Numerical investigations of stainless steel melt motions on the surface of uranium dioxide

The paper contains the results of numerical simulation of stainless steel melt motions on the surface of uranium dioxide. The investigations are performed for purposes of understanding of the fuel rod behavior during the core disruptive accident in the fast reactors. The systems of mass, energy and momentum conservation equations are solved to simulate melt motion on the surface of the fuel pin. Heat transfer and friction between melt and pin's surface and melt and coolant flow are taken into consideration. The dependences of mass of the melt and the features of the melt motion on coolant velocity and contact angle between melt and surface of the fuel rod are presented.

CFD Validation With a PIV Provided Experimental Data for the Coolant Velocity Measurement in Reactor Vessel Down-Comer

The description of the fluid flow and the coolant velocity field within a Pressurized Water Reactor (PWR), for the safety analysis is always desirable. In this work, a validation of CFD code ANSYS Fluent performed in the frame of experimental investigations to study the velocity field of coolant flow in a single phase at a reactor vessel down-comer. Under steady-state conditions. Several Experiments using Particle Image Velocimetry, have done at small hemispherical vessel, which designed by the College of Nuclear science and Technology at Harbin Engineering University (HEU) to obtain experimental data for velocity field. The measurements of the fluid flow velocities at two different locations as investigation area in the down-comer under the inlet part, for two different inlets velocities have experimentally calculated and comprehensively simulated using FLUENT. A 3D model of hemispherical cylinder, created by commercial package SolidWorks 2016 and star –CCM code has used as tool for geometry meshing and the simulations process performed with ANSYS-FLUENT code. RANS was first calculated with boundary conditions such as the velocity used at the inlet and the outlet. Two different locations were been selected as in the experimental model and the velocity has measured. The results of CFD analyses demonstrated very good agreement with the experimental data. The results that obtained by the experiment and Fluent help to understand the velocity distribution in the down-comer.

Introductory measurements on the physical model of the VVER 440 nuclear reactor II. fuel cell assembly

Qualitative and quantitative analysis of the relationship between the coolant temperature in the fuel cell assembly outlet and the mean coolant temperature profile in the thermocouple plane is required for safe and effective loading of nuclear fuel cells. Physical model of the VVER 440 nuclear reactor fuel cell assembly serves to analyze the influence of the coolant mass flow on the coolant velocity and temperature profiles at the plane of the thermocouple position in the fuel cell assembly.

Effect Of U-9mo/Al Fuel Densities On Neutronic And Steady State Thermal Hydraulic Parameters Of Mtr Type Research Reactor

<p>The objectives of this research work are to carry out a detailed neutronic and steady state thermal hydraulics analysis for a MTR research reactor fuelled with the low enrichment U-9Mo/Al dispersion fuels of various uranium densities. The high density uranium fuel will increase the cycle length of the reactor operation and the heat flux in the reactor core. The increasing heat flux at the fuel will causing increase the temperature of the fuel and cladding so that the coolant velocity has to be increased. However, the coolant velocity in the fuel element has a limit value due to the thermal hydraulic stability considerations in the core. Therefore, the neutronic and the steady state thermal hydraulic analysis are important in the design and operation of nuclear reactor safety. The calculations were performed using WIMS-D5 and MTRDYN codes. The WIMS-D5 code used for generating the group constants of all core materials as well as the neutronic and steady state thermal hydraulic parameters were determined by using the MTRDYN code. The calculation results showed that the excess reactivity increases as the uranium density increases since the mass of fuel in the reactor core is increased. Using the critical velocity concept, the maximum coolant velocity at fuel channel is 11.497 m/s. The maximum temperatures of the coolant, cladding and fuel meat with the uranium density of 3,66 g/cc are 70.85°C, 150.79°C and 153.24°C, respectively. The maximum temperatures are fulfilled the design limit so reactor has a safe operation at the nominal power.</p>

Effect of Cooling Rates on Mechanical Behavior of U-10Mo Monolithic Mini-Plate

To investigate the effect of cooling on the thermo-mechanical behavior of U-10Mo fuel plate during shutdown step, Finite Element (FE) analysis was performed on the plate L1P756 from RERTR-12 experiments [1]. Changes in cooling rates were simulated by varying the coolant velocity on the two sides of the plate. Since coolant velocity was directly related to heat transfer coefficient (hc), different cooling velocities have been implemented by changing heat transfer coefficient corresponding to coolant velocity ranging from 10% to 200% of the baseline coolant velocity. Also, this study investigated the effect of strain rate on residual stresses of the mini-plates, which may be caused by the cooling rate. From numerical analysis results, it was found that cooling time increases as the coolant velocity decreases. It was observed that the cooling time is seven times longer if the coolant velocity is reduced 90%. A plate with two times faster coolant than the baseline reduced the cooling time by half of the original cooling time. As the cooling proceeded, von Mises stress was being increased in the plate and the highest stress at a certain time during the shutdown period was observed in the plate with the fastest coolant flow. However, no difference in residual stress was found at all different cooling rates at the end of the shutdown step. For strain rate effect analysis, the maximum strain rate was calculated to be 3 s−1 as soon as the cooling was started and the strain rate drastically decreased close to zero. The change of strain rate in time was found the same in all cases with different cooling rates. Therefore, it turned out that the cooling rate did not affect the residual stress of the cladding considered in this study.