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Slurry sampling-TXRF and ultra-high-pressure digestion ICP-OES methods were developed for the direct determination of Ca, Co, Cr, Al, Cu, Fe, Mn, Na, Ni, Ti in different particle size nuclear-grade boron carbide powders. The dispersive effect of polacrylateamine (NH4PAA) was used as a dispersion agent. Different zeta potential values and NH4PAA concentrations could get stable and homogeneous slurries. It was found that pH at 6.0 and NH4PAA 0.5 wt% provided the best conditions. Optimization of the slurry concentration of TXRF was performed for the net elemental intensity of Ca, Ti, Fe, and the internal standard element Ga. Through experimental results, we used the 10 mg·mL−1 as a suitable slurry concentration. The analytical results obtained using TXRF and ultra-high-pressure digestion ICP-OES methods were in good agreement with the recommended method DC-arc-OES. Besides, the detection limit of TXRF and ICP-OES is in the range of 0.1–1.0 μg·g−1 (expect Al and Na) which was lower than the DC-arc-OES method. The reference material of ERM 102 was used to validate the accuracy and get good results. The recovery rates of TXRF are between 83% and 115% for Cu (2.4–25 μg·g−1), Cr (12–234 μg·g−1), Ca (158–211 μg·g−1), Co (2.9–6.5 μg·g−1), Fe (965–1547 μg·g−1), Mn (17–24 μg·g−1), Ni (56–128 μg·g−1), and Ti (12–80 μg·g−1).

Research reactor’s fuel element integrity is essential for nuclear safety. In normal operations, radionuclides could be well contained in fuel element. Unfortunately, under severe conditions, the amount of radionuclides may increase, releasing to the primary coolant and, as a result, crack or damage the fuel element mechanically or chemically. Thus, it is imperative to help operators take measures effectively, locating damaged fuel assembly in reactor cores rapidly. In this paper, a quantitative fuel failure positioning method based on cesium (134Cs and 137Cs) detection was studied. An exact model to describe the relation between cesium radioactivity and fuel burnup based on nuclide conversion chain was put forward. Radioactivity measurement data has approved the validation of this method when it applied to HFETR. Moreover, based on the measurement of 24Na activity, we proposed an approach to identify fuel failures and cladding corrosion. The validation results further indicate the accuracy and good applicability of this method, that provides guarantee for the safe operation of HFETR.

A variety of new materials have been developed during the past two decades in China to support the design and construction of key components for next step fusion devices. Most recently, a domestic project, promoted by the engineering design of China Fusion Engineering Test Reactor (CFETR), has been launched to preliminarily investigate the performance of advanced fusion materials after neutron irradiation. The goal of this paper is to introduce the preparation for the coming neutron irradiation campaign. The development status and acceptance of some outstanding fusion materials are briefly reviewed with the main description focusing on some high-performance 9Cr-ODS steels, Cu–0.3Al2O3 alloys, W-K and W-ZrC alloys for blanket/divertor components. The principles for screening suitable materials out from several candidates are suggested, which consider low activation, sufficient production scale, homogeneous microstructures, safety margin and repeatability of basic properties as the basic requirements. As a recommended approach for neutron irradiation tests, the small sample testing technology (SSTT) is highlighted in this paper. Further development of SSTT using inverse finite element method (FEM) and energy equivalent principle is performed for new designs of small tensile samples.

The main task of High Flux Engineering Test Reactor (HFETR) is to carry out the irradiation test of nuclear materials, which require accurate irradiation neutron flux, however it is difficult due to specified fuel cell geometry and sophisticated in-core loading patterns of HFETR. This paper introduces the neutron flux calculation method of irradiation in HFETR, which can obtain the neutron flux of various shaped materials in any irradiation channels, and describes the calculation process which completed by four codes including HEFT-lat, HEFT-core, MCNPIP and MCNP. The theory and function of each program are introduced respectively. The calculated neutron fluxes in different irradiation channels of HFETR are obtained, such as at the central hole of fuel element and the 9# channel which located at the reflector. Compared with the measurement value, the numerical results demonstrate that the calculation method is reliable and competent for the irradiation design of HFETR.

The High Flux Engineering Test Reactor (HFETR) is loaded with complex geometry assemblies, taking on strong heterogeneity. These features call for more advanced core analysis and fuel management methodologies compared with traditional PWR. Based on the two-step method, a fuel management simulation platform HEFT was developed, which is a 3-D core fuel management transport calculation program of HFETR. In HEFT, the lattice code HEFT-lat has the abilitiesto describe complex assembly geometriesof HFETR, whereby mitigate errors brought by geometrical approximations.DNTR, a triangular mesh nodal SN method code, is employed to solve the transport equation. This paper introduces the development backgrounds of HEFT, introduces the principle and function of the three main modules of HEFT, that is HEFT-lat?HEFT-core and HEFT-int, the calculation method of lattice parameter and reactor loop calculation method are described. By follow-up calculation of 81-I to 89-II of HFETR core and comparison of intial critical keff, the control rod position during shutting down and the neutron flux, thus obtains the calculation deviation. The result shows the validity of the HEFT code, the lattice and reactor core calculation model. Thus, HEFT has already successfully applied to the fuel management calculation of HFETR.Copyright © 2016 by ASME

TGPAP resins were cured using different contents of DDM as the hardener, and were subjected to irradiation in a nuclear fission reactor. The TGPAP/DDM resin systems showed excellent radiation resistance in an integrated neutron flux of 4.71 × 10 22 n/m 2 (1.77 × 10 22 n/m 2 with E > 0.1 MeV) and γ irradiation dose of 25.9 MGy. Hardener contents that affected the crosslinking degree of resins had important effects in irradiation resistance. Positron annihilation lifetime analysis revealed that the size of free-volume holes in the irradiated samples was not changed after neutron irradiation with 1.77 × 10 22 n/m 2 ( E > 0.1 MeV).

Shape-memory polymer (SMP) materials have several drawbacks such as low strength, low stiffness and natural insulating tendencies, which seriously limit their development and applications. Much effort has been made to improve their mechanical properties by adding particle or fiber fillers to reinforce the polymer matrix. However, this often leads to the mechanical properties being enhanced slightly, but the shape-memory effect of reinforced SMP composites being drastically reduced. The experimental results reported here suggested that the mechanical resistive loading and thermal conductivity of a composite (with hybrid filler content of 7.0 wt%) were improved by 160 and 200%, respectively, in comparison with those of pure bulk SMP. Also, the glass transition temperature of the composite was enhanced to 57.28 °C from the 46.38 °C of a composite filled with 5.5 wt% hybrid filler, as determined from differential scanning calorimetry measurements. Finally, the temperature distribution and recovery behavior of specimens were recorded with infrared video in a recovery test, where a 28 V direct current circuit was applied. The effectiveness of carbon black and short carbon fibers being incorporated into a SMP with shape recovery activated by electricity has been demonstrated. These hybrid fillers were explored to improve the mechanical and conductive properties of bulk SMP. Copyright © 2010 Society of Chemical Industry

Dielectric elastomer (DE) is the most promising electroactive polymer material for smart actuators. When a piece of DE film is sandwiched between two compliant electrodes with a high electric field, due to the electrostatic force between the two electrodes, the film expands in-plane and contracts out-of-plane so that its thickness becomes thinner. The thinner thickness results in a higher electric field which inversely squeezes the film again. When the electric field exceeds the critical value, the dielectric field breaks down and the actuator becomes invalid. An elastic strain energy function with two material constants is used to analyze the stability of the dielectric elastomer actuator based on the nonlinear electromechanical field theory. The result shows that the actuator improves its stability as the ratio k of the material constants increases, which can be applied to design of actuators. Finally, this method is extended to study the stability of dielectric elastomers with elastic strain energy functions containing three and more material constants.

The constitutive relation and electromechanical stability of Varga-Blatz-Ko-type compressible isotropic dielectric elastomer is investigated in this paper. Free-energy in any form, which consists of elastic strain energy and electric energy, can be applied to analyse the electromechanical stability of dielectric elastomer. The constitutive relation and stability is analyzed by applying a new kind of free energy model, which couples elastic strain energy, composed of Varga model as the volume conservative energy and Blatz-Ko model as the volume non-conservative energy, and electric field energy with constant permittivity. The ratio between principal planar stretches m(t 0 ) (λ 2 = m(t 0 )λ 1 ), the ratio between thickness direction stretch and length direction stretch 0 n(t 0 ) (λ 3 = n(t 0 )λ 1 ), and power exponent of the stretch k(t 0 ) are defined to characterize the mechanical loading process and compressible behavior of dielectric elastomer. Along with the increase of material parameters m(t 0 ) , n(t 0 ) , k(t 0 ) and poison ratio V , the nominal electric field peak is higher. This indicates that the dielectric elastomer electromechanical system is more stable. Inversely, with the increase of the material parameter α , the nominal electric field peak, critical area strain and the critical thickness strain increase, coupling system is more stable.

Silicone rubber is a common dielectric elastomer material. Actuators made from it show excellent activate properties including very large strains (up to 380%), high elastic energy densities (up to 3.4 J/g), high efficiency, high responsive speed, good reliability and durability, etc. When voltage is applied on the compliant electrodes of the dielectric elastomers silicone rubber, the polymer shrinks along the electric field and expands in the transverse plane. In this paper, a theoretical analysis is performed on the coupling effects of the mechanical and electric fields. A nonlinear field theory of deformable dielectrics and hyperelastic theory are adopted to analyze the electromechanical field behavior of these actuators. Applied elastic strain energy function is obtained from the representative Yeoh model. The electric energy function involves invariant and variable dielectric constant respectively. Then deduce the constitutive relation for the dielectric elastomer film actuator based on the selected function. Also the mechanical behavior of the dielectric elastomer silicone rubber undergoing large free deformation is studied. The constitutive modules of dielectric elastomer composite under free deformation and restrained deformation are derived. The Barium Titanate (BaTiO3) with high permittivity was incorporated into the raw silicone to fabricate a new dielectric elastomer, the experimental results that the elastic modulus and dielectric constant were significantly improved. Finally the Yeoh model was developed to characterize the elastic behavior of the new dielectric elastomer. The constitutive modules of dielectric elastomer composite under free deformation and restrained deformation are derived. This is a promising analysis method for the study of the coupled fields and mechanical properties of the dielectric film actuator.

Dielectric elastomer(DE) could be used in generator design and fabrication, which has been verified by experiments. The function principle of DE generator is contrary to that of DE actuator. By imposing a low voltage to the dielectric elastomer membrane, electric charges are accumulated on the two surfaces. Then we apply mechanical force to the sides of the membrane to produce pre-stretch, and the thickness of the membrane becomes thinner and the capacitance increases, where mechanical energy is converted to elastic energy. After the mechanical force being withdrawn, because of elasticity, the thickness of membrane increases while the capacitance decreases, and elastic energy is converted to electrical energy. This is a work cycle of conversion from elastic to electric energy. Researchers have always been expecting to find a model that can well predict and evaluate the performance of dielectric elastomer generator. Suo et al. proposed the typical failure model of neo-Hooken type dielectric elastomer generator and calculates the maximal energy converted in a mechanical and electrical cycle. In this paper, we demonstrate the area of allowable states of various Mooney-Rivlin type dielectric elastomer generators, which can be employed to direct the design and fabrication of Mooney-Rivlin silicone generator, and the results coincide with Suo's theory.

Dielectric elastomers have received a great deal of attention recently for effectively transforming electrical energy to mechanical work. Their large strains and conformability make them enticing materials which can be applied in many domains: biomimetics, aerospace, mechanics, medicals, etc. In order to maximize actuator performance, the dielectric elastomer actuators should have a high dielectric constant and high dielectric breakdown strength. Here we have investigated the increase in permittivity of a commercial silicone elastomer by the addition of carbon nanotube. The percolation threshold of the composites is obtained to be low. Experimental results suggest that for the case of conductive filler particle-elastomer matrix interaction, actuation strain increases with increasing carbon nanotube content.

In this paper, a novel kind of deployable morphing wing base on shape memory polymer (SMP) composite is designed and tested. While the deployment of the morphing wing still relies on the mechanisms to ensure the recovery force and the stability performance, the deploying process tends to be more steady and accurate by the application of SMP composite, which overcomes the inherent drawbacks of the traditional one, such as harmful impact to the flight balance, less accuracy during the deployment and complex mechanical masses. On the other hand, SMP composite is also designed as the wing's filler. During its shape recovery process, SMP composite stuffed in the wing helps to form an aerofoil for the wing and withstand the aerodynamic loads, leading to the compressed aerofoil recovering its original shape. To demonstrate the feasibility and the controllability of the designed deployable morphing wing, primary tests are also conducted, including the deploying speed of the morphing wing and SMP filler as the main testing aspects. Finally, Wing's deformation under the air loads is also analyzed by using the finite element method to validate the flight stability.

It has been the focus to develop low shrinkage dental composite resins in recent ten years. A major difficulty in developing low shrinkage dental materials is their deficiency in mechanical properties to clinical use. This paper reviews the present investigations of low shrinkage dental composite resins and attempts to develop a novel system with multifunctional POSS incorporated. In this paper, it is especially interesting to evaluate the influences of shrinkage with different weight percentage of POSS (0~15wt%) incorporated in dental composite resins. Their double bond conversions are evaluated and their microstructures are characterized with Fourier-transform infra-red spectroscopy and X-ray diffraction. Their mechanical properties are also presented in this paper. The results show that the shrinkage of nanocomposites with POSS can be reduced effectively from 3.53% to 2.18%. The mechanical properties of this novel system, such as strength, hardness and toughness, are also enhanced greatly. Especially with 2wt%POSS incorporated, the best integrative improved effects are revealed. The mechanism of shrinkage is discussed.

Dielectric elastomers (DE) are one of the important electroactive polymers used as actuators in adaptive structures due to their outstanding abilities to generate very large deformations while subjected to an external electric filed. In this paper, Mooney-Rivlin elastic strain energy function with two material constants is applied to analyze the electromechanical stability performance of DE. This elastic strain energy couplied with the electric energy incorporating linear permittivity is the main item to construct the free energy of the system. Particular numerical results are also processing for further understanding of DE's typical stability performance. The proposed model offers great help in guiding the design and fabrication of actuators featuring DE.

The dielectric elastomer film will encounter electrical breaking-down frequently in its working state due to the coupling effect of electric field and mechanical force field. Referring to the electromechanical coupling system stability theory of dielectric elastomer proposed by Suo and Zhao, the electromechanical stability analysis of dielectric elastomer has been investigated. The free energy function of dielectric elastomer can be represented by the principle of superposition based on Suo's theory. Unstable domain of electromechanical coupling system of Neo-Hookean type silicone was analyzed by R. Diaz-Calleja et al. In the current work, the elastic strain energy function with two material constants was used to analyze the stable domain of electromechanical coupling system of Mooney-Rivlin type silicone, and the results seem to support R. Diaz-Calleja's theory. These results provide useful guidelines for the design and fabrication of actuators based on dielectric elastomer.

A new concept of a morphing wing based on shape memory polymer (SMP) and its reinforced composites is proposed in this paper. SMP used in this study is a thermoset styrene-based resin in contrast to normal thermoplastic SMP. During heating, the wing curled on the aircraft can be deployed, providing main lift for a morphing aircraft to realize the stable flight. Aerodynamic characteristics of the deployed morphing wing are calculated by using CFD software. The static deformation of the wing under the air loads is also analyzed by using the finite element method. The results show that the used SMP material can provide enough strength and stiffness for the application. Finally, preliminary testing is conducted to investigate the recovery performances of SMP and its reinforced composites. During the test, the deployment and the wind-resistant ability of the morphing wing are dramatically improved by adding reinforced phase to the SMP.

Dielectric elastomers (DEs) are one particular type of electroactive polymers. The excellent features of merit possessed by dielectric elastomers make them the most performing materials which can be applied in many domains: biomimetics, aerospace, mechanics, medicals, etc. In order to maximize actuator performance, the dielectric elastomer actuators should have a high dielectric constant and high dielectric breakdown strength. In this paper, multi-walled carbon nanotube (MWNT) is used to develop a particulate composite based on silicone elastomer matrix, with dielectric permittivity improved. And the composite is designed to a new configuration of dielectric elastomer actuator to show electrically activated linear contractions. Prototype samples of this folded actuator, along with the fabrication and analysis is discussed here.

We studied a typical failure model of a Mooney-Rivlin–type silicone energy harvester, illustrated the allowable area under equal-biaxial and unequal-biaxial conditions, calculated the energy generated in one cycle of an energy harvester, designed a new harvester, and conducted its primary tests. When the ratio between principal planar stretches p=1 (λ2=pλ1) and the material constant ratio k=0.1 (C2=kC1), the energy density generated by the harvester is 6.81 J/g. We think that these results can be used to facilitate the design and manufacture of dielectric elastomer energy harvesters.

Dielectric elastomers are one of the important electroactive polymers used as actuators in adaptive structures due to their outstanding ability to generate very large deformations when subjected to an external electric field. In this paper, the Mooney–Rivlin elastic strain energy function with two material constants is used to analyze the electromechanical stability performance of a dielectric elastomer. This elastic strain energy together with the electric energy incorporating linear permittivity are the main items to construct the free energy of the system. Particular numerical results are also calculated for a further understanding of the dielectric elastomer's typical stability performance. The proposed model offers great help in guiding the design and fabrication of actuators featuring dielectric elastomers.

We would like to thank Diaz-Calleja et al. [Appl. Phys. Lett.93, 101902 (Year: 2008)] for their insight and help on “On electromechanical stability of dielectric elastomers;” unstable domain of electromechanical coupling system of neo-Hookean-type silicone was analyzed by Diaz-Calleja et al. Different from that given in the paper of Diaz-Calleja, in the current work, the elastic strain energy function with two material constants was used to analyze the stable domain of electromechanical coupling system of Mooney–Rivlin-type silicone, and the results seem to support the theory of Diaz-Calleja.