A molten salt nuclear reactor a neutron moderator core that has an inner region that defines channels of a first diameter separated by a first pitch and, an outer region that defines channels of a second diameter separated by a second pitch. The first diameter is larger than the second diameter and the first pitch is larger than the second pitch. This configuration allows for an increased capture of neutrons by fertile elements in the outer region. That is, less neutrons are lost to the outside of the core. The configuration is such that the neutron multiplication factor is larger than one in the inner portion and lower than one in the outer portion.

A passive reactor cavity cooling system according to the present invention includes: a reactor cavity formed between a reactor vessel and a containment structure enclosing the reactor vessel; a first cooling system to control external air to sequentially pass through an air falling pipe and an air rising pipe provided in the reactor cavity, so that residual heat of a core transferred to the reactor cavity is discharged to the atmosphere; a second cooling system having a water cooling pipe disposed in an inner space of the containment structure or in a wall of the containment structure to discharge the residual heat of the core transferred to the reactor cavity to outside; and a functional conductor having an insulating property in a normal operation temperature range of the reactor and a heat transfer property in an accident occurrence temperature range of the reactor which is a higher temperature environment than the normal operation temperature range, wherein the air falling pipe and the water cooling pipe are disposed behind the air rising pipe with respect to a direction viewed from the reactor vessel, and the functional conductor is disposed between the air falling pipe and the air rising pipe.

This patent application is for a process of nuclear power generation with ˜KW output by making the Thorium fuel of LiF+BeF.sub.2+ThF.sub.4 in a Thorium Molten Salt Reactor (Th-MSR) to undergo fission along the thorium fuel cycle by providing thermal neutrons which were obtained by slowing down of fast neutrons from n external neutron generators with the help of graphite moderators carefully arranged inside the Th-MSR.

The molten salt that entered the reactor at a temperature of 600° C. becomes hot to 750° C. due to nuclear fission, goes through a heat exchanger and returns to the reactor. The output power of this reactor is proportional to the number of thermal neutrons supplied to the inside of the reactor, and when the external neutron generator is turned ON-OFF, nuclear power generation is also ON-OFF.

This Th-MSR power generation process with thermal neutron generators, which Dr. Choi is applying for a patent, will be one of the most innovative ways to generate ˜kW range nuclear power with the use of 100% non-radioactive nuclear fuel since until now all the Th-MSR power generation scheme relied upon neutrons from the natural decay of Uranium-235 mixed with the Thorium fuel of LiF+BeF.sub.2+ThF.sub.4 with a mixing ratio of 80% ThF4 to 20% UF4. Key Word Thorium Molten Salt Reactor, Thermal Neutron Generator

A method of cooling a nuclear reactor core is disclosed. The method includes contacting the nuclear reactor core with an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions. Nuclear reactors are also disclosed. The nuclear reactor has a neutron moderator that is an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions, or the nuclear reactor has an emergency core cooling system including a vessel containing a volume of an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions. The nuclear reactor can also have both an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions as a neutron moderator and an emergency core cooling system that includes an aqueous solution comprising at least one of polyhedral boron hydride anions or carborane anions.

A passive reactor cavity cooling system according to the present invention includes: a reactor cavity formed between a reactor vessel and a containment structure enclosing the reactor vessel; a first cooling system to control external air to sequentially pass through an air falling pipe and an air rising pipe provided in the reactor cavity, so that residual heat of a core transferred to the reactor cavity is discharged to the atmosphere; a second cooling system having a water cooling pipe disposed in an inner space of the containment structure or in a wall of the containment structure to discharge the residual heat of the core transferred to the reactor cavity to outside; and a functional conductor having an insulating property in a normal operation temperature range of the reactor and a heat transfer property in an accident occurrence temperature range of the reactor which is a higher temperature environment than the normal operation temperature range, wherein the air falling pipe and the water cooling pipe are disposed behind the air rising pipe with respect to a direction viewed from the reactor vessel, and the functional conductor is disposed between the air falling pipe and the air rising pipe.

The technical solution relates to a fluoride salt-cooled high-temperature nuclear reactor with low output.

A molten salt nuclear reactor a neutron moderator core that has an inner region that defines channels of a first diameter separated by a first pitch and, an outer region that defines channels of a second diameter separated by a second pitch. The first diameter is larger than the second diameter and the first pitch is larger than the second pitch. This configuration allows for an increased capture of neutrons by fertile elements in the outer region. That is, less neutrons are lost to the outside of the core. The configuration is such that the neutron multiplication factor is larger than one in the inner portion and lower than one in the outer portion.