China Mianyang Research Reactor Research Articles

Prototype design and experimental study of fission neutron imaging at China Mianyang research reactor

Taking advantage of the special reaction principle between neutrons and elements, the neutron imaging method is better suited to testing the structure and the defects of light materials that are covered by heavy materials. In contrast to thermal or cold neutron imaging, the fast neutrons are best suited to testing the large samples composed of various materials. Fission neutrons emitted from the reactor are more stable than those from other neutron sources. Based on the beamline for thermal neutron imaging at China Mianyang Research Reactor (CMRR), a combination of filters could increase the proportion of the fission neutrons. Various fission neutron collimators were calculated, designed and measured. The flux of fission neutrons was close to 3 × 105 cm−2 s−1, when the collimation ratio was about 172. A fission neutron imaging system was built as well. The field of view (FOV) was as large as 400 mm × 400 mm, and the experimental spatial resolution was better than 0.5 mm. The fission neutron tomography was tested. The reconstruction results were comparable to the tomography performed in NECTAR at FRM-II. In addition, a serial time acquisition method was applied in the tomography to reduce the white noise. The ART reconstruction method may improve the quality of the reconstruction images.

Investigations of microstructure and tensile properties of neutron irradiated 6061 aluminum alloys

Effects of neutron irradiation on the microstructure and mechanical properties of CMRR (China Mianyang Research Reactor) structural material pure aluminum and 6061 alloy were studied by scanning/transmission electron microscopy (S/TEM) and tensile tests. The fast neutron (E > 0.1 MeV) fluences of 1.09–2.89 × 1022 n•cm−2 produced damage doses of 1.6–4.2 displacements per atom (dpa). Voids and faulted 1/3<111> dislocation loops were observed in both pure aluminum and 6061 alloy. In particular, voids tended to preferentially aggregate on coarse Cu-rich and fine Mg2Si precipitates which contributes to the higher irradiation tolerance in terms of void formation for 6061 alloy, suggesting that the uniformly distributed precipitates can act as trapping sites for defect clusters during irradiation and thus promote recombination. The size and density of Mg2Si precipitates showed a slight increase and Cu-rich precipitates emerged in 6061 alloy after neutron irradiation. Moreover, radiation-induced segregation was also detected along the grain boundaries. After tensile testing, the pure aluminum showed a lower yield strength and larger uniform elongation than 6061 alloy, where a moderate uniform elongation was still reserved after irradiation to 4.2dpa. The severely reduced ductility in 6061 alloy is supposed to be caused by the transmutation product silicon which contributes to the increase of dispersed multiple precipitates after irradiation. Our results indicate that precipitates especially Mg2Si play a decisive role in void suppression, but are not suitable in diminishing the radiation hardening.

HETU: a new high-resolution stress and texture neutron diffractometer at China Mianyang Research Reactor

HETU is a new high-resolution stress and texture neutron diffractometer installed at the C1 neutron guide at China Mianyang Research Reactor. The diffractometer is designed for precise residual stress and texture analysis of engineering components, as well as in situ investigations under various sample environments for engineering materials. The wavelength range of monochromatic incident neutrons is 1.634–5.800 Å, provided either by a double-focusing perfect single-crystal silicon monochromator in high instrument resolution mode or by a highly oriented pyrolytic graphite monochromator in high neutron flux mode. The intrinsic peak widths of HETU have been measured using a standard silicon powder sample, and residual stress measurements of an aluminium alloy shrink-fit ring and plug have been carried out. These results demonstrate that HETU is a reliable and appropriately designed diffractometer for promoting materials investigation.

Design and performance of the high-resolution stress and texture neutron diffractometer HETU

The high-resolution stress and texture neutron diffractometer HETU at the China Mianyang Research Reactor is dedicated to measuring and analysing the residual stress and texture of engineering materials. The instrument can provide a high instrument resolution and a high neutron flux at the sample position. This article presents the HETU neutron optics design based on Monte Carlo simulation and the first assessment of its experimental performance. The technical parameters of the monochromators, slit system, radial collimators and detector were determined. A double-focusing silicon monochromator with (311) and (400) planes and a highly oriented pyrolytic graphite (HOPG) monochromator with (002) and (004) planes were selected to provide either high instrument resolution or high neutron flux modes. The highest instrument resolution of Δd/d = 1.65 × 10−3 is obtained when using Si(400), while the highest neutron flux at the sample position is 3.0 × 107 n s−1 cm−2 at the wavelength of 2.37 Å reflected by HOPG(004). The HETU diffractometer started operation in early 2022.

In-pile tritium release behavior and the post-irradiation experiments of Li4SiO4 fabricated by melting process

Understanding the tritium release and retention behavior of candidate tritium breeder materials is crucial for breeder blanket design. Recently, a melt spraying process was developed to prepare Li4SiO4 pebbles, which were subsequently subjected to the in-pile tritium production and extraction platform in China Mianyang Research Reactor (CMRR) to investigate their in-situ tritium release behavior and irradiation performance. The results demonstrate that HT is the main tritium release form, and adding hydrogen to the purge gas reduces tritium retention while increasing the HT percent in the purge gas. Post-irradiation experiments reveal that the irradiated pebbles darken in color and their grains swell, but the mechanical properties remain largely unchanged. It is concluded that the tritium residence time of Li4SiO4 made by melt spraying method at 467 °C is approximately 23.34 h. High-density Li4SiO4 pebbles exhibit tritium release at relatively low temperatures (＜600 °C) that is mainly controlled by bulk diffusion. The diffusion coefficient at 525 °C and 550 °C is 1.19 × 10−11 cm2/s and 5.34 × 10−11 cm2/s, respectively, with corresponding tritium residence times of 21.3 hours and 4.7 hours.

Monte Carlo simulations of LUOSHU: a new 46-meter small-angle neutron scattering instrument in China

The LUOSHU small-angle neutron scattering spectrometer is one of the neutron scattering instruments under construction at China Mianyang Research Reactor. Quantitative characterization of nanoparticles is now in a higher demand for research interests in material science, physics, chemistry, biology. Therefore, as a general-purpose small-angle scattering spectrometer, LUOSHU is aimed to provide a large accessible Q range, flexible resolution and sufficient neutron flux. Monte Carlo simulations have been performed on LUOSHU from the neutron source to sample platform to optimize the parameters of the bender part, collimation system, and the velocity selector. And the instrument layout is optimized base on the simulation results. Finally, the maximum neutron intensity of the neutron beam at the sample stage can reach 1.01 × 107 N·s-1·cm-2 and its divergence is 0.63.

In-situ tritium release behavior and post-irradiation experiments of Li2TiO3 pebbles developed by freeze-drying method

To assess the overall performance of potential solid tritium breeders for China Fusion Engineering Test Reactor (CFETR), we conducted a series of In-situ irradiation experiments on the in-pile tritium production and extraction experimental platform at China Mianyang Research Reactor (CMRR). In 2019, we performed an in-pile tritium release experiment (IPTRE-2) on Li2TiO3 (∼90 T.D%, 6Li 7.5%, ∼30.17 g) ceramic pebbles, which are the latest developed breeders. The Li2TiO3 pebbles were produced at the Institute of Nuclear Physics and Chemistry (INPC), China Academy of Engineering Physics (CAEP), using a freeze-drying method. This paper reports on the In-situ tritium release behavior and the post-irradiation experiments of Li2TiO3 pebbles. We established the relationship between tritium residence time and temperature, which can be expressed as lgτ=-0.74+1622.4/T. Our findings indicate that the Li2TiO3 pebbles remained structurally stable without fragmentation, but their color darkened and the degradation of mechanical properties due to the reduction of Ti in Li2TiO3.

Design of a three-detector system on LUOSHU: a small-angle neutron scattering instrument at China Mianyang Research Reactor

The LUOSHU small-angle neutron scattering instrument is one of the neutron scattering instruments under construction at the China Mianyang Research Reactor. Research interests in the fields of materials science, physics, chemistry and biology require that LUOSHU provide a wide range of measured scattering vector magnitudes (Q), a large dynamic Q range and high resolution. A movable and combined three-detector system that consists of a high-resolution position-sensitive 3He multi-tube rear detector and two L-shaped front detectors is designed in order to expand the Q range and dynamic Q. Analytical calculations validate that, with the three-detector system, LUOSHU can cover a Q range of four orders of magnitude. Also, the three-detector system will extend the dynamic Q range and provide simultaneous Q max/Q min higher than 800 in operation, satisfying the requirements of in situ experiments.

An in-pile demonstrated platform for the evaluation of tritium extraction technologies in China Mianyang Research Reactor

The preliminary design of the tritium extraction system for CFETR breeding blanket has been completed. In the design, two molecular sieve packed columns are connected in series to achieve both hydrogen-helium separation and tritium enrichment. The first column primarily focuses on hydrogen-helium separation and volume reduction, while the second column, which is thinner and longer than the first, is mainly used for tritium enrichment. To achieve tritium-helium separation and tritium storage simultaneously, a U-shaped tritium storage bed is utilized. To verify the feasibility of these tritium extraction technologies, an in-pile tritium release and recovery platform was constructed in China Mianyang Research Reactor (CMRR). This paper provides a detailed description of the in-reactor irradiation device and the design and composition of tritium extraction system. Moreover, an in-situ experiment was conducted in early 2022 to produce and recover tritium with a total activity level of approximately one hundred curies. The experiment obtained various parameters, including tritium release form and ratio of Li4SiO4 with high 6Li abundance, tritium extraction rate, tritium recovery rate of the whole system and tritium penetration in 316 L stainless steel. These results allow for a preliminary evaluation of the feasibility of the designed tritium extraction technologies.

Grazing-incidence small angle neutron scattering achieved in spectrometer SANS-Suanni of transmission geometry

Current work presents the design and applications of the grazing-incidence small-angle neutron scattering (GISANS) based on SANS-Suanni spectrometer at the 20 MW China Mianyang research reactor (CMRR)-based neutron center. A multi-dimensional sample stage with both front and back slits were designed and set up on SANS-Suanni for achieving the geometry. Experimentally, thin films samples with mono-dispersed silica on sapphire substrates were prepared for collecting two-dimensional (2D) GISANS patterns at beam size setting of 4 mm width and 5 mm height. Typical signals such as the specular reflection peak, Yoneda peak, as well as the sample scattering, etc. were obtained. Moreover, integrated 1D GISANS profiles in different directions, namely vertical and horizontal directions of the incident beam (0V, 0H), and horizontal direction of the Yoneda peak (YH) were obtained via rectangular integration. Accordingly, incident angle (αi) as about 0.76° and the contrast of the sample systems as around 4.07 × 1010 cm−2 were determined. Moreover, the overlapping of 0H curves and the SANS profiles indicates that GISANS can cover some of the structural information as SANS provided, along with the capability of measuring the thin film samples.

Upgrade of Xuanwu: A dual-mode neutron powder diffractometer at CMRR

Neutron diffraction (ND) is a well-established technique of great significance in condensed physics and materials science. Although it has particular advantages against its brother X-ray diffraction (XRD), intensity is still a limiting factor counteracting its application. Herein, we report the upgrade of Xuanwu, a high-resolution neutron powder diffractometer at the China Mianyang Research Reactor (CMRR). A doubly focusing monochromator system made of Si blades is applied to enhance the intensity from 2 × 105n⋅cm−2⋅s−1 to 2.39 × 106n⋅cm−2⋅s−1 with changeable wavelength. The high-resolution mode with a best resolution 1.6‰ is reserved, which means the working style is optional between high-resolution and high-intensity, making Xuanwu more applicable in expanded scopes.

Review: Current progresses of small-angle neutron scattering on soft-matters investigation

A review of the recent works on soft-matters based on small-angle neutron scattering (SANS) is presented. This Review is intended to be a relatively comprehensive source for applying SANS on soft-matters investigation, including the basic principles and theory, the major characteristics of the SANS such as chain labeling and contrast variation/matching based on hydrogen/deuterium replacement, as well as corresponding typical application examples. Through the demonstration of applications in sample systems such as polymer solutions, polymer blend, semi-crystalline polymer, polymer nano-composites, hydrogel, and bio-materials, the advantages of SANS on soft-matters are demonstrated. Specifically, examples of the recent SANS investigation on spectrometer SANS-Suanni of 20 MW China Mianyang Research Reactor (CMRR) were included. As the users of neutron facilities are increasing steeply along with newly established neutron sources as well as experienced ones, this Review is intended to be of interest to the SANS, soft matter, and nano-materials science communities.

Experimental study of simultaneous high-temperature and high-pressure assembly of Paris-Edinburgh press for neutron diffraction

Paris-Edinbrugh (PE) press has been widely used in high pressure &lt;i&gt;in-situ&lt;/i&gt; neutron diffraction experiments due to its advantages of large sample size, portability and simple structure. However, with the characteristics of uniaxial load of PE press, the weak lateral support makes the gasket and cell assembly continue flowing outward. So, the development of cell assembly of PE press that can simultaneously work under high pressure and high temperature (high &lt;i&gt;P&lt;/i&gt;-&lt;i&gt;T&lt;/i&gt;) is a great challenge. In this work, we design three-segment high &lt;i&gt;P&lt;/i&gt;-&lt;i&gt;T&lt;/i&gt; assembly of PE press for neutron diffraction, which can significantly improve the heating efficiency, thermal insulation, and stability of assembly. By using the fanned Cu foil leads of thermocouple, we realize the &lt;i&gt;in-situ&lt;/i&gt; measurement of assembly temperature under a high pressure up to 5 GPa. The designed HPT-3 and HPT-3.5 assemblies can arrive at 2034 K and 1515 K respectively, which are measured by thermocouple. The high &lt;i&gt;P&lt;/i&gt;-&lt;i&gt;T&lt;/i&gt; experiments of HPT-3 assembly are carried out on a high-pressure neutron diffraction spectrometer (Fenghuang) of China Mianyang Research Reactor (CMRR). The results show that the designed assembly can simultaneously achieve high &lt;i&gt;P&lt;/i&gt;-&lt;i&gt;T&lt;/i&gt; of 8.5 GPa and 1508 K with collecting the high-quality neutron diffraction data of MgO cylindrical sample.

Design and simulations of spin-echo small angle neutron scattering spectrometer at CMRR

Current work presents the design and simulations of the spin-echo small-angle neutron scattering (SESANS) spectrometer at the 20 MW China Mianyang research reactor (CMRR)-based neutron center. Firstly, the components of the SESANS are introduced. Secondly, the Monte Carlo simulations of the key components for determining the technical parameters are presented. The bending radius of the focusing monochromator is set to 2.5 m. The length and radius of curvature of the S-Bender is set to 300 mm and 2.0 m, respectively. Accordingly, simulation results of the virtual spectrometer indicate that the neutron beam transmission is about 0.09 at wavelength of 0.4 nm. Thirdly, the finite element simulation and the testing of the magnetic field suggest that the optimized ampere-turns are 8400 and 8289.9, respectively. Accordingly, the simulation results indicate that the field integral homogeneity of main coil, V-coil, and field stepper are better than 2.91 × 10−6 T m, 2.3 × 10−6 T m, and 3.14 × 10−6 T m, respectively. Last, a multilayer flipper-permalloy with 100 nm FeSi and 10 nm Cr (or Ta) alternately sputtered on a Si wafer was designed and tested. Neutron experiments demonstrate that the maximum flipper efficiency reaches 0.98 and remains stable with increasing the strength of the main fields from 50 Gs to 200 Gs, when the corresponding wavelength is 0.31 nm. Based on the optimized parameters, the SESANS is under construction, and it will be completed at the end of 2021.

Systematic Investigation of Solution-State Aggregation Effect on Electrical Conductivity in Doped Conjugated Polymers

Systematic Investigation of Solution-State Aggregation Effect on Electrical Conductivity in Doped Conjugated Polymers

The neutron scattering platform of China Mianyang Research Reactor (CMRR) and recent applications

The neutron scattering platform of China Mianyang Research Reactor (CMRR) and recent applications

A two-dimensional neutron detector assembly at the China Mianyang Research Reactor

A two-dimensional neutron detector consisting of 96 3He position-sensitive proportional counters was assembled at the China Mianyang Research Reactor. With a count rate limit that is higher than that of the initial multi-wire proportional chamber detector at CMRR, it will be used for the small-angle neutron scattering spectrometer Suanni. The problems caused by low air pressure and γ radiation in the working environment are pretreated, and detector performance is evaluated and compared with that of the initial proportional chamber. Now the new detector is ready to be used for Suanni.

An in-pile experimental loop for the irradiation of tritium breeding ceramics in China Mianyang research reactor (CMRR)

• An in-pile irradiation loop has been established in CMRR for in-situ tritium extraction study. • It allows loading or unloading the breeder pellets online by a special designed pneumatic system. • Several typical experiments have been performed to demonstrate its capability. A new in-pile experimental loop has been established in CMRR for ceramic tritium breeder irradiation. The most typical of this loop is the capability of online reloading of irradiated samples. The irradiation temperature in the pellets bed can be controlled within the range of 300～750 °C, with a spatial inhomogeneity of ±10 °C. Up to now, a series of irradiation experiments have been carried out on three different breeder materials, i.e. Li 4 SiO 4 (7.5 % 6 Li), Li 4 SiO 4 (93 % 6 Li) and Li 2 TiO 3 (7.5 % 6 Li) pellets, indicating the stability of the facility.

Investigation of flexural behavior and microstructure of Amosic-3 silicon carbide composites under neutron irradiation

SiC/SiC composites prepared by the chemical vapor infiltration process have been investigated under neutron irradiation at approximately 40 °C to doses of 0.03 and 0.2 displacements per atom (dpa) in the China Mianyang Research Reactor. Irradiation effects were characterized by three-point flexural tests, micro-Raman spectra and transmission electron microscopy observations. The results demonstrated that the ultimate flexural stress and flexural modulus decreased remarkably with irradiation doses up to 0.2 dpa. Micro-Raman spectra of the Amosic-3 fiber and SiC matrix revealed that both reduction of Si–C bonds and enhancement of Si–Si bonds were increased from 0.03 to 0.2 dpa. Microstructural observation revealed that the Amosic-3 fiber suffered from grain fragmentation and amorphization. Meanwhile, matrix amorphization is generated preferentially at the site of stacking fault structures. In addition, it suggested that in the current work, up to 0.2 dpa, full amorphization was not completed in the Amosic-3 fiber, PyC and SiC matrix.

MyNeutronDAQ: A general program for data acquisition of neutron scattering spectrometers at China Mianyang Research Reactor and on‐line data‐analysis

AbstractMyNeutronDAQ, a graphical user interface (GUI) program for data acquisition of neutron scattering spectrometers at China Mianyang Research Reactor (CMRR) and on‐line data‐analysis has been developed. The program is written in Microsoft Visual C++, which runs under Windows operating systems. Based on the characters of the hardware connection and time‐to‐digital converter (TDC) systems of the spectrometers (taking the time‐of‐flight and polarized neutron reflectometer [TPNR] Diting as the example), a valid event identification and screening protocol is embedded into the program. Moreover, the program design and key features of MyNeutronDAQ such as visualization interface, optional output data format, batch mode, and functions of user‐friendly on‐line analysis, are presented. Taking the program specifically for small‐angle neutron scattering (SANS) Suanni as the example, specific applications of the MyNeutronDAQ are further presented.