利用TALYS和EMPIRE研究质子诱发钼靶核反应

利用加速器直接生产99Mo和99mTc在核医学领域具有良好的发展前景,精确可靠的核反应数据对于同位素生产具有重要意义。本文通过对EXFOR数据库中natMo(p, x)96m+gTc、100Mo(p, x)99Mo、100Mo(p, 2n)99mTc核反应截面实验数据进行分析,采用多项式拟合实验数据给出参考值。并利用TALYS-1.95和EMPIRE-3.2.3程序结合不同能级密度、预平衡发射等模型 计算了40 MeV能量以下natMo(p, x)96m+gTc、100Mo(p, x)99mTc、100Mo(p, 2n)99mTc核反应的激发函数。对于natMo(p, x)96m+gTc核反应,TALYS-1.95程序采用能级密度输入参数ldmodel 6时,preeqmode 1, 2模型计算结果与实验数据符合最好。对于100Mo(p, x)99Mo核反应,TALYS-1.95程序采用能级密度输入参数ldmodel 6时,preeqmode 4模型计算结果与实验数据符合最好。对于100Mo(p, x)99Mo核反应,EMPIRE-3.2.3程序LEVDEN 2模型计算结果与实验数据符合最好。     

碳纳米颗粒的放射性99mTc标记

探索了影响氯化亚锡还原法制备碳纳米管和不同粒径纳米碳黑的99mTc标记化合物的多种因素, 在给定实验条件下, 99mTc的标记率能够稳定达到90％以上。 细胞培养液中标记物的放射化学纯度在2.5 h中保持在(86±4)%范围内。 制备的标记化合物满足碳纳米颗粒细胞摄取率测定和细胞毒性机制研究的实验要求。 实验结果提示, 99mTc标记过程是基于还原得到的低价Tc在碳纳米颗粒表面上的物理吸附机理。 The effects of experimental conditions on preparation of 99mTc labeled carbon nanotubes and nanocarbon blacks by SnCl2 were investigated. At given conditions the labeling yields were over 90%. In a culture medium, the radiochemical purity of the labeling compounds kept (86±4)% within 2.5 h. The 99mTc labeled multi walled carbon nanotubes (MWNTs) and nanocarbon blackes (NCBs) obtained in this work met satisfactory experimental demands for study of cellular uptake and toxicity. The experiments showed that the labeling process was based on physical adsorption of low valent technetium resulted from reduction reaction on the surface of the carbon nanomaterials.     

利用FLUKA研究加速器生产医用放射性同位素的产额

针对目前核医学广泛关注的医用放射性同位素99Mo/99mTc、64,67Cu、68Ge/68Ga、82Sr/82Rb、211At、225Ac等,本文利用FLUKA程序对加速器生产上述同位素的产额及产物分布进行了研究。研究表明,医用放射性同位素的产额随束流能量增加而增加,增加趋势逐渐降低;产额随辐照时间的增长而增加,随辐照后冷却时间的增长而降低,变化情况主要取决于目标医用同位素的半衰期;入射束流在同位素靶的有效射程内产生医用放射性同位素,选取合适的靶厚可以优化目标医用同位素的比活度值等;此外,束流能量越高产生的杂质核素种类及产额也相应增加,合适的辐照能区和辐照时间等,可以降低后续目标医用同位素分离纯化等工作的复杂程度。本文通过FLUKA的计算初步为加速器生产医用同位素提供了重要的依据。     

缺陷态对Y掺杂BaZrO3的质子导电性的影响

核能是一种新型能源, 其开发和利用对氢同位素分离和纯化提出了迫切要求. BaZrO₃基钙钛矿氧化物是一种有效分离纯化氢同位素的材料, 本文采用高温固相法制备了BaZr_1-xY_xO_3-δ (0≤ x ≤0.3)系列样品, 射线衍射光谱分析表明Y的最大掺杂浓度在0.24-0.26之间. 在600 ℃干燥氢气气氛下, 由电化学阻抗谱测试可知, 掺20 mol%Y 的BaZr_1-xY_xO_3-δ样品电导率可达σ =0.00150 S/m, 较BaZrO₃基质材料的电导率高接近两个数量级. 利用热释光谱和发射光谱研究了系列样品缺陷类型, 结果表明BaZrO₃基质材料存在两种对质子传导有利的氧空位(V_o^..); 当掺入Y 后, 除氧空位之外, 样品还出现了带负电的质子俘获型缺陷Y_Zr', 且 Y_Zr'缺陷的数量随着Y掺杂浓度增加而增多; 同时出现了缺陷陷阱深度变浅导致对质子捕获能力降低的现象, 有利于提高质子导电性. 本文通过发射光谱和热释光谱相结合, 有效地研究了BaZr_1-xY_xO_3-δ材料的缺陷类型.     

自由电子激光用于阈能反应分子法激光分离铀同位素的研究

 提出了自由电子激光的一种可能应用。指出静电电子加速器驱动的FEL技术目前已有能力满足阈能反应分子法激光分离铀同位素的要求。阈能反应分子法由于只需一次激光激发,因此从原理上讲,它的一次分离系数很高,优于原子法与其他分子法,在高浓铀小规模(10kg级/年)生产中有其可行性。     

FE L用于阈l能反应分子法激光分离铀同位素研究

提出了自由电子激光(FEL)的一种可能应用.指出静电电子加速器驱动的FEL技术目前已有能力满足阈能反应分子法激光分离铀同位素的要求.阈能反应分子法由于只需一次激光激发,因此从原理上讲,它的一次分离系数很高,优于原子法与其他分子法,在高浓铀小规模(10kg/a)生产中有其可行性.     

232Th 中子诱发裂变产额数据比对评价

232Th 中子诱发裂变产额在Th/U 燃料循环的核能开发中具有重要的意义,在现有国际评价产额数据库基础上,结合最新的实验数据,对产物核的质量分布和反应堆计算所需的重点产物核进行了比对。这些产物核包括95Mo,99Tc,101Ru,103Rh,109Ag,133Cs,147Sm,149Sm,150Sm,151Sm,152Sm,143Nd,145Nd 和153Eu 等,对有分歧的133Cs,152Sm 和153Eu 累积产额数据进行了评价调整。最后推荐给出了n+232Th 裂变的产额数据库,作为CENDL 库的组成部分。The yields of n+232Th fission are important in study of the Th/U fuel cycle. Based upon the evaluated nuclear data libraries and recent experimental data,comparison and evaluation for yield mass distribution and cumulativeyield were performed for those products are needed and important in reactor calculations,including 95Mo,99Tc,101Ru,103Rh,109Ag,133Cs,147Sm,149Sm,150Sm,151Sm,152Sm,143Nd,145Nd adn 153Eu etc. Adjustments were made for 133Cs, 152Sm and 153En which have discrepancies among the libraries. Database for n+233Th fission yield is recommended as a part of CENDL update.     

骨显像放射性药物锝-双膦酸盐配合物99mTc-MDP的结构

运用密度泛函理论方法对锝标记双膦酸盐配合物^99mTc-MDP进行了结构预测和计算, 其中MDP代表亚甲基双膦酸. 根据几何异构、构象异构、电荷异构和自旋态异构等特性预测该化合物共有14种异构体. 基于B3LYP/LANL2DZ水平优化的分子结构和计算的总能量,确定了两种稳定异构体,并与实验结构进行了比较. 运用B3LYP/6-31G*(LANL2DZ用于Tc, cc-pVDZ-pp用于Tc)和B3LYP/DGDZVP方法对化合物的稳定结构进行了计算. 理论计算值与实验值吻合较好,而基     

减速剂与受控链式反应

 重核的裂变开辟了丰富的核能资源。然而裂变却泾渭分明地表现为过程与效果截然迥异的两种方式,且唯有受控裂变以链式反应的方式进行,核能才得以用于生产和科研而造福人类。为此目的,“减速剂”发挥着必不可缺的关键性作用。那么,在这一过程中减速剂到底是如何发挥其作用,而人们又是根据什么原则来选用它的呢? 一、减速剂的作用原理与机制 核弹以极纯的U-235为核燃料,达到“临界体积”（58厘米³,1.083千克）的铀块是借助于俘获宇宙线中源自恒星热核聚变的（或铀块中自发裂变产生的）中子的“点火”而触发快速链式反应的。但反应堆不能使用纯U-235,因其临界体积太小,裂变不能控制,故只能使用天然铀或浓缩铀（分别含0.715％和5％以上的U-235）,以使临界体积极大地增大,才能达到施加控制、实现核能的缓慢释放的目的。     

基底复制技术研究

研究了基于Au和Ag两种分离材料,环氧复制和电镀Ni后再环氧复制的基底复制技术.采用直流磁控溅射技术在不同工艺的复制基底上镀制Mo/Si多层膜反射镜,利用反射率计测量其反射率.测量结果表明:电镀Ni后再环氧复制的Au基底反射率最高.     

Feasibility studies towards future self-sufficient supply of the 99Mo-99mTc isotopes with Japanese accelerators

In order to establish a self-sufficient supply of ^99mTc, we studied feasibilities to produce its parent nucleus, ⁹⁹Mo, using Japanese accelerators. The daughter nucleus, ^99mTc, is indispensable for medical diagnosis. ⁹⁹Mo has so far been imported from abroad, which is separated from fission products generated in nuclear reactors using enriched ²³⁵U fuel. We investigated ^99mTc production possibilities based on the following three scenarios: (1) ⁹⁹Mo production by the (n, 2n) reaction by spallation neutrons at the J-PARC injector, LINAC; (2) ⁹⁹Mo production by the (p, pn) reaction at E_p = 50–80 MeV proton at the RCNP cyclotron; (3) ^99mTc direct production with a 20 MeV proton beam from the PET cyclotron. Among these three scenarios, scenario (1) is for a scheme on a global scale, scenario (2) works in a local area, and both cases take a long time for negotiations. Scenario (3) is attractive because we can use nearly 50 PET cyclotrons in Japan for ^99mTc production. We here consider both the advantages and disadvantages among the three scenarios by taking account of the Japanese accelerator situation.     

Production scheme for diagnostic-therapeutic radioisotopes by accelerator neutrons

Interest has been growing in the development of medical radioisotopes used for noninvasive nuclear medicine imaging of disease and cancer therapy. Especially the development of an alternative production scheme of ⁹⁹Mo, the mother radioisotope of ^99mTc used for imaging, is required, because the current supply chain of the reactor product ⁹⁹Mo is fragile worldwide. We have proposed a new production scheme of ⁹⁹Mo as well as therapeutic radioisotopes, such as ⁶⁴Cu and ⁶⁷Cu, using accelerator neutrons provided by the ^natC(d,n) reaction. Based on this scheme we have obtained high-quality ^99mTc, ⁶⁴Cu, and ⁶⁷Cu suitable for clinical use by developing both production and separation methods of the radioisotopes. We proposed a new facility to constantly and reliably produce a wide variety of high-quality, carrier-free radioisotopes, including ⁹⁹Mo, with accelerator neutrons. We report on the development of the proposed scheme and future prospects of the facility toward the domestic production of medical radioisotopes.     

Detailed investigation of the β-decay of the 9/2+ ground state of 99Nb to levels in 99Mo

The decay of ⁹⁹Nb to ⁹⁹Mo has been investigated. The use of the ion-guide technique for on-line mass separation and of a Ge-array for γ-ray detection have allowed the observation of decay branchings lower than 10^?3. Mediumspin levels, some already known from reaction studies and new ones at high energy, are populated. The β-feeding patterns of the decays of the 9/2⁺ states in ⁹⁹Nb and in its isotones ⁹⁷Y, and ¹⁰¹Tc are qualitatively reproduced by QRPA calculations.     

Fuel cycle for a fusion neutron source

The concept of a tokamak-based stationary fusion neutron source (FNS) for scientific research (neutron diffraction, etc.), tests of structural materials for future fusion reactors, nuclear waste transmutation, fission reactor fuel production, and control of subcritical nuclear systems (fusion–fission hybrid reactor) is being developed in Russia. The fuel cycle system is one of the most important systems of FNS that provides circulation and reprocessing of the deuterium–tritium fuel mixture in all fusion reactor systems: the vacuum chamber, neutral injection system, cryogenic pumps, tritium purification system, separation system, storage system, and tritium-breeding blanket. The existing technologies need to be significantly upgraded since the engineering solutions adopted in the ITER project can be only partially used in the FNS (considering the capacity factor higher than 0.3, tritium flow up to 200 m³Pa/s, and temperature of reactor elements up to 650°C). The deuterium–tritium fuel cycle of the stationary FNS is considered. The TC-FNS computer code developed for estimating the tritium distribution in the systems of FNS is described. The code calculates tritium flows and inventory in tokamak systems (vacuum chamber, cryogenic pumps, neutral injection system, fuel mixture purification system, isotope separation system, tritium storage system) and takes into account tritium loss in the fuel cycle due to thermonuclear burnup and β decay. For the two facility versions considered, FNS-ST and DEMO-FNS, the amount of fuel mixture needed for uninterrupted operation of all fuel cycle systems is 0.9 and 1.4 kg, consequently, and the tritium consumption is 0.3 and 1.8 kg per year, including 35 and 55 g/yr, respectively, due to tritium decay.     

Calculation of the temperature in the container unit with a modified design for the production of <Superscript>99</Superscript>Mo at the VVR-Ts research reactor facility (IVV.10M)

The temperature regime is calculated for two different designs of containers with uranium-bearing material for the upgraded VVR-Ts research reactor facility (IVV.10M). The containers are to be used in the production of ⁹⁹Mo. It is demonstrated that the modification of the container design leads to a considerable temperature reduction and an increase in the near-wall boiling margin and allows one to raise the amount of material loaded into the container. The calculations were conducted using the international thermohydraulic contour code TRAC intended to analyze the technical safety of water-cooled nuclear power units.     

Beta-delayed proton emission from 97Cd and 99Cd

Two new β-delayed proton precursors, ^97,99Cd, have been identified at the ISOLDE on-line isotope separator. The proton branching ratio for ⁹⁹Cd is (1.7^+1.1_?0.5) × 10^?3. The ⁹⁹Cd proton spectrum is discussed in terms of the statistical model with Porter-Thomas fluctuations. The half-life of ⁹⁹Cd was determined to be 16±3 sec. A search for ⁹⁸Cd was also performed and it was found to be a pure β-emitter with a probable half-life of ≈ 8 sec.     

Nuclear level structure of99Tc

The gamma rays of⁹⁹Tc excited through negatron decay of⁹⁹Mo have been studied by internal conversion spectroscopy, using a high resolution double focusing beta-ray spectrometer. Conversion electrons were observed for all transitions reported before. In addition a new gamma ray of energy 989.37±1.02 keV could be identified and ascribed for the first time to the decay of⁹⁹Mo. Gamma-ray energies have been determined with high precision. Multipolarity data, obtained from the measurements of absolute or ratio of conversion coefficients of gamma rays, were utilized for assigning possible spins and parities to the levels of⁹⁹Tc. From our present data combined with other studies spins and parities; 7/2+, 1/2?, 5/2+, 3/2?, 3/2+ and 5/2? have been given to the 140, 142, 181, 514, 922 and 1131 keV levels respectively. The experimental level scheme is discussed in terms of theoretical predictions.     

Minimization of Entropy Generation Rate in Hydrogen Iodide Decomposition Reactor Heated by High-Temperature Helium

The thermochemical sulfur-iodine cycle is a potential method for hydrogen production, and the hydrogen iodide (HI) decomposition is the key step to determine the efficiency of hydrogen production in the cycle. To further reduce the irreversibility of various transmission processes in the HI decomposition reaction, a one-dimensional plug flow model of HI decomposition tubular reactor is established, and performance optimization with entropy generate rate minimization (EGRM) in the decomposition reaction system as an optimization goal based on finite-time thermodynamics is carried out. The reference reactor is heated counter-currently by high-temperature helium gas, the optimal reactor and the modified reactor are designed based on the reference reactor design parameters. With the EGRM as the optimization goal, the optimal control method is used to solve the optimal configuration of the reactor under the condition that both the reactant inlet state and hydrogen production rate are fixed, and the optimal value of total EGR in the reactor is reduced by 13.3% compared with the reference value. The reference reactor is improved on the basis of the total EGR in the optimal reactor, two modified reactors with increased length are designed under the condition of changing the helium inlet state. The total EGR of the two modified reactors are the same as that of the optimal reactor, which are realized by decreasing the helium inlet temperature and helium inlet flow rate, respectively. The results show that the EGR of heat transfer accounts for a large proportion, and the decrease of total EGR is mainly caused by reducing heat transfer irreversibility. The local total EGR of the optimal reactor distribution is more uniform, which approximately confirms the principle of equipartition of entropy production. The EGR distributions of the modified reactors are similar to that of the reference reactor, but the reactor length increases significantly, bringing a relatively large pressure drop. The research results have certain guiding significance to the optimum design of HI decomposition reactors.