Method for accurately obtaining reactivity feedback changes in transient process of fast neutron reactor

Abstract

The invention discloses a method for accurately obtaining reactivity feedback changes in the transient process of a fast neutron reactor. By considering spatial distribution of reactivity feedback, accurate fuel temperature reactivity feedback change, coolant density reactivity feedback change, axial expansion reactivity feedback change, radial expansion reactivity feedback change, assembly bending reactivity feedback change and control rod driving mechanism expansion reactivity feedback change in the transient process are obtained, and finally the three-dimensional reactivity feedback quantity in the transient process of the fast neutron reactor is obtained. The method is high in universality and wide in application range, the transient process of the reactor can be accurately simulated,calculation time is shortened, and accurate and reliable reactivity feedback parameters are provided for a design task of the reactor core.

Description

technical field [0001] The invention belongs to the technical field of nuclear reactor engineering, in particular to a method for accurately obtaining reactivity feedback changes in fast neutron reactor transient processes. Background technique [0002] In order to quickly analyze the process of transient accidents in fast neutron reactors, according to the characteristics of fast neutron reactors, the "point reactor dynamics" method based on the point reactor equation has become the main method for fast reactor transient analysis. [0003] [0004] In the formula: [0005] n(t)——neutron density in the reactor at time t [0006] ρ(t)——the reactivity of the reactor at time t [0007] β—effective delayed neutron fraction [0008] Λ—neutron generation time [0009] lambda i ——The decay constant of delayed neutrons of group i [0010] C i (t)——concentration of delayed neutron precursor nuclei in group i at time t [0011] beta i ——The proportion of delayed neutrons i...

AI Technical Summary

Problems solved by technology

In fast neutron reactors, changes in material temperature will cause large deformations in the core, and reactor components will bend. At this time, using a single reactivity feedback coefficient and equivalent temperature cannot simulate the reactivity feedback caused by component bending. , so it is necessary to combine the mechanical model to accurately analyze the deformation and reactivity feedback at different positions and different nodes of the reactor during the process; at the same time, the control rod drive mechanism located outside the reactor will also expand when heated, causing the control rods to be in the core after expansion. The rod position becomes smaller and inserted deeper, which also brings reactive introduction

Therefore, the model combined with the "direct method" and the single-channel model cannot accurately consider the spatial distribution of the reactivity feedback, and can only obtain the changes in fuel temperature, coolant density, axial geometric expansion of the core, and radial geometric expansion of the core. Reactive Feedback Caused by Four Causes of Inflation

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