MODEL FOR CALCULATING THE TEMPERATURE IN THE FUEL RODS OF THE FA-X FUEL ASSEMBLY PRODUCED FOR SUBCRITICAL INSTILLATION AND REACTOR WWR-M

I Chernov,А Кushtym

doi:10.15276/opu.2.61.2020.04

Abstract

The TVS-X fuel rod model designed by NSC KIPT as an alternative fuel for subcritical assembly (SCA, KIPT, Kharkov) and research reactor (WWR-M, INR, Kiev) is described. The model is a program that allows calculating the temperature distribution on the radius and height of the fuel element containing both uranium oxide pellets and dispersion fuel based on the UO2+Al composition with different contents of the fuel phase, as well as the different geometric characteristics of the fuel element and the values of the coolant parameters: the temperature at the entrance to the hydraulic channel and the coolant speed. Comparative calculations of temperature distribution during operation are carried out. As a result, it has been shown that for conditions of operation in the SCA (linear power of fuel rod is 2.62 kW/m), the fuel center temperature reaches ~140 °C for UO2 and ~112 °C for the UO2+Al composition. For operating conditions in the WWR-M reactor (linear power of fuel rod is 12.1 kW/m), the fuel center temperature reaches ~626 °C for ceramic (UO2) and ~381 °C for metal-ceramic fuel (UO2+Al). The calculations show a significant effect of the type of fuel material (UO2 or UO2+Al dispersion composition) on the fuel center temperature, taking into account the operating conditions in the subcritical assembly and the WWR-M research reactor. The maximum temperature of the cladding for the WWR-M operating conditions was 86.5 °C, and the maximum temperature of the cladding for the SCA operating conditions is 27 °C, which does not exceed the boiling point (vaporization) under the nominal conditions of their operation. Cross-section area of fuel rods, heat transfer coefficient and temperature distribution of the coolant are calculated. The software module allowed to estimate the temperature distribution of fuel element with different types of nuclear fuel for the conditions of research nuclear assemblies.

Highlights

Preliminary evaluation of the axial and radial temperature distribution is required for the developed container and coupled fuel rods
The aim of this work is to develop a simple model to calculate the stationary distribution of the temperature across the radius and the height of the fuel pellet column in the fuel rods with a different type of fuel (UO2 and UO2+aluminum λ (Al)) and with the possibility of variation of parameters among which are the geometric dimensions of the cladding and fuel mandrel, the temperature and the coolant flow rate at the inlet to the fuel assembly
The calculations show a significant effect of the fuel material type (UO2 or dispersion composition UO2+Al) on the fuel center temperature as applied to the conditions of operation in the subcritical assembly SCA and the research reactor WWR-M

Summary

Introduction

Evaluation of temperature distribution in the fuel rod is the most important factor that affects many internal processes and determines overall reliability and performance of the fuel rod. The aim of this work is to develop a simple model (a computer program) to calculate the stationary distribution of the temperature across the radius and the height of the fuel pellet column in the fuel rods with a different type of fuel (UO2 and UO2+Al) and with the possibility of variation of parameters among which are the geometric dimensions of the cladding and fuel mandrel, the temperature and the coolant flow rate at the inlet to the fuel assembly. The output text file OutputData.txt contains the calculation results: – the flow area and heat transfer coefficient of the coolant, – temperature distribution of the coolant, shell, outer surface and center of the fuel core along the height of the fuel rods, – temperature distribution along the radius of the fuel stack. Input Data and calculation results The basic data for calculating temperatures in the FA-Kh fuel assemblies are fuel rod geometric characteristics, types of materials, heat generation (calculated from the total nominal power of the SCA and WWR-M cores), inlet coolant temperature and coolant flow rate (Fig. 6 and Table 1)

Average linear heat rate FR

Conclusions