Behavior of mechanical properties of nickel-alloyed reactor pressure vessel steel under neutron irradiation and post-irradiation annealing

The effect of neutron irradiation and post-irradiation thermal annealing on tensile and impact properties of Cr–Ni–Mo steel used for WWER-1000 reactor pressure vessel (RPV) manufacturing was studied. A gap in yield stress and ultimate tensile stress fluence dependence at the fluence range of 0–3×10²³ neutrons m⁻² was observed while ductile-to-brittle transition temperature (DBTT) was continuously increasing with damage dose. The post-irradiation annealing recovery of tensile properties was found to be higher than the one of impact properties. Over-recovery of tensile properties due to 460 and 490°C post-irradiation annealings were observed. The annealing effectiveness of WWER-440 and WWER-1000 grades was compared. Nickel was supposed to affect both the radiation sensitivity and the post-irradiation residual DBTT shift of WWER-1000 type steel.     

中子与γ射线辐照对B4C/环氧树脂屏蔽材料性能的影响

中子与γ射线辐照对屏蔽材料性能的影响直接关系到了核设施的运行安全性。本研究以B4C/环氧树脂屏蔽材料作为研究对象,对比了在1 MGy γ射线及叠加1.19×1015cm-2中子辐照两种辐照环境下屏蔽材料力学性能、断口组织形貌、特征化学产物及热稳定性能的变化规律。结果表明：持续约11.6 d的γ射线辐照及叠加持续约3 h的中子辐照后屏蔽材料力学性能持续降低,但均未降低到辐照前的50%以下,屏蔽材料在此条件下产生了辐照降解,但未发生失效。与单独的γ射线辐照相比,叠加中子辐照后屏蔽材料1H-NMR图谱δ=7附近峰的强度没有明显变化,说明未继续发生苯环上C-H键的断裂。屏蔽材料热失重50%质量损失温度T50%由辐照前的526.3℃降低到了γ射线辐照后的453.2℃及γ射线叠加中子辐照后的463.9℃,屏蔽材料辐照后热稳定性降低。     

Irradiation and annealing effects on delamination toughness in carbon/epoxy composite

Gamma irradiation to various doses (4.8-27.2 MGy) was performed on unidirectional carbon fiber/epoxy resin composite plates. Unidirectional composite coupons irradiated to various doses were annealed at 180 and 250 °C, in vacuum. The strain energy release rate G_IC, as a measure of delamination fracture toughness, was determined by Mode I fracture testing on double cantilever beam coupons. The glass transition temperature (T_g) of the tested coupons matrices was determined in DMA tests. The effects of irradiation and annealing on G_IC values - the mean values of 10 propagation points (G_IC,mean) and that of fracture initiation (G_IC,init) - were established. These values were analyzed as a function of irradiation dose and annealing temperatures, having in mind glass transition temperature values changes, as well as the possible mechanisms and phenomena of irradiation and annealing.     

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 irradiation and post-irradiation annealing on the yield stress and microstructure of vanadium-carbon alloys

Vanadium and vanadium-carbon alloys containing 0.15, 0.3 and 1 at% carbon were irradiated in JMTR with fast neutrons (E_n > 1 MeV) at 773 K to a dose of 5 × 10²⁴n/m². Tensile test and microstructural observations were carried out after irradiation and post-irradiation annealing. All of the. specimens showed radiation hardening. The irradiation produced voids, dislocations and radiation-induced quasi-carbides, which were formed by the agglomeration of vacancies and carbon atoms. The radiation anneal hardening in the alloys occurred at 873 K. The void number densities in the alloys had a peak at 873 K while the quasi-carbides decomposed at the same temperature. Therefore, invisible voids existing in the as-irradiated condition would grow by absorbing the vacancies, which were released in the process of decomposition of the quasicarbides during annealing, and the increase of the visible voids would effectively contribute to the radiation anneal hardening of these alloys.     

Formation of Au nanoparticles in silica by post-irradiation and thermal annealing

SiO₂ + Au thin films were prepared on SiO₂ substrates using ion beam assisted deposition (IBAD). The film was annealed at different temperatures. After each annealing, the optical absorption spectrum was taken to monitor the gold nanocluster formation in the thin film. By using Doyle’s formula, the size of the nanoclusters was determined and plotted as a function of the annealing temperature. Separately, other identical films were bombarded with ions of different energies and different fluence to monitor the nanoclusters forming during the bombardments. We have compared the effect of electronic energy deposition of the energetic ions with the effect of annealing at various temperatures.     

γ射线辐照对聚砜结构与性能的影响

应用力学性能测试、傅立叶变换红外光谱分析、扫描电镜断口形貌分析、差示扫描量热分析、凝胶渗透色谱分析、X射线光电子能谱分析等多种手段从多个角度研究了聚砜材料在γ射线辐照下的老化行为,并研究了吸收剂量对材料结构和性能的影响.结果表明,聚砜材料的拉伸强度、弯曲强度、冲击强度、玻璃化温度、数均分子量、峰值分子量和数均聚合度等均随吸收剂量的增加而下降;化学结构在辐照过程中基本上没有变化;其断口表面的光滑程度随辐射剂量的增加而增大;弯曲强度、冲击强度和重均分子量随吸收剂量变化曲线的上升段表明,在低吸收剂量下聚砜材料内部交联反应占优势;这些曲线的下降段表明,在中高吸收剂量下聚砜内部降解反应占优势.动力学分析表明,聚砜在化学上的降解属于无规降解类型,间接证明了聚砜在低吸收剂量下交联反应占优势,在中高吸收剂量下降解反应占优势.     

Effect of electron irradiation on the mechanical properties of DGEBA/DDM epoxy resins

The thermomechanical properties of diglycidyl ether of bisphenol A (DGEBA)/4-4 diaminodiphenylmethane (DDM) resins are analysed as a function of the irradiation dose. Irradiation results in a decrease of the glass transition temperature and of the elastic modulus in the rubbery region, ascribed to a destruction of crosslinks. The Arrhenius diagrams show that the α relaxation becomes faster, that the β process is enhanced but that γ relaxation is less modified by the irradiation. The effects of irradiation on the stress–strain curves suggest a spatial heterogeneity of the crosslink density.     

高剂量γ辐照对SEBS／PS共混物性能的影响

研究了高剂量(0～2.0 MGy)γ辐照对不同配比苯乙烯一-乙烯-丁烯-苯乙烯嵌段共聚物/聚苯乙烯(SEBS/PS)共混物(100/0～50/50)力学性能、电性能以及热稳定性能的影响.结果表明,PS的加入,可以有效改善SEBS的辐照稳定性.PS的含量越高,辐照后SEBS/PS共混物的拉伸强度、体积电阻率的下降幅度越小,介电损耗因子的上升幅度越小,热稳定性能越好.但PS的加入减少了共混物中聚烯烃相的含量,使得共混物的断裂伸长率受辐照的影响较大,特别在高剂量辐照后,PS的含量越高的共混物断裂伸长率下降越明显.     

Effect of gamma irradiation on the properties of tyre cords

Gamma irradiation of high tenacity Nylon 6.6 (Ny 66) and polyester (PET) tyre cords was investigated. The untreated and treated tyre cords with different twist levels were irradiated at different dose rates in air. The effects of irradiation on both Ny 66 and PET cords were not found to be depending on the twist levels of the cords. The changes in the mechanical and thermal properties with absorbed dose at two different dose rates were measured. The mechanical properties were observed to deteriorate with increasing dose for Ny 66 cords, whereas remained almost unchanged for PET cords both in greige and dipped forms. Hot shrinkage value for the greige Ny 66 cords was found to be improved, i.e. decreased. This decrease was much lower for greige PET than Ny 66 cords. It is concluded that PET cord has higher radiation resistance than Ny 66 cord and the effects of high energy irradiation on tyre cords have to be taken into consideration during tyre design if pre-vulcanization with high energy radiation is to be applied.     

Effects of irradiation and design basis accident conditions on thermal properties of epoxy coating system for nuclear power plant

In this work, the thermal properties of epoxy coating system on carbon steel liner in an atomic reactor container have been investigated in terms of irradiation and design basis accident (DBA) conditions. Two epoxy coating systems were irradiated by different dose rates, i.e. 1×10⁶ and 5×10⁵ rad/h in a total dosage of 2×10⁸ rad/h. And, DBA tests were applied to them based on the specification. The glass transition temperature (T_g) and thermal stability of the epoxy coating systems after tests were measured by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. As a result, the irradiation led to the fracture of internal structure in cured epoxy systems, resulting in significantly decreasing the thermal stability, as well as, the T_g. Also, the higher dose rate made a relaxation of epoxy resins to reduce the hardening of the network system. Whereas, the DBA test made an important role in the thermal stability in the epoxy coating systems, resulting in post-curing of the uncured epoxy resins. Consequently, it could be found that the thermal properties of the epoxy coating system were greatly influenced on the irradiation and DBA tests, which were probably due to the modification of internal network structure of the epoxy resins.     

辐射硫化和增容剂对氯丁／聚丙烯酸钠遇水膨胀橡胶性能的影响

采用γ射线辐射硫化技术制备了氯丁/聚丙烯酸钠遇水膨胀橡胶,考察了在一定吸收剂量时增容剂对膨胀橡胶的力学性能、膨胀性能和质量损失率的影响,以及吸收剂量对质量损失率的影响.结果表明,增容剂有利于提高力学和膨胀性能,降低质量损失率,吸收剂量提高有利于质量损失率的降低.     

Effects of irradiation with gamma and beta rays on semiconductor Hall effect devices

The effects of short duration irradiation with low dose rate gamma and beta rays on the input resistance and the output Hall voltage of InSb, GaAs, Si, and Ge semiconductor Hall effect devices were systemically studied. Both gamma and beta irradiation can cause the input resistance of Hall effect devices to increase linearly with increasing irradiation time, in the absence of a magnetic field. When the devices were placed in a magnetic field, the output Hall voltage and input resistance increased nonlinearly with increasing gamma irradiation time. The effects of both gamma and beta irradiation persisted long after the irradiation itself, and without annealing. The effects from irradiation in Hall effect devices can be mainly ascribed to the degradation of the charge carriers’ transport properties caused by radiation-induced defects. The radiation resistance of the Hall effect devices was estimated by considering changes of the input resistance under the same irradiation conditions. The Ge and Si Hall effect devices demonstrated a better radiation resistance than the InSb and GaAs Hall effect devices due to their large displacement threshold energy.     

Influence of post irradiation annealing on the mechanical properties and defect structure of AISI 304 steel

The effect of post irradiation annealing on the mechanical properties and the radiation induced defect structure was investigated on stainless steel, of type AISI 304, that was irradiated up to 24 dpa in the decommissioned Chooz A reactor. The material was investigated both in the as-irradiated state as well as after post irradiation annealing. In the as-irradiated specimen the typical radiation induced defects were found as well as γ′-precipitates (Ni₃Si). Annealing at 400 °C had almost no effect on the radiation induced defects, but annealing at 500 °C resulted in the immediate unfaulting of the Frank loops. As to the mechanical properties, annealing at 400 °C did not strongly affect the yield strength and the ductility of the material, although the fraction of intergranular fracture during slow strain rate tensile tests under pressurised water reactor conditions, was significantly reduced. Annealing at 500 °C did reduce the yield strength and restored substantially the ductility and the strain hardening capability of the material. The microstructure investigated by transmission electron microscopy correlates to the mechanical test results. It was found that the observed defect changes after post irradiation annealing provide a reasonable explanation for the observed changes of the mechanical properties.     

Effects of fast neutron and gamma irradiation on electrical conductivity of some borate glasses

Electrical conductivity of samples of Li₂O-B₂O₃ binary glass system containing Al₂O₃, PbO, Fe₂O₃, TiO₂ or V₂O₅ was measured at temperatures ranging between 30 and 200 °C before and after irradiation with fast neutrons or γ-rays. Base and Al₂O₃-containing glasses showed an initial rise in conductivity with the increasing temperature, followed by a steep drop, then a more gradual increase. Glass samples containing lead or one of the transition metal oxides showed a linear pattern of electrical conductivity in response to heating. In these glasses activation energy varied depending on the coordination number of the transition metal ion involved. These changes in electrical conductivity in response to temperature are ascribed to changes in the internal structure of the lithium borate glass, which is also affected by the presence of aluminum, lead or transition metals. The effects of exposing the studied glasses to irradiation were attributed to irradiation-induced changes in the configuration of the glass network, including the formation of matrix defects.     

IPN’s of acrylic acid and N-isopropylacrylamide by gamma and electron beam irradiation

Interpenetrating networks (IPN) of temperature sensitive N-isopropylacrylamide (NIPAAm) and pH sensitive acrylic acid (AAc) monomer were prepared in two consecutive steps. Hydrogels of AAc were synthesized by gamma radiation from a ⁶⁰Co gamma source and an electron beam from a Van de Graaff accelerator. A second hydrogel of NIPAAm was synthesized within the first AAc hydrogel by polymerization and cross-linking with a redox initiator and cross-linking agent. The thermal and pH sensitivity of the hydrogels were determined by measuring the swelling, and the morphology and composition by SEM.     

Effects of prehydrostatic loading on mechanical and physical properties of nuclear-grade graphites

The effects of prehydrostatic loading on mechanical and physical properties were examined for two isostatistically-molded graphites, grades IG-11 and Iso-20. The increase in loading levels caused the monotonic decrease in specimen volume of both graphites, the change of which was much larger in the case of IG-11 graphite than of Iso-20. The electrical resistivity increased continuously with an increase in prehydrostatic loading levels, where the effect was more pronounced for IG-11 than for Iso-20 graphite. The manner in which the Young's moduli of the two materials changed after prehydrostatic loading was clearly different from each other, i.e., for IG-11 it decreased continuously with increasing pressure, whereas it increased at small hydrostatic pressures and leveled off above 300 MPa for Iso-20. A clear difference was also observed for the flexural strength of both materials: Its continuous decrease was caused by prehydrostatic loading for IG-11 graphite, whereas for Iso-20 it remained at the original value up to 500 MPa and decreased abruptly above that pressure level. An explanation of these features was provided from the viewpoint that microcracks are induced by hydrostatic loading.     

退火温度对CsI薄膜闪烁特性的影响

采用热蒸发法在玻璃衬底上沉积CsI薄膜,然后进行不同温度的真空热处理.用X射线衍射仪、扫描电子显微镜对CsI薄膜样品进行分析,测得241Am的脉冲高度谱,通过单光子法测量样品的光产额.结果表明,该CsI薄膜沿(200)晶面择优取向生长.退火温度对CsI薄膜的晶体结构和闪烁性能有很大的影响.CsI薄膜经过250℃退火后,(200)晶面衍射峰明显增强,结晶状态最佳,光产额最高,而退火温度达400℃时,薄膜结构发生显著变化,闪烁性能急剧下降.     

辐照对肌肉蛋白凝胶性能的影响

肌肉蛋白的凝胶性能是肉类及其制品重要的功能特性,决定着肉制品独特的质构、多汁性、脂肪含量、感官特性等品质。作为一种新颖的食品保鲜技术,辐照有可能导致蛋白分子组成及其结构发生变化,从而对肌肉蛋白的凝胶形成能力及其凝胶性能产生影响。本文在介绍肌肉蛋白凝胶形成机理的基础上,综述了辐照对肌肉蛋白凝胶持水性、力学性能特征和结构影响的研究:过高剂量辐照容易引起肌肉蛋白持水性的下降,造成肉制品的汁液流失;辐照条件或辐照原料不同,辐照对肌肉蛋白凝胶质构和流变学特性所产生的影响不同,而肌肉蛋白及其凝胶结构的辐照效应则更为复杂。论文还展望了辐照对肌肉蛋白凝胶性能影响的研究。