Study on the layout of the SCWR fuel assembly

The supercritical water reactor (SCWR) is the only light water reactor of the six reactor types recommended by the Generation IV International Forum (GIF). Compared with traditional LWR, SCWR may achieve high thermal efficiency and simple plant equipment. Related researches are being carried out worldwide, among which the optimal design for fuel assembly and core is an important trend. This paper analyzes the current fuel assembly (FA) designs and calculates their local power peaking factors with MCNP code under the condition of using the same enrichment fuel and containing no burnable poison, and finds that the local power peaking factors of these FAs are a little far away from the design objective. This paper analyzes several factors influencing local power peaking factor, and shows that in the case of uniform moderation, the square FA depress local power peaking factor with the disadvantage of making the fuel assembly under-moderation as a whole and decrease consequently the Keff, which is mainly caused by the arrangement of the fuel rods. The paper also comes to a conclusion that, compared to the square FA, the hexagonal FA will easily resolve the contradiction between the uniform moderation and full moderation, achieving the optimization of the fuel assembly design. (authors)