculation was conducted to assess the effect of model simplification, material homogenization and selection of neutron spectrum structures. It was found that in fusion shielding assessment, the calculation based on simplified model is not conservative. The maximum difference from detail model calculation could be3times, higher than the usually used safety factor "2".The study above helped to provide important data and guidance for ITER shielding improvement and safety license application. More comprehensive understanding about fusion reactor shielding was provided and further works on the shielding criteria for fusion reactors could be proceeded.