LaBr3(Ce)探测器探测效率影响因素研究

LaBr₃（Ce）晶体是一种性能优异的新型无机闪烁体,是制作闪烁体探测器的优异材料。LaBr₃（Ce）探测器在核测井、环境监测、核医学等领域得到了广泛应用。探测器的探测效率是探测器设计和研制的一个重要指标,利用Geant4工具包建立LaBr₃（Ce）探测器的探测模型,对影响探测器的探测效率的相关因素进行研究。结果表明：探测效率与晶体截面形状、尺寸有关：矩形截面的探测效率低于圆形和方形截面,而且晶体径向尺寸越大而长度越短,探测效率越高;LaBr₃（Ce）探测器的探测效率与射线的能量有关：能量越高,探测效率越低;同时,若是发散的放射源,与探测器间距越小闪烁体的探测效率越高。通过探测器探测效率的影响因素分析,对基于LaBr₃（Ce）探测器研究和设计具有一定的参考价值和指导意义。     

MC模拟计算混凝土的γ射线衰减参数

利用MC模拟计算了不同混凝土的γ射线衰减参数,并与文献中XCOM计算的数值对比,结果符合性较好。基于此模型,结合复合材料的均匀填充模型,研究了50%含量不同粒径的WO₃对混凝土材料在663 keV能量下的衰减系数。结果表明,WO₃颗粒越均匀细小,衰减系数越大,粒径100 nm比1 mm的WO₃对复合材料的质量衰减系数提高了8.94%。     

席夫碱型阳离子共价有机聚合物对99TcO-4化学替代物ReO-4的高效吸附分离

高锝酸根（TcO^-₄）的裂变产额高、环境迁移能力强、半衰期长，高效分离去除TcO^-₄在放射性环境治理和乏燃料后处理过程中具有重要意义。然而目前只有少数材料可以从水溶液体系中吸附TcO^-₄，研发动力学快和耐酸性的吸附材料仍然具有挑战。为此，通过席夫碱反应合成了两种阳离子共价有机聚合物材料（BPA-TAB-Cl和BPA-TAE-Cl）吸附ReO^-₄（TcO^-₄的非放射性类似物）。两种材料均具有超快的吸附动力学，几乎可以定量地在20 s内去除溶液中的ReO^-₄。即使在pH=2溶液中，材料的吸附能力也没有受到明显影响。在溶液中NO^-₃浓度超过ReO^-₄浓度100倍的情况下，两种材料也可以分别去除84%和79%的ReO^-₄，显示出优异的吸附选择性。在四次吸附-解吸循环之后，两种材料的吸附能力几乎没有变化。最后，吸附机理证实阴离子交换后两种材料中均存在ReO^-₄。结果表明，利用共价有机聚合物去除放射性污染物具有广阔前景。     

用于氙氪吸附分离的金属-有机骨架材料耐辐照性能的初步研究

由于乏燃料后处理废气中放射性氙（Xenon,Xe）和氪（Krypton,Kr）的去除需求以及高纯度Xe气体的商业价值,Xe和Kr的吸附分离越来越受到重视。目前Xe/Kr的分离主要采用能源和资本密集型的低温精馏法。以金属-有机骨架材料为吸附剂的多孔材料已经展示出在相对较高温度下选择性吸附Xe和Kr的能力,有望替代低温精馏法实现低成本的Xe/Kr分离。实验研究了三种热稳定性良好的金属-有机骨架材料(Co/DOBDC、Ni/DOBDC、Co₃（HCOO）₆)对Xe和Kr的吸附分离性能。从材料在273 K温度下对Xe和Kr的吸附等温线、亨利常数、亨利选择性和理想吸附溶液理论（Ideal Adsorbed Solution Theory,IAST）选择性等测试和计算结果来看,Co/DOBDC和Ni/DOBDC在常压下对Xe具有较大的吸附容量,适用于Xe吸附存储的应用场景;Co₃（HCOO）₆在低压吸附下具有大的Xe亨利常数、Xe/Kr亨利选择性和Xe/Kr IAST选择性,适用于Xe和Kr吸附分离的应用场景。...     

CeBr3探测器原位测量海洋γ放射性核素模拟研究

针对海洋环境本底复杂、人工γ放射性核素含量低导致目标核素测量精度低的问题,提出将CeBr₃闪烁体探测器应用于海洋γ放射性核素原位测量的方案。通过MC模拟,计算分析了CeBr₃探测器对海洋环境中常见人工γ放射性核素的探测效率、有效探测距离、在海水中的本底能谱(包括探测器自身放射性)、最小可探测活度浓度(MDAC)等,并与传统NaI(Tl)、LaBr₃(Ce)探测器的性能进行了对比分析。研究结果表明,所提出的海洋原位γ放射性测量方案能够弥补传统低分辨率NaI(Tl)探测器与复杂本底LaBr₃(Ce)探测器在海洋环境下对γ射线测量的不足,对提升海洋原位γ探测器在海洋放射性污染监测的智能预警能力以及对海洋环境资源的保护能力等方面具有重要意义。     

单晶硅表面钝化层在低能电子辐照前后的SIMS和XPS分析

为了研究低能电子辐照对单晶硅器件表面钝化材料中产生的化学微结构的变化,在轻掺杂P型单晶硅基底上制作了三种表面钝化膜,分别是单一SiO₂钝化膜、SiO₂/Si₃N₄复合钝化膜、硼硅玻璃/Si₃N₄复合钝化膜,开展了表面钝化单晶硅在最大能量70 keV的加速器电子束下的辐照实验。样品在空气气氛下辐照6 h,用二次离子质谱（SIMS）测试了辐照前后三种表面钝化膜中Si、N、B的纵深变化,同时用Ar离子刻蚀X射线表面光电子能谱（XPS）对Si元素的化学结合状态进行测试分析。结果表明：对单一SiO₂钝化的轻掺杂P型材料,辐照在SiO₂/Si界面产生明显的材料结构变化,界面附近的SiO₂不再是完整化学计量比,而是SiO_x（x<2）;对SiO₂/Si₃N₄复合钝化的轻掺杂P型材料,辐照对SiO₂/Si₃N₄界面结构影响较小,主要的影响仍然在SiO₂/Si界面,SiO₂辐照分解后产生的游离O元素可扩散到SiO₂/Si₃N₄界面;辐照在硼硅玻璃/Si界面和硼硅玻璃/Si₃N₄界面引起的变化小于在SiO₂/Si界面和SiO₂/Si₃N₄界面的变化。研究表明低能电子辐照对单晶硅表面钝化层的化学微结构损伤主要存在于SiO₂/Si界面,该结构损伤并不能通过SiO2/Si₃N₄复合钝化得到明显改善,而采用硼硅玻璃/Si₃N₄复合钝化有助于增强单晶硅表面及钝化层各界面材料结构的稳定性。     

阻氚用Fe-Al渗铝层表面稳态相Al2O3膜生长机理研究

为阐释Fe-Al渗铝层表面暂态相Al₂O₃膜向稳态相α-Al₂O₃膜的转变机理，探索稳态相α-Al₂O₃膜制备的氧化工艺参数范围，采用掠入射角X射线衍射仪、辉光放电光谱仪、聚焦离子束、透射电镜等，结合热重分析对CLAM钢基体Fe-Al渗铝层在940～980 ℃、1 Pa～20 kPa参数下的氧化生长行为进行了深入表征与机理分析。研究结果表明，在1 Pa～20 kPa氧分压范围内Al₂O₃膜生长初期反应速率常数随着氧分压的升高而增大，而后期反应速率常数反而随之下降；采用掠入射角X射线衍射仪对3～180 min氧化不同时期表面Al₂O₃膜的相结构进行了掠入射角分析，推测Al2O3膜的生长经历了从氧化初期形成暂态相γ-Al₂O₃（15 min）→过渡态相α-（Al_0.948Cr_0.052）₂O₃（30 min）→稳态相α-Al₂O₃（120～180 min）的演变过程，最短相转变时间约60～90 min，连续Al₂O₃膜厚度约2 000 nm；同时，结合聚焦离子束对30、120 min形成的Al₂O₃膜表面进行了精确定向切割制样，并采用透射电镜选区电子衍射分析验证了相转变前Al₂O₃膜结构为过渡态相α-（Al_0.948Cr_0.052）₂O₃（113），转变后为稳态相α-Al₂O₃（113），证实了Cr作为第三组元促进暂态相向稳态相α-Al₂O₃的转变规律。     

溴化镧/氯化镧电流型闪烁探测器性能研究

掺铈溴化镧(LaBr₃∶Ce)及掺铈氯化镧(LaCl₃∶Ce)是近年来出现的性能优良的新型无机闪烁体。本文对LaBr₃∶Ce和LaCl₃∶Ce电流型闪烁探测器的性能进行了研究,计算了探测器的相对灵敏度随入射γ射线能量的变化曲线,测定了其对¹³⁷Cs和⁶⁰Co的灵敏度,并检验了其γ/n分辨本领。结果表明,溴化镧和氯化镧探测器具有较高的γ灵敏度响应和γ/n分辨,适于测量低强度快脉冲中子、γ混合场中的γ射线束。     

高温结晶合成Mn2O3@MoS2复合材料及其对铀的吸附性能

采用高温熔盐电解法合成了MoS₂,为了提高MoS₂对铀的吸附性能,以MoS₂为基底复合Mn₂O₃。MoS₂的片层结构有效地分散了Mn₂O₃的团聚,同时引进了亲铀氧基团。采用电子扫描显微镜及能谱(SEM & EDS)、X射线衍射仪(XRD)、Zeta电位仪等对Mn₂O₃@MoS₂复合材料进行了表征,表征结果表明,高温结晶合成的Mn₂O₃@MoS₂复合材料具有完整的微观形貌和稳定的晶体结构。通过静态吸附批实验探究了在不同变量下Mn₂O₃、MoS₂和Mn₂O₃@MoS₂三个材料对溶液中铀的吸附效果,结果表明,Mn₂O₃@MoS₂的吸附性能优于Mn₂O₃和MoS₂,在pH=5.5时,吸附平衡时间为90 min,吸附动力学遵循准二级动力学模型,吸附等温线符合Langmuir模型。Mn₂O₃@MoS₂的单层饱和吸附容量为117.5 mg/g,在293.15~318.15 K的温度梯度中,升温有利于吸附进行。     

聚苯胺/TiO2复合材料对U(Ⅵ)吸附性能的研究

采用溶胶-凝胶法合成二氧化钛（TiO₂），并将苯胺聚合在TiO₂表面制备了聚苯胺（PANI）/TiO₂复合材料（PANI/TiO₂）。使用FT-IR、TGA和XPS表征了制备的TiO₂、PANI和PANI/TiO₂的表面功能基团、热稳定性和表面元素组成。研究了溶液pH值、吸附时间、U(Ⅵ)浓度和温度等因素对TiO₂、PANI和PANI/TiO₂吸附U(Ⅵ)的影响，探讨了3种材料对U(Ⅵ)的吸附动力学、等温线和热力学性质。FT-IR、TGA和XPS表征结果表明，成功制备了PANI/TiO₂复合材料。TiO₂、PANI和PANI/TiO₂吸附U(Ⅵ)的最佳pH值分别为5.0、4.5和5.0；吸附过程均符合Langmuir吸附等温模型和准二级吸附方程，TiO₂、PANI和PANI/TiO₂的单层饱和吸附量分别为11.49、22.41、43.29 mg/g；3种吸附剂对U(Ⅵ)的吸附过程均为自发的吸热过程。同时，PANI/TiO₂具有较好的循环使用性能，第5次使用时，吸附量仅降低了15.4%。     

Hydrogen dynamics in electrochromic multilayer systems investigated by the N technique

The resonant reaction ¹H(¹⁵N, γ)¹²C was used to determine the depth distribution of hydrogen in two electrochromic multilayer systems. The systems can be bleached and colored by applying an external voltage. To test models explaining this effect by a change of H content (c_H) in electrochromic layers, H profiles of the systems were measured as a function of the applied voltage. For NiO_x, c_H was found to vary as predicted, whereas for WO₃, c_H changes were smaller than expected. Additionally, H uptake into the ITO electrode was observed.     

Electronic structure of In_2O_3 nanowires synthesized at low temperature

In₂O₃ nanowires with uniform morphology and single crystalline structure were synthesized at low temperature of 400℃⁴50℃using InSb as the precursor via VLS mechanism.The nanowires have uniform diameter of about 40 nm and are up to tens of micrometres in length and grew along the[100]direction as established by high resolution electron microscopy.The electronic and local structures of ln203 nanowires,compared to that of In203 powder,have been studied with X-ray absorption fine structure（XAFS） at In K-edge and O K-edge.The XAFS results reveal the stronger In-O bonding in In₂O₃ nanowires compared to bulk In₂O₃.     

Irradiation-induced nanostructures in cadmium niobate pyrochlores

This paper reports the formation processes of crystalline Cd nanostructures on ion-cut surfaces of cadmium niobate pyrochlores (Cd₂Nb₂O₇). Irradiation with 3 MeV He⁺ ions has been performed at low temperatures (295 K) to induce material decomposition and aggregation of host atoms. The irradiation also leads to surface exfoliation due to rupture of gas (He and O₂) filled blisters. Nanoparticles and nanowires are observed on the ion-cut surfaces at low and higher doses, respectively. These structures are examined and characterized using a suite of experimental tools. Both the particles and wires are found to be single crystals that primarily consist of metallic Cd.     

The constitution of the uranium-tin-palladium system

The Pd-rich region of the isothermal section of the ternary U---Sn---Pd system at 1050°C was investigated by metallography, X-ray microanalysis and X-ray diffraction. The fcc -Pd(Sn, U) solid solution dissolves up to 16 at.% Sn and 15 at.% U. The AuCu₃ type phases SnPd₃ and UPd₄ are the end members of a single-phase region. SnPd₂ and UPd₃ are in equilibrium with this solid solution of the composition U_0.68Sn_0.32Pd₃ and with the ternary phase USnPd₂. The Gibbs energies of formation of SnPd₂, SnPd₃ and UPd₄ were used and ideal behaviour of the (Sn, U) Pd_3+x solid solution was assumed to calculate the Gibbs energy of formation of UPd₃ which gives Δ_fG° = −312 kJ/mol at 1050°C. In addition, the annealing experiments in the Pd-rich region of the binary U---Pd system were extended to 950°C which confirm the phase-field distribution established at 1050°C in earlier work.     

Influence of the surface conditions on permeation in the deuterium–MANET system

The condition of the surfaces is of crucial importance for the deuterium permeation through materials. In this work a study of the surface constants for the adsorption (σk₁) and release (σk₂) of deuterium under different surface conditions on the martensitic steel DIN 1.4914 (MANET) has been carried out. The growth of an oxide surface layer (Cr₂O₃) of about 25–30 nm in a MANET sample, heat treated in an oxidizing environment, compared to the bare MANET that have a ‘natural' oxide of about 5 nm has provoked a reduction of both the permeation rate and the recombination coefficient (about 3 orders of magnitude). In addition, the permeation governing process has changed from diffusion-limited to surface-limited. The measurements of the permeation rate of deuterium were performed by a gas-phase permeation technique over the temperature range 574–746 K and for deuterium driving pressures in the range from 3 to 10⁵ Pa.     

A generalized model for radiation-induced amorphization and crystallization of U3Si and U3Si2 and recrystallization of UO2

A rate-theory model of radiation-induced amorphization and crystallization of U₃Si during ion irradiation has been generalized to include U₃Si₂ and UO₂. The generalized model has been applied to ion-irradiation and in-reactor experiments on U₃Si and U₃Si₂ and provides an interpretation for the amorphization curve (dose required to amorphize the material as a function of temperature), for the ion-radiation-induced nanoscale polycrystallization of these materials at temperatures above the critical temperature for amorphization, as well as for the role of the small crystallites in retarding amorphization. An alternative mechanism for the evolution of recrystallization nuclei is described for a model of irradiation-induced recrystallization of UO₂ wherein the stored energy in the UO₂ is concentrated in a network of sinklike nuclei that diminish with dose due to interaction with radiation-produced defects. The sinklike nuclei are identified as cellular dislocation structures that evolve relatively early in the irradiation period. The complicated kinetics involved in the formation of a cellular dislocation network are approximated by the formation and growth of subgrains due to the interaction of shock waves produced by fission-induced damage to the UO₂.     

DBD plasma assisted atomic layer deposition alumina barrier layer on self-degradation polylactic acid film surface

In this work, the plastic of polylatic acid(PLA) film is coated by alumina(Al_2O_3)through dielectric barrier discharge plasma assisted atomic layer deposition(DBD PA-ALD) for the proposal of the barrier property enhancement. The influence of ALD Al_2O_3 thickness on properties of barrier, mechanical, optical and degradation is investigated in detail. It is obtained that the growth rate of Al_2O_3 in DBD PA-ALD is as quick as 0.12 nm/cycle. After coated～40 nm Al_2O_3, the water vapor transmission rate of PLA is reduced by two orders of magnitude.Additionally, it is noticed that the tension strength of the coated film is improved slightly,whereas the light transmission rate is decreased with the increase of Al_2O_3 thickness. The degradation test shows that Al_2O_3 coating almost does not affect the self-degradation rate of PLA film.     

钙-铀-碳酸络合物对红土吸附铀性能的影响

采用静态实验法研究了钙-铀-碳酸络合物对红土吸附铀性能的影响。结果表明:溶液的pH值、总碳酸和钙离子浓度增大会抑制红土对铀的吸附,当pH=7.0,红土投加量为1g/L,钙离子、总碳酸根和初始铀浓度分别为0.4mmol/L、3.8mmol/L和50mg/L时,红土对铀的最大吸附容量约为4.20mg/g。铀在红土上的吸附形态为UO2(CO3)2-2、UO2(CO3)4-3和UO2CO3(aq)。利用铀-碳酸络合物总量c(UCO3)T可预测红土吸附铀的容量qe,c(U-CO3)T与qe呈非线性关系,其方程为qe=18.2(c(UO2+2)·c(CO2-3)(K1+K2c(CO2-3)+K3c2(CO2-3)))0.36。该研究成果可为铀污染土壤的修复和治理提供技术和理论参考。     

Design of a gadolinia bearing mixed-oxide fuel assembly for pressurized water reactors

A study on neutronics design of a gadolinia (Gd₂O₃) bearing mixed-oxide (MOX) fuel assembly (MOX-UO₂ (Gd₂O₃) assembly) was performed for the purpose of suppressing the use of fresh lumped burnable poison rods (BPRs). The MOX-UO₂ (Gd₂O₃) assembly investigated consists of MOX and UO₂ (Gd₂O₃) fuel rods, which have already been verified through both fabrication and irradiation experiences. In all, 16 UO₂ (10 wt% Gd₂O₃) fuel rods are located at every corner and the peripheral region of the MOX-UO₂ (Gd₂O₃) assembly in order to reduce the power peaking of MOX fuel rods due to the thermal neutron inflow, and to reduce the reactivity penalty at the end of cycle (EOC). Since fresh BPRs are not expected to be inserted and UO₂ (Gd₂O₃) fuel rods are located at every corner of the assembly, the number of splits in plutonium (Pu) content can be only two, which is less than three splits required for a standard MOX assembly. Core characteristics of an equilibrium core loaded with MOX-UO₂ (Gd₂O₃) assemblies are evaluated and it is verified that adoption of the MOX-UO₂ (Gd₂O₃) assembly is effective to avoid the use of fresh BPRs with securing both the core safety and cycle length. The simplication of the splits in Pu content is also supposed to be beneficial, since it has the possibility of reduce MOX fuel fabrication costs.     

草酸铈成核和晶体生长动力学

为研究草酸盐沉淀动力学,本研究用草酸铈代替草酸钚对成核和晶体生长动力学进行了研究,并提出了一种在测定成核动力学时确定稀释倍数的有效方法。在25~50 ℃时,在硝酸铈浓度为0.030~0.400 mol/L、草酸浓度为0.250~0.800 mol/L、母液草酸浓度0.100 mol/L的条件下,分别研究了草酸铈成核和晶体生长动力学方程。结果表明：成核时稀释倍数对成核速率的测量影响很大,定义的稀释过饱和比S_n值为1.65时得到的稀释倍数最佳。草酸铈成核过程可分为均相成核和异相成核,成核速率方程可表示为：R_N=A_N0·exp［-E_a/RT］·exp［-B_N/(ln S)²］,其中均相成核时：A_N0=3.86×10³⁰/(m³·s),E_a=67.4 kJ/mol,B_N=55.3;异相成核时：A_N0=3.10×10²⁰/(m³·s),E_a=19.1 kJ/mol,B_N=11.5。晶体生长速率方程可表示为：G=k_g0·exp［-E_a/RT］·δ^g(t),其中k_g0=4.81×10⁵ m/s,E_a=80.3 kJ/mol,g=2.09,草酸铈的晶体生长受界面反应过程控制。该装置和沉淀动力学测量方法可用于其他草酸盐成核和晶体生长动力学的研究。