Correlation of neutron and heavy-ion damage: I. The influence of dose rate and injected helium on swelling in pure nickel

Displacement damage structures in pure nickel at the 1 dpa level are compared for two widely disparate damage rates, 10⁻⁷ dpa/s for neutron irradiations and 3 X 10⁻³ dpa/s for self-ion bombardments over a range of temperatures spanning those for void formation. Peak swelling at about 0.7% is found at 400° and 600°C, respectively. At equivalent swelling temperatures, voids in the ion-bombarded material are larger and fewer than those from neutron irradiation, especially at temperatures above the peak swelling temperature.Additions of 20 appm He, matching that generated in the neutron irradiations, were made to the ion-bombarded nickel either prior to ion bombardment (preinjection) or during ion bombardment (simultaneous injection). This helium caused increased swelling at the upper and lower temperature extremes. Simultaneously implanted helium did not otherwise significantly affect microstructures, whereas preinjected helium increased the dislocation density and caused more but smaller voids over the full temperature range of swelling.     

Effects of 14 MeV neutron irradiation on creep of nickel and niobium

Flux, stress and temperature effects on the creep strength of nickel and niobium were observed in situ at the RTNS-II 14 MeV neutron source at Lawrence Livermore National Laboratory. Creep tests were done on Ni and Nb near 0.3 $\text{T}{}_{\mathrm{m}}$ with stresses to 280 MPa in a high vacuum test unit using a digital computer for control and data acquisition. Cyclic flux tests produced dramatic changes in creep rate. This creep behavior is attributed to the point defect fluctuations in the crystal structure. Analysis of creep and stress relaxation under steady state flux indicates that an intermediate temperature, thermally activated deformation mechanism is rate controlling.     

PDSOI CMOS SRAM总剂量辐射及退火效应的研究

通过对PDSOI CMOS静态随机存储器(SRAM)在静态偏置条件下器件功耗电流和功能错误数随辐射总剂量、退火时间的变化规律,以及不同温度(25℃和100℃)条件的退火行为进行研究,探讨了SOI工艺SRAM的总剂量辐射损伤机制及辐照环境中功耗电流变化与器件功能之间的相关性,为进一步深入研究大规模SOI集成电路的抗总剂量...     

Observation of micro-cavities in nickel during He and D irradiation and post-irradiation annealing

Changes in sizes and morphology of small cavities in nickel irradiated by 25 keV helium ions and 20 keV deuterons were investigated during irradiation and on annealing after irradiation by means of transmission electron microscopy. In the early stage of He⁺ irradiations at 600 and 700° C, roundish cubes appeared, gradually changed to octahedra. and, then, by the truncation of apexes, finally reached cubo-octahedra. Nucleation and growth behavior of cubic cavities in D⁺ irradiated nickel was different from the case of He⁺ irradiation. On annealing of the He⁺ irradiated specimen, only octahedral cavities showed marked growth, finally changing to roundish cubes at 750° C. Cavities of roundish cubes and cubo-octahedra did not grow nor change their shapes remarkably by the annealing. The cubic cavities formed by D⁺ irradiation at 360° C showed gradual shrinkage on annealing at 600° C and disappeared at 625° C. The changes of cavities during irradiation and on annealing were interpreted by the effect of the internal gas pressure.     

The effect of neutron irradiation on the precipitate distribution in adjusted uranium

Precipitates in α-uranium are thought to be very important in controlling the swelling that occurs in the reactor. Cross sections from the 30 mm diameter adjusted uranium fuel bars were cut and heat-treated to give a UAl₂ precipitate distribution peaking at about 30 nm diameter. Alternate sections were irradiated to 500 MWd/te at 673 K. Comparisons before and after irradiation show that a new precipitate population is formed during irradiation. Since new precipitates can form, mechanisms of swelling resistance based on the effects of aluminium in solution are no longer tenable.     

The neutron irradiation effect on mechanical properties of HIP joint material

Dispersion strengthened copper (DSCu) and stainless steel are the candidate material for the heat sink and the structural material of the ITER shielding blanket and these materials are joined by hot isostatic pressing (HIP). In this study, the neutron irradiation effect on mechanical properties of HIP joint material was examined by tensile and impact tests using specimens with irradiation damage of about 1.5 dpa. The results of tensile tests show that tensile strength of HIP joint material was about the same as that of DSCu base material, and this trend did not change after neutron irradiation. On the other hand, the impact value of HIP joint material was smaller than that of DSCu base material because of the diffusion of main elements at joint boundary. It was shown that embrittlement by the neutron irradiation effect is smaller than that of the effect by HIP joint.     

The effect of low-fluence neutron irradiation on silver-electroded lead-zirconate-titanate piezoelectric ceramics

The properties of several different versions of near equi-molar proportioned lead-zirconate-titanate ceramic piezoelectric plates were measured after irradiation for up to 48 h in an MTR hollow fuel element. The irradiation temperature was 180 ± 50°C and the maximum fluences 3.5 × 10¹⁹ thermal and 1.4 × 10¹⁹ fission neutrons/cm². The irradiation decreased the capacitance, increased the thickness-mode resonant frequencies and decreased the elevated temperature electromechanical coupling in all of the samples tested. The effects are considered to be due to a change in the electrode bonding and a reduction in the polarisation of the ceramic.     

Evolution of the nanostructure of VVER-1000 RPV materials under neutron irradiation and post irradiation annealing

A high nickel VVER-1000 (15Kh2NMFAA) base metal (1.34 wt% Ni, 0.47% Mn, 0.29% Si and 0.05% Cu), and a high nickel (12Kh2N2MAA) weld metal (1.77 wt% Ni, 0.74% Mn, 0.26% Si and 0.07% Cu) have been characterized by atom probe tomography to determine the changes in the microstructure during neutron irradiation to high fluences. The base metal was studied in the unirradiated condition and after neutron irradiation to fluences between 2.4 and 14.9 × 10²³ m⁻² (E > 0.5 MeV), and the weld metal was studied in the unirradiated condition and after neutron irradiation to fluences between 2.4 and 11.5 × 10²³ m⁻² (E > 0.5 MeV). High number densities of ∼2-nm-diameter Ni-, Si- and Mn-enriched nanoclusters were found in the neutron irradiated base and weld metals. No significant copper enrichment was associated with these nanoclusters and no copper-enriched precipitates were observed. The number densities of these nanoclusters correlate with the shifts in the ΔT_{41 J} ductile-to-brittle transition temperature. These nanoclusters were present after a post irradiation anneal of 2 h at 450 °C, but had dissolved into the matrix after 24 h at 450 °C. Phosphorus, nickel, silicon and to a lesser extent manganese were found to be segregated to the dislocations.     

Combined effects of neutron irradiation and hydrogen absorption on mechanical properties of pure iron

To obtain a fundamental knowledge of the combined effect of neutron-irradiation and hydrogen, mechanical properties and the fracture mode were studied for pure neutron irradiated iron, followed by hydrogen charging. The effect of interaction between neutron irradiation and hydrogen absorption for a pure iron could be clarified. Under the hydrogen charged condition, the ductility is higher in the neutron irradiated specimen than in the unirradiated. The cause could be sought in hydrogen trap sites of the iron and the fracture mode. As a result of interaction between many irradiation defects and hydrogen atoms, the fracture mode of a hydrogen charged specimen after irradiation, is a mixed mode of quasi-cleavage crack and dimple pattern. That of a hydrogen charged unirradiated specimen is predominantly intergranular cracking.     

The effect of neutron irradiation on the structure and properties of ferrito-pearlitic steels

Specimens of steels 1Kh17N2, 2Kh13, and 30KhMA, which are susceptible to heat treatment, and of steel 1Kh17 containing niobium, which is not susceptible to heat treatment were subjected to irradiation with fast neutrons at temperatures of 70° and 500–600 °C.As a result of irradiation at 500–600 °C the mechanical properties of steels 1Kh17N2, 2Kh13, and 30KhMA undergo considerable change, but no change is observed in steel 1Kh17 containing niobium. Metallographic examination shows that the increases in the strength properties of the steels mentioned during irradiation at 500–600 °C is connected with a change in structure. In the opinion of the authors the observed changes in microstructure are due to the formation of displacement spikes in the irradiated material.     

The effect of vacancy loops on the swelling expected for 316 steel under dual-beam irradiation

The theoretical interpretation of simultaneous heavy-ion irradiation and continuous helium injection experiments is extended to include the role of vacancy loops in the evolution of the microstructure. Whilst we find that their inclusion does not alter our previous conclusions concerning the role of the gas in explaining a high-temperature swelling peak, they do influence the details of the swelling response. This detailed influence is such that the results expected from dual-ion simulation experiments should be both more representative of the neutron irradiations and easier to observe than we had previously believed.     

The effect of neutron irradiation on the thermal conductivity of beryllium oxide

The thermal conductivity of irradiated hot pressed beryllia has been measured over the temperature range 0–85° C. Increasing fission neutron dose decreases the thermal conductivity and reduces its temperature dependence. At sufficiently high doses, the thermal conductivity remains constant over the temperature range studied. The irradiation-induced change in conductivity anneals out on heating at elevated temperatures; for two hour anneals, recovery starts at 400° C but is not complete until 1400° C is reached. Irradiation at higher temperatures (500–660° C) causes a considerably smaller change in conductivity than for equivalent doses at pile temperatures (75–100dg C).     

The effect of neutron irradiation on the tensile properties of zircaloy-2

Tensile specimens of annealed, 13.1 per cent coldworked, and tempered 25.5 per cent cold-worked Zircaloy-2 were irradiated at 220° C and 280° C with integrated fast-neutron fluxes of 3.6 × 10¹⁹ n/cm² and 2.7 × 10²⁰ n/cm² respectively.Post-irradiation tensile tests performed at room temperature and 280° C showed that considerable irradiation hardening occurred in all the irradiated material. This change was characterized by an increase in the proportional limit, yield stress, and ultimate tensile strength, and a decrease in the total and uniform per cent elongations. The per cent changes in mechanical properties as a result of the irradiation were greater in the annealed material than in the cold-worked material. The tensile properties of irradiated 13.1 per cent cold-worked material were almost identical to those for the irradiated tempered 25.5 per cent cold-worked material for both levels of irradiation.A yield point was developed in irradiated annealed material tested at 280° C whereas no yield point was present in the same material tested at room temperature.Results are also given for post-irradiation annealing studies performed on the annealed and cold-worked material irradiated at 280° C.     

The effect of neutron irradiation on the internal friction of zinc monocrystals and polycrystals

By an investigation of the effect of neutron irradiation on the internal friction of zinc polycrystals and monocrystals, we determined the value of the critical stress amplitude _cr before and after irradiation.It was shown that the value of _cr, which may be related to the beginning of the motion of dislocations, increases as a result of irradiation. The increase of _cr in irradiated zinc is explained by the fact that the dislocations are held fixed as a result of interaction with point defects.In addition, we studied the effects of the orientation of the basal plane (0001) with respect to the longitudinal axis of the zinc monocrystal specimen on internal friction and on _cr. The results of the investigations of the effect of orientation on internal friction and on _cr are compared with well-known representations of slippage obtained from static studies of monocrystals in tension along one axis.The authors express their gratitude to S. T. Konobeevskii for his comments on the results of the work.     

The effect of neutron irradiation on the structure and mechanical properties of alloy steels

We have studied the effect of neutron irradiation at temperatures of 200–500°C with various integral doses (1.5·10²⁰·10²¹ neutrons/cm²) on the properties and microstructure of some steels with different chemical compositions and initial structures. We have shown the effect of alloying by various elements on the sensitivity of the steel to irradiation and the temperature of annealing of radiation defects of hardening.Translated from Atomnaya Énergiya, Vol. 15, No. 1, pp. 30–37, July, 1963