Reaction kinetic analysis of damage rate effects on defect structural evolution in Fe–Cu

In Fe–Cu alloys, Cu precipitates are formed during high-energy particle irradiation. If there exists energetic binding between vacancies and Cu atoms, vacancy clusters (voids) are formed in precipitates at an initial stage of irradiation, separate from voids in the matrix, because of the migration of Cu atoms with vacancies. In this paper, the damage rate dependence on the formation and annihilation of voids in the precipitates and in the matrix is simulated by reaction kinetic analysis. The initial formation of voids at precipitates, the annihilation of them with an increased dosage and new formation of voids in the matrix are simulated, and the results are compared with the experiments. In a high damage rate of 3.3 × 10^[−7] dpa/s, the formation of voids in Cu precipitates is not significant, but the formation of voids in the matrix is dominant, different from those in a low damage rate of 1.5 × 10^[−10] dpa/s

Contribution of cadmium to the total amount of positron creation in a reactor-based slow positron beamline

In the slow positron beamline at the Kyoto University Research Reactor (KUR), positron creation was enhanced by increasing the gamma-ray intensity at the positron source via the reaction of¹¹³Cd(n, γ)¹¹⁴Cd. To achieve this, a cadmium (Cd) cap was attached to the positron source, surrounding it, and thus, without intentional cooling, the temperature was able to reach near the melting point of Cd via nuclear heating. In this study, the degree to which the Cd cap contributes to the quantity of positron creation was estimated by using the Monte Carlo calculation code PHITS (Particle and Heavy Ion Transport code System), which simulates radiation transportation and interaction with matter. As a result, the number of positrons created was found to become 2.0 ± 0.1 times higher by using the Cd cap at the KUR slow positron beamline. The use of the Cd cap was confirmed to be significantly effective for enhancing positron creation

Microstructural Evolution in Austenitic Stainless Steels Irradiated by Neutrons with Improved Control

Nucleation and growth of interstitial type dislocation loops were investigated by fusion neutron irradiation and fission neutron irradiations with improved control. The density of loops formed by both irradiations increased linearly with the fluence. The average size of loops also increased. The rate equation analysis showed that the loops were nucleated directly by the defect processes in a cascade zone, not by the reaction among the freely migrating point defects in the matrix. If the rate of loop formation is assumed to be directly proportional to the energy of a primary knock-on atom (PKA) produced by a neutron, the threshold energy of 80 keV and the rate of loop formation of 0.05 were obtained

Photoluminescence, morphology, and structure of hydrothermal ZnO implanted at room temperature with 60 keV Sn+ ions

Hydrothermal ZnO wafers implanted at room temperature with 60 keV Sn^+ ions are examined by means of photoluminescence (PL), atomic force spectroscopy (AFM), and X-ray diffractometry techniques. The PL intensity significantly decreases in the wafers implanted to doses of 4.1 × 10^[13] ions/cm^2 and higher. The AFM measurements indicate that surface roughness variation is not the cause of the significant decrease in PL intensity. Furthermore, the PL deep level (DL) band peak blueshifts after illuminating the implanted samples with the He-Cd laser 325 nm line; meanwhile, the DL band intensity first increases and then decreases with illumination time. These abnormal behaviors of the DL band are discussed

Reaction kinetic analysis of reactor surveillance data

Available online 30 January 2015In reactor pressure vessel surveillance data, it was found that the concentration of matrix defects was very low even after nearly 40 years of operation, though a large number of precipitates existed. In this paper, defect structures obtained from surveillance data of A533B (high Cu concentration) were simulated using reaction kinetic analysis with 11 rate equations. The coefficients used in the equations were quite different from those obtained by fitting a Fe-0.6 wt%Cu alloy irradiated by the Kyoto University Reactor. The difference was mainly caused by alloying elements in A533B, and the effect of alloying elements was extracted. The same code was applied to low-Cu A533B irradiated with high irradiation damage rate, and the formation of voids was correctly simulated