Configurations of molten fuel salt reactors are described that utilize neutron-reflecting coolants or a combination of primary salt coolants and secondary neutron-reflecting coolants. Further configurations are described that circulate liquid neutron-reflecting material around an reactor core to control the neutronics of the reactor. Furthermore, configurations which use the circulating neutron-reflecting material to actively cool the containment vessel are also described.

A diffuser extension sleeve 40 includes: a fixer 41 fixed to an upper portion of a diffuser in which an edge of an inlet mixer 25 is inserted, the inlet mixer 25 guiding circulating water, which is transported from a recirculating pump by pressure, downward along an inner surface of a reactor pressure vessel; a spacer 42 having a lower portion inserted in a gap defined by an outer surface 25a of the inlet mixer and an inner surface 26a of the diffuser; and a support 43 supporting the spacer 42 from the fixer 41 side and guiding movement of the spacer 42 in a longitudinal direction of the inlet mixer 25.

A diffuser extension sleeve 40 includes: a fixer 41 fixed to an upper portion of a diffuser in which an edge of an inlet mixer 25 is inserted, the inlet mixer 25 guiding circulating water, which is transported from a recirculating pump by pressure, downward along an inner surface of a reactor pressure vessel; a spacer 42 having a lower portion inserted in a gap defined by an outer surface 25a of the inlet mixer and an inner surface 26a of the diffuser; and a support 43 supporting the spacer 42 from the fixer 41 side and guiding movement of the spacer 42 in a longitudinal direction of the inlet mixer 25.

A reactor measurement-pipe maintenance clamp apparatus includes a first clamp mechanism and a second clamp mechanism. The first clamp mechanism includes clamps to fix the measurement pipe between the clamps, first clamp operation bolts that are allowed to be turned by remote control from above a reactor core, and wedge mechanisms to convert the turning of the clamp operation bolts to displacement of the clamps in a radial direction of the diffuser to generate clamping forces for securing the measurement pipe. The second clamp mechanism includes a support clamp to hold the support, a second clamp operation bolt that is allowed to be turned by remote control from above the reactor core, and a wedge mechanism to convert the turning of the second clamp operation bolt to displacement of the support clamp in a tangential direction of the diffuser to generate clamping force for fixing the support.

Slip joint clamps seat on a diffuser end via external features of the diffuser, like guide ears, regardless of slip joint wear or damage. The clamps can be opened and closed to surround an inlet mixer forming a slip joint with the diffuser without disassembly. Slip joint clamps drive or bias the inlet mixer in a lateral direction largely perpendicular to the axial orientation and end of the diffuser to achieve a desired preload force in the inlet mixer and clamp connection. Clamp arms include rotatable halves that, when joined, form a complete fill between an inner surface of the diffuser and outer surface of the inlet mixer. A lateral drive pushes the inlet mixer against the clamp and may include a resistive element. An accessible set of guide ear bolts and lateral driving bolts permit exterior manipulation to axially mount or laterally bias the clamp in the slip joint.

Slip joint clamps seat on a diffuser end via external features of the diffuser, like guide ears, regardless of slip joint wear or damage. The clamps can be opened and closed to surround an inlet mixer forming a slip joint with the diffuser without disassembly. Slip joint clamps drive or bias the inlet mixer in a lateral direction largely perpendicular to the axial orientation and end of the diffuser to achieve a desired preload force in the inlet mixer and clamp connection. Clamp arms include rotatable halves that, when joined, form a complete fill between an inner surface of the diffuser and outer surface of the inlet mixer. A lateral drive pushes the inlet mixer against the clamp and may include a resistive element. An accessible set of guide ear bolts and lateral driving bolts permit exterior manipulation to axially mount or laterally bias the clamp in the slip joint.

A method and apparatus of limiting power of a boiling water nuclear reactor system includes a reactor pressure vessel, a reactor core disposed in the reactor pressure vessel, a core shroud surrounding the reactor core, a downcomer region disposed between an inner surface of the reactor pressure vessel and the core shroud, a steam line connected to an upper end of the reactor pressure vessel and a condenser system that receives steam from the reactor pressure vessel. A portion of the condenser system condensate is returned to the reactor pressure vessel of the boiling water reactor inside the core barrel above the core rather than into the downcomer. Returning the condensate in this way increases the effectiveness of an isolation condenser system or if the condensate is a portion of the feedwater from the main condenser it provides an effective means to regulate core flow and core power.

A method and apparatus of limiting power of a boiling water nuclear reactor system includes a reactor pressure vessel, a reactor core disposed in the reactor pressure vessel, a core shroud surrounding the reactor core, a downcomer region disposed between an inner surface of the reactor pressure vessel and the core shroud, a steam line connected to an upper end of the reactor pressure vessel and a condenser system that receives steam from the reactor pressure vessel. A portion of the condenser system condensate is returned to the reactor pressure vessel of the boiling water reactor inside the core barrel above the core rather than into the downcomer. Returning the condensate in this way increases the effectiveness of an isolation condenser system or if the condensate is a portion of the feedwater from the main condenser it provides an effective means to regulate core flow and core power.

An apparatus and method to remotely perform automated piping and piping attachment weld inspections. The apparatus has two spaced positioning arms that rotate out from one side of a frame structure and a kicker arm that rotates out from an opposite side of the frame structure at a location between the two positioning arms. The positioning arms and the kicker arm wedge the frame structure between an object to be scanned and an opposing structure. A scanning subassembly supported on the frame structure is configured to pivot and move in an appropriate direction and to pilot a transducer around the surface of the object to be scanned.

Cleanup systems include plural coolant inputs that are physically combined to create a single flow at a desired filtering temperature. Filter(s) are used to clean the coolant, and coolant flowing therethrough will damage the filter or not be adequately filtered if having temperature in excess of an operating temperature of the filter. The inputs have different temperatures, and mixing them creates a combined flow at a desired temperature. The amount of each flow is selected based on its individual temperature to achieve this desired temperature. The combined flow is then conditioned with the filter at an operable temperature and returned to the coolant origin for the inputs. No heat exchangers or heat loss to outside heat sinks are required. Cleanup systems may be used with any coolant loop, including Rankine-cycle electricity generation systems like nuclear power plants, combustion boilers, and steam generators, and heat transfer systems.