To estimate the structural damages of materials in accelerator facilities, displacement per atom (dpa) is widely employed as a damage index, calculated based on the displacement cross-section obtained using a calculation model. Although dpa is applied as standard, the experimental data of the displacement cross-section for a proton in the energy region above 20 MeV are scarce. Among the calculation

In the event of a severe accident, past experiences such as Three Mile Island and Fukushima Daichi have shown that the reactor core of a light-water nuclear reactor, if not properly safeguarded, could go through a meltdown. This will be followed by the formation of a corium, a mix of molten fuel elements, and liquid metals from the Reactor Pressure Vessel (RPV). In the worst-case scenario, a melt through

The interaction of cesium hydroxide and a calcium silicate insulation material was experimentally investigated at high-temperature conditions to evaluate the possibility of unprecedented cesium retention under severe accident of boiling water reactor. The temperature where the interactions occurred and chemical species of cesium after the interaction were examined in this study. A thermogravimetry

Anomaly detection in vibration signals is an important technique for fault diagnosis, monitoring, and maintenance in nuclear power plants. Therefore, various signal-analysis methods that apply statistical, machine-learning, and deep-learning techniques have been proposed. In particular, deep neural networks (DNNs) have excellent recognition accuracy and do not require the designing of a feature extractor

In the lower chamber of pressurized water reactor (PWR), the flow distribution device is the core module to distribute coolant into the core. It has complex structure and numerous design parameters. Therefore, it has important theoretical and practical significance to optimize the device. The mesh independence verification, turbulence model selection, and data processing all can influence the numerical

After the termination of a loss-of-coolant accident (LOCA), the reactor continues to be cooled for a long term until fuel assemblies are withdrawn from the reactor core. The fuel cladding tube degrades in strength due to high-temperature oxidation during a LOCA event. It is important to confirm that fuel rods exposed to LOCA conditions can withstand earthquakes during the long-term cooling in terms

Present safeguards verification methods for small samples of high-radioactivity nuclear material (e.g. spent nuclear fuel solution) in reprocessing facilities use destructive analysis techniques since passive non-destructive techniques are incapable of directly determining the nuclear material content. To supplement these methods, the Japan Atomic Energy Agency and European Commission Joint Research

When water contacts with porous materials, water and chemical species dissolved in the water transfer into the inside of the porous materials. Here, to study the transfer of uranyl and europium ions on a dry silica gel plate, we dropped a small amount of aqueous solution (~0.5 μL) dissolving the two ions on a dry silica gel plate, and the distributions of the two ions spread on the silica gel plate

In the nations which have nuclear facilities, the precautionary urgent protective action based on the emergency action levels (EALs) is adopted for the decision-making in the early phase of nuclear disaster in line with the strategy introduced in the Safety Standards of International Atomic Energy Agency (IAEA). In this phase, the decision-makers are forced to make choices from the evacuation or the

BackSide-Illuminated (BSI) CMOS Image Sensors (CISs), with developed performance on quantum efficiency and sensitivity, have been applied for aerospace missions and gradually replaced FrontSide-Illuminated (FSI) CISs. Two types of BSI CISs with different epitaxial layer thicknesses were irradiated by 14-MeV neutron up to 3.40 × 1011 n/cm2 to analyze the degradation induced by neutron irradiation. Dark

The physical implication of the eigenfunction of the adjoint of the natural mode equation is studied. The eigenfunction at a phase space position is theoretically derived to be proportional to the amplitude of the neutron flux sufficiently long time after a source is placed at the position. Meanwhile, the time change rate and distribution of the neutron flux originated in the source must converge to

A deep-penetration shielding experiment was performed at the CERN High-energy AcceleRator Mixed-field (CHARM) facility. The protons (24 GeV/c) were injected into a 50-cm-thick copper target and the released neutrons were transmitted through a bulk concrete shield located vertically upward from the target, where they were measured with bismuth and aluminum activation detectors placed at various penetration

A new approach to solve the inverse equation of point kinetics is presented. The neutron density history can be considered as a series of infinite Bernoulli numbers. In order to simplify the problem, the proposed method uses an approximation which considers only two derivatives of the neutron population density. The reactivity is calculated for different forms of neutron population density and for

A new gap conductance model is proposed in this study as a combination of Toptan’s model and the Ross-Stoute model. A variance-based sensitivity analysis is performed to understand how simulation results depend on all input parameters of the proposed model. Additionally, new modeling options (e.g. fill gas thermal conductivity, temperature jump distance, thermal accommodation coefficient, etc.) are

Introduction: Studies on migration behaviors of colloidal materials through engineered and natural barriers are highly important for the safety assessment of radioactive waste repositories since the fate and transport of radionuclides may be significantly affected by interactions with colloids.Methods: Poly (ethylene glycol) coated gold nanoparticles (AuNPs) were used as a model colloid and the effects

After direct discharges of highly contaminated water of the Fukushima Daiichi Nuclear Power Plant (1 F) from April to May 2011, Kanda suggested that relatively small amounts of run-off of radionuclides from the 1 F port into the Fukushima coastal region subsequently continued by his estimation method. However, the estimation period was limited to up to September 2012. Therefore, this paper estimatesthe

In-vessel retention (IVR) is a strategy for severe accident management in which the lower head of the reactor vessel is submerged in a water-flooded reactor cavity. Critical heat flux (CHF) data for IVR are important for estimating cooling capacity of the reactor vessel. The existing CHF data for IVR which were obtained for the specific geometries and thermal-hydraulic conditions of actual plants are

A new approach for generating nuclear data from experimental cross-section data is presented based on Gaussian process regression. This paper focuses on the generation of nuclear data for proton-induced nuclide production cross-sections with a nickel target. Our results provide reasonable regression curves and corresponding uncertainties and demonstrate that this approach is effective for generating

An effective dose calculation method is important in the design of efficient shields in radiation facilities. Some analytical methods have been shown to provide a simple and quick design analysis; however, no suitable method exists that can be applied to a room located directly under an X-ray irradiation room. We propose a new analytical method that uses the multiple reflection ratio predetermined

Governing the rate of heat transport by condenser tubes in the passive containment cooling system (PCCS), the steam condensation over a vertical cylinder in the presence of air was investigated experimentally. The main objective of this study was to explore if the condensation heat transfer coefficient relies on the tube dimension, which has been a variable missed in most condensation models or has

An equation of power in subcritical quasi-steady state has been derived based on one-point kinetics equations for the purpose of utilizing it for the development of timely reactivity estimation from complicated time profile of neutron count rate. It linearly relates power, P, to a new variable q, which is a function of time differential of the power. It has been confirmed that the points (q, P) calculated

After the core meltdown in the Fukushima Daiichi (1F) nuclear power plant, various compounds in metal boride systems could potentially form as a result of the reactions between B4C (control material) and Fe, Zr alloys (control-blade sheaths, zircaloy claddings, channel box, etc.). Some previous studies have focused on the properties of intermetallic compounds of the Zr-B and Fe-B systems, such as ZrB2

Measuring the surface tension of molten ZrO2 is critical to determine the progression of a severe accident in a nuclear power plant. However, no experimental reports have been published pertaining to the surface tension of liquid ZrO2 because of its high melting point, high reactivity, and high vapor pressure, among other factors. Thus, in this study, the surface tension of ZrO2 was measured by using

(2020). Applying the continuous-energy Monte Carlo calculation code, MVP3, to analysis of kinetic parameters measured for light-water moderated UO2 and MOX cores of the TCA and EOLE critical facilities. Journal of Nuclear Science and Technology. Ahead of Print.

Investigated numerically are the effects of the rotational speed of the screw conveyor and the reactor temperature on the changes in the diameter of graphite particles passing through a laboratory-scale enclosed screw-conveyor reactor. Also investigated experimentally are a thermal gasification of graphite particles to carbon–oxygen compounds to determine a kinetic reaction model and kinetic parameters

An uncertainty analysis of the OECD/NEA LWR UAM benchmark Phase I was performed by CASMO5 using JENDL-4.0 and ENDF/B-VII.1, and the individual influence of nuclide/reaction covariance data was estimated to preliminary discuss the important covariance data on the uncertainties of lattice physics parameters used in core calculations. In the boiling water reactor and pressurized water reactor UO2 fuel

The pebble-bed type reactor is one of the mainstreams for high-temperature gas-cooled reactor (HTGR), whose core is a packed bed composed of numerous spherical pebbles. In this work, discrete element model (DEM) is used to simulate the pebble flows in a thin pebble bed, and the packing peaks, top angles, trajectory and velocity deviations, retention time, and ratios are analyzed in detail. The effects

The low temperature heat capacity of Cs2Si4O9, which is one of the cesium chemisorbed compounds onto stainless steel during severe accidents of the light water nuclear reactor, was experimentally determined for the first time in the temperature range of 1.9–302 K. The experimentally determined heat capacity, Cpo(298.15 K), and the standard entropy, So(298.15 K), were 249.4 ± 1.1 J K−1 mol−1 and 322

As the main control room of nuclear power plants (NPPs) has been gradually digitized, new human reliability problems may emerge because of a series of new changes in the cognitive processes, behavioral patterns, and error mechanisms of operators. Aiming to address this situation, this paper proposes a method as guidance for human reliability analysis (HRA) of different cognitive Stages. This method

Titanite (CaTiSiO5) a mineral that has shown promise as an actinide-bearing host phase. Natural titanites contain radionuclides which result in radiation damage to the crystal structure and could even lead to an amorphous state (metamict state). It is imperative to understand how the chemical durability of the titanites would be affected by such radiation damage and leaching solutions. Natural metamict

To evaluate the fracture resistance of high-burnup advanced fuel cladding tubes during the long-term core cooling period following loss-of-coolant accidents (LOCAs), laboratory-scale four-point-bend tests were performed using the following advanced fuel cladding tubes with burnups of 73–84 GWd/t: low-tin ZIRLOTM, M5®, and Zircaloy-2 (LK3). Three four-point-bend tests were performed on the high-burnup

This study investigates the fragility assessment of the electrical cabinet facility, a steel structural form that exhibits behavior and response patterns distinct from the normal structure. To evaluate this cause, a set of 40 ground motions was spectrally matched to the design response spectra (RG 1.60) and incremental dynamic analysis was considered. The two design guidelines including earthquake

Pool scrubbing codes combining bubble dynamics and aerosol transport models are used to determine the pool scrubbing efficiency. However, the effect of bubble parameters, diameter and bubble rising velocity (vb), on retention efficiency was not yet analysed much in detail. In this experimental study, the effects of air content, S/P temperature, submergence, and downcomer diameter on bubble parameters

As a follow-up measure to improve safety after the Fukushima nuclear disaster in 2011, a level 3 probabilistic safety assessment (PSA) was enacted as a notice in Korea. In this study, as a part of developing a Korean-specific level 3 PSA code, the radiation-induced cancer risk model for the Korean population was developed for reflecting ethnic and regional characteristics. The Korean-specific risk

The two-phase flow in helically coiled tubes (HCTs) is rather important in many industries, such as the heat exchange facility in nuclear power plant. In this work, a double-sensor conductivity probe was used to study the air/water bubbly flow in HCTs. The cross-sectional distribution profile of the interfacial parameters (void fraction, interfacial area concentration, bubble size, etc.) of air–water

To suggest efficient process of the fuel debris treatment after the retrieval from the Fukushima Daiichi Nuclear Power Plant (1F), thorough investigation is indispensable on potential source of U in the fuel debris. The present study aims to estimate chemical forms of U in the in-vessel fuel debris, especially in the minor phases such as metallic phases, by performing the thermodynamic calculation

ABSTRACT The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., suffered a meltdown as a result of a large tsunami triggered by the Great East Japan Earthquake on 11 March 2011. To proceed with environmental recovery, a radiation distribution map that indicates the distribution of radioactive substances is extremely important to establish detailed

The analysis method of Fast Neutron Multiplicity Counting (FNMC) plays an increasingly important role in the measurement of nuclear material properties. Based on the assumption of point model, fast neutron multiplicity measurement equation is derived which can be used to measure the mass of Pu sample. However, the deviation of the simulated measurement of 1 kg Pu sample reaches 16.6% and increases

An efficient numerical scheme for time-dependent MOC calculations is proposed. In the present scheme, one of the most successful factorization method, the multigrid amplitude function (MAF) method, is employed to achieve faster computation with the minimum degradation for the temporal integration of the scalar flux. In addition, the MAF method is re-derived based on the linear source approximation

Neutron flux per pulse reached world record at neutron source in Japan Proton Accelerator Research Complex (J-PARC). In the J-PARC, mercury target system is used as a spallation neutron source. A target vessel has a multi-walled protection system that comprises a mercury vessel enclosed with a double-walled water shroud. This is to prevent the leakage of the mercury outside the target vessel. The multi-walled

To better understand the failure limit of fuel cladding during the pellet-cladding mechanical interaction (PCMI) phase of a reactivity-initiated accident (RIA), pre-cracked and hydrided cladding samples with base metal final heat-treatment status of cold worked (CW) and recrystallized (RX) were tested under biaxial stress conditions (strain ratios (εz/εθ) of 0 and 0.5). Displacement-controlled bia

Helium gas is used as the coolant in high temperature gas-cooled reactor while its insulation property is not good and brings big challenges to insulation design work. In this paper, breakdown voltages of two parallel-plate electrodes in millimeter-scale gaps at atmospheric pressure are calculated numerically with a two-dimensional hydrodynamic model. The Finite-Difference Flux-Corrected Transport

To estimate the subcriticality in dollar units for an arbitrary state-change, the time-domain decomposition-based integral method (TDDI) is proposed using the point kinetics theory based on the fundamental mode approximation. In a general transient subcritical system, reactivity, neutron source intensity, and point kinetics parameters can vary simultaneously. Furthermore, the state-change may not necessarily

ABSTRACT We have estimated source term and analyzed processes of atmospheric dispersion against atmospheric discharge of radioactive materials due to the Fukushima Daiichi Nuclear Power Station (FDNPS) accident by atmospheric-dispersion calculation using the Worldwide version of System for Environmental Emergency Dose Information (WSPEEDI). On the basis of this experience, we developed an atmospheric-dispersion

Gamma-gamma coincidence measurement utilized in γ-ray spectroscopy experiments is well known to be effective for the improvement of signal-to-noise ratio in a γ-ray spectrum. We study its applicability to the determination of long-lived radioactive nuclides in environmental samples. The γ-ray simulation code Geant 4.10.2 was used. A conventional and effective detector system comprising five Ge detectors

For the direct vitirification of low level radioactive wastes containing metallic aluminum, the oxidation and vitirification of aluminum was carried out using lead borate glass as a flux. Among the six fluxes employed in this study, 0.11Na2O ・3PbO ・B2O3 was the most suitable for the oxidation and vitirification of aluminum based on the initial oxidation rate and alumina solubility. The increase of

In order to effectively conduct the defect detection of nuclear fuel pellets end face and avoid the leakage of nuclear radiation, a defect detection system for the nuclear fuel pellets end face based on machine vision is proposed. Firstly, aiming at the complexity of the defect detection of nuclear fuel pellets, a set of image acquisition system lighted by left-right symmetric grating is designed.

In view of the complexity of current detection efficiency calibration of radioactive gas sources, a method using solid planar sources to be equivalent to gas sources was studied. For the 50 mL gas source box, an optimal equivalent scheme was selected by Monte Carlo Simulations. Then, the full-energy-peak efficiency curve of gas sources at the measurement position of 25 cm, with source-to-detector distance

This paper aims to propose a new methodology for optimizing fuel loading pattern in a nuclear reactor which is important for its higher safety and economic efficiency. Previous researches have proposed various methodologies to decide better loading patterns automatically. However, the processes still require manual operations of engineers to automatically design actual loading patterns. Swarm intelligence

The EPRI (1991) and the Clark et al. (2014) drift-flux correlations implemented in RELAP5/MOD3 code were benchmarked against the low-pressure void fraction data collected by Clark et al. (2014) at Purdue University and the high-pressure data collected by Anklam and Miller (1982) at ORNL. The Clark et al. correlation (2014) was found to perform best at low pressures of Clark et al. tests (2014), but

Oxygen measurement and control system is critical for minimizing corrosion in nuclear systems. Oxygen measurement and control tools use lead-bismuth eutectic (LBE) and pure lead as a coolant or as a spallation target. Oxygen can be supplied by either gas phase (H2O or O2) or solid phase (PbO dissolution); thus, oxygen control includes both gas phase and solid phase methods. This article focuses on

A hybrid method for estimation of atmospheric concentrations of multiple radionuclides was developed and applied to NaI(Tl) pulse height records measured in Ibaraki Prefecture in the morning of 15 March 2011 when three radioactive plumes from the Fukushima Dai-Ichi Nuclear Power Plant Accident passed. The method is based on the simple principle for separation from deposited radionuclides’ contribution

Monitoring only neutron flux in a nuclear reactor core has an advantage of offering reactor power monitoring accuracy. We started the development of a new nuclear instrumentation based on the measurement of prompt gamma rays emitted from metals placed at the neutron flux monitoring positions. The thermal neutron flux at the position of each placed metal piece can be monitored by measuring the prompt

Severe accident codes (e.g. MAAP, RELAP, and MELCORE) model various physical phenomena during severe accidents. Many analyses using these codes for safety margin evaluation are impractical due to large computational costs. Surrogate models have an advantage of quickly reproducing multiple results with a low computational cost. In this study, we apply the singular value decomposition to the time-series

Currently, most Iodine-129 (129I) present in the environment is anthropogenic; it has been released from European nuclear reprocessing plants and transported into the northern part of the Arctic Ocean via ocean circulation. This study investigates the 129I distribution in the Chukchi Sea and Bering Sea by considering water mass structure. The range of 129I concentration is 0.89–5.03 × 107 atoms L−1

Median root prior expectation maximization (MRPEM) algorithm that belongs to the Bayesian iterative approximation is used in passive gamma emission tomography (GET) to reconstruct passive gamma emitter distribution. The algorithm converges slowly and may involve iterations of 50–200. Fast processing of the algorithm was integrated into MRPEM to accelerate the convergence. Then, the integrated MRPEM

(2019). Corrections. Journal of Nuclear Science and Technology. Ahead of Print.

(2018). Correction. Journal of Nuclear Science and Technology. Ahead of Print.

(2018). Erratum. Journal of Nuclear Science and Technology. Ahead of Print.

(2017). Erratum. Journal of Nuclear Science and Technology. Ahead of Print.