A nuclear reactor system includes a nuclear reactor core disposed in a pressure vessel. Nuclear reactor system further includes control drums disposed longitudinally within the pressure vessel and laterally surrounding fuel elements and at least one moderator element of the nuclear reactor core to control reactivity. Each of the control drums includes a reflector material and an absorber material. Nuclear reactor system further includes an automatic shutdown controller and an electrical drive mechanism coupled to rotatably control the control drum. Automatic shutdown controller includes a counterweight to impart a bias and an actuator. To automatically shut down the nuclear reactor core during a loss or interruption of electrical power from a power source to the electrical drive mechanism, the actuator is coupled to the counterweight and responsive to the bias to align the absorber material of one or more control drums to face inwards towards the nuclear reactor core.

An enhanced architecture for a nuclear reactor core includes several technologies: (1) nuclear fuel tiles (S-Block); and (2) a high-temperature thermal insulator and tube liners with a low-temperature solid-phase moderator (U-Mod) to improve safety, reliability, heat transfer, efficiency, and compactness. In S-Block, nuclear fuel tiles include a fuel shape designed with an interlocking geometry pattern to optimize heat transfer between nuclear fuel tiles and into a fuel coolant and bring the fuel coolant in direct contact with the nuclear fuel tiles. Nuclear fuel tiles can be shaped with discontinuous nuclear fuel lateral facets and have fuel coolant passages formed therein to provide direct contact between the fuel coolant and the nuclear fuel tiles. In U-Mod, tube liners with low hydrogen diffusivity retain hydrogen in the low-temperature solid-phase moderator even at elevated temperatures and the high-temperature thermal insulator insulates the solid-phase moderator from the nuclear fuel tiles.

A modular nuclear reactor system includes a lift-out, replaceable nuclear reactor core configured for replacement as a singular unit during a single lift-out event, such as rather than lifting and replacing individual fuel assemblies and/or fuel elements. The system includes a reactor vessel and a power generation system configured to convert thermal energy in a high temperature working fluid received from the reactor vessel into electrical energy. The reactor vessel includes: a vessel inlet and an adjacent vessel outlet arranged near a bottom on the vessel; a vessel receptacle configured to receive a unified core assembly; locating datums in the base of the vessel receptacle and configured to constrain a core assembly in multiple degrees of freedom; and an interstitial zone surrounding the vessel receptacle and housing a set of control or moderating drums.

A modular nuclear reactor system includes a lift-out, replaceable nuclear reactor core configured for replacement as a singular unit during a single lift-out event, such as rather than lifting and replacing individual fuel assemblies and/or fuel elements. The system includes a reactor vessel and a power generation system configured to convert thermal energy in a high temperature working fluid received from the reactor vessel into electrical energy. The reactor vessel includes: a vessel inlet and an adjacent vessel outlet arranged near a bottom on the vessel; a vessel receptacle configured to receive a unified core assembly; locating datums in the base of the vessel receptacle and configured to constrain a core assembly in multiple degrees of freedom; and an interstitial zone surrounding the vessel receptacle and housing a set of control or moderating drums.

The reactor core includes at least one module, solid and liquid neutron moderators. The module contains a casing, at least one heat pipe, one fuel element and thermal insulation. The heat pipe is in the shape of a casing with a wick and contains a coolant. The fuel element is made of nuclear fuel, arranged in the evaporation area of the heat pipe around its casing in thermal contact with it, and enclosed in a can. Low-melting metals with a high boiling point are used as the coolant of the heat pipe. Thermal insulation is arranged between the can and the casing of the module. At least one hole is made in the solid neutron moderator, in which at least one module is arranged. The space between the casing of the module and the solid neutron moderator is filled with a liquid neutron moderator.

The reactor core includes at least one module, solid and liquid neutron moderators. The module contains a casing, at least one heat pipe, one fuel element and thermal insulation. The heat pipe is in the shape of a casing with a wick and contains a coolant. The fuel element is made of nuclear fuel, arranged in the evaporation area of the heat pipe around its casing in thermal contact with it, and enclosed in a can. Low-melting metals with a high boiling point are used as the coolant of the heat pipe. Thermal insulation is arranged between the can and the casing of the module. At least one hole is made in the solid neutron moderator, in which at least one module is arranged. The space between the casing of the module and the solid neutron moderator is filled with a liquid neutron moderator.

A nuclear energy reactor core includes at least one module, solid and liquid neutron moderators. The module comprises the housing, at least one heat pipe, at least one fuel element, casing and heat insulation. The heat pipe is configured as the housing and wick, and comprises the evaporating coolant. The fuel element consists of the shell and nuclear fuel. The heat pipe evaporation and fuel elements are enclosed into the casing filled with the liquid coolant. The high-melting hot metals, for example, lithium, calcium, lead, silver, are used as the heat pipe coolant and liquid coolant of the casing. The heat insulation is arranged in the space between the casing and module housing. The solid neutron moderator has at least one hole, wherein at least one module is located. The space between the solid neutron moderator and module is filled with the liquid neutron moderator.

A nuclear energy reactor core includes at least one module, solid and liquid neutron moderators. The module comprises the housing, at least one heat pipe, at least one fuel element, casing and heat insulation. The heat pipe is configured as the housing and wick, and comprises the evaporating coolant. The fuel element consists of the shell and nuclear fuel. The heat pipe evaporation and fuel elements are enclosed into the casing filled with the liquid coolant. The high-melting hot metals, for example, lithium, calcium, lead, silver, are used as the heat pipe coolant and liquid coolant of the casing. The heat insulation is arranged in the space between the casing and module housing. The solid neutron moderator has at least one hole, wherein at least one module is located. The space between the solid neutron moderator and module is filled with the liquid neutron moderator.

A thermal bridge for improving thermal transfer between a fuel element to a fuel block wherein there is provided a high temperature gas cooled nuclear reactor fuel block comprising a fuel channel and a coolant channel wherein the fuel channel comprises a fuel element, the fuel channel further comprising a thermal bridge thermally linking the fuel element and the fuel channel, wherein the thermal bridge comprises a melting point greater than the working temperature of the fuel block, thereby improving thermal transfer from the fuel element to the fuel block, thereby improving thermal transfer to the coolant channel.

A thermal bridge for improving thermal transfer between a fuel element to a fuel block wherein there is provided a high temperature gas cooled nuclear reactor fuel block comprising a fuel channel and a coolant channel wherein the fuel channel comprises a fuel element, the fuel channel further comprising a thermal bridge thermally linking the fuel element and the fuel channel, wherein the thermal bridge comprises a melting point greater than the working temperature of the fuel block, thereby improving thermal transfer from the fuel element to the fuel block, thereby improving thermal transfer to the coolant channel.