Study of Helium Swelling in Nitride Ceramics at Different Irradiation Temperatures.

Maxim V Zdorovets,Kanat Dukenbayev,Artem L Kozlovskiy

doi:10.3390/ma12152415

Abstract

This paper presents the results of a systematic study of helium swelling and the subsequent process of degradation of the near-surface layer of aluminum-based nitride ceramics. The samples were irradiated with 40 keV He2+ ions at temperatures of 300 and 1000 K with a fluence of 1 × 1017–5 × 1017 ions/cm2. The choice of radiation doses and temperature conditions was due to the possibility of simulating reactor tests of structural materials. It has been established that an increase in the irradiation fluence leads to the formation of large agglomerates of clusters of helium bubbles, as well as an increase in the degree of roughness and waviness of the surface with the formation of crater-like inclusions. In the case of irradiation at high temperatures, there was a slight decrease in the average size of helium inclusions compared with irradiation at room temperature. However, the density of inclusions and surface roughness were much higher. It is established that irradiation at room temperatures leads to a sharp decrease in ceramics density, as well as deformation of the crystal structure due to an increase in the density of dislocations and macrostresses in the structure. The decrease in ceramics density due to the formation of helium inclusions led to an increase in porosity and a defective fraction in the structure of the surface layer of ceramics.

Highlights

IntroductionDegradation of the surface can lead to a decrease in thermal conductivity, deterioration of insulation and optical characteristics, which leads to destabilization of reactor operation
One of the most acute problems of structural materials used in the nuclear industry is the accumulation of helium and the further helium embrittlement of material surface layer [1,2,3].Degradation of the surface can lead to a decrease in thermal conductivity, deterioration of insulation and optical characteristics, which leads to destabilization of reactor operation
In the case of nuclear reactions, helium occurs in the entire volume of the material—that somewhat reduces the probability of agglomeration in the surface layer, while in the case of contact with the coolant, the main accumulation occurs in the small surface layer

Summary

Introduction

Degradation of the surface can lead to a decrease in thermal conductivity, deterioration of insulation and optical characteristics, which leads to destabilization of reactor operation. In this case, the accumulation of helium in the structure of structural materials occurs as a result of its low solubility, as well as a high rate of mobility and the possibility of agglomeration. The emergence of helium in the structure occurs as a result of the initiated nuclear reactions under the effect of neutrons, and in the case of surface layer contact with the coolant [4,5,6,7,8,9,10].

Methods

Results

Conclusion