China Institute Of Atomic Energy Research Articles

Neutronic simulation of China experimental fast reactor start-up tests- part II: MCS code Monte Carlo calculation

The International Atomic Energy Agency and the China Institute of Atomic Energy proposed a coordinated research project (CRP) to establish a benchmark, based on the China Experimental Fast Reactor (CEFR) start-up tests which include fuel loading and criticality, measurements of control rod worth and reactivity coefficients, and foil activation measurements. As a participant in the CRP, the computational reactor physics and experiment laboratory of the Ulsan National Institute of Science and Technology has been studying and analyzing the neutronic performance of the CEFR. The verification and validation are performed for the simulations in the CEFR analysis. A verification process of the methodology was conducted to compare the predicted results with those obtained by a well-known MCNP6.1 Monte Carlo code. The results obtained by the MCS code were compared against the experimental data. The difference in various wire models at the critical state are evaluated in this study.

The study of neutron sensitivity of the MCP based on recoil proton detection

A new neutron detector based on a recoil proton and a microchannel plate (MCP) has been developed for the measurement of ultrafast pulse neutrons. In order to know the performance of the detector, the neutron sensitivity was investigated through simulation and experiment. A model of Monte Carlo simulation was set up for neutron sensitivity simulation. In this model, the yields and average energy of protons emitted from polyethylene targets of different thicknesses were calculated as a function of neutron energy. Then, the yields of secondary electrons produced by the recoil protons in the microchannel of the MCP were also calculated. The neutron sensitivity of the detector was finally obtained. The results show that the detector can achieve a neutron sensitivity of more than 10−15 C cm2 if the neutron energy is greater than 1 MeV. Experiments were performed to test the neutron sensitivity on the accelerator at the China Institute of Atomic Energy. The simulated results agreed with those of the experiments considering the uncertainties. The theoretical model of the detector for the calculation of the neutron sensitivity was correct. The performance of the detector accorded with the anticipative purpose.

Preliminary Study of the High Temperature Superconducting Solution for 2 GeV CW FFAG Magnet

Proton beam with an average power of 5 MW-10 MW have important applications in particle physics towards the intensity frontier, as well as in the advanced energy, and material science. The fixed field alternating gradient (FFAG) accelerator combines the advantages of existing accelerators, which has a higher limitation of beam energy than high power cyclotron and has a higher beam-to-grid efficiency than existing high power linac and synchrotron, thus is considered as a good candidate for high power proton machine. By utilizing the strong focusing and large acceptance features of FFAG in the theoretical framework of the fixed field and fixed frequency of isochronous cyclotron, a continue wave FFAG capable of producing 2 GeV/3 mA protons (with an beam power of 6 MW) has been proposed in China Institute of Atomic Energy (CIAE). Due to the beam loss of high power proton beams, the resulting high radiation will deposit a large amount of radiation dose and heat load on the superconducting (SC) magnet. As the high temperature superconductors (HTS) have a much larger thermal margin due to high critical temperature (> 90 K) and high upper critical field (>100 T) than the traditional low temperature superconductors, and have been also considered have the lower overall construction costs and power consumption than the conventional magnet, currently the HTS magnet is the favorable solution for the 2 GeV FFAG magnet design. In this paper, the lattice design along with the requirements on the F-D-F magnet of the 2 GeV FFAG design is briefly introduced first. Then, the design of the F-D-F magnet is outlined. The details of the HTS coil design utilizing ReBCO conductor and operating at ~30 K is also included.

Magnetic Field Measurement, Shimming and Processing for 230 MeV Superconducting Cyclotron Main Magnet

A 230 MeV compact superconducting cyclotron CYCIAE-230 is being constructed by the China Institute of Atomic Energy, which can be used for proton therapy and space radiation physics research. The technology of magnetic field measurement, shimming and processing is the primary task to realize the isochronous acceleration of cyclotron. The CYCIAE-230 has high magnetic field, high field gradient and dense rotation orbits. Therefore, the isochronous field and tune diagram need to be amended simultaneously. The first harmonic is also shimmed at the same process to ensure a good extraction efficiency by using precessional extraction. The precision of field measurement, shimming and processing is much higher and the algorithm is much more difficult than those in normal temperature cyclotron. In addition, the compact structure of the magnet has very narrow installation space, which makes the design of the mapper more difficult. The process of main magnet construction includes strict control of room temperature and electromagnetic compatibility (EMC), precise measurement of magnetic field, comprehensive research of beam dynamics and multi-dimensional numerical control (NC) processing under the control of complex algorithms. In this paper, the magnetic field measurement, shimming and processing of the main magnet will be illustrated in detail.

Electron inducing soft errors in 28 nm system-on-Chip

ABSTRACT The 28 nm system-on-chip (SoC) was irradiated by 12 MeV electron at the China Institute of Atomic Energy (CIAE) for the first time. Soft errors in the on-chip memory (OCM), D-Cache, Register and BRAM blocks were investigated. The obtained device cross sections are almost in the range of 10−13 cm2 to 10−11 cm2 for the blocks. The results demonstrate that electron fluence per pulse and the corresponding prompt dose rates have no influence on the soft errors in 28 nm SoC. The discrepancy was analyzed between proton and electron inducing soft errors in D-Cache and BRAM blocks, too. The secondary electron is considered as the dominant reason for soft errors caused by 12 MeV electron in 28 nm SoC.

Physical Experiments on the HEAVEN-I KrF Laser Facility

The HEAVEN-I KrF excimer laser facility is housed at the China Institute of Atomic Energy, Beijing, China. There are six laser beams at this facility, whose combined energy is up to 100 J with a pulsewidth of 28 ns at a wavelength of 248 nm. The uniformity distribution of laser intensity is less than 2%. The diameter of the focal spots was about 500 μm, producing a laser intensity of about 1012 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . HEAVEN-I's capability to provide extremely uniform focal profiles and its deep ultraviolet (UV) wavelength facilitate the conducting of experiments with laser-produced shocks with negligible effects from laser imperfections and laser-plasma instability. Thus, the laser facility was used in the research of high-energy-density physics and other related field physical experiments, such as the shock dynamics and the equation of state at high pressure, simulation of space debris, and direct laser-driven quasi-isentropic compression. Sidelight shadow photography and imaging velocity interferometer system for any reflector (VISAR) were developed for the purpose of active diagnostics for physical experiments.

New measurement of the 74Ge(p, γ)75As reaction cross sections in the p-process nucleosynthesis

The 74Ge(p,γ)75As reaction plays a crucial role in producing the lightest p-nucleus 74Se. In this work, we present the measurement of the 74Ge(p,γ)75As cross sections in the range of Ep = 1.4-2.8 MeV with an in-beam method at the tandem accelerator of China Institute of Atomic Energy. The present result is in good agreement with the previous experiments at higher energies, and extends the measurement down to lower energies of astrophysical interest. Theoretical calculations are also performed using the EMPIRE nuclear reaction code and well reproduce all experimental cross sections, which shed some light on the existing discrepancy in the previously reported experimental and theoretical values at the lowest energies. The resulting reaction rates exhibit a considerable increase of up to 47% within the p-process relevant temperatures when comparing with the REACLIB compilation.

International cooperation in age-dating uranium standards for nuclear forensics using the 231Pa/235U radiochronometer

During 2017–2018 Los Alamos National Laboratory, Lawrence Livermore National Laboratory and the China Institute of Atomic Energy collaborated in an interlaboratory 231Pa/235U radiochronometry exercise. The laboratories used different analytical methods to obtain a consensus model purification date for CRM U010 of December 28, 1958 ± 198 days and for CRM U850 of May 20, 1958 ± 363 days. These results agree with previously reported model dates using the 230Th/234U radiochronometer as well as the production histories of these materials. The concordance of interlaboratory data confirms the ability of laboratories to make reproducible radiochronometry measurements using distinct analytical approaches.

Proton-induced single-event effects on 28 nm Kintex-7 FPGA

Proton experiments were performed on Kintex-7 XC7K70T field programmable gate array by using a self-developed test system at EN tandem accelerator in Peking University. The single-event upset and multiple-bit upsets induced by low-energy proton were presented, and a cross section peak under the low-energy protons was tested. Also, the experiments under high-energy protons were performed on the proton cyclotron accelerator in the China Institute of Atomic Energy, cross sections of some blocks in FPGA were obtained. Data of low-energy and high-energy experiments showed that the LET threshold of some resources were different. Results suggest that the low-energy proton-induced single event effect must be considered.

Development of Precise Magnetic Field Shimming Algorithm for Inclined 45° Continuous Cutting on Spiral Pole of SC Cyclotron

China Institute of Atomic Energy has developed a 230 MeV compact superconducting cyclotron CYCIAE-230 to meet the demands of proton therapy in China. Physical design requires a strict control of the average field error and first harmonic in the main field. A processing method of inclined 45° continuous cutting on the two pole sides is at the first time proposed to shim the field in compact superconducting cyclotron. For a spiral magnet pole, the field generated by the 45° continuous cutting on edges is relatively complicated to be calculated precisely by finite element method. In this paper, the analytical model of the linear equation for field shimming calculation is established. The shape function caused by the local cutting is solved by the magnetic saturation approximation. And then the shimming process is built with an iterative procedure based on the ridge regression method. The shimming algorithm is applied in CYCIAE-230, which achieve good results to reduce the shimming times and further the construction period. The process of the shimming algorithm and the corresponding shimming effect in CYCIAE-230 will be presented in detail.

14 MeV high intensity cyclotrons: Two projects in progress

A 14 MeV high intensity compact cyclotron, CYCIAE-14, was built at China Institute of Atomic Energy (CIAE). In order to provide high quality proton beams for instant radiopharmaceutical distribution, and to produce a variety of radioactive ion beams taking use of the solid target, CYCIAE-14 adopts an injection system based on the external H- ion source, axial injection, and spiral inflector with a designed high beam intensity, while most PET cyclotrons adopt internal ion source. With the different using for the cyclotron, there are two projects. One project with 200μA/14 MeV can be used for isotope production of 11C, 15O, 13N and 18F. Another project with more than 400μA with 14 MeV can be used for more isotopes produced such as 64Cu, 124I and 99mTc. This paper will introduce the cyclotron of CYCIAE-14 with the two projects, and some experiments finished on the cyclotron will also be given in the paper, for example the 18F and 89Zr production, BNCT test.

Experimental study of the spectroscopic factors of Sn116–125

Enriched targets of $^{116,118,120,122,124}\mathrm{SnO}_{2}$ were bombarded with proton and deuteron beams, and the angular distributions of $(p,d)$ and $(d,p)$ on tin isotopes were accurately measured using the high-precision Q3D magnetic spectrograph at the Beijing HI-13 tandem accelerator of the China Institute of Atomic Energy. Distorted-wave Born approximation calculations were performed to extract the neutron spectroscopic factors (SFs) using two different sets of systematic optical potential parameters for these neutron transfer reactions. The SFs of $^{116--125}\mathrm{Sn}$ were obtained and compared to previous values. Our results are consistent with the average of the previous data within the error range. It is worth noting that the reaction products corresponding to $^{119}\mathrm{Sn}_{\text{G.S.}}$ and $^{119}\mathrm{Sn}_{\text{0.024}}^{*}$, to $^{123}\mathrm{Sn}_{\text{G.S.}}$ and $^{123}\mathrm{Sn}_{\text{0.025}}^{*}$, and to $^{125}\mathrm{Sn}_{\text{G.S.}}$ and $^{125}\mathrm{Sn}_{\text{0.028}}^{*}$ were first distinguished by the present experiment; therefore, our results of the low lying states of $^{119,123,125}\mathrm{Sn}$ are more reliable. However, the first excited state of $^{121}\mathrm{Sn}$ is only 0.006 MeV; we failed to identify the products that correspond to the ground state and the first excited state, and the extracted SFs of $^{120}\mathrm{Sn}_{\text{G.S.}}\ensuremath{\bigotimes}n\ensuremath{\rightarrow}^{121}\mathrm{Sn}_{\text{0.006.}}$ and $^{121}\mathrm{Sn}_{\text{0.006}}\ensuremath{\bigotimes}n\ensuremath{\rightarrow}^{122}\mathrm{Sn}_{\text{G.S}}$ are not reliable. A simple linear formula was used to analyze the relationship of SFs with neutron separation energy ${S}_{n}(N)$ and the even-$A$ Sn pairing gap $\mathrm{\ensuremath{\Delta}}(N)$, and SFs are found to be positively correlated to ${S}_{n}(N)$ and $\mathrm{\ensuremath{\Delta}}(N)$.

Research on 129I measurement with 300 kV AMS system at CIAE

Systemic research of 129I AMS measurement was carried out based on the 300 kV terminal voltage accelerator mass spectrometry system which designed and constructed by China Institute of Atomic Energy (CIAE). Through ion transport, gas stripping, charge state selection, interference exclusion, this method get high efficiency, high sensitivity for 129I. Measurement efficiency of system is about 28% and measurement sensitivity of 129I/127I is 1 × 10−14.

Benchmark experiment with iron slab by Time-of-flight technique at CIAE

In order to validate the evaluated nuclear data, leakage spectra in the range of 0.8 to 15 MeV from samples were measured by time-of-flight (TOF) technique using a D-T neutron source. An experimental system for benchmark validation of nuclear data with slab samples has been set up at China Institute of Atomic Energy (CIAE). In this study, test samples are iron slabs, of which the thickness are 5cm, 10cm and 15cm, and the measured angles were chosen to be about 60° and 120°. By comparing measured leakage spectrum with calculated ones by MCNP-4C code, using the data from the CENDL-3.1, ENDF/B-VIII.0, JENDL-4.0 and JEFF-3.3 nuclear data files, and the comparison was made by the spectrum shape and by the C/E values in different energy regions.

Measurements of neutron-induced light-charged particle emission reactions

In the past two decades cooperating with Frank Laboratory of Neutron Physics (FLNP), Joint Institute for Nuclear Research (JINR) measurements of (n, α) reaction cross sections for 6Li, 10B, 25Mg, 39K, 40Ca, 54,56,57 Fe, 58Ni, 63Cu, 64,67 Zn, 95Mo, 143Nd and 147,149 Sm nuclei were performed in the MeV neutron energy region based on the 4.5 MV Van de Graaff accelerator at Peking University. In recent years, our measurements were extended in three aspects. Firstly, measurements were expanded from two-body reactions to three-body reactions such as 10B (n, t2 α). Secondly, the neutron energy region was extended from below 8 MeV to 8 - 11 MeV by using the HI-13 tandem accelerator of China Institute of Atomic Energy (CIAE), with which cross sections of 54,56 Fe(n, α)53,51Cr reactions were measured. Thirdly, based on the newly-built China Spallation Neutron Source (CSNS) Back-n WNS (White Neutron Source), differential and angle-integrated cross sections for 6Li(n, t) and 10B(n, α) reactions were measured in the neutron energy region from 1 eV to 3 MeV.

Validation of Neutron Evaluated Data Based on The Experimental Reactivity Worth of Tungsten Target in CiADS

Measurement of a cylindrical tungsten target reactivity worth has been performed on the light water zero-power reactor of VENUS-II at China Institute of Atomic Energy (CIAE) in order to verify the neutron evaluated data related to the engineering design of Chinese initiative Accelerator Driven Systems (CiADS). The reactivity worth of the tungsten target was measured and processed as -1.234±0.114mk by a period method. The experimental result was compared with the simulation ones calculated by MCNP with five different libraries, i.e., ENDF/B-VII.0, ENDF/B-VII.1, JENDL-4.0, CENDL-3.1 and JEFF-3.2. By comparing the results of experiment and simulation, the simulated results from ENDF/B-VII.0, JENDL-4.0 and JEFF-3.2 are higher than the experimental result, however that from CENDL-3.1 is lower. The result from ENDF/B-VII.1 library shows better agreement with the experiment one and the relative deviation is less than 2%. Through the analysis of the differences of the results, non-tungsten elements cross sections in the ENDF/B-VII.1 mainly affect the tungsten radiation capture and elastic scattering reaction rates in the energy range of 10-9-10-7 MeV, which results in a better simulated tungsten target reactivity worth value. Therefore, it is recommended that the tungsten target reactivity worth should be calculated with the ENDF/B-VII.1.

Measurement of leakage neutron spectra with D-T neutrons and evaluated nuclear data

Benchmarking of evaluated neutron nuclear data libraries was performed for ∼14.8 MeV neutrons on the several targets, such as gallium, graphite, silicon carbide, uranium and tungsten samples. The experiments were performed at China Institute of Atomic Energy (CIAE). The neutron leakage spectra from the samples were measured at 60◦ and 120◦ by a TOF technique with a BC501A scintillation detector. The measured spectra are rather well reproduced by MCNP-4C simulations with the CENDL3.1, JENDL-4.0 and the new release ENDF/B-VIII.0, JEFF-3.3 evaluated nuclear data libraries and so on. There have some difference between experiments and simulations for the elastic and inelastic contributions in the partial energy range. And the discrepancies of the neutron leakage spectra in the MCNP simulations originate simply from the differences in the spectra distributions of the neutron reaction channels in the evaluated nuclear data libraries.

A method of designing binary energy degrader

In order to improve the efficiency of the single event effect (SEE) experiments on the 100 MeV proton cyclotron of China Institute of Atomic Energy, a binary energy degrader that can lower the initial proton energy to other values rapidly is designed for the 100 MeV protons provided by the accelerator. The energy degrader is comprised of six aluminum plates of 0.5, 1, 2, 4, 8, 16 and 32 mm at thickness, where the thickness of the latter plate is twice that of the previous one. We introduce the concept of relative thickness, which can also represent the order of the energy of the produced protons, and the state or operation of the degrader. The energy interval of 61 protons with energy above 9.69 MeV, produced by the degrader, is between 0.84 MeV and 4.09 MeV. And their energy straggling degree is less than 10%, and full width at half maximum of the scattering angle is less than 45 mrad. So the energy degrader basically meets the requirements of the proton SEE experiments. The influence of the initial proton energy accuracy of the protons directly provided by the accelerator on the residual energy after they have passed through the degrader is discussed. It is found that the lower the residual energy, the greater the influence is. In addition, the degrader is also suitable for protons in the 70－100 MeV energy range that the accelerator can directly provide, and more continuous energy can be obtained by using more plates designed with this method. The design method of the energy reducer proposed in this paper is simple and effective, and has a strong reference value.

Single-event effects induced by medium-energy protons in 28 nm system-on-chip

Single-event effects (SEEs) induced by medium-energy protons in a 28 nm system-on-chip (SoC) were investigated at the China Institute of Atomic Energy. An on-chip memory block was irradiated with 90 MeV and 70 MeV protons, respectively. Single-bit upset and multi-cell upset events were observed, and an uppermost number of nine upset cells were discovered in the 90 MeV proton irradiation test. The results indicate that the SEE sensitivities of the 28 nm SoC to the 90 MeV and 70 MeV protons were similar. Cosmic Ray Effects on Micro-Electronics Monte Carlo simulations were analyzed, and it demonstrates that protons can induce effects in a 28 nm SoC if their energies are greater than 1.4 MeV and that the lowest corresponding linear energy transfer was 0.142 MeV cm2 mg−1. The similarities and discrepancies of the SEEs induced by the 90 MeV and 70 MeV protons were analyzed.

Neutronic simulation of China Experimental Fast Reactor start-up tests. Part I: SARAX code deterministic calculation

As one of participants of recent coordinated research project proposed by International Atomic Energy Agency and China Institute of Atomic Energy, the computational reactor physics and experiment laboratory of Ulsan National Institute of Science and Technology, Republic of Korea, is currently focused on a study involving the neutronic simulation of the China Experimental Fast Reactor (CEFR) start-up tests. The CEFR start-up tests include obtaining measurements of the criticality, control rod worth, sodium void reactivity, temperature reactivity, and subassembly swap reactivity. The fast reactor neutronic analysis code SARAX is selected for performing such simulations for additional validation. The obtained numerical results are compared with measurement data. In addition, the differences in the expected results of the heterogeneous and homogeneous models are quantified in this study. According to the simulation, the calculated results agreed well with the measured values in the case of the majority of the neutronic characteristics.