The present invention concerns a nuclear reactor, preferably a pool-type nuclear reactor cooled by liquid metal or molten salts, having a core formed of a bundle of fuel elements and immersed in a primary fluid for cooling the core; the fuel elements are provided with expanders acting in a direction perpendicular to the axes of the fuel elements and having low thermal expansion elements which engage alternatively with high thermal expansion elements to amplify the radial expansion of respective end elements which, when a predetermined temperature is exceeded, engage with each other and space the fuel elements from one another and in particular their active part to introduce negative reactivity into the core.

The present invention concerns a nuclear reactor, preferably a pool-type nuclear reactor cooled by liquid metal or molten salts, having a core formed of a bundle of fuel elements and immersed in a primary fluid for cooling the core; the fuel elements are provided with expanders acting in a direction perpendicular to the axes of the fuel elements and having low thermal expansion elements which engage alternatively with high thermal expansion elements to amplify the radial expansion of respective end elements which, when a predetermined temperature is exceeded, engage with each other and space the fuel elements from one another and in particular their active part to introduce negative reactivity into the core.

The purpose of the present invention is to provide a neutron-absorbing material which has high neutron absorption performance, is less apt to suffer structural degradation caused by irradiation with neutrons or rays, and has satisfactory water resistance. The glass composition according to the present invention is characterized by containing Gd2O3, B2O3, CeO2, and Bi2O3 when the components are expressed in terms of oxide, the total amount of Gd2O3 and B2O3 being 65 mol % or greater in terms of oxide amount.

The purpose of the present invention is to provide a neutron-absorbing material which has high neutron absorption performance, is less apt to suffer structural degradation caused by irradiation with neutrons or rays, and has satisfactory water resistance. The glass composition according to the present invention is characterized by containing Gd2O3, B2O3, CeO2, and Bi2O3 when the components are expressed in terms of oxide, the total amount of Gd2O3 and B2O3 being 65 mol % or greater in terms of oxide amount.

A molten salt reactor includes a nuclear reactor core for sustaining a nuclear fission reaction fueled by a molten fuel salt. A molten fuel salt control system removes a volume of the molten fuel salt from the nuclear reactor core to maintain a reactivity parameter within a range of nominal reactivity. The molten fuel salt control system includes a molten fuel salt exchange system that fluidically couples to the nuclear reactor core and exchanges a volume of the molten fuel salt with a volume of a feed material containing a mixture of a selected fertile material and a carrier salt. The molten fuel salt control system can include a volumetric displacement control system having one or more volumetric displacement bodies insertable into the nuclear reactor core. Each volumetric displacement body can remove a volume of molten fuel salt from the nuclear reactor core, such as via a spill-over system.

A molten salt reactor includes a nuclear reactor core for sustaining a nuclear fission reaction fueled by a molten fuel salt. A molten fuel salt control system removes a volume of the molten fuel salt from the nuclear reactor core to maintain a reactivity parameter within a range of nominal reactivity. The molten fuel salt control system includes a molten fuel salt exchange system that fluidically couples to the nuclear reactor core and exchanges a volume of the molten fuel salt with a volume of a feed material containing a mixture of a selected fertile material and a carrier salt. The molten fuel salt control system can include a volumetric displacement control system having one or more volumetric displacement bodies insertable into the nuclear reactor core. Each volumetric displacement body can remove a volume of molten fuel salt from the nuclear reactor core, such as via a spill-over system.

A nuclear reactor includes a passive reactivity control nuclear fuel device located in a nuclear reactor core. The passive reactivity control nuclear fuel device includes a multiple-walled fuel chamber having an outer wall chamber and an inner wall chamber contained within the outer wall chamber. The inner wall chamber is positioned within the outer wall chamber to hold nuclear fuel in a molten fuel state within a high neutron importance region. The inner wall chamber allows at least a portion of the nuclear fuel to move in a molten fuel state to a lower neutron importance region while the molten nuclear fuel remains within the inner wall chamber as the temperature of the nuclear fuel satisfies a negative reactivity feedback expansion temperature condition. A duct contains the multiple-walled fuel chamber and flows a heat conducting fluid through the duct and in thermal communication with the outer wall chamber.

A nuclear reactor includes a passive reactivity control nuclear fuel device located in a nuclear reactor core. The passive reactivity control nuclear fuel device includes a multiple-walled fuel chamber having an outer wall chamber and an inner wall chamber contained within the outer wall chamber. The inner wall chamber is positioned within the outer wall chamber to hold nuclear fuel in a molten fuel state within a high neutron importance region. The inner wall chamber allows at least a portion of the nuclear fuel to move in a molten fuel state to a lower neutron importance region while the molten nuclear fuel remains within the inner wall chamber as the temperature of the nuclear fuel satisfies a negative reactivity feedback expansion temperature condition. A duct contains the multiple-walled fuel chamber and flows a heat conducting fluid through the duct and in thermal communication with the outer wall chamber.

A nuclear reactor includes a passive reactivity control nuclear fuel device located in a nuclear reactor core. The passive reactivity control nuclear fuel device includes a multiple-walled fuel chamber having an outer wall chamber and an inner wall chamber contained within the outer wall chamber. The inner wall chamber is positioned within the outer wall chamber to hold nuclear fuel in a molten fuel state within a high neutron importance region. The inner wall chamber allows at least a portion of the nuclear fuel to move in a molten fuel state to a lower neutron importance region while the molten nuclear fuel remains within the inner wall chamber as the temperature of the nuclear fuel satisfies a negative reactivity feedback expansion temperature condition. A duct contains the multiple-walled fuel chamber and flows a heat conducting fluid through the duct and in thermal communication with the outer wall chamber.

A nuclear reactor includes a passive reactivity control nuclear fuel device located in a nuclear reactor core. The passive reactivity control nuclear fuel device includes a multiple-walled fuel chamber having an outer wall chamber and an inner wall chamber contained within the outer wall chamber. The inner wall chamber is positioned within the outer wall chamber to hold nuclear fuel in a molten fuel state within a high neutron importance region. The inner wall chamber allows at least a portion of the nuclear fuel to move in a molten fuel state to a lower neutron importance region while the molten nuclear fuel remains within the inner wall chamber as the temperature of the nuclear fuel satisfies a negative reactivity feedback expansion temperature condition. A duct contains the multiple-walled fuel chamber and flows a heat conducting fluid through the duct and in thermal communication with the outer wall chamber.