Neutron activation analysis is a highly sensitive and convenient method for qualitative analysis, but it was thought to be unsuitable for quantitative analysis. However, we have applied this method to quantitative analysis and have succeeded in measuring neutron capture cross-sections with high accuracy. By paying careful attention to uncertainty factors related to measurements, such as sample...
Fission observables such as neutron multiplicity, the spectrum, and the mass/charge distributions of fission fragments/products play an important role in evaluating safety and effectiveness for nuclear applications. However, these types of data are limited due to the difficulties of experiments and their associated factors. Moreover, theoretical calculations for these observables are also...
To realize a decarbonized society, various organizations are developing small modular reactors and micro-reactors [1]. Toshiba Energy Systems & Solutions has been developing a MoveluX$^{\mathrm{TM}}$ reactor system with 10 MWt and 3-4 MWe power output. The MoveluX$^{\mathrm{TM}}$ core uses less than 5% LEU as the nuclear fuel. Furthermore, calcium hydride (CaH$_2$) is also used as the...
Thermal neutron scattering law (TSL) is one of the important nuclear data that affect reactor characteristics such as criticality in the core design of thermal reactors. TSL describes neutron scattering due to atomic and molecular dynamics within materials. Evaluated nuclear data files include the latest TSLs, which were derived by molecular dynamics calculations [1]. The derived TSLs are...
This talk will introduce and discuss the current status and issues of the evaluation of thermal scattering laws (TSL) in the development of the Japanese Evaluated Nuclear Data Library, JENDL.
In thermal neutron reactors, the TSL of the moderator has a significant impact on core calculations. In the JENDL series, the latest version, JENDL-5, is the first to include an original evaluation of...
The analysis of the properties of nuclei in the neutron-rich region, one of the challenges in nuclear reactions, is very important in the study of superheavy element synthesis and the r-process in astrophysics. However, most nuclei in this region are not yet known [1]. As a means of reaching this region, a method based on multinucleon transfer reactions has been proposed [2].
At present,...
Recently, multi-nucleon transfer (MNT) reactions have attracted attention as a method of producing neutron-rich nuclei [1]. However, the reaction mechanism is not yet well understood due to its novelty and complexity. In this study, we construct a dynamical model that describes the dynamics of the MNT reaction and verify the model by comparing it with experimental data to clarify the reaction...
A shielding experiment campaign using NE213 liquid scintillator was conducted to measure high-energy neutrons at the CHARM facility located in CERN [1]. From the neutron spectra obtained with the NE213 scintillator, it was observed that the high-energy components originated from nuclear reactions between the Cu target and 24 GeV/c proton beam.
However, significant discrepancies between...
To develop technologies for criticality safety management during the fuel debris retrieval at the Fukushima Daiichi Nuclear Power Plant, we conduct experiments under various core conditions assumed for fuel debris. JAEA modified the Static Experiment Critical Facility (STACY) from a solution fuel system to a light-water moderated heterogeneous system for critical experiments to study the...
Tungsten is applied to a target at proton accelerator facilities, e.g., ESS and COMET (J-PARC). Additionally, tungsten is used as a shielding material, such as the ADS facility by JAEA [1]. Thus, activation of tungsten by high-energy protons receives attention because residual $\gamma$-ray dose rate has impact on a maintenance schedule. To derive the dose rate, nuclide production cross section...
We studied the decay branching ratios of $^{197m}$Hg (24 h) and $^{195m}$Hg (42 h) by offline $\gamma$-ray spectroscopy of a natural platinum foil irradiated by $\alpha$-particles at 29 MeV. We observed strong cooling time dependence in the isomeric ratios of $^{197}$Hg and $^{195}$Hg determined by the conventional activation cross section formula. To eliminate the cooling time dependence, we...
Recently nuclear medicine therapy using nuclides emitting $\alpha$ rays and Auger electrons is gathering attention [1]. $\alpha$ rays and Auger electrons have a higher linear energy transfer than $\beta$ rays and are expected to enable the therapy with little damage to normal cells surrounding the tumor. Especially Auger electron emitters have an advantage that their daughter nuclei are less...
Nuclear security at nuclear reactor facilities is a significant concern, particularly with regards to the theft and smuggling of nuclear material, as well as sabotage of the facilities. One crucial task to prevent these security incidents is the development of non-destructive detection techniques for identifying nuclear material. Although numerous techniques have been proposed, further study...
Measurement of high-energy gamma radiation in high-dose-rate environments is difficult due to problems such as the dead time of a detector. However, there is a need for measurement techniques under high dose rates, such as radiation detection and nuclear data measurement inside nuclear reactors and in radiation contaminated areas. In particular, this issue must be solved in applications such...
We are developing a measurement system for the simultaneous determination of (n,$\gamma$), (n,f), (n,n’), and (n,2n) reaction cross sections using the surrogate reaction method. The system consists of LaBr$_3$(Ce) scintillators for high-energy $\gamma$ rays, Ge detectors for low-energy discrete $\gamma$ rays, Si detectors for scattered particles, and solar cell charged-particle detectors for...
Strontium-88, which has a neutron magic number of 50, is important in s-process nucleosynthesis because it acts as a bottleneck in the s-process reaction network due to the small (n, $\gamma$) cross section. Therefore, the neutron captures cross sections need to be known with high precision for the reliable determination of the s-process abundances. However, there is disagreement between...
To calculate reliably and accurately concentrations and activities for nuclides generated or depleted by fission and radioactive decay in nuclear fuel, it is necessary to use the updated nuclear decay data such as half-lives, branching ratios, and $\gamma$-ray spectra. The Evaluated Nuclear Structure Data File (ENSDF) contains required decay data for all nuclides, which is periodically revised...
Multinucleon transfer (MNT) reactions have attracted attention in the field of nuclear physics and astronomical nucleosynthesis as a reaction which produces neutron-rich nuclei as evaporation residues (ER). But detailed feature of reaction mechanism is not understood. Detailed experimental data are necessary to develop a model to guide an optimal reaction and experimental condition. We have...
Nuclide inventory calculations with MVP-BURN and JENDL-4.0 were performed for the twelve fuel samples taken from two 15×15 PWR fuel assemblies irradiated in Three Mile Island (TMI) Unit 1[1,2]. The calculated results of $^{134}$Cs for the one-cycle-irradiation fuel samples and those of $^{133}$Cs for the two-cycle-irradiation fuel samples were compared with the measured data. The averaged...
The JENDL-5 [1] covariance library, covering 105 nuclides, was generated using the AMPX-6 code system [2]. Additionally, a covariance library was also generated from ENDF/B-VIII [3] for JENDL-5 nuclides lacking covariance data. These covariance libraries facilitated the estimation of keff uncertainty attributable to the nuclear data of the Indonesian RSG GAS Multipurpose Research Reactor...
The experiments at JAEA have produced a wide variety of nuclei and various excited states through multi-nucleon transfer reactions and successfully observed their fission [1]. The fission fragment mass distributions (FFMDs) obtained in this experiment show a mass asymmetry even in the high excitation energy region. This phenomenon can be explained by multi-chance fission (MCF). In a previous...
Diminishing the amount of high-level nuclear waste accumulated through reactor operation has always been a one of the most important obstacles regarding the long-term implementation of nuclear technologies. While the main efforts have been targeting minor actinides (MAs), long-lived fission products (LLFPs) remain another clear target for which several solutions have already been proposed....
Technetium-99 is a long-lived fission product (LLFP) which undergoes $\gamma$-decay with a half-life of 211,100 years. This long-lived nature and relative abundance of production (approximately 6% of fission events produce $^{99}$Tc) and environmental mobility makes long term waste storage challeng-ing. As such it is a possible candidate for being reduced via nuclear transmutation. The...
In recent years, the synthesis of new superheavy element$(\mathrm{SHE})$ as been paid attention around the world. When synthesizing SHEs, hot fusion using $^{48}$Ca as projectile and actinides as targets is successful for many SHEs up to Og (Z=118) [1,2]. In synthesizing SHEs after Z=119 by hot fusion, if $^{48}$Ca is used as projectile, it is necessary to use nuclides after Es (Z=99) as...
The US nuclear safety analysis code system SCALE6.2 [1] is also widely used in Japan, but the bundled AMPX continuous energy libraries are produced only from the US nuclear data library ENDF/B. Thus I produced an AMPX continuous energy library of JENDL-5 with the AMPX-6 code [2] bundled in SCALE6.2. In this nuclear data processing I found out that several produced AMPX continuous energy files...
The Japan Aerospace Exploration Agency (JAXA) plans to develop the charged particle spectrum in space to observe the radiation dose for astronauts for Artemis programs. Also, the National Institute of Information and Communications Technology (NICT) plans to develop a spectrum to observe solar flares precisely. Both spectrometers based on Cherenkov radiation are aimed to observe the charged...
The Heavy-Water Thermal Neutron Facility at the Kyoto University Research Reactor (KUR) has been used for boron neutron capture therapy (BNCT) since 1974. After facility upgrades in 1996, it was renamed the Heavy-Water Neutron Irradiation Facility (HWNIF), and the neutron energy spectrum was measured using the multifoil activation method. In 2010, KUR switched from high- to low-enrichment...
The mass and total kinetic energy (TKE) distribution of fission fragments brings essential information on fission dynamics. The fission dynamics have been investigated theoretically with the multi-dimensional Langevin approach, in particular, for actinide nuclei [1]. In this approach, the deformation potential plays a key role in determining the fragment distribution. In order to understand...
In high-energy and high-intensity neutron environments, such as the fusion reactor blanket, large angle scattering reaction cross sections significantly affect neutron transport calculation results. C. Konno has identified discrepancies between experimental and calculated values in the blanket benchmark experiments in Japan Atomic Energy Agency (JAEA) [1]. Therefore, benchmarking studies for...
Understanding nuclear fission is critical for updating and improving the nuclear data. In particular, significant questions remain regarding fission near the mass number $A=257$, where the dramatic changes in fragment mass distribution due to variations in neutron number are observed. These phenomena are generally attributed to shell effects, although a detailed explanation has yet to be...
The Intranuclear Cascade model has been improved for calculating alpha induced reaction. Alpha inelastic reaction is dominant for the alpha incident reaction, so that its cross section must be calculated accurately. However, it is difficult to optimize the inelastic reaction and fragmentation reaction for all fragment channel in parallel. Therefore, in this study, we focus on the inelastic...
The intranuclear cascade model has been improved for calculating proton-induced reactions; the calculation results near 0 degrees remain unsatisfactory. It is known that several types of giant resonances exist near 0 degrees. In this study, giant resonances were incorporated, and comparisons with experimental data were conducted to examine mass and energy dependencies. The experimental data...
The four-dimensional Langevin model [1,2,3] is a nuclear physics model that allows for the independent treatment of each fission fragment and accurately reproduces the total kinetic energy (TKE). However, due to the multidimensional nature of the model, it is challenging to quantitatively determine which physical quantities exhibit a strong correlation with nuclear fission. In this study, we...
At present, using the fusion reaction between the projectile and target nuclei, up to Og has been successfully synthesized and projects to synthesis of new superheavy elements (SHEs) are underway at several facilities around the world. However, the synthesis probability of SHEs is extremely low, and most of them undergo quasi-fission, which cannot sustain a compound nucleus after contact....
Activation analyses are essential in planning and execution of reactor decommissioning, where the ORIGEN-2 and ORIGEN-S codes are often used in Japan. This presentation points out problems in these codes and introduces the ORIGEN code, which is bundled in the US nuclear safety analysis code system SCALE6.2 [1] or later. ORIGEN solves most of the problems but SCALE6.2 bundles only the libraries...
Nuclear data are essential for the research and development of nuclear energy systems and accelerator facilities, and applications involving radioactive isotopes. However, the increasing complexity of theoretical models and the demands of large-scale computations have made sustainable nuclear data evaluation challenging with limited human resources. To overcome these difficulties and continue...
The negative muon ($\mu^-$), which is the second generation of charged lepton and has a 200 times heavier mass than an electron, forms an exotic atom with a nucleus in materials. After the atomic cascade, some of the muons are captured to the nucleus, $\mu^- + p \rightarrow n + \nu_{\mu}$, with competing for the decay in the atomic orbit, $\mu^- +\rightarrow e^- + \nu_{\mu} + \nu_e$. The...
In the TEPCO’s Fukushima Daiichi Nuclear Power Plant accident, fuel debris was formed by fuel melting and mixing with in-core structures. Although the detailed properties of the fuel debris are still unknown, it is thought to contain materials such as iron and concrete. Then, in order to understand the criticality characteristics of fuel debris, JAEA is conducting a comprehensive numerical...
Institute for Integrated Radiation and Nuclear Science, Kyoto University (KURNS) has been operated two research reactors, namely, Kyoto University Research Reactor (KUR) and Kyoto University Critical Assembly (KUCA).
KUR whose maximum power is 5MW starts its operation in 1964 and it has been utilized mainly for supplying fast and thermal neutron in various kinds of research field,...
The Japan Atomic Energy Agency (JAEA) has been developing various non-destructive assay (NDA) techniques [1] to verify nuclear materials. However, one major challenge in NDA is measuring highly radioactive materials. To address this, neutron resonance analysis (NRA) has been proposed as a promising active neutron NDA technique. NRA combines neutron resonance transmission analysis (NRTA) [2]...
Delayed gamma ray assay (DGA) is a promising technique for estimating fission rate ratio of uranium (U) and plutonium isotopes contained in spent nuclear fuel [1]. The accuracy of DGA relies on that of the data of fission product yield and decay (FPY & FPD). To enhance the accuracy of the FPY & FPD data, differential measurements have been conducted in the LINAC neutron source facility in...
Radioisotopes (RIs) are widely used as tracers and radiation sources in basic research in physics, chemistry and biology, as well as in medical, agricultural and industrial applications. We are developing production technologies for useful RIs and promoting RI application research in various research fields using the heavy-ion accelerators in the RIKEN RI Beam Factory [1–3]. More than 100 RIs...
Time Projection Chambers (TPCs) and silicon (Si) semiconductor detectors are useful to examine residual nuclei in nuclear reaction.
We developed MAIKo and MAIKo+, which are TPC-based active target systems [1]. They enable tracking of low-energy charged particles over a large solid angle by using gas as both the detection medium and target. We utilize them to study triple-alpha reaction,...
