An analytical multigroup benchmark for (n, γ) and (n, n′, γ) verification of diffusion theory algorithms

The angular flux for the “rod model” describing coupled neutron/gamma (n, γ) diffusion has a particularly straightforward analytical representation when viewed from the perspective of a one-group homogeneous medium. Cast in the form of matrix functions of a diagonalizable matrix, the solution to the multigroup equations in heterogeneous media is greatly simplified. We shall show exactly how the one-group homogeneous medium solution leads to the multigroup solution.     

Thermal neutron cross-section and resonance integral of the W(n, γ)W reaction

We measured the thermal neutron cross-section and the resonance integral of the reaction ¹⁸⁶W(n, γ)¹⁸⁷W by the activation method using a ¹⁹⁷Au(n, γ)¹⁹⁸Au monitor reaction as single comparator. The high-purity natural W and Au metallic foils with and without a cadmium shield case of 0.5 mm thickness were irradiated in a neutron field of the Pohang neutron facility. The induced activities in the samples were measured by high-resolution γ-ray spectrometry with a calibrated p-type high-purity Ge detector. The necessary correction factors for γ-ray attenuation (F_g), thermal neutron self-shielding (G_th), and resonance neutron self-shielding (G_epi) effects, and the epithermal neutron spectrum shape factor (α) were taken into account. The thermal neutron cross-section for the ¹⁸⁶W(n, γ)¹⁸⁷W reaction has been determined to be 37.2 ± 2.1 barn, relative to the reference value of 98.65 ± 0.09 barn for the ¹⁹⁷Au(n, γ)¹⁹⁸Au reaction. The present result is, in general, in good agreement with most of the experimental data and the recently evaluated value of ENDF/B-VII.0 by 5.7%. By assuming the cadmium cut-off energy of 0.55 eV, the resonance integral obtained is 461 ± 39 barn, which is determined relative to the reference values of 1550 ± 28 barn for the ¹⁹⁷Au(n, γ)¹⁹⁸Au reaction. The present resonance integral value is in general good agreement with the recently measured values by 9%. The present result is lower than the evaluated ones by 10-13%.     

Systematics studies of (n, α) reaction cross sections at 14.5 MeV neutrons energy

A new semi-empirical formula for the calculation of the (n, α) cross-section at 14.5 MeV neutron energy is obtained. It is based on the pre-equilibrium exciton and evaporation models and uses the Droplet model of Myers and Swiatecki to express the reaction energy Q(n, α). The systematics behavior of the different terms of the Droplet model involved in Q(n, α) was checked individually before choosing the pertinent terms and setting up the formula. Fitting this formula to the existing cross-section data, the adjustable parameters have been determined and the systematics of the (n, α) reaction have been studied. The predictions of this formula are compared with those of the existing formulae and with the experimental data. The formula with five parameters is found to give a better fit to the data than the previous comparable formulae.     

Excitation functions of (n, α) reaction cross-sections for some important isotopes from threshold to 20 MeV

The (n, α) reaction cross-sections from threshold to ∼20 MeV on some important nuclides ⁴²Ca, ^50,53Cr, ^56,57Fe, ^58,62Ni, and ^63,65Cu involved in the reactor shielding design have been calculated using the Hauser–Feshbach statistical model with preequilibrium effects by involving PCROSS option in Empire 2.19. The transmission coefficients for neutrons in the entrance channel are calculated using the optical model potential of Koning. In the exit channel optical model potential of Avrigeanu has been used. The experimental values have been chosen carefully for all the isotopes, from EXFOR data base. The calculations are compared with existing experimental data as well as with evaluated data files (ENDF/B-VI.0 and JENDL-3.3). A good agreement between the calculated and experimental data validates the nuclear model approaches with increased predictive power to supplement and extend the nuclear database that is required for several applications.     

Simulation of e–γ–n targets by FLUKA and measurement of neutron flux at various angles for accelerator based neutron source

A 6 MeV Race track Microtron (an electron accelerator) based pulsed neutron source has been designed specifically for the elemental analysis of short lived activation products where the low neutron flux requirement is desirable. The bremsstrahlung radiation emitted by impinging 6 MeV electron on the e–γ primary target, was made to fall on the γ–n secondary target to produce neutrons. The optimisation of bremsstrahlung and neutron producing target along with their spectra were estimated using FLUKA code. The measurement of neutron flux was carried out by activation of vanadium and the measured fluxes were 1.1878 × 10⁵, 0.9403 × 10⁵, 0.7428 × 10⁵, 0.6274 × 10⁵, 0.5659 × 10⁵, 0.5210 × 10⁵ n/cm²/s at 0°, 30°, 60°, 90°, 115°, 140° respectively. The results indicate that the neutron flux was found to be decreased as increase in the angle and in good agreement with the FLUKA simulation.     

Effects of γ-ray irradiation on the C-V and G/ω-V characteristics of Al/SiO2/p-Si (MIS) structures

The effect of the ⁶⁰C_o (γ-ray) exposure on the electrical characteristics of Al/SiO₂/p-Si (MIS) structures has been investigated using capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements. The MIS structures were stressed with a bias of 0 V during ⁶⁰C_oγ-sources irradiation with the total dose range from 0 to 25 kGy. The C-V and G/ω-V characteristics were measured at 500 kHz and room temperature before and after ⁶⁰C_oγ-ray irradiation. The results indicated that γ-irradiation caused an increase in the barrier height Φ_B, interface states N_ss and depletion layer width W_D obtained from reverse bias C-V measurements. The series resistance R_s profile for various radiation doses was obtained from forward and reverse bias C-V and G/ω-V measurements. Both C-V and G/ω-V characteristics indicate that the total dose radiation hardness of MIS structures may be limited by the decisive properties of the SiO₂/Si interface to radiation-induced damage. After γ-irradiation, the decrease in capacitance of MIS structure results in the increase in the semiconductor depletion width.     

Calculation and analysis of n+Zr reactions in the En ⩽ 250 MeV energy range

All of reaction cross sections, angular distributions, energy spectra, γ-ray production cross sections, and the double differential cross section for neutron, proton, deuteron, triton, helium and alpha emission are calculated and analyzed for n+^{90,91,92,94,96,nat}Zr at incident neutron energies from 0.1 to 250 MeV. The optical model, intranuclear cascade model, the unified Hauser–Feshbach theory and the exciton model which included the improved Iwamoto–Harada model are used. Theoretical calculated results are compared with existing experimental data and other evaluated data from ENDF/B-VI.8, ENDF/B-VII.0 and JENDL-3.3. The optical model potential parameters are obtained according to the experimental data of total, nonelastic cross sections and elastic scattering angular distributions.     

Point by Point model calculation of the prompt neutron multiplicity distribution P(ν) for spontaneous and neutron induced fission of actinides

The prompt neutron multiplicity distribution P(ν) is a very sensitive quantity which depends on the model calculation of the multi-parametric matrix ν(A,TKE) and on the fission fragment distributions.     

离子交换浓集-α谱仪测定水中U,Th和~(234)U/~(238)U,~(230)Th/~(232)Th

研究了水中10~(-3)ppm级铀、钍在硫酸盐型D235和氢型D033大孔离子交换树脂上定量浓集的条件。被树脂吸附的铀和钍经洗脱后,分别用恒电流电镀,制备无自吸收U,Th α源,进行α谱仪测量。方法用于测定水中10~(-3)ppm级U和~(234)U/~(238)U时,精密度在±10%以内,Th和~(230)Th/~(232)Th精密度在±7%以内。     

动力堆辐照元件中燃耗测定和~(149)Sm,~(150)Sm含量,~(154)Eu/~(155)Eu,~(154)Eu/~(152)Eu比值与燃耗的关系

本文用同位素稀释质谱法,以~(148)Nd为燃耗监测体对某动力堆元件的燃耗进行了测定。还测定了裂变产物中的高中子毒物~(149)Sm的含量。对~(150)Sm的含量测定结果表明,它能反映出核燃料燃烧的程度,为一直线关系。γ谱法测得的~(154)Eu/~(155)Eu比值和燃耗呈曲线关系。     

Cross Section Measurements for ~(111)Cd(n,p)~(111m)Ag,~(106)Cd(n,2n)~(105)Cd,~(110)Cd(n,2n)~(109)Cd,~(116)Cd(n,2n)~(115m)Cd and ~(116)Cd(n,2n)~(115g)Cd Reactions

Activation cross sections for cadmium were measured in the neutron energy range from 13.40 MeV to 14.80 MeV using the T(d,n)~4He reaction as neutron source. The cross sections of ~(27)Al(n,α)~(24)Na reaction is used as standard one.     

Cross Section Measurements for ~(199)Hg(n,p)~(199)Au,~(198)Hg(n,p)~(198)Au,~(196)Hg(n,p)~(196)Au and ~(196)Hg(n,d np pn)~(195)Au Reactions

Introduction The importance of nuclear data for fusion power reactor design has been acknowledged, in particular for safety, environment reasons and economics. The 14 MeV neutron activation cross sections are the key nuclear data for environmental impact, material recycling, waste handling. Due to the large     

Evaluation of Neutron Monitor Cross Sections for ~(59)Co(n,x)~(56, 57, 58)Co,~(52, 54, 56)Mn,~(59)Fe Reactions

The neutron monitor cross sections for ~(59)Co(n,x)~(56, 57, 58)Co,~(52, 54, 56)Mn,~(59)Fe reactions were evaluated based on recent experimental data and theoretical cal culations from threshold energy to 100 MeV.     

Measurements of Lα, Lβ X-ray production cross sections of Bi by 17-40 keV electron impact

We present results of measurements of L_α, L_β X-ray production cross sections for the element Bi (Z = 83) by 17-40 keV electron impact. The target used in the experiment was prepared by evaporating the element Bi to the thick pure carbon substrate. The effects of multiple scattering of electrons when penetrating the target film, of electrons reflected from the thick pure carbon substrate and of bremsstrahlung photons produced by the impact of incident electrons on the target are corrected by means of Monte Carlo simulation. The experimental data, reported here for the first time in the energy region of 17-40 keV, are compared with the DWBA theory and the PWBA-C-Ex theory. They are in good agreement.     

基于GeTHU测量确定natPb(p,x)207Bi和natPb(p,x)194Hg的反应截面

加速器驱动次临界系统(Accelerator Driven Sub-critical System,ADS)是最具潜力的下一代核能系统选型之一，准确评估ADS散裂靶内产生的长寿命放射性核素含量是应用研究中的重要课题，利用质子活化法可以有效评价质子与散裂靶材料发生相互作用产生长寿命核素的反应截面。4个质子辐照天然铅样品分别被能量为40 MeV、70 MeV、100 MeV和400 MeV的质子照射90 min、75 min、40 min和25 min，在冷却约20 a后，利用中国锦屏地下实验室(China Jinping Underground Laboratory,CJPL)的超低本底γ谱仪GeTHU进行测量，使用SAGE(Simulation and Analysis for Germanium Experiments)模拟框架计算了GeTHU的探测效率，测定了能量为40 MeV、70 MeV、100 MeV和400 MeV质子与天然铅发生^natPb(p,x)²⁰⁷Bi和^natPb(p,x)¹⁹⁴...     

水溶液中新核心[99Tcm(CO)2(NO)]2+和[99Tcm(CO)2(NO)-L] (L=DTPA,EDTA,EHIDA)的制备

研究了水溶液中制备[99Tcm(CO)2(NO)-L](L=DTPA,EDTA,EHIDA)配合物的2种方法:(1) 由前体[99Tcm(CO)3-L]制备[99Tcm(CO)2(NO)-L];(2)由[99Tcm(CO)2(NO)(H2O)3]2+中间体制备[99Tcm(CO)2(NO)-L];并确定了最佳标记条件.TLC和HPLC结果表明,2种方法得到的配合物放化产率均在90%以上.初步建立了1套在水溶液中简单、高效制备新的[99Tcm(CO)2(NO)]2+类配合物的方法.+基团取代原三羰基锝配合物得到的[99Tcm (CO)2(NO)-L]配合物具有良好的体外稳定性,取代后的配合物脂溶性和电荷性质都发生了改变,为99Tcm放射性药物的研制开辟了新思路.     

~58(Co)核(πg9/2,νg9/2)拉长组态实验研究

寻找原子核拉长态的主要兴趣在于它是一个纯核壳模型组态,它常常被用来定义相应的组态空间大小,确认多核子壳模型计算中的剩余相互作用,并且在全微观三核子转移反应DWBA分析中提供好的波函数。实验上观测到的纯壳模波函数并不多,主要是在一些较轻的核上观测到的,此工作的主要目的是在中等重核上观测寻找原子核拉长态。利用ΔE-E望远镜及北京Q3D磁谱仪系统,在HI-13串列加速器提供的35MeVα离子轰击下,测量了~(56)Fe(α,d)~(58)Co核反应的精细能谱和微分截面角分布。借助全微观DWBA理论分析,相应于核反应俘获的p-n核子对具有(1g_(9/2))~2的组态,观测到迄今所能看到的最高拉长态(1g_(9/2),1g_(9/2))_9。还对6.4MeV高激发能级核反应截面的反常增强,p-n核子对耦合成最小角动量的实验证据进行了讨论(这一点在s-d壳核上至今未看到),并且首次确认了6.4MeV能级的自旋宇称J~π=1~ 。     

MEASUREMENT OF EXCITATION FUNCTIONS FOR REACTIONS ~(107)Ag(α,n)~(110m)In,~(107)Ag(α,2n)~(109)In AND ~(109)Ag(α,2n)~(111)In

Nuclides ~(110)In,~(109)In and ~(111)In are useful radioisotopes,especially ~(111)In,which has suitable short—life(2.83d)for being produced by accelerator,is oneof the photon emitters most widely used for radiomedical application,mainlyfor antibody and cell labelling     

THE EVALUATIONS AND THEORETICAL CALCULATIONS OF ~(235)U(p,n)~(235)Np,~(235)U(p,2n)~(234)Np AND ~(235)U(d,2n)~(235)Np REACTION CROSS SECTIONS

The excitation functions of ~(235)U(p,n)~(235)Np,~(235)U(p,2n)~(234)Np and~(235)U(d,2n)~(235)Np reactions were calculated and evaluated respectively. Up to now,the experimental data for ~(235)U(p,n)and(p,2n)reactions in theenergy region from threshold to 25 MeV have not been found;Argonne Na-tional Lab.(ANL)and Lawrence Radiation Lab.at Berkeley(BRK)havemeasured the excitation function of~(235)U(d,2n)~(235)Np reaction respectively;buttheir data appear in great difference. New experimental data have to wait for being measured for unpredictabletime delays.In order to meet the practical requirements,the theoretical calcula-tion and experimental evaluation are carried out.     

SIMULTANEOUS EVALUATION FOR (n,f)CROSS SECTION OF ~(235)U,~(239)Pu,~(238)U AND(n,γ) CROSS SECTION OF ~(238)U

Using all experimentally measured data,which are available up to now,thefollowing cross sections and ratios were first evaluated respectively:fissioncross sections for ~(235)U,~(238)U,~(239)Pu;capture cross section for ~(238)U;and ratiosfor ~(239)Pu(n,f)/~(235)U(n,f),~(238)U(n,f)/~(235)U(n,f),~(238)U(n,γ)/~(235)U(n,f).