According to embodiments, modeling through evaluation of thermal-hydraulic analysis of a unique containment facility may be provided. Also, orders for nuclear power plants in other countries may be obtained, and a relative technological advantage may be achieved among nuclear power plant developing countries. In addition, a power plant may be designed through conservative and realistic modeling, and costs required for power plant design may be reduced by optimizing a design margin of a containment facility.

A method for simulating the flow of a fluid in a vessel of a nuclear reactor is provided. The nuclear reactor includes the vessel and a core inside the vessel, the core including nuclear fuel assemblies, each one extending in an axial direction, including nuclear fuel rods and a grid for maintaining the rods, and being spaced apart from another by a clearance between the grids in a transverse direction. This method for simulating a fluid flow in the vessel of a nuclear reactor includes determining of head loss coefficients in the core, and computing the fluid pressure and speed component(s) in the core using the equation: P=KV where P is the component of the fluid pressure, K is a matrix including the determined head loss coefficients, and V is a vector including the fluid speed component(s). A transverse head loss coefficient in the assemblies is determined from a transverse Reynolds number, and an axial head loss coefficient in the clearance is from the dimension of the clearance in the transverse direction.

A method for simulating the fluid flow in a vessel of a nuclear reactor is provided. The reactor includes a core inside the vessel, the core including a lower plate, an upper plate and fuel assemblies extending between the plates, and having a volume axially delimited by first and second interfaces corresponding to the plates. The method includes computing, for the core volume, the fluid pressure and speed, from an initial value of the speed or pressure in the first interface and respectively in the second interface, and using the fluid mass, movement quantity and energy balance equations. The method includes determining an additional volume inside the vessel, the additional volume being outside the core volume, axially at one end thereof and axially delimited by two interfaces, one of which is the first or second interface; and the computing, for the additional volume and using the equations, the pressure and speed, from an initial value of the speed or pressure in each of the interfaces of the additional volume.

Provided is a method of the simulation construction for measurement of the control rod insertion time including a three-dimensional modeling operation of an inside wall of the nuclear reactor, a control rod, etc; a flow field configuration operation wherein the flow field is differentially configured by a variable grid system comprising variable cells which change the configuration and by an aligned grid system comprising fixed cells which maintains the configuration; a calculation operation of simulation estimated value for the insertion time by analyzing the thermal-hydraulic phenomenon using the three-dimensional CFD; and a cell change operation, wherein an error between the estimated value and the actual value is verified whether the error lies within the reference range, and, when the error exceeds the reference range, the size of the variable cell and/or of the size of the fixed cell is changed.

Described herein are methods for analyzing an operating envelope of a nuclear reactor. An example method includes obtaining operating envelope parameters associated with a first reactor core by performing a plurality of thermo-hydraulic and thermo-mechanical calculations for the first reactor core, where the first reactor core includes a first fuel-cladding material and has a first fuel pin geometry; obtaining operating envelope parameters associated with a second reactor core by performing a plurality of thermo-hydraulic and thermo-mechanical calculations for the second reactor core, where the second reactor core includes a second fuel-cladding material and has a second fuel pin geometry; and assessing an expandable operating envelope by comparing the respective operating envelope parameters associated with the first reactor core and the second reactor core, where the first and second fuel-cladding materials are different materials. The example method can include iteratively performing the steps described herein.

A plant operation assistance system includes: a data obtaining unit-configured to obtain monitoring data indicating state quantity of a plant, the state quantity being detected by a sensor; an identifying unit configured to identify, based on the state quantity, a probability distribution of the monitoring data; a model generation unit configured to generate, based on a plant parameter composed from a database including design information of the plant, a stochastic model of the plant; a data processing unit configured to assign the probability distribution to the monitoring data obtained by the data obtaining unit; and a prediction unit configured to input the monitoring data assigned with the probability distribution, into the stochastic model, and predicts a state of the plant.

The present invention relates to a method for analyzing a severe accident at a nuclear power plant by using a modular analysis code, comprising the step of: receiving the input of a nuclear power plant to be analyzed and an accident sequence; selecting, from a modular analysis code, an individual module for analyzing a severe accident that is triggered by the accident sequence; setting an accident simulation variable for simulating the severe accident from a nuclear power plant input model; determining whether the accident simulation variable is valid; and, if determined to be valid, analyzing the severe accident through the modular analysis code by using the accident simulation variable, wherein the individual module of the modular analysis code includes: a master module; a first module for analyzing in-core phenomena in the event of a severe accident; a second module for analyzing ex-core phenomena in the event of a severe accident; and a third module for analyzing behaviors of fission products in the event of a severe accident by using in-core thermal-hydraulic information and ex-core thermal-hydraulic information calculated by the first module and the second module, and information movement among the first module, the second module, and the third module is achieved through the master module.

In a device for and a method of reconstructing axial measurement values in a nuclear fuel, which is a device that calculates an axial reaction rate distribution by reconstructing a plurality of measurement values measured by a plurality of neutron flux detectors that are disposed at predetermined intervals in a fuel assembly along the axial direction of the fuel assembly, because a reconstruction parameter generator that generates a reconstruction parameter on the basis of core design data, or core analysis data, and a data adjustment factor; and an axial reaction rate distribution generator that calculates an axial reaction rate distribution on the basis of the measurement values that are measured by the neutron flux detectors and the reconstruction parameter that is generated by the reconstruction parameter generator are provided, an accurate axial measurement distribution in the nuclear fuel is obtained by reconstructing the measurement values.

Provided is a three-dimensional thermal-hydraulic analysis method and system for a reactor core. The method includes: analyzing a type of a reactor core, dividing an outer-layer mesh and a computational mesh, and establishing a conservative mapping relationship and a set of transport equations; decomposing a coolant viscosity-induced frictional effect, and representing a turbulent mixing-induced exchange of a physical quantity through a source term; establishing a three-dimensional set of governing equations including mass, momentum, and energy conservation equations to describe a flow and heat transfer phenomenon within coolant channels, and forming a fully assembled matrix system based on the set of transport equations; setting a boundary condition and an initial condition for a physical field of the reactor core, and setting an initial field; and iteratively solving the fully assembled matrix system, and obtaining a thermal-hydraulic parameter.