GaN器件辐伏同位素电池的电输出性能研究

利用⁶³Ni和3H源分别辐照两种可作为辐伏电池换能单元的GaN基PiN结型器件,其输出短路电流（I_sc）和开路电压（V_oc）分别为：对于⁶³Ni源,I_sc＝5.4 nA,V_oc＝771 mV;对于3H源,I_sc＝10.8 nA,V_oc＝839 mV。其开路电压显著优于单晶硅基器件辐伏电池的输出结果,但与理论值有一定的差距。可能是GaN材料生长过程中产生的缺陷、电极欧姆接触不良以及器件结构等原因,导致短路电流和开路电压未能达到期望值。这些是提升GaN换能单元辐伏电池的电输出性能应解决的重要技术问题。     

称重法测量强63Ni薄膜源活度的研究

为解决因⁶³Ni源的β射线能量低,使强⁶³Ni源活度难以直接测量的问题,依据放射性物质活度和质量的关系,利用称重法对化学镀镍工艺制备的强⁶³Ni源活度进行间接测量。结果显示,不同编号的⁶³Ni镀层质量为0.92~2.16 mg,根据⁶³Ni比活度、镀层中Ni含量计算对应镀层活度为4.1×10⁸~9.6×10⁸ Bq。考虑天平、Ni含量分析的系统误差,该活度数据的可靠性较高。     

62Ni同位素的分离制备

微型核电池是目前航天器仪器、设备理想的电源。⁶³Ni是镍电池的核心工作物质。通过在反应堆中辐照高丰度的稳定同位素⁶²Ni,能产生放射性同位素⁶³Ni。为保证⁶²Ni的丰度达到要求,本文开展了⁶²Ni同位素的分离制备研究,进行了磁场及束流输运计算,对离子源及接收器口袋进行了改进设计,制定了电磁分离法分离高丰度⁶²Ni的工艺流程。利用现有的电磁同位素分离器,开展了用电磁分离法分离高丰度、高纯度⁶²Ni稳定同位素的实验,最终获得了丰度≥90%的⁶²Ni同位素。     

核电厂液态流出物中63Ni的排放、剂量评估及监测方法研究

⁶³Ni是核电厂液态流出物中排放量较大的核素,在排放的裂变产物和活化产物中占比在10%以上,但我国核电厂目前对液态流出物中的⁶³Ni没有开展监测,没有相关监测数据的积累。本文在核电厂排放的⁶³Ni的来源分析及国外压水堆核电厂排放统计参考值调研的基础上,对⁶³Ni排放的剂量评估和测量方法进行了分析研究,并提出我国核电厂开展液态流出物中⁶³Ni监测的建议。     

63Ni毒剂报警源制备工艺的研究

离子迁移谱技术是现场快速检测化学战剂的有效手段，⁶³Ni毒剂报警源是离子迁移谱技术常用的离子化源。为进行⁶³Ni毒剂报警源的制备，设计活度测量和电镀装置，优化电镀参数，并进行平行性实验和牢固性测试。结果表明，最佳电镀条件为温度20 ℃、电流密度20 mA/cm²、pH 2~3、电镀时间10 min；平行性实验和牢固性测试显示，该方法制备的放射源一次电镀合格率达100%，镀层和镍片结合牢固。该方法制备的放射源满足离子迁移谱技术对离子化源的需求。     

低中放固体废物处置场下伏地层包气带中63Ni的测量

为明确⁶³Ni在低中放废物处置场下伏地层包气带中的吸附能力以及迁移规律,本文建立了一种包气带土壤中⁶³Ni的快速分析方法：包气带土壤样品在300℃灰化3 h后,用9 mol/L HCl浸取处理,处理后的样品采用2次丁二酮肟沉淀分离纯化⁶³Ni,纯化后的⁶³Ni用液体闪烁计数器测量。结果表明：镍的平均化学回收率为(97.6±2.4)%,0.5 g土壤样品测量1 h检测限为0.18 Bq/g,对⁶⁰Co、⁶⁵Zn、⁵⁴Mn、⁵⁵Fe等潜在干扰核素的去污因子均大于10~3,2 h可完成放化分离过程。用加标样品对分析方法进行验证,结果表明,预期值和测量值的相对偏差小于±3%。     

核电站液态流出物中63Ni的快速分离与测定

本文通过系统调研,以Ni特效树脂为⁶³Ni分离富集材料、低本底液闪谱仪为测量仪器,经过大量条件实验进行方法优化,建立了一套核电站液态流出物中⁶³Ni的快速分析方法。本方法取样量小,6个平行样品的化学回收率为(93.2±3.6)%,放化回收率为(92.1±2.8)%,探测限为67.4 mBq/L,对干扰核素去污因子高,其中对Fe、Co、Zn、Mn的去污因子分别为10²、10⁴、10²及10⁴,分析周期短(约9 h):同时使用建立的方法进行了液态流出物样品的分析,证明本方法可应用于核电站液态流出物的快速监测,并发现不同类型反应堆运行时液态流出物中⁶³Ni的浓度可能会存在较大差异。     

镍特效树脂分离富集核电厂液态流出物中的63Ni及其测量方法研究

为准确评估核电厂液态排放对公众造成的辐射影响,需对液态流出物中排放量较大、半衰期较长的⁶³Ni进行分析。本工作以镍特效树脂作为分离纯化材料,结合阳离子树脂、原子吸收光谱和液闪谱仪,建立了快速分析核电厂液态流出物中⁶³Ni的方法。用本工作建立的方法和GB/T 14502-1993方法比对分析了核电厂的液态流出物样品,化学回收率均高于70%,方法探测下限为0.005 Bq/L,比对结果的E_n值均远小于1,表明该方法的分析结果准确可靠。相比于GB/T 14502-1993方法,本方法操作简单、分离流程短、工作效率高,适用于核电厂液态流出物中⁶³Ni的富集和分离。     

GaAs基β辐射伏特效应微电池的参量优化设计研究

考虑放射性同位素源自吸收效应,提出基于半导体材料GaAs和同位素源⁶³Ni的微电池最优化设计方案,并通过蒙特卡罗程序MCNP模拟计算β粒子在半导体材料中的输运过程,对同位素源与半导体材料的厚度,换能单元PN结结深、耗尽区宽度、掺杂浓度、少子扩散长度,及电子空穴对的产生及收集情况等进行了研究和分析,给出了不同结深下,各物理参量的最佳设计值。在源活度为3.7×10⁷ Bq,PN结表面积为0.01 cm²时,提出的辐射伏特效应微电池最优化设计方案可实现：短路电流密度为379.68 nA/cm²,开路电压为1.375 V,填充因子为84.39%, 最大输出功率为440.4 nW/cm²,能量转化率为4.34%。     

正脉冲电镀法制备φ33 mm模拟镍源

mA量级直流恒流电源具有过保护电压较低的缺点,不适于制作大面积、高活度⁶³Ni放射源。本文以正脉冲电源为解决方案,系统研究在简单组分的镀镍溶液中,各工艺条件对电镀结果的影响。研究结果表明,在阴极电流密度为18 mA/cm²、室温、脉宽80%、频率5 kHz条件下电镀2.5 h,可获得95%以上的⁵⁸Ni沉积率。     

Fragmentation by Beta-Decay in Tritium-Labelled Compounds, (III)

The potential energy curves of LiHe⁺, BeHHe⁺ and FHe⁺ in the ground state are calculated with a scale factor optimized STO-6G basis set, and these potential curves are compared with those of HHe⁺, CH₃He⁺, NH₂He⁺ and OHHe⁺ already reported. In the T→He⁺ β-decay, ground state daughter ions HHe⁺, LiHe⁺ and BeHHe⁺ are found to be bound, whereas CH₃He⁺, NH₂He⁺, OHHe⁺ and FHe⁺ ions dissociate into a He atom and residual fragments.     

Reaction balance and efficiency analysis of a D-D fusion/fission hybrid with satellite D-3He reactors

Selected reactor physics and isotope balance characteristics of a fusion hybrid supported D-³He satellite nuclear energy system are formulated and investigated. The system consists of two types of reactors: a parent D-fueled fusion device and a number of smaller reactors optimized for D-³He fusion. The parent hybrid station breeds the helium-3 for the satellites and also breeds fissile fuel for an existing fission reactor economy. Various hybrid operational regimes are examined in order to determine favorable reactorQ values and effective fusion and fission efficiencies. A number of analytical correlations between power output, plasma energetics, blanket neutronics, breeding capacity, and energy conversion cycles are established and evaluated. Numerical examples of performance parameters such as fission-to-fusion power, overall conversion efficiency, and the ratio of satellite to parent fusion power are presented. The range of reactor efficiencies is elucidated as affected by the internal plasma power balances. As an upper bound based on optimistic injection and direct conversion efficiencies, we find the D-³He satellite system power output attaining at best 1/3 of the parent fusion power.     

Design study of a 120-keV,3He neutral beam injector

We describe a design for a 120-keV, 2.3-MW,³He neutral beam injector for use on a D-³He fusion reactor. The constraint that limits operating life when injecting He is its high sputtering rate. The sputtering is partly controlled by using an extra grid to prevent ion flow from the neutralizer duct to the electron suppressor grid, but a tradeoff between beam current and operating life is still required. Hollow grid wires functioning as mercury heat pipes cool the grid and enable steady state operation. Voltage holding and radiation effects on the acceleration grid structure are discussed. We also briefly describe the vacuum system and analyze use of a direct energy converter to recapture energy from unneutralized ions exiting the neutralizer. Of crucial importance to the technical feasibility of the³He-burning reactor are the injector efficiency and cost; these are 53% and $5.5 million, respectively, when power supplies are included.The beam is composed of 91 separate, parallel currents that flow in the gaps between the elements or wires of a grid. Each such flow is referred to as a beamlet. The current densities in Figs. 5, 8, and 9 are values within a beamlet, as measured at the beam-forming grid. They are not values averaged over the entire beam cross-section.     

Recent advances in AMS of Cl with a 3-MV-tandem

Accelerator mass spectrometry (AMS) of ³⁶Cl (t_1/2 = 0.30 Ma) at natural isotopic concentrations requires high particle energies for the separation from the stable isobar ³⁶S and was so far the exclusive domain of tandem accelerators with at least 5 MV terminal voltage. Using terminal foil stripping and a detection setup consisting of a split-anode ionization chamber and an additional energy signal from a silicon strip detector, a ³⁶S suppression of >10⁴ at 3 MV terminal voltage was achieved. To further increase the ³⁶S suppression energy loss straggling in various counter gases (C₄H₁₀, Ar-CH₄ and C₄H₁₀-Ar) and the effect of “energy focusing” below the maximum of the Bragg curve was investigated. The comparison of experimental data with simulations and published data yielded interesting insights into the physics underlying the detectors. Energy loss, energy straggling and angular scattering determine the ³⁶S suppression. In addition, we improved ion source conditions, target backing materials and the cathode design with respect to sulfur output and cross contamination. These changes allow higher currents during measurement (³⁵Cl⁻ current ≈ 5 μA) and also increased the reproducibility. An injector to detector efficiency for ³⁶Cl ions of 8% (16% stripping yield for the 7+ charge state in the accelerator, 50% ³⁶Cl detection efficiency) was achieved, which can favorably be compared to other facilities. The memory effect in our ion source was also thoroughly investigated. Currently our measured blank value is ³⁶Cl/Cl ≈ 3 × 10⁻¹⁵ when samples with a ratio of 10⁻¹¹ are used in the same sample wheel and ³⁶Cl/Cl ≈ 5 × 10⁻¹⁶ if measured together with samples with a ratio of 10⁻¹² or below. This is in good agreement with the lowest so far published isotope ratios around 5 × 10⁻¹⁶ and demonstrates that 3 MV tandems can achieve the same sensitivity for ³⁶Cl as larger machines.     

Experimental study of the excitation functions of deuteron induced reactions on Sn up to 40 MeV

Using the stacked-foil activation technique, cross-sections of deuteron induced reactions on natural Sn were measured up to 40 MeV. Excitation functions are reported for the product nuclides ¹¹¹In, ¹¹³Sn, ^117mSn, ^125mSn, ^125gSn, ¹¹⁵Sb, ^116mSb, ¹¹⁷Sb, ^118mSb ^120mSb, ¹²²Sb, ¹²⁴Sb and ¹²⁵Sb and compared with the earlier published data sets. For all excitation functions comparisons with theoretical calculations using the ALICE-IPPE, EMPIRE, EAF and the TALYS codes were performed.     

贫铀/聚乙烯交替球壳中裂变反应率的测量与分析

为校验次临界能源堆的概念设计,采用活化法在贫铀/聚乙烯球壳交替装置上开展14 MeV中子学积分实验。用HPGe探测器测量²³⁸U(n,f)及²³⁵U(n,f)反应的裂变碎片¹⁴³Ce衰变产生的293.3 keV特征γ射线,得到装置中与入射D粒子束成90°方向上的²³⁸U(n,f)及²³⁵U(n,f)反应率分布,相对不确定度为5.1%~6.9%。采用MCNP5程序在ENDF/B-Ⅵ库下进行模拟计算,计算结果较实验结果高约5%。     

Investigation of activation cross-sections of deuteron induced reactions on vanadium up to 40 MeV

Experimental excitation functions for deuteron induced reactions up to 40 MeV on natural vanadium were measured with the activation method using a stacked foil irradiation technique. From high resolution gamma spectrometry cross-section data for the production of ⁵¹Cr, ⁴⁸V, ^48,47,46Sc and ⁴⁷Ca were determined. Comparisons with the earlier published data are presented and results for values predicted by different theoretical codes are included. Thick target yields were calculated from a fit to our experimental excitation curves and compared with the earlier experimental data. Depth distribution curves used for thin layer activation (TLA) are also presented.     

替代241Am低能光子源的准单色X射线机的研制

研究了用滤光片法产生50～60 keV的准单色X射线的条件,对输出的X射线进行了数种金属滤光片实验研究,选出合适的滤光片,通过实验对准直器的机械结构进行了确定。采用自行设计委托加工的X射线管、准直器和购买的高压电源,组装成符合实验要求的X射机。该装置输出了50～60 keV能量段的准单色光谱,在料位计上能替代²⁴¹Am低能光子源。     

Determination of the 129I transmutation rate and 129I(n, 2n)128I correction using gas mass spectrometry

Two groups of ¹²⁹I and ¹²⁷I targets were analyzed using a gas quadrupole mass spectrometer (QMS) to determine the transmutation rates via the melting method. Sodium iodide was chosen to make the target. The iodine composition in the ¹²⁹I targets is 82.7% ¹²⁹I and 17.3% ¹²⁷I. The transmutation rate of the ¹²⁹I(n, γ)¹³⁰I reaction was determined by measuring the ¹³⁰Xe with QMS. An equivalent corrective method was brought out to correct the ¹²⁹I(n, 2n)¹²⁸I branch which is interfered with by the ¹²⁷I(n, γ)¹²⁸I reaction. And the correction formula was deduced in theory. For very little ¹²⁸Xe from the ¹²⁹I(n, 2n)¹²⁸I reaction, the equivalent corrective method could not be suitable here. However, it is suitable for the mass of ¹²⁸Xe from ¹²⁹I(n,2n)¹²⁸I reaction that reaches the accurately detective level of the mass spectrometry.     

Measuring the Photoneutrons Originating from D(γ, n)H Reaction after the Shutdown of an Operational BWR

The purpose of this study is to measure the photoneutron emission rate after the shutdown of an operational BWR. The photoneutrons originate from the D(γ, n)H reaction in the moderator region, while the high-energy gamma rays are generated from ¹⁴⁰Ba-¹⁴⁰La transient equilibrium of fission products in irradiated fuel. The photoneutron emission rate is measured by means of the photoneutron signal ratio of the Start-up Range Neutron Monitor (SRNM). The ratio is defined as a ratio of the photoneutrons to neutrons originating from spontaneous fission and the oxygen (γ, n) reaction of actinides (²⁴²Cm, ²⁴⁴Cm, etc.) in irradiated fuel. The principle of the measurement of the photoneutron signal ratio is the large difference between the decay constants of the ¹⁴⁰Ba-¹⁴⁰La transient equilibrium and those of the actinides. The measurement of the SRNM signal was continuously carried out over several months, and the photoneutron signal ratio was evaluated by using the least-squares method to fit a theoretical model to SRNM signal data. The measurements were performed in the middle of the cycle at three BWR cores. Comparisons of the measured photoneutron signal ratio and the calculated one showed reasonable agreement. This demonstrates the validity and usefulness of the measurement. The absolute value of photoneutrons in the SRNM signal ranged from approximately 1 to 35 counts per second during a five-day cooling period after shutdown. Converting the absolute value to the relative fraction of photoneutrons in the SRNM signal results in a range from approximately 2 to 50%.