A method for determination of the s orbital component of ~(12)Be ground state

The ambiguity of the structure of ~(12)Be especially in the configuration of Be ground state has attracted a lot of attention recently.We notice that the nuclear reaction cross section or at low energy region is sensitive to the surface structure of ~(12)Be,which is greatly impacted by the ground state configuration of ~(12)Be especially by the occupancy probability of the s orbital component.By using existed interaction cross section data of ~(12)Be on C at 790 MeV/nucleon and Glauber model,the upper limit of the s orbital occupation probability of ~(12)Be ground state is roughly determined to be about 56%with Single Particle Model calculations.This demonstrates that the method is very promising to determine the s orbital component of ~(12)Be with proper nuclear-matter density distribution calculations for different orbitals of ~(12)Be ground state.Hence we bring forward to determine the s orbital component of ~(12)Be by measuring the ctr of ~(12)Be on C and Al at several tens of MeV/nucleon.In this paper,the feasibility and detailed experimental scheme of the ctr measurement are carefully studied.The precision of the s orbital occupation probability of ~(12)Be ground state is expected to achieve 9%by using the proposed 2%ctr data.     

~(99)Mo-~(99m)Tc同位素辐照靶件研制

本文叙述了用含10%~(235)U燃料棒芯体,研制~(99)Mo-~(99m)Tc同位素辐照靶件的制备工艺。研制工艺分为:将燃料芯体铝包壳用碱溶法减壁厚,芯体切割,压密合,旋压端塞,焊封以及质量检验等工艺。研制出的靶件经入堆考验和同位素分离等实验,证明性能良好,结构合理。为钼-鍀同位素实验研究和生产创造了有利条件。     

An investigation of the role of spectroscopic factors in the breakup reaction of ~(11)Be

The experimental elastic cross section data of the projectile11 Be on target12 C at 49.3 Me V/nucleon energy is analysed. The calculations for the elastic scattering are performed by the phenomenological optical model. The different optical potentials to include breakup effects into the calculations, which are neutron+12C, neutron+10Be and10Be+12C, are described with the aid of the global potentials for neutron interactions and fitted to experimental data for the core and target interaction. Also, the first analysis of the optical model for10 Be on target12 C at 39.1 Me V is done for building the interaction potential of the core and the target for11 Be. For investigating the effects of the spectroscopic factors, obtained factors from the direct capture process using the nuclear level density are compared with the previous cross section and spectroscopic factor results. Obtained results for the elastic cross section reproduce the experimental data very well and show the requirement of including spectroscopic properties such as, spectroscopic factors and density of the excited states, to explain this elastic cross section data.     

Uncertainty quantification in (α,n) neutron source calculations for an oxide matrix

We present a methodology to propagate nuclear data covariance information in neutron source calculations from (α,n) reactions. The approach is applied to estimate the uncertainty in the neutron generation rates for uranium oxide fuel types due to uncertainties on 1) ^17,18 O(α,n) reaction cross-sections and 2) uranium and oxygen stopping power cross sections.The procedure to generate reaction cross section covariance information is based on the Bayesian fitting method implemented in the R-matrix SAMMY code. The evaluation methodology uses the Reich-Moore approximation to fit the ^17,18 O(α,n) reaction cross-sections in order to derive a set of resonance parameters and a related covariance matrix that is then used to calculate the energy-dependent cross section covariance matrix. The stopping power cross sections and related covariance information for uranium and oxygen were obtained by the fit of stopping power data in the α-energy range of 1 keV up to 12 MeV.Cross section perturbation factors based on the covariance information relative to the evaluated ^17,18 O(α,n) reaction cross sections, as well as uranium and oxygen stopping power cross sections, were used to generate a varied set of nuclear data libraries used in SOURCES4C and ORIGEN for inventory and source term calculations. The set of randomly perturbed output (α,n) source responses, provide the mean values and standard deviations of the calculated responses reflecting the uncertainties in nuclear data used in the calculations. The results and related uncertainties are compared with experiment thick target (α,n) yields for uranium oxide.     

An efficient method for mapping the ~(12)C+~(12)C molecular resonances at low energies

The ~(12)C+~(12)C fusion reaction is famous because of its complication of molecular resonances,and it plays an important role in both nuclear structural research and astrophysics. It is extremely difficult to measure the cross sections of ~(12)C+~(12)C fusions at energies of astrophysical relevance because of the very low reaction yields. To measure the complicated resonant structure that exists in this important reaction, an efficient thick target method has been developed and applied for the first time at energies E_(c.m.)5.3 MeV. A scan of the cross sections over a relatively wide range of energies can be carried out using only a single beam energy. The result of measurement at E_(c.m.)=4.1 MeV is compared with results from previous work.This method will be useful for searching for potentially existing resonances of ~(12)C+~(12)C in the energy range 1 MeVE_(c.m.)3 MeV.     

~(181)Ta中子俘获截面测量

用“瞬发γ射线法”,测量了10—100 keV能区~(181)Ta的中子俘获截面。选择~(197)Au的俘获截面作为标准。用~7Li(p,n)~7Be反应产生中子。俘获γ事件用二个Moxon-Rae探测器探测。测量结果与近期其他作者的数据作了比较。     

HTR-PM中~(14)C产生与释放行为研究

~(14)C具有较长的半衰期,可与稳定同位素一起进入生物圈,从而在核电站的环境影响评价中受到关注.本文基于HTR-PM给出了产生~(14)C的各反应模型,并代以HTR-PM参数,对HTR-PM中~(14)C的年产生量和气态释放量作出估算.最后,将计算结果与CANDU堆型进行了比较.     

Product yields for the photofission of ~(232)Th,~(234,238)U,~(237)Np,and ~(239,240,242)Pu actinides at various incident photon energies

Photofission fragments mass yield for~(232)Th,~(234;238) U,~(237) Np, and~(239;240;242) Pu isotopes are investigated.The calculations are done using a developed approach based on Gorodisskiy's phenomenological formalism. The Gorodisskiy's method is developed to be applied for the neutron-induced fission. Here we revised it for application to photofission. The effect of emitted neutron prior to fission on the fission fragment mass yields has also been studied. The peak-to-valley ratio is extracted for the240 Pu isotope as a function of energy. Obtained results of the present formalism are compared with the available experimental data. Satisfactory agreement is achieved between the results of present approach and the experimental data.     

Feasibility analysis of ~(60)Co production in pressurized water reactors

The radioactive isotope ~(60)Co is used in many applications and is typically produced in heavy water reactors. As most of the commercial reactors in operation are pressurized light water reactors(PWRs), the world supply of high level radioactive cobalt would be greatly increased if~(60)Co could be produced in them. Currently,~(60)Co production in PWRs has not been extensively studied;for the ~(59)Co(n, c)~(60)Co reaction, the positioning of ~(59)Co rods in the reactor determines the rate of production. This article primarily uses the models of~(60)Co production in Canadian CANDU power reactors and American boiling water reactors; based on relevant data from the pressurized water Daya Bay nuclear power plant, a PWR core model is constructed with the Monte Carlo N-Particle Transport Code; this model suggests changes to existing fuel assemblies to enhance ~(60)Co production. In addition, the plug rods are replaced with ~(59)Co rods in the improved fuel assemblies in the simulation model to calculate critical parameters including the effective multiplication factor,neutron flux density, and distribution of energy deposition.By considering different numbers of ~(59)Co rods, the simulation indicates that different layout schemes have different impact levels, but the impact is not large. As a whole, the components with four~(59)Co rods have a small impact, andthe parameters of the reactor remain almost unchanged when four ~(59)Co rods replace the secondary neutron source.Therefore, in theory, the use of a PWR to produce ~(60)Co is feasible.     

我国膳食中~(90)Sr、~(137)Cs、~(226)Ra、~(228)Ra、~(210)Pb 和~(210)Po含量及其所致内照射剂量

作为1990年全国总膳食调查的放射性物质部分,本文报道了组成我国膳食的各类食品中~(90)Sr、~(137)Cs、~(226)Ra、~(228)Ra、~(210)Pb 和~(210)Po 含量的测定结果;按调查所得膳食组成和食品中核素含量,估算了我国居民(成年男子)当前这些核素经食入所致年摄入量和待积有效剂量当量。结果表明,每年食入所致总待积有效剂量当量约为0.24 mSv,贡献较大的食品是蔬菜、水产品和谷类,贡献较大的核素为~(210)Pb、~(210)Po 和~(228)Ra。这些结果更新了我国膳食中这些核素的资料,补充了来自饮水的数据。文中还讨论了我国膳食组成的地区差异及其对居民摄入量和所致内照射剂量的影响。     

The cross section calculation of ~(112)Sn(α,γ) ~(116)Te reaction with different nuclear models at the astrophysical energy range

The theoretical cross section calculations for the astrophysical p process are needed because most of the related reactions are technically very difficult to be measured in the laboratory. Even if the reaction was measured,most of the measured reactions have been carried out at the higher energy range from the astrophysical energies.Therefore, almost all cross sections needed for p process simulation have to be theoretically calculated or extrapolated to the astrophysical energies.~(112)Sn(α,γ)~(116)Te is an important reaction for the p process nucleosynthesis. The theoretical cross section of ~(112)Sn(α,γ)~(116)Te reaction was investigated for different global optical model potentials,level density, and strength function models at the astrophysically interested energies. Astrophysical S factors were calculated and compared with experimental data available in the EXFOR database. The calculation with the optical model potential of the dispersive model by Demetriou et al., and the back-shifted Fermi gas level density model and Brink-Axel Lorentzian strength function model best served to reproduce experimental results at an astrophysically relevant energy region. The reaction rates were calculated with these model parameters at the p process temperature and compared with the current version of the reaction rate library Reaclib and Starlib.     

New measurement and evaluation of the excitation function of Ni(p,n) reaction for the production of Cu

One of the radioisotopes for which a growing interest exists in nuclear medicine is ⁶⁴Cu. Its branched decay makes it suitable for both diagnostic and therapeutic purposes. Activation cross sections of the proton induced reaction on enriched ⁶⁴Ni have been studied using the stacked foil technique up to 24 MeV. The experimental cross sections are compared with values available from literature. Thick target yields, based on the discrete measured values of the cross sections are calculated and allow a better estimation of the optimum production parameters.     

Measurement of ~(232)Th(n,2n)~(231)Th reaction cross-sections at neutron energies of 14.1 MeV and 14.8 MeV using neutron activation method

In this study, the activation cross-sections were measured for ~(232)Th(n,2n)~(231)Th reactions at neutron energies of 14.1 and 14.8 MeV, which were produced by a neutron generator through a T(d,n)~4He reaction. Induced gamma-ray activities were measured using a low background gamma ray spectrometer equipped with a high resolution HPGe detector. In the cross-section calculations, corrections were made regarding the effects of gamma-ray attenuation, dead-time, fluctuation of the neutron flux, and low energy neutrons. The measured cross-sections were compared with the literature data, evaluation data(ENDF-B/VII.1, JENDL-4.0 and CENDL-3.1), and the results of the model calculation(TALYS1.6).     

Evaluation of 17O(n,a)14C Cross Section

The ¹⁷O(n, a)¹⁴C cross section has been evaluated for incident neutron energies from 10^?5eV to 20MeV for accurate calculation on the ¹⁴C production in nuclear reactors. Evaluation was based on the single-level Breit-Wigner formula for the thermal to resonance energy regions. In the higher energy region, a multi-step evaporation model code PEGASUS was used, and the results were normalized using the ¹⁶O(n, a) cross section ratio of JENDL-3 evaluation to PEGASUS calculation. Results are given in tabular and graphical forms, and also as one-group cross sections using typical BWR, PWR and FBR spectra of ORIGEN-2.     

Investigation of isotope composition of nuclear fragments with angular momentum and Coulomb effects in peripheral ~(84)Kr+ ~(112,124)Sn collisons at 35 A MeV

New theoretical calculations are performed to investigate the Coulomb proximity and angular momentum effects on multifragmentation picture for84Kr+112,124 Sn collisions at an incident beam energy of 35 Me V/nucleon.Charge and isotopic distributions and the mean neutron-to-proton ratios of the fragments are reproduced within the microcanonical Markov chain calculations on the basis of Statistical Multifragmentation Model. It is shown that the Coulomb interactions and angular momentum effects are very important to reproduce isotopic composition of nuclear fragments in peripheral heavy-ion collisions at Fermi energies. Our results imply that it is possible to investigate in laboratories the modification of structure parameters of fragments, such as the symmetry energy coefficient, at subnuclear densities in dense environment of other species.     

~(45)Sc(n,2n)~(44g+m)Sc反应的同质异能素截面比

水文介绍用活化法测量14.6MeV中子引起的~(45)Sc(n,2n)~(44g+m)Sc反应的同质异能素截面比,及用自编的EPRIR程序计算的该核素带有预平衡机制的统计模型同质异能素截面比。通过实验值与理论值的比较,可以验证实验自旋切割因子值,并讨论预平衡机制对该反应的贡献。     

Theoretical calculation and evaluation of n +~(240,242,244)Pu reactions

The nuclear data of n+~(240;242;244)Pu reactions for incident energy below 200 MeV are calculated and evaluated to meet the requirement in the design of an accelerator-driven subcritical system. The optical model is used to calculate the total, nonelastic, shape elastic cross sections, shape elastic scattering angular distributions, and transmission coefficients. The distorted-wave Born approximation is applied to calculate the direct inelastic scatterings to the discrete excited states. The nuclear reaction statistical models and fission theory are applied to describe neutron, proton, deuteron, triton, helium-3, alpha and c emissions, and fission consistently. The results thus obtained are compared with experimental data and the evaluated data obtained from ENDF/B-VII.1 and JENDL-4.0.     

35MeV以下56Fe(n,p)56Mn反应截面及协方差评价

56Fe(n,p)56Mn通常作为标准反应来监测中子场通量,该反应截面数据的准确性直接影响到活化法测量结果的精确度,进而影响到实验待测物理量的精度。本文开展了56Fe(n,p)56Mn反应截面实验测量数据评价工作与协方差计算工作,首先系统分析EXFOR中现有的56Fe(n,p)56Mn反应截面实验测量数据,对实验数据进行了归纳总结分析,并从中子源、测量方法、探测器类型等方面对56Fe(n,p)56Mn直接测量实验数据进行评价。然后,拟合给出适用入射中子能量区间为295～35 MeV的激发曲线。随后,针对评价中重点推荐的实验数据开展了关联协方差矩阵的计算工作。最后,使用核反应计算程序TALYS对56Fe(n,p)56Mn激发曲线进行了调参计算并和评价数据进行了比较分析。该工作拓展了现有的中子活化反应截面实验数据的评价方法,结果提高了35 MeV以下中子诱发56Fe(n,p)56Mn反应的评价数据精度。     

Research of Radioisotope Production with Fast Neutrons, (VII)

Production of radioisotopes of high specific activity was studied in the JRR-1 reactor using several (n,p) and (n,α) reactions, such as ²⁴Mg(n,p)²⁴Na, ²⁷A1(n,α)²⁴N_a, ³⁵Cl(n,p)³⁵S, ³⁵C1(n,α)³²P, ⁵⁸Ni(n,p)⁵⁸Co, ⁶⁴Z_n (n,p) ⁶⁴C_u and ⁶⁷Z_n(n,p) ⁶⁷Cu. The target materials for these reactions were irradiated in several experimental holes of JRR-1 and the radioisotopes formed in the target materials were separated. The amount of the radioisotopes produced and the specific activity were determined, and the possibility of producing high specific activity radioisotopes by these reactions was investigated. The specific activity of the radioisotopes produced by the (n,p) and (n,γ) reactions was more than several hundreds times higher than when produced by the corresponding (n,γ)reactions. Although the yield of the radioisotopes by the former two reactions was fairly small, practical production of high specific activity radioisotopes by this method was thought to be possible, at least for elements of lower atomic number such as those studied in the present work.

For each experimental hole, the thermal and the fast neutron fluxes were determined respectively by the reactions ¹⁹⁷Au(n,γ)¹⁹⁸Au and ⁵⁸Ni(n,p)⁵⁸Co. In order to apply these (n,p) and (n,α) reactions effectively to radioisotope production, such basic informations as the dependence of the reactions on neutron energy and the effect of irradiation position on the reaction yield were studied on the basis of the neutron flux distribution, and the cross section of the reactions for fast neutrons in JRR-1 was estimated.     

Possibilities for Producing Radionuclides in Nuclear Power Plants with RBMK Reactors

It is shown that radiation doping of silicon and the production of medical and industrial radioisotopes in the reactors at the Leningrad nuclear power plant are possible and safe. The production of cobalt with specific activity ~100 Ci/g in an RBMK-1000 reactor is studied. Some promising developments for improving the quality of the radioisotopes produced are described. It is shown that the production volumes can be increased by linking up other nuclear power plants with RBMK reactors into the production chain.