The neutron transmission spectrum through a high-purity ^238 U slab (dimensions: 100 mm × 100 mm × 20 mm) irradiated by a broad-spectrum neutron field was measured at 0^∘ using the time-of-flight (TOF) method. The experiment was carried out at the Radioactive Ion Beam Line of the Heavy Ion Research Facility in Lanzhou at the Institute of Modern Physics, Chinese Academy of Sciences. Broad-spectrum neutrons were generated by bombarding a tungsten target with 80.5 MeV/u ^12 C ions. GEANT4 calculations were performed under the same experimental conditions by combining the INCL++, BIC, and BERT physics models with the evaluated nuclear data libraries ENDF/B-VIII.0, JEFF-3.3, and JENDL-4.0. The calculations reproduce the measured spectrum reasonably well over most of the investigated energy range; however, they overestimate the data below 10 MeV and tend to underestimate the measured yield above 70 MeV. The present results provide benchmark information for validating neutron-transport simulations relevant to accelerator-driven systems.

This study investigates the prompt radiation field in the accelerator-target reactor coupling region of the China initiative Accelerator-Driven System (CiADS). This coupling region, which is comprised of the subcritical reactor, the radiation shielding room, and the bending magnet room, features a complex, multisource radiation environment arising from fission radiation, spallation radiation, and beam loss radiation. To accurately model this scenario, a hybrid PHITS-MCPL-FLUKA computational approach was developed, enabling the detailed analysis of the source contributions, energy spectra, radiation field spatial distributions, and shielding. The results reveal that the spallation neutrons are the principal contributors to the biological shielding requirements of the subcritical reactor, while beam loss radiation is the primary consideration for the shielding design of the side walls in the radiation shielding room. Moreover, localized shielding applied to the reactor cover can effectively mitigate radiation hazards to certain reactor equipment. This comprehensive evaluation of the radiation characteristics and shielding strategies provides critical guidance for optimizing the radiation protection design, enhancing operational safety, and supporting the long-term stable operation of CiADS.

Understanding evaporation behavior of lead-bismuth eutectic (LBE) is essential for the operation and maintenance of nuclear installations with liquid LBE as coolant or spallation target. In the present study, the nonequilibrium evaporation behavior of LBE has been investigated in the temperature range of 473-673 K in Ar/ 5%H2 atmosphere using transpiration method. An experimental apparatus with a cylindrical containment severing as LBE evaporation pot has been built to simulate the actual operational situations for a nuclear research facility. The concentrations of bismuth and LBE vapors in carrier gas were determined under non-equilibrium conditions. The observed LBE concentration is in the range of 10_6 and 10_ 5 mol/m3 and the corresponding bismuth-to-lead mass ratio of LBE vapor is less than 4% in most of the experiments. Compared to the predicted saturation vapor pressures based on OECD Nuclear Energy Agency (NEA) recommended method, the observed vapor pressures are several orders of magnitude higher. This suggests that extreme cautions should be given when saturated vapor pressure at equilibrium is applied to actual operational scenarios for nuclear facilities operating under non-equilibrium and low temperature conditions. The results obtained in this study provide foundational data for the safe operation of China initiative Accelerator Driven System (CiADS) in the future.

Cross sections of the 64Zn(n, p)64Cu, natZn(n, x)67Cu, 66Zn(n, 2n)65Zn and 70Zn(n, 2n)69mZn reactions have been measured by using the activation technique at 14.0 MeV neutron energy. The neutrons were produced via the 3H(d, n)4He reaction. The present experimental data illustrated satisfactory agreement with most of the previously reported experimental data. Experimental data are compared with evaluated nuclear data of the CENDL-3.2, ENDF/B-VIII.0, JENDL-5, BROND-3.1 and JEFF-3.3 libraries. Besides, these excitation functions were calculated by using theoretical model of the TALYS-1.96 code from thresholds up to 20 MeV. A group set of parameters was obtained which better reproduce the experimental data than the default parameters.

An Extended-range Bonner sphere spectrometer (EBSS) has been developed to investigate the neutron spectra of the China initiative Accelerator Driven System. This paper presents the design, calibration, and validation measurements of the EBSS system using a standard 241Am-Be neutron source and the cosmic ray neutrons. The EBSS system was simulated using the PHITS code, and the geometric structures were designed using the response functions obtained by simulations. The EBSS system comprises of seven polyethylene-only spheres and seven extended-range spheres encased in lead, copper, or tungsten shells along with a bare 3He proportional counter. To verify the accuracy of the simulated response functions, the EBSS system was calibrated with monoenergetic neutron beams of 565 keV at the China Institute of Atomic Energy in Beijing. The EBSS system was used to measure neutron count rates of the 241Am-Be neutron source and cosmic ray neutrons. Subsequently, the measured neutron count rates were converted into neutron spectra by the unfolding software. Experimental findings demonstrate the precise capability of the EBSS system to measure neutron spectra across a wide range of neutron radiation fields.

To measure the extended-range neutron spectra and calibrate the extended-range neutron dosemeters of the China initiative Accelerator-Driven System (CiADS), an Extended-range Bonner Sphere Spectrometer (EBSS) has been developed. The EBSS was designed based on the PHITS codes, investigating various combinations of materials and diameters of the neutron moderators and the neutron multipliers for extended-range neutrons. Finally, seven polyethylene-only spheres and seven extended-range spheres were selected and subsequently built. The neutron multipliers of the extended-range spheres embedded concentric shells of lead, copper and tungsten. The response functions of the EBSS were analyzed and experimentally validated. It was subsequently tested with 252Cf neutron source and cosmic ray neutron source. The results demonstrate that the EBSS is capable of accurately measuring neutron spectra.

The cross sections for the 55Mn(n,2n)54Mn, 181Ta(n,2n)180gTa, and 181Ta(n,p)181Hf reactions were measured to be 705.1 ± 26.1 mb at 14.0 MeV, 1362.7 ± 87.2 mb at 13.6 MeV, and 2.31 ± 0.09 mb at 13.6 MeV, respectively, by using an off-line γ-ray spectroscopic technique. The neutrons were produced via the 3H(d,n)4He reaction. The monitor reactions 27Al(n,α)24Na and 93Nb(n,2n)92mNb were used for neutron flux determination. The results from the present work were compared with those of the literature and the evaluated data from ENDF/B-VIII.0, JEFF-3.3, JENDL-5, CENDL-3.2, and BROND-3.1 libraries. Besides, the cross sections were also estimated with the TALYS-1.96 nuclear model code using different level density models for a better description of the present work and literature data. The present experimental results were found to be in good agreement with most of the available literature data and with the evaluated data.

Cross sections for the neutrons around 14 MeV interaction with natural titanium were precisely measured by neutron activation and off-line measurement technique. The fast neutrons were produced by 3H(d,n)4He reaction and the neutron energy was obtained by using the cross section ratio method of 90Zr(n,2n)89Zr to 93Nb(n,2n)92mNb reactions. Experimental cross sections have been acquired for natTi(n,x)46Sc, natTi(n,x)47Sc, 50Ti(n,x)47Ca and 48Ti(n,x)48Sc reactions. The measured cross section data are compared with the experimental data available in the previous literature and evaluated nuclear data from the ENDF/B-VIII.0, JEFF-3.3, JENDL-5, BROND-3.1, CENDL-3.2 and FENDL-3.2b libraries. Furthermore, excitation functions for these reactions were calculated by using the theoretical model based on Talys-1.96 code with default and adjusted parameters. Within experimental error, evaluated nuclear data are mostly consistent with experimental data. The excitation function with adjusted parameters can roughly reproduce the experimental data.

Excitation functions of the natFe (p, x) 52,54Mn, 55Co, 51Cr, 52Fe, and 46Sc reactions were measured at the proton energy of 87, 94 and 100 MeV, using the stacked foil activation technique followed by the off-line gamma-ray spectrometry. The experiment was carried out on the separated sector cyclotron at the Institute of Modern Physics, Chinese Academy of Sciences. The natNi (p, x)57Ni and natAl (p, x)22Na reactions with known cross sections was used to monitor the proton beam intensity. The results from this work were compared with the existing literature data available in EXFOR data library and were found to be in good agreement. TALYS-1.95 is able to reproduce, in most cases, the experimental trend. Our experimental results were also compared with evaluated nuclear data from the ENDF/B-VIII.0, JENDL-4.0/HE, and PADF-2007 libraries as a function of proton energy, which reproduced the trend of the excitation functions of the experimental natFe (p, x) reaction cross-sections. These data expand our knowledge on the related excitation functions to confirm the existing trends and to give additional experimental values on a wider energy range.

The experimental cross-sections of the natMo(p,xn)93m+g,94g,95m,95g,96m+gTc, 100Mo(p,x)99Mo and 100Mo(p,2n)99mTc nuclear reactions were measured up to 18.3 MeV, by the stacked-foil activation technique at the superconducting linear accelerator of the Institute of Modern Physics, Chinese Academy of Sciences. And the proton beam current was monitored by the independent natCu(p,x)65Zn and natTi(p,x)48V reactions. The experimental results were compared with the literature data taken from EXFOR database, evaluation data of the charged-particle cross section database and theoretical values by using TALYS-1.95 code with six level density models. The obtained results for most of the radionuclides show good agreement with the available literature data. Besides, the theoretical calculations predicted by the TALYS-1.95 code demonstrate similar trends with experimental data. Although in some cases, cross-sections results are sensitive to the nuclear level densities. Evaluated nuclear values of the charged-particle cross section database correspond well with our measurements for 96m+g,99mTc and 99Mo.

This work presents the thick target production yields of 94gTc, 95gTc, 95mTc, 96m+gTc, 99mTc and 99Mo radionuclides produced by 8.0-18.0MeV proton induced reactions on natural molybdenum targets. The measurements were carried out at the superconducting linear accelerator of the Institute of Modern Physics, Chinese Academy of Sciences by using the stacked-foil activation technique. In addition, the proton beam current was determined by the natTi(p,x)48V monitor reaction. The obtained results were compared with the available literature data from EXFOR database, the calculation results using our fitted experimental cross-sections data and the theoretical calculations predicted by TALYS-1.95 and FLUKA-2020.0. Our measurements are in good agreement with the calculations results using our fitted data. Besides, our data have similar trends with the theoretical calculations predicted by TALYS-1.95 and FLUKA-2020.0 although there are discrepancies between them for the radionuclides 94gTc, 99mTc and 99Mo.

Experimental cross-sections for the nuclear reactions ^nat Mo(p,x) ^96g(m+),95g,95m,94g,93g(m+) Tc, ^99(cum),93m,90(cum) Mo, ^96,95m,92m,91m(cum),90g(m+,cum) Nb and ^89g(m+,cum),88g(m+,cum),86(cum) Zr were measured up to 100 MeV, carring out at separated sector cyclotron of the Heavy Ion Research Facility in Lanzhou, using the stacked-foil activation technique. The cross-sections of these nuclides in this work fill the gap in 75–100 MeV energy range. In addition, our experimental results were compared with the previously published values taken from EXFOR database and the theoretical calculations predicted by TALYS-1.95 code with six level density models, which are important input parameters affecting the excitation functions. In terms of results, our measurements show good agreement with the theoretical calculations for most of the radionuclides. Level density models still needs to be further optimized in the description of excitation functions.

Stacked-foil activation technique and high-resolution gamma spectrometry were used to investigate new excitation functions of proton-induced nuclear reactions on natNi targets in the energy range of 75-100 MeV. The stack foils were irradiated with 100 MeV protons at the separated-sector cyclotron of the Institute of Modern Physics, Chinese Academy of Sciences, China. The proton intensity for each nickel foil was determined using the Ni-nat(p, x)Ni-57 monitor reaction. The cross-sections of the Ni-nat(p, x)Ni-56,Co- 55,Co-57,Co-58, and 54Mn reactions were calculated and compared with the existing literature data presented in the Experimental Nuclear Reaction Data (EXFOR). Furthermore, evaluated nuclear data of the PADF-2007, ENDF/B-VIII.0, and JENDL-4.0/HE libraries as well as theoretical calculations of the TALYS code were used. Overall, our experimental data agree with the majority of the literature data. The results of TALYS code as well as the ENDF/B-VIII.0 and JENDL-4.0/HE libraries could reproduce most of the experimental trend, whereas the results of PADF-2007 library could not do so. The new experimental results provide cross-sections for proton-induced Ni-nat reactions in the energy range of 75-100 MeV and could serve as a technical assistance for radionuclide production and radiation safety practices.

Cross sections of the  112Sn(n,x)111In,  114Sn(n,2n)113Sn,  natSn(n,x)117mSn and  124Sn(n,2n)123gSn reactions have been measured by using the activation technique at 13.6 MeV neutron energy. The neutrons were produced via the  3H(d,n)4He reaction. The present experimental data illustrated satisfactory agreement with most of the available literature data. Experimental data are compared with the corresponding evaluated nuclear data from the ENDF/B-VIII.0, JENDL-4.0/HE, BROND-3.1, CENDL-3.2 and JEFF-3.3 libraries, and the agreement are generally acceptable. Besides, different nuclear level density models have been used for the estimation of the desired excitation functions with TALYS-1.95 code.

Lead-bismuth eutectic(LBE) is the candidate material of spallation target for China initiative Accelerator Driven System(CiADS). Long-term irradiation makes the LBE highly radioactive. Most of the spallation target radionuclide studies focused on the effects of the proton beam and ignored fission neut-rons from the reactor. In this paper, both the fission neutrons and the high-energy protons have been taken into account in the radionuclide calculations of LBE and spallation target structural parts by coup-ling codes FLUKA and MCNP. Contributions from the fission neutron and the high-energy proton have been compared in the aspects of the activity, main radionuclides, toxicity, and the decay photon of radio-active products. The main shell, guide tube, and beam tube are significantly affected by the fission neut-ron activation. When the reactor tends to be critical, the fission neutron-induced LBE target activations are even greater than that induced by the proton beam. In the LBE itself, 96.66％ of 210Po is induced by the fission neutrons. These results illustrate that fission neutrons are also essential for the radionuclides calculation of LBE and its structural parts. In addition, this study provides reference data for the radi-ation protection of CiADS and a more accurate method for the radionuclides study of the spallation tar-get in ADS systems.

Excitation functions of the Ti-nat(p, x)Sc-43,Sc-47, V-48 and Cu-nat(p, x)Cu-64, Zn-62,Zn-65 reactions were measured in the energy range of 8.8-18.4 MeV by using the stacked-foil activation technique and off-line gamma spectroscopy. The irradiation was carried out at the superconducting linac of the Institute of Modern Physics, Chinese Academy of Sciences. Besides, the reliability and effectiveness of theoretical data from the TALYS code, recommended data of the International Atomic Energy Agency (IAEA) and evaluated nuclear data of the ENDF/B-VIII.0, JENDL-4.0/HE and PADF-2007 libraries were evaluated and verified by comparing with experimental data. Our experimental results agree with most of the available literature data. TALYS-1.95 code could not reproduce, in most cases, the experimental data. Evaluated nuclear data from the ENDF/B-VIII.0, JENDL-4.0/HE and PADF-2007 libraries are able to reproduce, in most cases, the experimental data trend. Recommended data of the IAEA are in good consistent with our work and most of the available literature data.

The irradiation resistance capability of structural components in nuclear reactors has a great influence on the system's service life and safety. In this work, the CiADS coupling model between spallation target and subcritical reactor is established by MCNPx2.70, and the atomic dissociation cross sections for CiADS candidate materials are processed by the nuclear data processing software NJOY2016. The irradiation damages for three kinds of stainless steels, 316L, 15-15Ti, SIMP and one kind of ZTA ceramics are calculated and analyzed under three conditions with the number of fuel assemblies of 30, 42 and 72, respectively. When used as CiADS fuel cladding, SIMP steel has the lowest rate of irradiation damage among the three candidate steels. The calculated irradiation damage rate are 1.16, 1.61 and 12.0 dpa/a when the number of fuel assemblies are 30, 42 and 72, respectively. The irradiation damage rate for the fuel cladding made of ZTA materials is much higher than that of the candidate steels. The CiADS center tube suffers the strongest neutron irradiation for the portion near the reaction area between the accelerator beam and the spallation target. The maximum irradiation damage rate is about 2.7 dpa/a for the center tube made of 316L steel when the fuel assemblies are 30.

本文利用脉冲中子源法测量了铅基零功率反应堆Venus-Ⅱ在4种燃料棒装载情况下的次临界度,简要介绍了脉冲中子源法测量次临界度的原理、测量系统及实验结果等,通过面积比法分析了各探测器的计数率时间谱,确定了系统次临界度.测量结果表明,当系统有效增殖因数在0.94附近时,不同位置处的探测器测量结果之间呈明显差异.基于MCNP理论模拟计算,分别用空间修正因子和普适的微扰法对面积比测量结果进行必要修正,消除了空间效应对实验结果的影响.在系统有效增殖因数约0.94时,经修正的面积比法能精确给出系统的次临界度.本实验研究为ADS嬗变系统的次临界度精确测量提供了一种有效方法.

中子注量率及分布是反应堆的重要参数,本工作通过核数守恒在非稳态情况下的推导和求解,从理论上论证了次临界反应堆非稳态情况下中子注量率测量的可行性.将活化法和固体径迹法有机结合,利用固体径迹探测器标定活化片的测量数据,测量了启明星II零功率装置的He-3管实验孔道内及反应堆外壁的中子注量率的分布,并与模拟计算结果进行了比较,利用MCNPX程序得到的模拟计算结果与实验结果的趋势一致,证明了该测量方法可以测量低通量的中子注量率,可实现反应堆不同时刻、不同位置的中子注量率测量,为CiADS技术的研发提供了实验数据与技术支撑.

The China initiative Accelerator Driven System (CiADS) is the first integrated ADS facility designed to study the safety disposal of nuclear waste.As a nuclear facility,it will cause radiological impact on the environment.Therefore,the assessment of radiological impact on the environment around this facility will not only meaningful to the public health,but also offers significant guides to the shielding design of CiADS.Pebble samplings were collected around the campus of the Heavy Ion Research Facility in Lanzhou (HIRFL) and irradiated by a 241Am-Be neutron source.Based on the γ-spectrum measured by a HPGe detector before and after the neutron irradiation,the specific activities of induced radionuclides 24Na,54Mn,56Mn and 27Mg in these samples were analyzed and compared with the Monte-Carlo simulation values obtained with the Geant4 toolkit.The comparison between the experimental and simulated results indicates that Geant4 toolkit is feasible for radiation impact assessment of nuclear facilities,such as CiADS.Then the neutron spectrum outside the concrete shielding of HEBT tunnel of the CiADS have been simulated by the Geant4 toolkit,and the saturation activities of the induced nuclides in the first 10 cm pebble layer have been predicted.The results show that the saturation activities of induced radionuclides in pebbles outside the CiADS shielding are much lower than their exemption values and their radiation impacts to the environment could be ignored.