Concept of a safe tank-type water-moderated water-cooled reactor with fuel assemblies based on HTGCR fuel micropellets

The objective of this paper was to develop reactor that are passively safe, and to do this, the use of an HTGCR-type fuel assembly in a light water-moderated/cooled reactor was examined. Characteristics of the 500 and 1500 MWt VVER designs were used in this study, and the required thermal and nuclear characteristics of the HTGCR fuel assemblies to be used in these designs were determined. Optimum performance was obtained with an increase in fuel mass and adecrease in pellet size. The behavior of the modified HTGCR assembly was then examined during a large-break LOCA, with melting of the active zone. It was determined that with normal RHR in service, the fuel temperature would not exceed 1600 degree C. Consequently, the integrity of the individual fuel pellets would be intact in this accident scenario, and no fission products would be released. This passive feature may allow for the elimination of some safety systems or for the relaxation of safety system requirements. While reactor costs are estimated to be 10-15% higher, the total project costs would be expected to be lower