An aft plenum assembly for use with a nuclear thermal reactor including a pressure vessel and a nozzle assembly having a top plenum plate disposed within the pressure vessel, the top plenum plate defining a first plurality of fuel flow apertures, a bottom plenum plate disposed within the pressure vessel, the bottom plenum plate being parallel to the top plenum plate thereby defining a plenum space therebetween, the bottom plenum plate defining a second plurality of fuel flow apertures, and a plurality of tubular connections extending between the first plurality of fuel flow apertures of the top plenum plate and the second plurality of fuel flow apertures of the bottom plenum plate, wherein the aft plenum assembly is disposed between the pressure vessel and the nozzle assembly.

Disclosed herein is a reactor including a reactor vessel and a containment vessel configured to surround the reactor vessel. The containment vessel includes a thermal radiation shield disposed on an inner wall, and a gap between the reactor vessel and the containment vessel is in an atmospheric pressure and air atmosphere state.

A method and apparatus for extending the period a nuclear steam supply system spent fuel pool can be safely passively cooled by storing the spent fuel offloaded from the reactor, in the containment for one reactor operating cycle. During a refueling the spent fuel that is not to be returned to the reactor and the spent fuel that will be returned to the reactor are stored separately in shielded locations within the containment. After one operating cycle, the spent fuel stored within the containment that was not returned to the reactor just prior to the last operating cycle, is offloaded to the spent fuel pool and replaced by the newly offloaded spent fuel that is being retired.

Disclosed is an entropy-controlled solid solution matrix BCC alloy having strong resistance to high-temperature neutron radiation damage. The entropy-controlled solid solution matrix BCC alloy includes three or more multicomponent main elements selected from the element group consisting of Zr, Al, Nb, Mo, Cr, V, and Ti selected based on a neutron absorption cross-sectional area and a mixing enthalpy. Each of the elements is included in an amount of 5 to 35 at %, and the entropy-controlled solid solution matrix BCC alloy is a BCC-structure solid solution matrix alloy in a medium-entropy to high-entropy state. In this invention, damage caused by neutron radiation is reduced, and entropy is controlled to thus ensure a solid solution matrix BCC structure having a slow diffusion speed, and accordingly, resistance to void swelling due to radioactive rays is high.

An objective of the invention is to provide an austenitic stainless steel article having superior irradiation resistance and stress corrosion cracking resistance than before while maintaining mechanical properties equivalent to those of conventional ones. There is provided a dispersion strengthened austenitic stainless steel article, including: 16-26 mass % of Cr; 8-22 mass % of Ni; 0.005-0.08 mass % of C; 0.002-0.1 mass % of N; 0.02-0.4 mass % of O; at least one of 0.2-2.8 mass % of Zr, 0.4-5 mass % of Ta, and 0.2-2.6 mass % of Ti; and a balance consisting of Fe and inevitable impurities. The Zr, Ta and Ti components form inclusion particles in the stainless steel article by combining with the C, N and O components. The stainless steel article has an average grain size of 1 m or less and a maximum grain size of 5 m or less.

A passive safety and cooling system for nuclear fission reactors powered by a bundle of radioactive fuel rods enclosed in a pressure vessel provides four redundant levels of dissipating and containing heat. Metal layered with carbon nanotube surrounds the pressure vessel, lines the system's floor, and studs a concrete containment dome. A retractable ceramic tile outer dome contains, absorbs and blocks any remaining heat or nuclear reactions, and optionally, releases them to the atmosphere, for the ultimate dissipation.

A method and apparatus for extending the period a nuclear steam supply system spent fuel pool can be safely passively cooled by storing the spent fuel offloaded from the reactor, in the containment for one reactor operating cycle. During a refueling the spent fuel that is not to be returned to the reactor and the spent fuel that will be returned to the reactor are stored separately in shielded locations within the containment. After one operating cycle, the spent fuel stored within the containment that was not returned to the reactor just prior to the last operating cycle, is offloaded to the spent fuel pool and replaced by the newly offloaded spent fuel that is being retired.

A method and apparatus for extending the period a nuclear steam supply system spent fuel pool can be safely passively cooled by storing the spent fuel offloaded from the reactor, in the containment for one reactor operating cycle. During a refueling the spent fuel that is not to be returned to the reactor and the spent fuel that will be returned to the reactor are stored separately in shielded locations within the containment. After one operating cycle, the spent fuel stored within the containment that was not returned to the reactor just prior to the last operating cycle, is offloaded to the spent fuel pool and replaced by the newly offloaded spent fuel that is being retired.

A method and apparatus for extending the period a nuclear steam supply system spent fuel pool can be safely passively cooled by storing the spent fuel offloaded from the reactor, in the containment for one reactor operating cycle. During a refueling the spent fuel that is not to be returned to the reactor and the spent fuel that will be returned to the reactor are stored separately in shielded locations within the containment. After one operating cycle, the spent fuel stored within the containment that was not returned to the reactor just prior to the last operating cycle, is offloaded to the spent fuel pool and replaced by the newly offloaded spent fuel that is being retired.

Disclosed is a reactor thermal management system. A molten salt reactor vessel and a second component (e.g., a drain tank) fluidly coupled with the molten salt reactor vessel are configured to receive a flow of a molten salt therewith. The reactor thermal management system includes an internal shield or vessel encompassing the molten salt reactor vessel and the second component, the internal shield or vessel defining a first thermally insulative region therein. The internal shield or vessel is configured to maintain the first thermally insulated region above a melting temperature of the molten salt during operation of the molten salt reactor vessel.