Effect Of Neutron Irradiation Research Articles

ATF Claddings after High-Temperature Steam Oxidation: WDS and Nanoindentation Studies to Characterize in-depth Material Changes

After the Fukushima accident in 2011 year, ATF nuclear fuel cladding concept was accelerated to achieve the reactor operation with the new accident tolerant structural materials. However, several designed solutions do not fulfil the accident tolerant concept but particularly increase the corrosion resistance of Zr-cladding tubes at normal operating conditions, so-called “Advaced Technology Fuel, EATF”. Cr-coated zirconium claddings following the first concept, have been the widely tested and the first full Cr-coated fuel rods have been planned to operate in LWR reactor conditions around the 2022 year. Our contribution describes the Cr-coated Zr-%1Nb cladding tube microstructure after high-temperature steam oxidation at 1200°C by means of Scanning Electron Microscopy and nanoindenta-tion methods. The article is focused on WDS line-profile studies of oxygen and chromium diffusion into the Zr-matrix. The increased Cr-diffusion with oxygen is evident causing a change in local me-chanical properties which is well-described by measurements of nanohardness and Young's modulus. In addition, the developed methodology of the WDS & nanoindentation line-analyses was also opti-mized to apply in hot-cell conditions to measure the effect of neutron-irradiation on the different coat-ings and coating/matrix interface.

Study of the Neutron Radiation Effect on Bi-oriented Polyethylene Naphthalate Structure

Study of the Neutron Radiation Effect on Bi-oriented Polyethylene Naphthalate Structure

Effect of neutron irradiation on structure and decomposition of α-RDX: A ReaxFF molecular dynamics study

Classical molecular dynamics simulations have been performed to study the neutron irradiation effect on structure and thermal decomposition of α-RDX. Whole simulation is divided into two independent processes. One is the modeling process of neutron irradiated α-RDX. Appropriate PKA with different kinetic energies are selected to impact on the appropriate supercell of α-RDX to simulate the process of neutron irradiation. Results show the long-range order of the structure is almost unchanged, but the local structure is destroyed, and the whole explosive has not reacted. The other is the thermal decomposition process. RDF of thermally decomposed α-RDX irradiated by neutron with different energies are calculated, and the population of some typical fragments as time evolution for the α-RDX with and without neutron irradiation was studied. Results show that neutron irradiation almost has no effect on types of the decomposition products, but affects the number of products and reaction rate.

The Influence of Neutron and Gamma Radiation Fields on Gas-Filled Surge Arresters

Abstract The study examines the effect of neutron and gamma radiation on commercial gas surge arresters. The research is of experimental-theoretical nature. The experimental part of the research was performed un-der well-controlled laboratory conditions. The combined measurement uncertainty was about 5%. The experimental system is specially designed for the observed problem and has certain original solutions. The test procedure was fully automated and had software support in the experiment management and also for data collection and statistical processing. The obtained results show that neutron and gamma ra-diation improves the functional characteristics of gas surge arresters with a memory effect. The obtained results are explained in accordance with the theory of interaction of neutron and gamma fields with ma-terial and with the theory of electric discharge in gases. The results presented in this study are important for the design of surge protection in systems that can be found in the field of neutron and gamma radia-tion because they can achieve a positive synergistic effect of protection in hybrid schemes with other components for surge protection whose characteristics spoil this radiation.

Surface modification of ET-10 graphite by helium irradiation and preoxidation: Morphology, microstructure and chemical states

The synergistic effect of neutron irradiation and oxidising impurities inside reactors has a considerable influence on the modification and performance of nuclear graphite. We investigated the modification of the surface morphology, structure and functional groups of preoxidised ET-10 graphite by He+ beam irradiation. A distinct lamellar structure after high-temperature preoxidation indicates the depletion of the binders. Raman parameters |q−1| and ID1/(ID1+ID2) were calculated to reflect the variation in defect and crystallite size, and the crystallite size (La) of ET-10 graphite was reduced from 12.66 nm to 1.4 nm after irradiation. The high-temperature oxidation, on the one hand, increased La by the annealing recovery of defects; on the other hand, led to faster surface oxidation, destroying crystals and reducing La. Furthermore, changes in the electronic structure and elemental composition were qualitatively and quantitatively measured by X-ray photoelectron spectroscopy. The irradiation reduction occurred mainly at 5 × 1014 He+/cm2, where the ratio of O-containing groups was restored from the unirradiated 47% to 27%, which was close to the level of the graphite matrix. Lastly, while previous researches suggest that nuclear stopping power has a similar effect. The irradiation reduction is found to be related the energy transferred by the electron interaction combined with SRIM simulations.

Probabilistic failure assessment of an irradiated DEMO breeding blanket component under ferromagnetic loads: Impacts of material data scattering and uncertainty in local stress intensities

The most significant technical challenge in developing structural materials for in-vessel components in the Demonstration Power Plant (DEMO) fusion reactor is to qualify the lifetime of material to guarantee the lifetime of components. The qualification needs to be conducted theoretically rather than empirically because it is conducted based on the knowledge and data acquired in fission neutron irradiation experiments and various simulation irradiation experiments rather than in experiments performed in the actual fusion environment. Such experiments will not be achievable until the DEMO fusion reactor becomes operational. Consequently, various uncertainties are expected in irradiation data and loading conditions.The probabilistic approach, where the probability of failure is calculated based on the probability density function of postulated load distribution and material property distribution, is one path to mitigate such uncertainties. In this approach, those probabilities constitute the subjective probability based on the theoretical understanding of fusion neutron irradiation effects on materials to maximize the confidence in the estimated value.A case study of the Japanese DEMO breeding blanket is the basis for the discussion of the technical issues involved in the probabilistic approach. The breeding blanket design was simplified, the failure probability was estimated, and the impact of electromagnetic force on ferromagnetic material caused by a strong magnetic field induced by toroidal field coils was considered. The discussion of the impact of the irradiation damage is based on the irradiation data for F82H reduced-activation ferritic/martensitic steel. A direction for the development of fusion structural materials is suggested in terms of design technology and the statistical quality of the irradiation database.

Deformation dynamics of a neutron-irradiated aluminum alloy: An in situ synchrotron tomography study

To reveal the effects of long-term neutron irradiation on the mechanical behavior of nuclear materials, in situ quasi-static uniaxial tensile tests are conducted on an LT21 aluminum (Al) alloy from a decommissioned research reactor. Scanning/Transmission electron microscopy (SEM/TEM), and micro CT are first applied to characterize the microstructures of LT21 Al alloys aged naturally and neutron-irradiated for 30 years. In situ synchrotron micro computed tomography (CT) is adopted to characterize the deformation and damage dynamics of this LT21 Al. A new particle tracking analysis technique is proposed to quantify the displacement/strain fields and microstructural evolution (e.g., particle movement and pore growth) in the irradiated sample. Long-term irradiation induces considerable microstructural changes in the LT21 Al alloy, including the precipitation/aggregation of micron-sized Si particles and nanoscale Mg2Si particles. In addition, the size of pores and particles in the irradiated material appear considerably larger than that in the unirradiated material. During tension, the alloy undergoes elastic-plastic deformation followed by shear-dominated necking failure. The porosity and pore size exhibits an overall increase with increasing loading. Formation of new pores occurs in two modes, formation at the particle-matrix interfaces and random formation across the sample. For mode one, pores tend to nucleate at the top and bottom ends of a particle (relative to the loading direction). Formation of new pores and growth of initial and newly-nucleated pores occur simultaneously and contributes approximately equally to damage accumulation in the irradiated LT21 Al alloy before necking occurs. The deformation dynamics deepens our understanding of the aging of nuclear materials.

A peridynamic elasto-plastic damage model for ion-irradiated materials

This study presents the novel peridynamic constitutive relations formulated in order to predict the plastic deformation and damage evolution in irradiated materials. The plastic behaviour of the material in which radiation induced defects contribute to the defined peridynamic porosity is described by the Gurson–Tvergaard–Needleman (GTN) yield criterion with irradiation hardening. The definition of peridynamic porosity is proposed as a volume of discontinuities created in the volume of peridynamic particles. The new constitutive relations for irradiation hardening based on the dilatational part of elastic strain energy are formulated. The physical relevance of coupling the porosity with the nonlinear irradiation hardening is discussed. The expressions for the yield function, kinetics of evolution of radiation induced porosity, irradiation hardening and plastic flow rule are derived in terms of the peridynamics variables. The peridynamic predictions are calibrated based on the experimental data obtained during the advanced experimental campaigns dedicated to irradiated materials to verify the validity of the proposed constitutive model. Ion irradiation campaigns were carried out to mimic the effects of neutron irradiation. A series of indentation experiments were conducted to elucidate the effects of material structure modification and assess the hardening effect originating from radiation defects.

Combined Effect of Neutron Radiation and Curcumin on Breast Cancer Cells Cytotoxicity in 3D Culture Medium

Introduction: Chemotherapy, biotherapy, and radiotherapy play a limited but important role in treating breast cancer. For more efficient treatment, combination therapy could be an appropriate option. In this study, radiotherapy using neutron radiation emitted from a 241Am-Be neutron source, as well as biotherapy using curcumin (80 μM) was combined to investigate the efficiency of treatment towards MCF-7 breast cancer in a three dimensional (3D) culture medium. Methods: MTT, neutral red uptake assay, nitric oxide, glutathione assay, catalase, cytochrome c, comet assay, and caspase-3 were used to determine the effect of neutron radiation and also neutron and curcumin combination on the viability of cancer cells. Results: The results of cytotoxicity test showed that neutron irradiation with or without curcumin at 5, 10, 15, and 20 h reduced the survival of tumor cells. Moreover, the rate of apoptosis due to the neutron effect at different irradiation times enhanced with the increasing time. Conclusion: Due to the significant anticancer effect of curcumin in 3D culture, using this molecule before or after neutron therapy is recommended.

Diagnostic Technique Characterizing Neutron Irradiation Effects on Additively Manufactured Inconel 625 Eliminating the Need for Remote Handling

Experimentally characterizing radioactive materials can be time consuming and expensive. This is mainly due to the size requirements of inspected specimens. Due to the growing interest in using additively manufactured components in next-generation reactors, there is an urgent need to develop new accelerated testing techniques with regard to characterizing radiation damage. This will ensure a more timely certification of the unique material structures inherent to additively manufactured parts. In this study, we investigate a means to reduce the time investment, and thus the human exposure to radioactive specimens in need of experimental characterization. We determine the feasibility of using ultra-small specimens in lieu of much larger specimens to characterize bulk material properties before and after irradiation. Experiments were conducted to investigate this technique and compare it to conventional bulk irradiations and characterization activities. It was found that discernable radiation damage existed in the ultra-small specimens even after relatively short neutron irradiation times. The results also demonstrate decreased radiation hardening in additive manufactured Inconel 625 material relative to its wrought forms.

Effect of dose rate on dislocation loop evolution in tungsten: Combination of defect generation rate and elastic interaction

Ion irradiation is often used to simulate neutron irradiation in reactor components, while the dose rate discrepancy makes it difficult to directly compare ion irradiation with neutron irradiation. A better understanding of dose rate effect is thus necessary to emulate neutron irradiation effect with ions. Here, based on in-situ 30 keV He+ irradiation in tungsten in TEM, we find that defect generation rate and elastic interaction are two key factors controlling dislocation loop evolution at different dose rates. By adjusting defect generation rate, the elastic interaction between the loops will play different roles. Finally, a schematical illustration is given to explain the different in loop density, size and spatial distribution caused by the combination of these two factors. Our results provide the underlying insights for understanding the dose rate effects of energetic ion irradiation.

Investigation on effect of neutron irradiation on welding residual stresses in core shroud of pressurized water reactor

This paper presents the results of investigating the change in welding residual stresses of the core shroud, which is one of subcomponents in reactor vessel internals, performing finite element analysis. First, the welding residual stresses of the core shroud were calculated by applying the heat conduction based lumped pass technique and finite element elastic-plastic stress analysis. Second, the temperature distribution of the core shroud during the normal operation was calculated by performing finite element temperature analysis considering gamma heating. Third, through the finite element viscoelastic-plastic stress analysis using the calculated temperature distribution and setting the calculated residual stresses as the initial stress state, the variation of the welding residual stresses was derived according to repeating the normal operation. In the viscoelastic-plastic stress analysis, the effects of neutron irradiation on mechanical properties during the cyclic normal operations were considered by using the previously developed user subroutines for the irradiation agings such as irradiation hardening/embrittlement, irradiation-induced creep, and void swelling. Finally, the effect of neutron irradiation on the welding residual stresses was analysed for each irradiation aging. As a result, it is found that as the normal operation is repeated, the welding residual stresses decrease and show insignificant magnitudes after the 10th refueling cycle. In addition, the irradiation-induced creep/void swelling has significant mitigation effect on the residual stresses whereas the irradiation hardening/embrittlement has no effect on those.

First-principle study of neutron irradiation induced performance degradation of amorphous porous silica.

Neutron irradiation induced degradation of porous silica film is studied by Molecular Dynamics and Density-Functional theory-based methods. The degradation of microscopic structure, thermal property, and optical property of porous silica film are systematically investigated. Low-energy recoil is used to simulate the neutron irradiation effect. The pair and bond angle distributions, and coordination number distributions reveal that, under neutron irradiation, the microscopic structure of porous silica film is obviously modified, and the coordination defects are induced. We find that the higher recoil energy, the more coordination defects are formed in the film. The increased defects lead to a decrease in thermal conductivity. In addition, neutron irradiation induces additional optical absorption peaks in UV region and increasement in refractive index, resulting in a noticeable reduction in light transmittance. The detailed calculation of density of states reveals that these optical absorption peaks originate from the irradiation induced defect states in band gap. Our work shows that low-energy neutron irradiation can induce obvious defect density and degrade thermal and optical properties of porous silica film, which are responsible for subsequent laser-induced damage.

Neutron irradiation effect on amorphous porous silica

AbstractPorous silica is widely used as antireflection films in inertial confinement fusion facilities and be irradiated by high fluence neutron. To date, the neutron irradiation effect of amorphous porous silica is still unclear. In this paper, we give a comprehensive insight into neutron irradiation effect on microstructure, mechanical, and optical properties of porous silica under 14 MeV neutron irradiation by using molecular dynamics and density‐functional theory‐based methods. We find that, for microstructure, neutron irradiation elongates Si–O bond distance, obviously reduces the max value of Si–O–Si bond angle, coordination number distribution, and increases Si3+ and non‐bridging oxygen defects. The bulk modulus, shear modulus, and Young's modulus are all obviously reduced due to neutron irradiation, but Poisson's ratio changes relatively small. The light transmittance is reduced, and the optical absorption coefficient is increased after neutron irradiation, especially in the photon energy range of 3–4 eV, which is detrimental to the resistance of laser‐induced damage. Moreover, we find that neutron irradiation has more influence on high‐porosity porous silica than low‐porosity porous silica, which is mainly due to the higher defect percentage in high porosity. Present work is expected to be valuable in the study of degradation mechanism of nuclear material under neutron radiation.

Engineering design of the CFETR machine

The China Fusion Engineering Test Reactor (CFETR) is the next step in China's roadmap for magnetic confinement fusion development. It aims to bridge the gap between the ITER fusion experimental reactor and the demonstration fusion power reactor (DEMO). The CFETR will be operated in two phases. Phase I aims to achieve fusion power of 50–200 MW, Qplasma = 1–5, TBR > 1.0 and neutron irradiation effects ∼ 10 dpa. Phase II aims to perform tokamak DEMO validation under fusion power > 1 GW, neutron irradiation effects ∼ 50 dpa and figQplasma > 10. To ensure that the CFETR machine can achieve these goals, the major/minor radii of plasma have been altered from R = 5.7 m/a = 1.6 m to R = 7.2 m/a = 2.2 m. The new machine can meet the targets of both Phase I and Phase II and achieve smooth transfer between them. The configuration of the CFETR machine is presented in this paper. Then, the design progress and status of some key components are described, including the magnet system, blanket system, diverter system, remote handling system, vacuum vessel, thermal shield and cryostat. The research and development of most components are underway and will be demonstrated in the near future.

Effects of neutron irradiation and post-irradiation annealing on pop-in crack propagation instabilities in 6061 aluminium alloy

This study analyses the increase of crack propagations instabilities (pop-in) with irradiation during fracture toughness testing of aluminium alloy 6061 alloy after neutron irradiation. The aim is to identify if the crack propagation instabilities are related to microstructural heterogeneities, i.e. weak zones, or if they are linked to a competition between testing machine stiffness and tearing modulus.An in-depth mechanical instability analysis was performed comparing the testing machine stiffness to the tearing moduli of the irradiated materials. For this purpose an experimental program was carried out in the hot cells facility at CEA Saclay to conduct mechanical and microstructural studies, after irradiation in a Material Testing Reactor (mean conventional thermal fluence: 6.8 × 1021 nth.conv.cm−2).The material hardening was quantified in this study using tensile tests after annealing heat treatments. The effect of this hardening on crack propagation instabilities was measured by fracture toughness tests on irradiated and precracked CT12.5 samples. Damage mechanisms were studied by scanning electron microscope fractography and classical ductile fracture micromechanisms were found for all conditions without notable differences between non irradiated and irradiated materials. The evolution of toughness with irradiation and subsequent heat treatments was therefore attributed to the matrix hardening/softening and its effect on nucleation of voids on brittle second phase particles.To investigate experimentally if the crack propagation instabilities were related to the tearing moduli, annealing heat treatments of the irradiated material were applied that softened the material. It was shown that with softening, the number of crack propagation instabilities decreased and eventually the pop-ins disappeared. The instability criteria using J-Δa R-curves of the toughness tests were applied and it was concluded that the increase in pop-ins with irradiation resulted from the decrease of the material tearing modulus and its interaction with the machine stiffness.The toughness test results of the irradiated material of the present study were compared with those of the literature and show very good agreement.

Radiation hardness of Hamamatsu H12700/H8500 MAPMTs, entrance glass windows, and p-terphenyl wavelength shifting coating under neutron and [formula omitted]Co gamma irradiation

Photomultiplier tubes, in particular multianode photomultiplier tubes, are often used in current accelerator-based nuclear and particle physics experiments for spatially resolved detection of single photons. With increasing luminosity and harsh radiation background, the radiation hardness of these sensors plays an increasingly important role. In an extensive experimental study we have investigated the effects of neutron irradiation, using a fission neutron source, and energetic 60Co γ-irradiation on commercially available Hamamatsu H12700/H8500 MAPMTs. In addition, individual components were irradiated, such as their glass windows and voltage dividers. Additionally, a p-terphenyl based wavelength shifting coating, which can be applied on the MAPMT window to enhance the photon yield, was also tested for its radiation tolerance.

Assessment of Radiation Effects on Attitude Estimation Processing for Autonomous Things

This article investigates and assesses neutron radiation effects on attitude estimation (AE) processing, typically embedded in inertial navigation systems (INSs) and upcoming autonomous things. Findings highlight the importance of radiation-induced critical failures that can upset the on-board AE processing and consequently the inertial navigation. Radiation tests and analyses were conducted by considering as on-board AE processing the execution of classical AE algorithm on multi-core computer hardware exposed to 14-MeV neutron and thermal neutron radiation. Three computing strategies and different case-study scenarios were tested and compared. Results suggest that the contribution of radiation-induced soft errors to be mitigated on the embedded AE processing is essentially related to single-event functional interrupts (SEFIs) that can lead the inertial navigation to critical failures.

Development of irradiation tolerant tungsten alloys for high temperature nuclear applications

Development of refractory metals for application as plasma-facing armour material remains among priorities of fusion research programmes in Europe, China and Japan. Improving the resistance to high temperature recrystallization, enhancing material strength to sustain thermal fatigue cracking and tolerance to neutron irradiation are the key indicators used for the down selection of materials and manufacturing processes to be applied to deliver engineering materials. In this work we investigate the effect of neutron irradiation on mechanical properties and microstructure of several tungsten grades recently developed. Neutron irradiation campaign is arranged for screening purposes and therefore is limited to the fluence relevant for the ITER plasma facing components. At the same time, the neutron exposure covers a large span of irradiation temperatures from 600 up to 1000 °C. Four different grades are included in the study, namely: fine-grain tungsten strengthened by W-carbide (W–4wt.% W2C), fine-grain tungsten strengthened by Zr carbides (W–0.5% ZrC), W alloyed with 10 at.% chromium and 0.5 at.% yttrium (W–10Cr–0.5Y) and technologically pure W plate manufactured according to the ITER specification by Plansee (Austria). The strengthening by W2C and ZrC particles leads to an enhanced strength, moreover, the W–0.5ZrC material exhibits reduced DBTT (compared to ITER specification grade) and is available in the form of thick plate (i.e. high up-scaling potential). The W–10Cr–0.5Y grade is included as the material offering the self-passivation protection against the high temperature oxidation.

BURNUP AND RADIATION EMBRITTLEMENT OF THE U-MO NEUTRON SOURCE TARGET

The burnup of uranium target plates of the NSC KIPT neutron source was studied. An analysis of experimental work on the effect of neutron irradiation on the strength and plastic properties of uranium and U-Mo alloys under conditions close to the operation of the target has been carried out. A description of the processes of radiation embrittlement is presented, taking into account the deformation and porosity of materials at various levels of burnup. An estimate of the expected service life of a uranium target under irradiation has been carried out.