Effect of Zirconium Addition to Austenitic Stainless Steels on Suppression of Radiation Induced Chromium Segregation at Grain Boundaries under Ion Irradiation

The effect of Zr addition to austenitic stainless steels on the suppression of radiation induced Cr segregation at grain boundaries under 400 keV He⁺ irradiation was studied. Type 316L stainless steel and steels with addition of 0.07, 0.21 or 0.41 mass% Zr were kept at 1,423K for 30 min, and then they were quenched into the water. Irradiation was done at 773K with the dose rate of 2.4×10^?4dpa/s. The total dose was 0.85 or 3.4dpa. After irradiation, profiles of Cr concentration across the grain boundaries were measured using an analytical electron microscope with 1 nm beam diameter. Concentration of Cr at the grain boundary is decreased by radiation induced segregation. However, it increased with the addition of Zr, and the Cr segregation is almost completely suppressed when Zr is added more than 0.21 mass%.

The effect of Zr addition on suppression of Cr segregation was analyzed focussing on the interaction between dissolved Zr atoms and point defects. The effect is based on vacancy trapping by the Zr atom, and the extent to which it suppresses Cr segregation can be empirically evaluated using a radiation induced segregation model by changing the effective vacancy migration energy.     

氦离子辐照烧结碳化硅损伤效应研究

利用中国科学院近代物理研究所320 kV高压平台提供的氦离子辐照烧结碳化硅,辐照温度从室温到1 000 ℃,辐照注量为1015~1017 cm-2。辐照完成后,进行退火处理,然后开展透射电子显微镜、拉曼光谱、纳米硬度和热导率测试。研究发现,烧结碳化硅中氦泡形核阈值注量低于单晶碳化硅。同时,氦泡形貌和尺寸与辐照温度、退火温度有关。另外,对辐照产生的晶格缺陷、元素偏析进行了研究。结果表明,辐照产生了大量的缺陷团簇,同时氦泡生长也会发射间隙子,在氦泡周围形成间隙型位错环。在晶界处,容易发生碳原子聚集。辐照导致材料先发生硬化而后发生软化,且热导率降低。     

注氘低活化马氏体钢在电子辐照下的缺陷行为

低活化铁素体/马氏体(RAFM)钢被视为国际热核聚变反应堆以及聚变反应堆的第1壁候选结构材料之一,很多国家均在研究不同的RAFM钢,中国低活化马氏体(CLAM)钢的研究亦正在进行。核聚变会产生氢、氦、氘及氚,这些气体元素与辐照缺陷结合在一起,对材料的辐照性能会产生较大影响。本文对注氘后不同温度下的辐照后微观结构进行研究。试验利用日本北海道大学的JEOL-1300高压电子显微镜研究注氘CLAM钢从室温到873K在1250keV电子辐照下的微观结构变化。研究结果表明,在电子辐照下,注氘产生的缺陷团会出现消失和长大两种现象,意味着间隙型与空位型位错环在注氘过程中同时产生。并研究了注氘产生的空洞。     

Low temperature neutron irradiation effects on microstructure and tensile properties of molybdenum

Polycrystalline molybdenum was irradiated in the hydraulic tube facility at the High Flux Isotope Reactor to doses ranging from 7.2 × 10⁻⁵ to 0.28 dpa at 80 °C. As-irradiated microstructure was characterized by room-temperature electrical resistivity measurements, transmission electron microscopy (TEM) and positron annihilation spectroscopy (PAS). Tensile tests were carried out between −50 and 100 °C over the strain rate range 1 × 10⁻⁵ to 1 × 10⁻² s⁻¹. Fractography was performed by scanning electron microscopy (SEM), and the deformation microstructure was examined by TEM after tensile testing. Irradiation-induced defects became visible by TEM at 0.001 dpa. Both their density and mean size increased with increasing dose. Submicroscopic three-dimensional cavities were detected by PAS even at 0.0001 dpa. The cavity density increased with increasing dose, while their mean size and size distribution was relatively insensitive to neutron dose. It is suggested that the formation of visible dislocation loops was predominantly a nucleation and growth process, while in-cascade vacancy clustering may be significant in Mo. Neutron irradiation reduced the temperature and strain rate dependence of the yield stress, leading to radiation softening in Mo at lower doses. Irradiation had practically no influence on the magnitude and the temperature and strain rate dependence of the plastic instability stress.     

金红石辐照损伤的分子动力学模拟

为了研究辐照条件下金红石的耐辐照损伤能力，采用GULP软件包拟合出了与实验值吻合的势函数，并采用LAMMPS软件包计算出了金红石的离位阈能和高能粒子反冲条件下的位移级联。通过统计球坐标系下266个出射方向的离位能，利用缺陷形成概率的定义得出Ti和O原子的离位阈能分别为(78.3±1.0) eV和(42.6±2.0) eV。采用VORONOI缺陷统计方法，计算了300 K、10 keV出射能量条件下缺陷数量随辐照时间演化信息，结果表明：Ti原子作为初始出射原子产生的缺陷数量整体高于O原子产生缺陷的数量，在最大无序阶段产生的空位、填隙和不同类型反位缺陷通过空位-填隙复合作用和kick-out机制逐渐减少，有效地降低了晶体的无序度，提高了基材耐辐照损伤性能。     

47MeV／u的C^6^＋在CaVSn：YIG中辐照效应的研究

用兰州重离子研究装置（ＨＩＲＦＬ）首次进行了４７ＭｅＶ／ｕ的Ｃ＾６＾＋离子辐照ＣａＶＳｎ：ＹＩＧ的实验。通过穆斯堡尔效应和正电子寿命测量对４７ＭｅＶ／ｕ的Ｃ＾６＾＋离子在ＣａＶＳｎ：ＹＩＧ中的辐照效应进行了初步研究。发现辐照导致内磁场方向趋于各向同性分布，由穆斯堡尔谱未观察到非晶化现象。缺陷的数量随Ｃ＾６＾＋离子在样品中电子能量损失的增加而增加。     

慢正电子束研究质子辐照CLAM钢产生的缺陷及其退火行为

为了研究中国低活化马氏体CLAM钢的辐照损伤机理,本文利用慢正电子技术研究了质子辐照CLAM钢时所产生的缺陷及其退火回复行为,发现辐照在材料中产生空位团数密度随质子注量增加而增多,而其尺度增大并不明显.辐照仅产生原子尺度的空位和空位团,400℃退火可以使缺陷很好地消除.此外分析了硅对CLAM钢辐照性能的影响,实验上没有观察到硅的添加抑制了质子辐照缺陷的产生.     

The effect of alloying elements on the vacancy defect evolution in electron-irradiated austenitic Fe-Ni alloys studied by positron annihilation

The vacancy defect evolution under electron irradiation in austenitic Fe-34.2 wt% Ni alloys containing oversized (aluminum) and undersized (silicon) alloying elements was investigated by positron annihilation spectroscopy at temperatures between 300 and 573 K. It is found that the accumulation of vacancy defects is considerably suppressed in the silicon-doped alloy. This effect is observed at all the irradiation temperatures. The obtained results provide evidence that the silicon-doped alloy forms stable low-mobility clusters involving several Si and interstitial atoms, which are centers of the enhanced recombination of migrating vacancies. The clusters of Si-interstitial atoms also modify the annealing of vacancy defects in the Fe-Ni-Si alloy. The interaction between small vacancy agglomerates and solute Al atoms is observed in the Fe-Ni-Al alloy under irradiation at 300-423 K.     

Polycrystalline CVD Diamonds for the Beam Calorimeter of the ILC

Polycrystalline artificial diamond produced by chemical vapor deposition (pCVD) is a possible sensor material for the beam calorimeter of the ILC. The requirements are linearity over a large range of flux and radiation hardness against a total ionizing dose of several MGy per year of operation. A hadron test beam at the CERN PS was used to study the linearity of the response of pCVD sensors. An electron test beam at the S-DALINAC was used to measure the charge collection distance (CCD) as a function of the absorbed dose up to several MGy. Current-voltage characteristics of these sensors were measured before and after the irradiation as well as the dependence of the CCD on the applied electric field before and after the irradiation.     

Helium-implanted CLAM steel and evolutionary behavior of defects investigated by positron-annihilation spectroscopy

China Low Activation Martensitic (CLAM) steel has been chosen as the primary candidate structural material for the first wall/blanket for fusion reactor. The excessive helium irradiation induced damage of CLAM steel at high temperatures and the evolution of defects were investigated in this paper. The samples were homogeneously implanted with 1e + 17 ions/cm² and 100 keV of helium at room temperature, 473, 673, and 873 K. Irradiation induced damage of CLAM steel and the annealing behavior of defects were probed by slow positron beam Doppler broadening technique. Helium implantation produced a large number of vacancy-type defects which bound with helium and formed helium–vacancy complexes. Target atoms’ displacement capacity was strengthened with rising irradiation temperatures, so the S parameter increased with increasing irradiation temperatures, and helium–vacancy complexes were main defects after helium implantation at damage layers. Helium bubbles would be unstable and the desorption of helium bubbles would promote the density of defects above 673 K. By analyzing the curves of S–W and annealing tests of irradiated specimen, it suggested that there werenot only one type of defect in damage layers. Though helium–vacancy complexes were primary defects after helium implanted, introducing excessive helium might also generated other point defects or dislocation loops in the material.     

两类钒基合金的辐照硬化研究

钒合金(V-Cr-Ti系列)是重要的聚变堆结构候选材料,但是相比于铁素体/马氏体钢等其他候选材料,有关钒合金(V-Cr-Ti)的辐照损伤研究较为缺乏。利用载能离子束模拟聚变堆中子辐照条件,对V-4Cr-4Ti和V-5Cr-5Ti两种样品进行了载能He离子和重离子辐照实验。实验采用离子束梯度减能方法在样品中产生辐照损伤的坪区,利用纳米压痕技术测试材料的辐照硬化效应。结果表明,样品纳米硬度的深度递减现象可以用Nix-Gao模型很好描述,高能重离子辐照的样品中软基体效应可以有效避免;在He离子辐照情形,He浓度(以原子百万分率计(Atomic parts per million,APPM))/位移损伤(以每原子平均离位数计(Displacement per atom,DPA))大于4 200/0.2时,两种钒合金样品出现硬化饱和现象;相近位移损伤水平下,He与空位的结合导致缺陷集团的加速长大,致使材料的辐照硬化远大于重离子辐照情形。     

Irradiation-induced decay of magnetic permeability of metglas 2605S-3 and mumetal

In order to compare the radiation resistance of amorphous and crystalline magnetic alloys, samples of commercial high-permeability alloys were irradiated with high-energy neutrons near the beam stop at LAMPF. Both crystalline and amorphous alloys showed a decrease of permeability with increasing fluence, while control samples held at the same temperature showed no change of permeability. Samples prepared from Mumetal and the amorphous alloy, Metglas 2605S-3 were tested. The permeability of the Metglas 2605S-3 sample showed a rate of decrease at least a factor of ten slower than for the crystalline alloys. The permeability decrease as a function of fluence for both alloys can be separated into two distinct stages. The first stage is thought to be due to short-range ordering which occurs at an enhanced rate due to the excess point defects produced by the irradiation. The second stage is believed to be caused by pinning of domain walls on defect clusters produced in the collision cascade.     

TEM and PAS study of neutron irradiated VVER-type RPV steels

Conventional transmission electron microscopy and positron lifetime and Doppler broadening positron annihilation spectroscopy techniques have been used to investigate the radiation-induced microstructural changes in surveillance specimens of VVER-type reactor pressure vessel (RPV) steels, and RPV steels irradiated in the research reactor. Defects visible in transmission electron microscopy consist of black dots, dislocation loops and precipitates concentrated along the dislocation substructure. Their size and density depend on the neutron flux and fluence. The parallel set of thermally aged specimens, specimens recovery annealed after irradiation and specimens irradiated in a lower neutron flux was investigated too. No defects discernible in transmission electron microscopy were found after accelerated irradiation in the research reactor. In addition to visible defects, the small-volume vacancy clusters were identified by positron annihilation spectroscopy.     

慢正电子束研究电子束固化涂层的微观结构

用慢正电子束多普勒展宽谱研究环氧丙烯酸酯体系电子束固化涂层。Ｓ－Ｅ曲线给出了稀释剂分子结构及其相对含量，辐射剂量，预聚物和交联剂含量等对ＥＢＣ涂层 观结构的影响，以及随深度变化的信息。     

Study of PRIMAVERA steel samples by positron annihilation spectroscopy technique II – Lifetime measurements

In the present article, a positron annihilation lifetime technique was used for the study of VVER-440/230 weld materials, manufactured in the frame of the international PRIMAVERA project on microstructural investigation of the irradiated WWER-440 reactor pressure vessel steel. The present results complement our previous report of positron angular correlation experiments and provide in-depth characterization of vacancy type defects behavior under irradiation and thermal treatment. The results give new insight into the previously published atom probe tomography and angular correlation of annihilation radiation studies. The measurements do not show any association of phosphorus or its segregation to the open volume defects investigated by positron annihilation spectroscopy. The embrittlement effects related to the phosphorus seem to be effectively annealed-out during 475 °C thermal treatment and the post annealing microstructure and mechanical properties of the material are consequently affected mostly by agglomerations of vacancy clusters coarsened during thermal treatment.     

辐射加工级电子束量热计设计

为设计一种可以用于测量辐射加工级电子束吸收剂量的量热计,采用高纯石墨为吸收体,发泡聚苯乙烯（EPS）为绝热层材料,结合MCNP吸收剂量模拟结果设计各个部分的结构,利用ANSYS模拟分析软件进行热分析,确定各个部分的具体尺寸。以此量热计为基础,在某公司的10 MeV电子加速器下进行实验,采用microK250高精密测温电桥测量电阻阻值,获得10 MeV标称能量下的电子束吸收剂量的测量结果,得到吸收体被照射时间变化与吸收剂量的比例关系。探讨量热计准确性的影响因素,在能量为10 MeV时测量电子束吸收剂量的总不确定度为1.43,本研究结果可为辐射加工级电子束的吸收剂量测量提供参考。     

鼻咽癌放射治疗时野外组织器官剂量的研究

本文借助非均匀组织等效似人体模型,模拟鼻咽癌放射治疗,研究了＾６０Ｃｏγ射线和电子直线加速器产生的６ＭＶＸ射线对野外组织器官的受照剂量。结果表明,离照射野越近组织器官受照剂量越高,加眼晶体、垂体、甲状腺等,但睾丸的受照剂量明显高于腹部;＾６０Ｃｏγ射线照射时野外组织器官的剂量明显高于６ＭＶＸ射线;＾６０Ｃｏγ射线照射时,在耳前野野外挡铅可使眼晶体、视网膜受照剂量下降２０％,睾丸表面挡铅可使睾丸受照     

Relaxation behaviour of radiochemically aged EPDM elastomers

EPDM-type elastomers (70% ethylene; 28% propylene; diene monomer: 2% norbornene) were characterised before and after irradiation using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Three formulations were studied: pure elastomer, cross-linked elastomer with dicumyl peroxide and protected with a phenolic-type antioxidant agent. Two irradiation methods were used: γ radiation, under oxygen, at a fixed dose rate of 1 kGy/h, for total integrated doses ranging from 50 to 450 kGy and electron irradiation, under inert atmosphere, at a dose rate of 500 kGy/h, for doses of 100 and 500 kGy. For both types of irradiation, for the three EPDM formulations and for any total integrated dose, DSC and DMA show that a cross-linking phenomenon predominates. Cross-linking increases with the total integrated dose. It is also observed that cross-linking is stronger with the γ irradiation than with the electron irradiation, which confirms the influence of the oxidising atmosphere.     

The use of the high voltage electron microscope to simulate fast neutron-induced void swelling in metals

Electron irradiation with the beam of a high voltage electron microscope can be used to produce void growth in metals, simulating the effect of high dose neutron irradiation. The advantages of the technique are the high dose rate, the relative simplicity of electron irradiation and the ability to make observations during irradiation. Problems of determining the vacancy creation rate are discussed. Secondary displacements are not important for 1 MeV electron irradiation of nickel or iron.     

碳化硅VDMOS的静态和动态辐射损伤及其比较

对总剂量辐射环境下不同偏置状态的碳化硅功率场效应管（SiC VDMOS）的动态特性进行了相关研究。在比较3种偏置状态下60Co γ射线辐照对于SiC VDMOS器件阈值电压和开关特性影响的基础上,进行了室温退火试验。结果表明,随60Co γ射线辐照剂量的增加,氧化层积累陷阱电荷,导致静态特性中阈值电压降低。同时器件动态特性中开启时间略微缩短,关断时间骤增,开关损耗增大。器件受辐照后耗尽层厚度和阈值电压发生的变化是其开启和关断响应差异性退化的主要原因。