ABSTRACT As a result of the Fukushima nuclear power plant accident in March 2011, massive amounts of soil were contaminated with radioactive Cs. To remediate the contaminated soil, we are developing a desorption technique for removing Cs from soil using subcritical water. In the contaminated soil, the radioactive Cs is stably trapped in the interlayers of the clay minerals, making the use of traditional

ABSTRACT Silicone rubber (SiR) is an important electrical insulating material for safety-related cables in nuclear power plants. This means that SiR must withstand the irradiation of gamma rays and the exposure to high-temperature steam. However, SiR is vulnerable to hydrolysis. Therefore, for the purpose of clarifying the behavior of SiR in such environments, sheets of SiR were exposed to steam at

ABSTRACT In the ‘evaporation and dryness due to the loss of cooling functions,’ which is one of the severe accidents at reprocessing plants in Japan, volatile ruthenium (Ru) compound is possible to be produced and released from high level liquid waste (HLLW) in the storage tank to the environment. This cause is considered that the volatile Ru compound is produced from ruthenium nitrosyl nitrate by

ABSTRACT The dissolution behaviors of spent fuel were studied and the secondary precipitate was obtained and characterized. The experimental results showed that the spent fuel sliced to 20–30 mm in length was completely dissolved within 5 hours in 6.5 M nitric acid at about 90°C and the precipitating of Ru happened in the course of dissolution, and the secondary precipitate formed in the following

ABSTRACT In order to validate the neutron absorption cross sections in the JENDL-4.0 nuclear data library, critical analysis was performed using a continuous-energy Monte Carlo calculation code for the light-water moderation UO2 cores loaded with the aqueous solution samples of eight elements (B, Rh, Cs, Nd, Sm, Eu, Gd, and Er). The concentrations of the elements in the solution samples were changed

ABSTRACT In the post-Fukushima accident era, the participation of local residents and their acceptance of nuclear power plants (NPPs) have become significant issues. Using the case of Qinshan NPP in China, this study examined the factors affecting public acceptance of NPPs and explored the ways in which public participation affects the public acceptance of NPPs through structural equation modeling

ABSTRACT The Japan Atomic Energy Agency is evaluating delayed gamma-ray spectroscopy as an active interrogation nondestructive assay technique to quantify the fissile composition of nuclear materials for improved safeguards verification in nuclear fuel cycle facilities. In this paper, we optimize a moderator to thermalize the 2.5 MeV neutrons emitted from a deuterium–deuterium (D–D) neutron generator

ABSTRACT To investigate the leaching behavior of radioactive nuclides in leaching samples comparable to core debris (partially molten ZrO2/UO2 between fuel rods) in the Fukushima Daiichi Nuclear Power Station (1 F NPS), the concentration of radionuclides in the leaching solution was measured. The leaching behaviors of actinides (U, Pu, and Np) and Cs from the samples were similar to those from spent

ABSTRACT Monte Carlo simulations of the void velocity measurement in a light-water moderated critical assembly CROCUS are performed using a continuous energy Monte Carlo code that has a special function to conduct frequency domain calculations using complex-valued weights of neutron noise. In the measurements that are simulated in this paper, two vertically aligned fission chambers detected the neutron

While designing deuteron accelerator neutron sources for radioisotope production, nuclear data for light elements such as Li, Be, and C have been systematically measured in the deuteron energy range from a few MeV to around 50 MeV. Currently, the experimental data available on double-differential thick-target neutron yields (DDTTNYs) are insufficient, especially for deuteron energies between 18 and

The HTGR reactor core is always composed of packed fuel pebbles and helium gas. The fluid flows around spherical particles and cylindrical rods are always encountered in the reactor core of nuclear powers. The flows past the spherical particles and cylindrical rods were simulated here. Two aspects were considered: comparison of heat transfers between the spherical particles and the cylindrical rods

This paper examines free-surface vortices and the vorticity distribution with time-dependent evolution within a closed pump intake under five pressure conditions. The location and the strength of these vortices, occurrence probability and perspective statistics, as well as vortex probability distribution are all systematically analyzed. Three cases were observed and analyzed: (a) Subcritical (Q= 19

The thermal-neutron capture cross sections (σ0) and resonance integrals (I0) were measured for the 243Am(n,γ)244gAm and 243Am(n,γ)244m+gAm reactions by a neutron activation method. Americium-243 samples were irradiated with a pneumatic tube and a hydraulic conveyer installed in the research reactor in Institute for Integral Radiation and Nuclear Science, Kyoto University. Alloy wires of Au/Al, Co/Al

Hydrogen (H) solubility, segregation, and hydrogen-induced intergranular fractures in eight symmetric tilt grain boundaries (GBs) in tungsten (W) are investigated through the first-principles calculations. The results show that there is an equilibrium distance, about 1.95 Å, between the H inserted in interstitial sites and its nearest W. Interactions between the inserted H and GBs are rather localized

Transient analysis of TMSR-SF0, a molten salt thermal-hydraulic experimental system of molten salt reactor, is investigated using RELAP5/MOD4.0 code. Simulation model consists of two coolant circuits. Variations in core power, primary mass flow, secondary mass flow, and air mass flow are studied separately. Both temporary and permanent phenomena of test facility are concerned in different circumstances

The nano-crystalline materials generally show better irradiation resistance than common poly-crystalline materials since grain boundaries (GBs) can usually enhance the annihilation of irradiation-induced defects. Although the defect annihilation mechanism has been thoroughly investigated in GBs in tungsten, the influences of defect migration behavior in GB-planes on the recombination capability between

An efficient reduced order model (ROM) for time-dependent diffusion calculations using the proper orthogonal decomposition (POD) is proposed. Employing the singular value decomposition (SVD) and low-rank approximation (LRA) for the flux distributions sampled from the detail full order model (FOM) solutions, the orthogonal basis suitable for a target problem is numerically obtained. In the present ROM

Ab initio calculations based on the density functional theory were performed to investigate the interaction between Ni and Si in the body-centred cubic Fe system. The Ni-Si interaction was first evaluated in the framework of small Ni-Si clusters, then followed by detailed analyses. The calculations showed that even though the formation of pure Ni clusters was not energetically favoured, the presence

A low-noise current-sensitive preamplifier was developed for aiming low-dose X-ray computed tomography with applying a charge-sensitive preamplifier. We compared the number of X-ray photons needed for current measurement with the new preamplifier with that needed with a conventional preamplifier. Also, the dose rates for above conditions were measured by a commercial dose rate meter. Results show that

The production and dispersion of contaminated aerosols during the laser cutting of corium can potentially provide useful insights into the dispersion of contamination during the evacuation of damaged reactors during decommissioning. Quantitative assessments of contamination dispersion are fundamental to the development of a safety case for the decommissioning of the Fukushima Daiichi plant. This collaborative

The voltage and power of the RF cavity of an accelerator were measured based on a calibration factor of the capacitor probe to assess the performance of the SC200 cavity. The calibration factor can be formulated using a low-frequency method and RF numerical simulation. Thereafter, based on it, the capacitor probe is utilized to measure the voltage and power of the RF cavity in a cool-measured and high-power

The independent and cumulative fission product yields (FPYs) and their covariance matrices were newly evaluated for thermal- and fast-neutron induced fission and spontaneous fission. We principally evaluated the independent isobaric charge distributions by taking account of available experimental data, especially putting emphasis on the shell and even-odd staggering in the fission yields by applying

For a subcritical reactor system driven by a periodically pulsed spallation neutron source in Kyoto University Critical Assembly (KUCA), the Feynman-α and the Rossi-α neutron correlation analyses were carried out to determine the prompt-neutron decay constant and quantitatively to confirm a non-Poisson characteristics of the neutron source. In these correlation analyses, a non-negligible contribution

It is important to perform neutron transport simulations with accurate nuclear data in the neutronics design of a fusion reactor. However, absolute values of large-angle scattering cross sections vary among nuclear data libraries even for well-examined nuclide of iron. Benchmark experiments focusing on large-angle scattering cross sections were thus performed to confirm the correctness of nuclear data

The concept of Pu-burner high temperature gas-cooled reactor (HTGR) has been proposed to more safely reduce the amount of recovered Pu. In the Pu-burner HTGR concept, coated fuel particles with ZrC-coated yttria-stabilized zirconia containing PuO2 (PuO2-YSZ) kernels are employed for very high burn-up and high nuclear proliferation resistance. The role of ZrC layer is that of oxygen getter. CeO2-YSZ

The gas production of wasteforms is a major safety concern for encapsulating active nuclear wastes. For geopolymers and cements, the H2 produced by radiolytic processes is a key factor because of the large amount of water present in their porous structure. Herein, the gas composition evolution around geopolymers was monitored online under 60Co gamma irradiation. The transient evolution of the hydrogen

Strontium-90 is one of the most important fission products due to the potential health risks of its uptake and retention in the human body. Conventional analysis techniques involve β counting, which requires ingrowth of 90Y over a period of two weeks. Accelerator mass spectrometry (AMS) has the potential to shorten the analysis time while offering a lower limit of detection than β counting. Here, Sr

The new critical assembly STACY will be able to contribute to the validation of criticality calculations related to the fuel debris. The experimental core designs are in progress in the frame of JAEA/IRSN collaboration. This paper presents the method applied to optimize the design of the new STACY core to measure the criticality characteristics of pseudo fuel debris that simulated Molten Core Concrete

A novel amine-functionalized magnetic large-pore SBA-15 obtained via in situ approach and the post-grafting method was employed as a new adsorbent for removal of uranium from aqueous solutions. Results indicated that the as-prepared adsorbent exhibited fast adsorption rates in the first hour, at the optimum pH 6. The adsorption process was fitted well to the Langmuir isothermal and the maximum adsorption

At Japan Atomic Energy Agency (JAEA) MOX fuel facilities, a worker usually wears a protective lead apron; therefore, the dose to the lens of the eye (lens dose) outside the apron is higher than that to the torso. To estimate the potential impact on the current facility operation of the International Commission of Radiological Protection (ICRP)-proposed lens dose limit reduction from 150 mSv/y to average

NO2 and NO generated during a boiling and drying accident, which affects the release of volatilized radioactive Ru into the atmosphere, were examined using various samples including simulated high-level liquid waste and a thermogravimetric analyzer. NO2 and NO in the gas flowing out of the analyzer were measured separately using a NOx analyzer equipped with NO2 and NO sensors. The samples were heated

Continuum strength function for the isoscalar monopole (IS0) and dipole (IS1) transitions in the α +   40 Ca system is investigated on the basis of the orthogonality condition model (OCM) under the absorbing boundary condition (ABC). The nuclear potentials are constructed from the double folding procedure with the effective nucleon–nucleon interaction of the density-dependent Michigan three range Yukawa

A security issue on nuclear facilities will give a significant effect on national security, economy, public health, or the combination among them. The evaluation of physical security effectiveness is done by considering it as a probability that the system will defeat an adversary at a particular time. This research examined the effectiveness of Physical Protection Systems (PPS) of a nuclear research

Hitachi has developed the chemical decontamination method to remove radioactive oxides on structural materials by alternately using a mixed solution of oxalic acid and hydrazine for a reductive process and potassium permanganate or permanganic acid solution for an oxidative process. In the decontamination of carbon steel (CS) by applying oxalic acid, a film of iron(II) oxalate dihydrate that has low

The effect of solution annealing and aging treatment on the intergranular carbide precipitation behavior of alloy 690 tubes for steam generators is investigated. The carbides precipitated on the grain boundaries were identified as chromium-rich M23C6 carbide, which has a cube-cube orientation relationship with the matrix on one side of neighboring grains. The carbide precipitation behavior is closely

Tungsten is widely used as a plasma-facing material in nuclear fusion reactors due to its favorable properties; however, the extensive exposure of energetic particles could lead to severe degradations on its surface. Therefore, we studied the surface modification resulted from helium implantation on the mechanically and electrochemically polished tungsten at an elevated temperature. Samples of both

In connection with the accuracy of the 10B(n, α) cross section in the thermal- and epithermal-neutron energy regions, criticality calculation results were examined for six benchmark sets of light-water-moderation critical experiments of UO2 and MOX fuel lattice cores with un-borated and borated water. Two of the benchmark sets were those implemented in the Tank-Type Critical Assembly (TCA). The others

The sources and mechanisms for the tritium release into the primary coolant in the JMTR and the JRR-3M containing beryllium reflectors are evaluated. It is found that the recoil release from chain reaction of 9Be is dominant and its calculation results agree well with trends derived from the measured variation of tritium concentration in the primary coolant. It also indicates that the simple calculation

Suppressing the kernel migration rates under normal operation condition is quite important from the viewpoint of the fuel integrity for High-Temperature Gas-cooled Reactors. It depends on both the fuel temperature and the fuel temperature gradient. The presence of the ideal axial power distribution to minimize the maximum kernel migration rate allows us to improve the efficiency of design work. Therefore

A reduced order model (ROM) for a safety analysis code (RELAP/SCDAPSIM) is developed and is applied to the statistical safety analysis in order to reduce computational load. The ROM that reproduces output of the safety analysis code (e.g., the peak cladding temperature) is constructed using the singular value decomposition and the low-rank approximation for time-series data of a safety analysis code

ABSTRACT Air dose rates within a range of 80 km from the Fukushima Dai-ichi Nuclear Power Plant measured via car-borne surveys using the KURAMA systems from 2011 to 2018 were analyzed. The ratio of the air dose rates relative to the first car-borne survey was 0.08 over a period of seven years, indicating a much more rapid decrease than that estimated by the physical decay of radiocesium (0.3). Differences

The nuclear security has been considered for the industrial terrorism preventions. In the fourth industrial revolution era, our life related systems are connected each other, which means the internet based networking is spread anywhere. It is suggested to make the modeling for the nuclear security in cyber information where the computer hacking is one of major incidents. The data and information could

Emphasis has been placed on the behavior of ruthenium (Ru) in the evaporation to dryness accident due to the loss of cooling functions (EDLCF) of high-level liquid waste in fuel reprocessing plants. It is because Ru would form volatile compounds such as ruthenium tetroxide (RuO4) and could be released into the environment with other coexisting gasses such as nitric acid (HNO3), water (H2O). To contribute

In order to clarify the cesium iodide (CsI) transport behavior with a focus on the mechanisms of gaseous iodine formation in the reactor coolant system of light water reactor (LWR) under a severe accident condition, a reproductive experiment of CsI transport behavior was conducted using a facility equipped with a thermal gradient tube. Various analyses on deposits and airborne materials during transportation

The tritium exhaust behavior from the Large Helical Device (LHD) was observed in the first deuterium plasma experimental campaign. Tritium in the exhaust gas was monitored at the conducted by use of the ionization chamber and water bubbler system with the discrimination of chemical forms. The observation results indicated that (i) tritium on the surface of the first wall and divertor tiles as plasma

The influence of materials of mineral-insulated (MI) cables on their electrical characteristics upon exposure to high-temperature conditions was examined via a transmission test, in the objective of achieving the stability of the potential distribution along the cable length. Occurrence of a voltage drop along the cable was confirmed for aluminum oxide (Al2O3) and magnesium oxide (MgO), as insulating

The passive gamma spectroscopy (PGS) is a useful technique to extract information on spent nuclear fuels without any destructive actions. This method requires a correlation between number densities (NDs) of target nuclides, and it is generally estimated by numerical simulation. Therefore, the prediction accuracy of these nuclide generations is one of the key issues in PGS. Nuclear data used in nuclear

In order to know the performance of evaluated nuclear data in reactor physics or radiation shielding calculations, its benchmark testing with integral data is mandatory. Nowadays we have a huge amount of integral data, but some of them are quite similar to each other. We need to know the independency of available integral data, and also to choose a proper set of a limited number of integral data for

The flexible fuel cycle initiative system (FFCI system) has been developed to reduce spent fuel (SF) amounts, to keep high availability factor for the reprocessing plant and to increase the proliferation resistance for the recovered plutonium (Pu). The system separates most uranium (U) from the SF at first and the residual material called recycle material (RM) which contains Pu, minor actinides (MA)

The dissolution behavior of hydrogen (H) at Fe/W interface and the effect of H on the strength of Fe/W interface are investigated by means of first-principle calculation. The dissolution of H atom at Fe/W interface would be easier than in bulk Fe or W due to the low charge density at Fe/W interface caused by the distortion of lattice. Hydrogen atom prefers to stay at Fe side of Fe/W interface due to

In this paper, a new particle-grid hybrid method is used for numerical simulations of the gas-liquid two phase flow. In this method, the main area of the fluid is calculated via the constrained interpolated profile/multi-moment method (CIP/MM FVM), and the interface of the two phases is calculated by the finite volume particle method (FVP). In the numerical calculation, the particles are distributed

Identification of flow regime and feature extraction of bubble characteristics in gas-liquid two-phase flow systems have been significant issues in various engineering disciplines, including nuclear thermal-hydraulics field. In nuclear safety analysis codes, flow regime transition criteria and bubble size-dependent correlations are often utilized to obtain solutions for the governing equations. However

ABSTRACT This paper presents a VVER-1000 coolant transient benchmark calculated using Serpent 2 generated group constants in the reactor dynamics code HEXTRAN coupled with the system code SMABRE. Two different sets of group constants applying different leakage correction methods are generated. The purpose of the paper is to validate the Serpent 2-HEXTRAN–SMABRE code sequence in plant transient calculations

ABSTRACT In this study, a compact fiber-optic laser-induced breakdown spectroscopy (LIBS) system was developed using a microchip laser (MCL) with a monolithic Nd:YAG/Cr:YAG composite ceramic, for remote analysis of hazardous environments, such as nuclear reactor cores. Short duration laser pulses exhibiting a near-Gaussian beam profile were obtained. The output properties of the laser, such as pulse

ABSTRACT For a highly enriched uranium subcritical core driven by an inherent or an external Am-Be source in Kyoto University Critical Assembly (KUCA), a series of the source multiplication measurements, the Feynman-α and the Rossi-α neutron correlation analyses was carried out to demonstrate quantitatively that the use of the former inherent source had some advantages over that of the latter external

ABSTRACT Titanate adsorbents have been used to remove Sr radioisotopes from contaminated water at the Fukushima Daiichi Nuclear Power Station site. This process leads to the generation of spent adsorbents, which require stabilization for long term storage and disposal. Geopolymers are candidates for matrices to achieve this consolidation. However, more data are needed to assess the leaching behavior

ABSTRACT 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

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