Thermal Column Research Articles

Measurements of neutron capture cross-section for nuclides of interest in decommissioning (II): 58Fe(n,γ)59Fe

ABSTRACT As nuclear facilities are dismantled in decommissioning, large amounts of various waste are generated. Even more inconveniently, such waste is radioactive due to neutron activation. Thus, the neutron capture cross-sections of nuclides targeted in decommissioning are required to evaluate the radioactivity produced. In this work, 58Fe nuclide was selected among objective nuclides for decommissioning, and its thermal-neutron capture cross-section was measured by a neutron activation method at the graphite thermal column of Kyoto University Research Reactor in 5-MW operation. The thermal-neutron capture cross-section was derived using Westcott’s convention. The present work obtained 1.36 ± 0.03 barns for the58Fe(n,γ)59Fe reaction. The present result supports the JENDL-5 evaluation within 2σ. If updated with currently recommended nuclear data, some of the reported past data would support the present result.

External Moderation of Reactor Core Neutrons for Optimized Production of Ultra-Cold Neutrons

The ultra-cold neutron (UCN) source being commissioned at North Carolina State University’s PULSTAR reactor is uniquely optimized for UCN production in the former graphite-filled thermal column outside of the reactor pool. The source utilizes a remote moderation design, which is particularly well suited to the PULSTAR reactor because of its high thermal and epithermal neutron leakage from the core face. This large non-equilibrium flux from the core is efficiently transported to the UCN source through the specially designed beam port in order to optimize UCN production at any given reactor power. The increased distance to the source from the core also greatly limits the heat load on the cryogenic system. A MCNP (Monte Carlo N-Particle) model of this system was developed and is in good agreement with gold foil activation measurements using a test configuration as well as with the real UCN source’s heavy water moderator. These results established a firm baseline for estimates of the cold neutron flux available for UCN production and prove that remote moderation in a thermal column port is a valuable option for future designs of cryogenic UCN sources.

Determination of the elemental composition and changes in thermal and electrical conductivity of “Hanford” and low-ash medium-grained graphite’s grade graphites depending on the fast neutrons fluence

Studying the properties of graphite recovered from operating nuclear reactors is vital for predicting the properties and integrity of graphite as part of assessing the continued operation and life extension of nuclear reactors. The purpose of the study is to determine the electrical conductivity and thermal conductivity of low-ash medium-grained graphite’s grade graphite in the thermal column masonry of the VVR-SM research reactor in the measurement temperature range corresponding to the conditions of normal operation of the reactor to determine the service life. In this work, the change in thermal conductivity and electrical conductivity of GMZ graphite was studied, as well as for comparison of Hanford grade graphite depending on the fluence of fast neutrons and the measurement temperature. The dependence of electrical conductivity and thermal conductivity on dose and temperature has been established. It has been shown that the greater the neutron fluence, the more both the thermal conductivity and electrical conductivity of the material decreases. The service life of the thermal column has been determined.

Objects May Be Closer than They Appear: Significant Host Galaxy Dispersion Measures of Fast Radio Bursts in Zoom-in Simulations

We investigate the contribution of host galaxies to the overall dispersion measures (DMs) for fast radio bursts (FRBs) using the Feedback in Realistic Environments (FIRE-2) cosmological zoom-in simulation suite. We calculate DMs from every star particle in the simulated L* galaxies by ray-tracing through their multiphase interstellar medium, summing the line-of-sight free thermal electron column for all gas elements within ±20 kpc of the galactic midplane. At z = 0, we find average (median) host-galaxy DMs of 74 (43) and 210 (94) pc cm−3 for older (≳10 Myr) and younger (≲10 Myr) stellar populations, respectively. Inclination raises the median DM measured for older populations (≳10 Myr) in the simulations by a factor of ∼2 but generally does not affect the younger stars deeply embedded in H ii regions except in extreme edge-on cases (inclination ≳85°). In kinematically disturbed snapshots (z = 1 in FIRE), the average (median) host-galaxy DMs are higher: 80 (107) and 266 (795) pc cm−3 for older (≳10 Myr) and younger (≲10 Myr) stellar populations, respectively. FIRE galaxies tend to have higher DM values than cosmological simulations such as IllustrisTNG, with larger tails in their distributions to high DMs. As a result, FRB host galaxies may be closer (lower redshift) than previously inferred. Furthermore, constraining host-galaxy DM distributions may help significantly constrain FRB progenitor models.

Simulation of Boron Dose and Irradiation Time in Lung Cancer Treatment with Boron Neutron Capture Therapy (BNCT) Using MCNP-6

<p>Boron Neutron Capture Therapy (BNCT) is a cancer radiation treatment. This approach employs a boron carrier agent in the form of a chemical that is injected into the body and then travels to the cancer cells. In a lung cancer case study, BNCT treatment simulation was carried out using Monte Carlo N Particle (MCNP) software version 6.2. The goal of this study was to determine the most effective boron concentration and irradiation duration in lung cancer therapy utilizing the BNCT method. The geometry based on a phantom model created by Oak Ridge National Laboratory (ORNL). The simulated cancer geometry, which is placed in the right lung's middle lobe. The skin, ribs, and right lung are among the organs at risk. The skin, ribs, and right lung are among the organs at risk. The neutron source for the simulation is the collimator output from the Kartini Nuclear Reactor's thermal column. In this simulation, the variations in boron concentrations were 40 g/g, 45 g/g, 50 g/g, 55 g/g, and 60 g/g of cancer tissue at 5 g/g intervals. The researchers discovered a link between boron injection concentration and irradiation time, with higher boron injection concentrations resulting in shorter irradiation times. The volume of boron injected determines the effective dose absorbed by healthy tissue surrounding cancer cells. The effective boron concentration for lung cancer therapy is 60 g/g, with deterministic cell killing in the rib marrow and right lung. When utilizing a boron concentration of 60 g/g, the irradiation time is 20.4 minutes. Boron concentrations of 60 g/g are projected to create an effective irradiation time for BNCT-based lung cancer therapy based on the ALARA principle due to their shorter duration when compared to other concentration variations.</p>

Design and simulation of neutron radiography system for an aqueous homogeneous solution reactor

AHR reactors are known for the production of radiopharmaceuticals. The ARGUS reactor is one of the most famous of these reactors, which has been designed originally for radioisotopes production. The ARGUS reactor produces a suitable neutron flux that can be used for other applications such as neutron radiography (NR). Here, a NR system is designed step by step using the Monte Carlo method. The length of the collimator, divergence angle, diameter of the aperture, and thermal column dimension are designed. The designed aperture and thermal column are selected from boron carbide and heavy water, respectively. The depth of the thermal column is changed until the ratio of thermal neutrons to total neutrons (TNC) reached above 90%. The hole inside the thermal column is designed and internal lining is done. The inner lining is made of cadmium and had a thickness of 1 mm, and the space between the inner and outer lining is filled with lead. To reduce the gamma dose to acceptable values, the position of the collimator is changed instead of using a gamma filter. By changing the depth of the hole and creating the convergence angle to the hole, the flux of thermal neutrons will be 1.8E+6 n.cm−2s−1 that satisfy the IAEA suggested values for NR. Then, the uniformity of the radiation field of the neutron flux output from the collimator is obtained. At the end, images of SI and BPI standards are recorded. The good quality and contrast of these images showed the acceptable design of the NR system for the ARGUS reactor.

Experimental study and numerical simulation of a structural concrete column for building heating integration and energy storage

A steel pipe assemblage is integrated into a structurally reinforced precast concrete column to demonstrate thermal energy storage (TES) and space heating capabilities. This thermal energy column is heated via hot water at varying flow conditions. The system is used as a thermal storage medium, as a means of reducing the demands on the building heat pump, and for regulating the thermal comfort of the building interior environment. The thermal performance of the energy column is examined experimentally and numerically in both charging and discharging phases. Two examples are used to demonstrate the improvements in the operation of building thermal equipment and in the building thermal environment offered by either passive or active discharging of the energy column. Following the conclusion of thermal evaluation, the structural performance of the column under axial compression was evaluated by loading the system to failure. The experiment was paused for visual observation at both the service level and nominal capacity milestones. The longitudinally embedded steel pipes developed comparable strains to the column longitudinal steel reinforcing bars. The structural capacity of the energy column can be accurately predicted using standard concrete design approaches that account for the mechanical influence of the embedded steel pipe assemblage. It is demonstrated that the developed concrete energy column provides a viable option for improving the building thermal energy efficiency and maintaining structural performance.

Design and Construction of Radio-Controlled Glider with Renewable Energy Capabilities

Thermal columns are a meteorological phenomenon which is frequently used by birds to rise without requiring wing power. Imitating this behaviour with an aircraft can utilize this lift to provide energy for the electrical components of the system. In this study, a radio-controlled glider with a built-in wind turbine and generator was designed and constructed. The generator is intended to provide renewable energy during glides, especially when thermal columns are harnessed. The glider was constructed using composite materials, which combine a high level of strength together with light-weight, improving energy efficiency. Turbine design was implemented using a duct-fan model which increases air flow to the generator. Test flight measurements indicate efficient battery recharging can be obtained during glides. The system may be implemented in manned or unmanned gliders, for agricultural, civil, or security uses, such as unmanned surveillance airplanes.

Thermal switch for localized heating based on spatial electric field distribution regulation

At present, the thermal switch for localized heating is becoming a hot research topic in MEMS packaging technology. A method of using a liquid-based thermal switch is proposed in this paper. A plate local heating device based on electric field distribution control is constructed, where a thermal liquid column can be formed under the action of the electric field. The electric field controls the formation and dissipation of the liquid column to realize the on-off and off-on function of the thermal switch. Through the control of the different conductive substrates in the plate, the localized heat transfer can be further realized, and the heat transfer position is precisely regulated. Furthermore, due to the fluidity of the liquid, the prepared thermal switch can also realize movable heating. The experimental results show that the heating time and speed can be controlled precisely by adjusting the driven voltage and the conductive area of the upper substrate.

Thermal neutron capture cross-section and resonance integral measurements of 186W(n,γ)187W reaction using the thermal column neutron source at the Dalat research reactor

The thermal neutron radiative capture cross-section (σ0) and the resonance integral (I0) of the reaction 186W(n,γ)187W were measured by the thin foil activation method using the well thermalized neutron source at the graphite thermal column facility of the Dalat research reactor. The activities of the irradiated target and monitor samples were measured using a high resolution HPGe gamma-ray spectrometer. The recent updated values of gamma-rays intensities and decay half-life of the 187W nucleus were applied in this experiment to substantially improve the cross-section results compared to the previous measurements. The thermal neutron capture cross- section and the resonance integral of the 186W(n,γ)187W reaction were determined relative to the standard reaction 197Au(n,γ)198Au. The values obtained are 31.76 ± 0.63 and 429.2 ± 25.6 barns for σ0 and I0 respectively. Our results and previous measured values are compared, and discrepancies are discussed.

An experimental investigation into the conversion of nuclear graphite by oxygen and carbon dioxide: Kinetics and change in pore structure

The study on the thermochemical conversion of release-measured nuclear-grade graphite recovered from the thermal column of a shut-down nuclear research reactor focuses on kinetic processes of gasification and oxidation of this graphite. More specifically, the kinetic parameters were determined and the evolution of the graphite structure during carbon conversion was investigated. For oxidation, the three conversion regimes of heterogeneous reactions in the temperature range of 500 °C to 950 °C were observed. The activation energy is approx. 288 kJ/mol in the kinetic regime limited by the chemical reaction (Regime I), approx. 185 kJ/mol in the pore diffusion regime (Regime II) and approx. 10 kJ/mol in the mass transfer regime (Regime III). With an increase of the partial pressure of oxygen, an increase of the pre-exponential factor in Regime I from 6.6 × 1012 1/s at 0.2 bar to 1.8 × 1013 1/s at 0.5 bar and to 2.0 × 1013 at 0.8 bar of oxygen was determined. A similar effect was observed in Regime II. A reaction order of 0.96 ± 0.16 was obtained for the oxidation reaction. In case of CO2 gasification at temperatures of 900 °C to 1400 °C, two regimes were identified. In Regime I, an activation energy of approx. 294 kJ/mol and a pre-exponential factor of 3.5 × 107 1/s were determined, the corresponding parameters being approx. 156 kJ/mol and 8.3 × 102 1/s for Regime II, respectively. Similar activation energy values for both oxidation and gasification reactions indicate that the structure of the nuclear graphite remains stable with proceeding carbon conversion. From the analysis of the development of the inner surface area and particle size distribution at increasing conversion rates, it can be concluded that the gasification of nuclear graphite mainly takes place on the outer surface. Using the ETV-ICP-OES analysis, it was found that the trace elements, Ca, Fe, S, V and Zn, were evaporated and no longer detectable in partially gasified nuclear graphite, whereas elements such as Ba, Cr or Mn are being accumulated in the solid residue.

Design of an out-of-tank neutron beam line for prompt gamma neutron activation analysis at low-power Miniature Neutron Source Reactor

Research reactors are strong and stable neutrons sources, and various researches and applications were carried out using their neutron and gamma beamlines. Some research reactors, such as Miniature Neutron Source (MNSR) Reactors, do not have beam tube in their original design, which can be considered as a disadvantage. The design and installation of beamlines can develop their applications. In this research, the design and optimization of a suitable neutron beamline for PGNAA is done at Isfahan MNSR. Designs are done to reach the appropriate neutron beam parameters and taking into account the geometrical limitations of the MNSR. Neutron beam parameters including thermal neutron flux, thermal to total neutron flux, and thermal neutron flux to gamma dose ratio are considered. For this, vertical beamlines with different diameters are simulated and the optimal diameter is determined. Also, for optimization of beam parameters, a thermal column and gamma filter are considered and optimal conditions are determined.

Effect of thermal dynamics and column geometry of pressure swing adsorption on hydrogen production from natural gas reforming

The present study investigates hydrogen purification from a surrogate gas using spent coffee grounds as a medium. The study was conducted using Aspen adsorption software, and the process was examined under isothermal, adiabatic, and non-adiabatic conditions. The surrogate gas mixture comprised 70% hydrogen and 30% carbon dioxide and was introduced into two stainless steel chambers containing the coffee media. The pressure was altered from 101.3 to 150 kPa as the chamber underwent the adsorption process. At an adsorption time of 60 s, all three conditions exhibited similar levels of purity and recovery, with the isothermal mode producing the highest values. Additionally, the effect of heat dissipation and column geometry on the adsorption performance was investigated by comparing the conventional isothermal column with the rectangular non-adiabatic plate column. The plate column is rectangular, with two chambers that use the heat generated during adsorption to regenerate the opposite column during the blowdown step. This effect was evaluated under different adsorption times of 30–180 s and hydrogen feed concentrations of 70–90%. The plate column had higher hydrogen purity and recovery of 99.99% and 77.41%, respectively, compared to 99.56 and 71.12% of the cylindrical column. Overall, the results indicate that spent coffee grounds can be effectively used as a medium to purify hydrogen from a surrogate gas mixture. A rectangular non-adiabatic plate column can further enhance the purification process by improving purity and recovery responses.

Effects of the 2018 European heatwave and drought on coastal biogeochemistry in the German Bight

In 2018, Europe experienced an unprecedented heatwave and drought, especially in central and northern Europe, which caused decreased terrestrial production and affected ecosystem health. In this study, the effects of this event on the marine environment are investigate, with a focus on the biogeochemical response in the German Bight of the North Sea. Using time series data from FerryBoxes, research cruises, monitoring programs and remote sensing we compare conditions in 2018 to climatological values. We find that (1) the heatwave caused rapid warming of surface waters, (2) the drought reduced river discharge and nutrient loads to the coast, and (3) these combined effects altered coastal biogeochemistry and productivity. During 2018, both water discharge and nutrient loads from rivers discharging into the German Bight were below the seasonally variable 10th percentile from March onward. Throughout the study domain, water temperature was near or below that threshold in March 2018, but higher than in other years during May 2018, representing not only a heat wave, but also the fastest spring warming on record. This extreme warming period saw concurrent high peaks in chlorophyll a, dissolved oxygen and pH, consistent with the development of a strong spring bloom. It appears that productivity was above 75th percentile of the 21-year record in most of the nearshore region, while offshore it was widely below the 25th percentile in 2018. The drought-related low discharge limited nutrient supply from the rivers, but likely increased water residence time nearshore, where a surge in primary production with efficient nutrient utilization during the spring depleted nutrients available for transport offshore. There, the heatwave-related rapid warming of surface water resulted in the establishment of a stable thermal water column stratification, hindering vertical nutrient supply to the surface layer during the summer.

Numerical investigation of thermo-fluid behaviour in a channel with PCM-filled columns

Microalgae has been identified as a potential source in the production of biofuel. Photobioreactors, which are used for microalgae production, normally experience temperature variations over the diurnal cycle due to changes in ambient conditions. Such temperature variations affect microalgae growth since microalgae are sensitive to these temperature variations. Hence, the thermal regulation of photobioreactors to minimize temperature variations will result in higher yield of microalgae. The present research is aimed to investigate a novel approach to thermally regulate photobioreactors using phase change materials (PCM) where the latent heat of the material is exploited as the energy storage mechanism. The present research uses a numerical approach to study the flow and thermal behaviors in a channel with a set of thermal energy storage columns placed at some offset from each other. The research aims to investigate the transient thermal response of the channel flow in the presence of these columns. Open source CFD software, OpenFOAM, is used to numerically simulate flow in a rectangular channel containing offset PCM columns. A parametric analysis to investigate the impact of various operating and geometric properties on the heat transfer to the PCM columns showed that geometric parameters such as the gap and blockage ratios, column aspect ratio, column shape and column arrangement in the channel influence thermal energy storage in PCM-filled columns.

Neutrons propagation in Lead: A feasibility study for experiments in the RSV TAPIRO fast research reactor

The increasing worldwide interest in Lead-cooled Fast Reactors (LFRs) substantiates the need to validate the analytical codes and methods used to support their design. For neutronic analyses, this is chiefly reflected in assessing the impact of nuclear data uncertainties on the integral and local parameters resulting from such analyses. The aim of refining nuclear data moves continuous efforts for more accurate measurements, be them differential or integral, for which adequate facilities are required. The availability at the ENEA's Casaccia research center of a fast source reactor – RSV TAPIRO – provides a unique opportunity to perform new integral experiments in support of fast reactors, including LFRs, owing to the well-characterized neutron spectrum of the thermal column. A series of experiments has been envisaged, dealing with the use of Lead in a reactor. The experiments concern the propagation of neutrons through blocks of materials representing relevant elements of a reactor core, and ranging from pure Lead to mixtures reproducing portions of the reflector and shield in LFRs. The paper is focused on the feasibility study of some of these experiments in which Lead and mixture blocks are inserted in the so-called thermal column of the RSV TAPIRO reactor and irradiated by the neutron flux emerging from the Copper reflector surrounding the reactor core.

Feasibility study of using the NUR research reactor for a BNCT installation and Monte Carlo optimization of a BSA

The aim of this work was devoted to study the feasibility of using the Algerian research reactor NUR for Boron Neutron Capture Therapy (BNCT) applications. To achieve this aim, an analysis of parameters and operational safety limits of the current core configuration X-1 with a removal of the thermal column was carried out. Furthermore, this study was followed by optimization calculations of the Beam Shaping Assembly (BSA) in the channel N∘5 using the Monte Carlo code MCNP5 simulations with a highlight of a new moderating material (Modified Fluental). Subsequently, a dosimetric study was performed using the MCNP5 code and the Snyder Head phantom by taking a Boron concentration of 65 ppm and 18 ppm in tumor and healthy tissue respectively. The in-phantom figures-of-merit have been calculated and provided promising results.

Modelling the interaction of the Astro Bio Cube Sat with the Van Allen’s Belt radiative field using Monte Carlo transport codes

PurposeThe AstroBio Cube Satellite (ABCS) will deploy within the inner Van Allen belt on the Vega C Maiden Flight launch opportunity of the European Space Agency. At this altitude, ABCS will experience radiation doses orders of magnitude greater than in low earth orbit, where CubeSats usually operate. The paper aims to estimate the irradiation effect on the ABCS payload in the orbital condition, their possible mitigation designing shielding solutions and performs a preliminary representativity simulation study on the ABCS irradiation with fission neutron at the TAPIRO (TAratura Pila Rapida Potenza 0) nuclear research reactor facility at ENEA.MethodsWe quantify the contributions of geomagnetically trapped particles (electron and proton), Galactic Cosmic Rays (GCR ions), Solar energetic particle within the ABCS orbit using the ESA’s SPace ENVironment information system. FLUKA (Fluktuierende Kaskade—Fluctuating Cascade) code models the ABCS interaction with the orbital source.ResultsWe found a shielding solution of the weight of 300 g constituted by subsequent layers of tungsten, resins, and aluminium that decreases on average the 20% overall dose rate relative to the shielding offered by the only satellite’s structure. Finally, simulations of neutron irradiation of the whole ABCS structure within the TAPIRO’s thermal column cavity show that a relatively short irradiation time is requested to reach the same level of 1 MeV neutron Silicon equivalent damage of the orbital source.ConclusionsThe finding deserves the planning of a future experimental approach to confirm the TAPIRO’s performance and establish an irradiation protocol for testing aerospatial electronic components.

Thermal-Neutron capture cross-section measurements of Neptunium-237 with graphite thermal column in KUR

ABSTRACT In terms of nuclear transmutation studies of minor actinides in nuclear wastes, the present work selected 237Np among them and aimed to measure the thermal-neutron capture cross-section of 237Np using a well-thermalized neutron field by a neutron activation method because there have been discrepancies among reported cross-section data. A 237Np standard solution was used for irradiation samples. The thermal-neutron flux at an irradiation position was measured with flux monitors: 45Sc, 59Co, 98Mo, 181Ta, and 197Au. The 237Np sample was irradiated together with the flux monitors for 30 minutes in the graphite thermal column equipped in the Kyoto University Research Reactor. The similar irradiation was repeated once more to confirm the reproducibility of the results. After irradiation, the 237Np samples were quantified using 312-keV gamma-ray emitted from 233Pa in radiation equilibrium with 237Np. The reaction rates of 237Np were obtained from the peak net counts of gamma-rays emitted from generated 238Np, and then the thermal-neutron capture cross-section of 237Np was found to be 173.8 ± 4.7 barn by averaging the results obtained by the two irradiations. The present result was in agreement with the reported data given by a time-of-flight method within a limit of uncertainty.

Thermal performance of cylindrical battery module with both axial and radial thermal paths: Numerical simulation and thermal resistance network analysis

In this paper, the thermal performance of a cylindrical battery module with axial-radial thermal paths is investigated by both numerical simulation and analytical thermal resistance network analysis. The 7×7 cylindrical lithium-ion batteries are arranged orthogonally in the module, with their base surface dissipating heat to the cold plate through bottom electrical insulation layer. The upper part of the battery is connected to the cold plate by the surrounding coaxial tube, thermal diffusion plate and thermal column, thus forming the cooperative cooling thermal structure in both axial and radial directions. The temperature distribution in the battery module is first analyzed by numerical modeling, and then the structural parameters are investigated including the spacing between the adjacent battery centers, the cross-sectional shape and area of thermal column, the thickness of thermal diffusion plate, the height of thermal diffusion plate and the length of coaxial tube. It is found that the effect of the cross-sectional area of the thermal column surpasses the other affecting parameters. For the thermal resistance analysis, the representative unit cell (RUC) with the corresponding thermal structure is examined and the analytical model of the battery module with internal heat source is established based on the criteria of minimized battery temperature gradient. The comparison between analytical solution and numerical simulation shows that the maximum relative deviations of battery temperature and temperature difference are 4.6% and 6.5%, respectively, validating the effectiveness of the analytical results. The present analytical method can be a useful tool in the fast analysis of the battery thermal designs with acceptable accuracy validated by real and mock-up battery experimental tests.