PASSIVE DECAY HEAT REMOVAL CAPABILITY OF FIXED BED NUCLEAR REACTOR FUEL CHAMBER

摘要

Fixed Bed Nuclear Reactor (FBNR) is one of new modular type reactors that has been proposed for INPRO-IAEA. FBNR offers some of the characteristics: Passive cooling, proliferation resistant, simple design, inherently safe, and reduced environmental impact. Through its characteristics, decay heat removal from the inherent part, Fuel Chamber, plays an important role for assuring the robustness of this reactor type. Author proposes two scenarios of passive cooling: First, cooling process by flooding the Fuel Chamber with sub-cooled water from higher-level tank which of heat transfer occurred by film boiling; Second, cooling process by flow of water through fuel particles due to the natural convection where in assumption that system doesn't fail on retaining the function of integrated steam generator. Initial conditions for this model are fuel temperature at 616 K and water temperature at 563 K. The continuity and momentum equations are applied only for the fluid phase but energy equation is applied for solid and fluid phases. Scenario one gives promising cooling process where 1.14 hours post-shutdown fuel particles can be cooled down to 533 K. Meanwhile, scenario two shows fuel temperature is kept below 630 K for the same time frame.