High-temperature, heat pipe-cooled, fast micro-reactor concept using stainless steel and uranium oxide fuel elements

The Design A micro-reactor concept here is a high-temperature, heat pipe-cooled, fast reactor with a thermal power of only 5 megawatts. A recuperated open-air Brayton cycle will permit the reactor system to generate approximately 2 megawatts of electricity. The active core is composed of 1134 fuel elements that are reflected on top and bottom by steel and beryllium oxide with an alumina side reflector containing control drums. The unique fuel element design features a steel-clad hexagonal-shaped UO2 fuel pellet with a central hole to accommodate a potassium heat pipe. The reactor system is similar to the Los Alamos National Laboratory's (LANL) Mega-Power concept, except the LANL stainless steel monolith core structure is replaced with these more readily manufacturable hexagonal-shaped fuel elements. Individual fabrication of these elements also leads to improved system reliability, because each element can be fabricated, assembled, inspected, and tested prior to core installation. These elements are also designed to alleviate excessive thermal stresses generated in the LANL steel monolith at operational temperatures in the 700 °C range. This new micro-reactor active core design concept, referred to as Design A, is herein evaluated and compared in terms of its design, neutronics, thermal properties, materials, and manufacturability to the LANL concept.