Illustrative embodiments provide a reactivity control assembly for a nuclear fission reactor, a reactivity control system for a nuclear fission reactor having a fast neutron spectrum, a nuclear fission traveling wave reactor having a fast neutron spectrum, a method of controlling reactivity in a nuclear fission reactor having a fast neutron spectrum, methods of operating a nuclear fission traveling wave reactor having a fast neutron spectrum, a system for controlling reactivity in a nuclear fission reactor having a fast neutron spectrum, a method of determining an application of a controllably movable rod, a system for determining an application of a controllably movable rod, and a computer program product for determining an application of a controllably movable rod.

A method regulates operating parameters comprising at least the mean temperature of the core (T.sub.m), and the axial power (AO) imbalance. The method includes development of a vector (U.sub.S) of control values of the nuclear reactor by a supervisor (31) implementing a predictive control algorithm; development of a vector (u.sub.K) of corrective values of the nuclear reactor controls by a regulator (33) implementing a sequenced gain control algorithm; development of a vector (U) of corrected values of the commands of the nuclear reactor, by using the vector (U.sub.S) of the values of the commands produced by the supervisor (31) and the vector (u.sub.K) of the corrective values of the commands produced by the regulator (33); and regulation of the operating parameters of the nuclear reactor, by controlling actuators using the vector (U) of the corrected values of the controls.

A nuclear power system includes a reactor vessel that includes a reactor core mounted, the reactor core including nuclear fuel assemblies configured to generate a nuclear fission reaction; a riser positioned above the reactor core; a primary coolant flow path that extends from a bottom portion of the volume below the reactor core, through the reactor core, within the riser, and through an annulus between the riser and the reactor vessel back to the bottom portion of the volume; a primary coolant that circulates through the primary coolant flow path to receive heat from the nuclear fission reaction and release the received heat to generate electric power in a power generation system fluidly or thermally coupled to the primary coolant flow path; and a control system communicably coupled to the power generation system and configured to control a power output of the nuclear fission reaction independent of any control rod assemblies during the normal operation.

It is possible to achieve self-support of the fuel assembly without an upper grid plate when the fuel assembly is mounted or replaced, and it is also possible to prevent the fuel assembly from floating during a reactor operation. According to the present invention, the lower portion of the lower tie plate 7 as a part of the fuel assembly 3, which is inserted into the fuel support 9, extends, and a stable member 21 is provided around the extension portion 20, and thereby it is possible to achieve the self-support of the fuel assembly without the upper grid plate. In addition, since an increase in a weight due to extension of the lower portion of the lower tie plate 7 can prevent the floating during the reactor operation, a floating preventing mechanism using the upper grid plate is not necessary. Hence, it is possible to achieve the self-support of the fuel assembly without an upper grid plate when the fuel assembly is mounted or replaced, and it is also possible to prevent the fuel assembly from floating during the reactor operation.

It is possible to achieve self-support of the fuel assembly without an upper grid plate when the fuel assembly is mounted or replaced, and it is also possible to prevent the fuel assembly from floating during a reactor operation. According to the present invention, the lower portion of the lower tie plate 7 as a part of the fuel assembly 3, which is inserted into the fuel support 9, extends, and a stable member 21 is provided around the extension portion 20, and thereby it is possible to achieve the self-support of the fuel assembly without the upper grid plate. In addition, since an increase in a weight due to extension of the lower portion of the lower tie plate 7 can prevent the floating during the reactor operation, a floating preventing mechanism using the upper grid plate is not necessary. Hence, it is possible to achieve the self-support of the fuel assembly without an upper grid plate when the fuel assembly is mounted or replaced, and it is also possible to prevent the fuel assembly from floating during the reactor operation.

Method of optimizing output of sensor for indicating location of metallic object. Sensor having primary electromagnetic coil to generate time varying magnetic field; secondary electromagnetic coil to detect time varying magnetic field as affected, by object to output, on basis of detected time varying magnetic field, signal indicative of location of object. Method includes steps of: supplying primary coil with alternating-current to result generated time varying magnetic field; locating object in first-position and recording signal output by secondary electromagnetic coil for range of frequencies of supplied alternating-current; locating object in second-position and recording signal output by secondary electromagnetic coil for range of frequencies of supplied alternating-current; calculating, for each of frequencies, a value for span to offset ratio of measured signals on basis of respective signals measured for object in first and second positions; determining frequency of supplied alternating-current which provides maximum span to offset ratio on basis of calculations.

Method of optimizing output of sensor for indicating location of metallic object. Sensor having primary electromagnetic coil to generate time varying magnetic field; secondary electromagnetic coil to detect time varying magnetic field as affected, by object to output, on basis of detected time varying magnetic field, signal indicative of location of object. Method includes steps of: supplying primary coil with alternating-current to result generated time varying magnetic field; locating object in first-position and recording signal output by secondary electromagnetic coil for range of frequencies of supplied alternating-current; locating object in second-position and recording signal output by secondary electromagnetic coil for range of frequencies of supplied alternating-current; calculating, for each of frequencies, a value for span to offset ratio of measured signals on basis of respective signals measured for object in first and second positions; determining frequency of supplied alternating-current which provides maximum span to offset ratio on basis of calculations.

Illustrative embodiments provide a reactivity control assembly for a nuclear fission reactor, a reactivity control system for a nuclear fission reactor having a fast neutron spectrum, a nuclear fission traveling wave reactor having a fast neutron spectrum, a method of controlling reactivity in a nuclear fission reactor having a fast neutron spectrum, methods of operating a nuclear fission traveling wave reactor having a fast neutron spectrum, a system for controlling reactivity in a nuclear fission reactor having a fast neutron spectrum, a method of determining an application of a controllably movable rod, a system for determining an application of a controllably movable rod, and a computer program product for determining an application of a controllably movable rod.

Illustrative embodiments provide a reactivity control assembly for a nuclear fission reactor, a reactivity control system for a nuclear fission reactor having a fast neutron spectrum, a nuclear fission traveling wave reactor having a fast neutron spectrum, a method of controlling reactivity in a nuclear fission reactor having a fast neutron spectrum, methods of operating a nuclear fission traveling wave reactor having a fast neutron spectrum, a system for controlling reactivity in a nuclear fission reactor having a fast neutron spectrum, a method of determining an application of a controllably movable rod, a system for determining an application of a controllably movable rod, and a computer program product for determining an application of a controllably movable rod.

An integral pressurized water reactor (PWR) comprises: a cylindrical pressure vessel including an upper vessel section and a lower vessel section joined by a mid-flange; a cylindrical central riser disposed concentrically inside the cylindrical pressure vessel and including an upper riser section disposed in the upper vessel section and a lower riser section disposed in the lower vessel section; steam generators disposed inside the cylindrical pressure vessel in the upper vessel section; a reactor core comprising fissile material disposed inside the cylindrical pressure vessel in the lower vessel section; and control rod drive mechanism (CRDM) units disposed inside the cylindrical pressure vessel above the reactor core and in the lower vessel section. There is no vertical overlap between the steam generators and the CRDM units.