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How are Metal Materials Corroded by the Water inside Primary Containment Vessel in 1F – Construction of Database for Corrosion under Irradiation Conditions – 

2021.10.07

A research group composed by Japan Atomic Energy Agency (JAEA), National Institute for Quantum Science and Technology (QST), Osaka Prefecture University, Tokyo Institute of Technology, Tohoku University and University of Tokyo constructed “Database for Corrosion under Irradiation Conditions” which is needed to consider the safety measures for the decommissioning processes of 1F. This database includes ①Radiolysis database for the water containing impurities such as seawater components and ②Corrosion database for the corrosion data under irradiation conditions, which is useful information for considering the possibility of an occurrence of a trouble caused by corrosion and corrosion protections. And ③Investigation sheets for corrosion risks is developed as results of considerations for the corrosion risks in the decommissioning processes of 1F.

In the ①radiolysis database, the 176 reactions and those rate constants were obtained from literature survey and arranged as necessary information for radiolysis calculations. Some reactions were optimized based on the experimental results obtained in this study.

In the ②corrosion database, the data about corrosion rates and corrosion potentials under irradiation were collected as individual research table, and summarized in a data table with the experimental condition obtained from literatures. New data were obtained about the effect of irradiation on corrosion of carbon steel at water line, the effect of the ozone, and the effect of irradiation on the corrosion behavior of carbon steel exposed to the water containing borate.

In the development of ③investigation sheet for corrosion risks, the corrosion risks were investigated and analyzed with subdividing structures, taking into account the decommissioning processes, and summarized in the corrosion map.

This database is expected to contribute to determine the preventative maintenance and safety measures to perform a long term decommissioning process of 1F more safely.

JAEA HP Press release (Japanese only)

Rational Protection of Airline Passengers from the Threat of Exposure to Solar Flares – Quantifying the risk of economic loss enables the formulation of optimal aircraft operation guidelines – 

2021.09.03

A research group composed by Japan Atomic Energy Agency (JAEA), Kyoto University, Aioi Nissay Dowa Insurance Co. Ltd., and National Institute of Maritime, Port and Aviation Technology (MPAT) analyzed the frequency and intensity of solar flares that have occurred over the past 2000 years, as well as four-dimensional spatial time series data of solar radiation dose rates obtained from the latest simulations. They succeeded in quantifying the risk of changing aircraft flight plans due to solar radiation exposure for the first time. Due to their research, it was found that the frequency of major solar flares that would require a reduction in flight altitude or cancellation is about once every 17 years, and the annual risk, taking into account the cost of countermeasures, is up to about $1,500 USD for a long-haul flight operating every day. This value is not as large as other aviation risks, such as volcanic eruptions, and suggests that air travelers can be reasonably protected from the threat of exposure due to solar flares. In the future, if it becomes possible to estimate the accumulated radiation dose on the route in real time, the risk can be further reduced to about one third. The results of this research are expected to be useful for the determination of guidelines for aircraft operations during solar flares and for the development of risk mitigation plan. The results of this research will be published in the online edition of Scientific Reports (Nature Research Journal) on September 2, 2021 (GMT 10:00).

JAEA HP Press release (Japanese only)

Non-destructive quantitative analysis of one of the most difficult-to-measure radionuclide 107Pd

2021.08.05

Considering the expanding demand for nuclear waste management of the spent nuclear fuel materials in near future, a non-destructive analytical scheme applicable to one of the most difficult-to-measure nuclides: 107Pd, which emits no decay gamma-rays and whose half-life is too long to be decayed out during a human lifetime, was designed. The scheme consists of a sophisticated instrument capable of the detection of gamma-rays by Ge detectors coupled with time-of-flight measurement of neutrons and a high-intensity pulsed neutron beam, and can simultaneously perform TOF-coupled prompt gamma-ray analysis (TOF-PGA) as well as PGA and neutron resonance capture analysis (NRCA). An analytical capability was evaluated by applying to simulated samples of the Tc-platinum group metals (Tc-PGMs) obtained by the group partitioning process of spent nuclear fuels, which contain not only 107Pd but also 99Tc and another difficult-to-measure fission product. It was confirmed that, although PGA and NRCA could accurately analyze both nuclides in individual single sub-stances, only TOF-PGA can analyze 107Pd as well as 99Tc in the Tc-PGMs simulated sample. The TOF-PGA measurement technique can be widely used for the non-destructive analysis of 107Pd and 99Tc in nuclear wastes. The results of this study have been published in the Analytical Chemistry entitled as “Non-destructive quantitative analysis of difficult-to-measure radionuclides 107Pd and 99Tc”. This work was supported in part by Grants-in-Aid for Scientific Research (JP17H01076).

JAEA HP Press release (Japanese only)

A reliable and robust non-destructive detection method for nuclear materials using a neutron source

2021.06.07

With the increase of today’s global terrorist threat, a large-scale terrorist attack using nuclear materials that can cause enormous damages can actually occur. Consequently, devices for nuclear security that are used to detect nuclear materials have grown increasingly important. The detection method called the active neutron method is the most potential candidate for it. In the active neutron method, neutrons are irradiated into a container containing nuclear materials and then measures the emitted fission neutrons. Though a conventional active method using a D-T tube has high performance to detect small nuclear materials, it has significant drawbacks of being massive and quite expensive. We therefore developed a new active neutron method that does not use a D-T tube. The new method that we call rotation method is a novel method for detecting nuclear materials using a neutron source such as californium. In this method, while a neutron source is rotated rapidly nearby a measurement object, neutron measurement is carried out by synchronizing the rotation motion. If the object contains a nuclear material, as the rotation speed increases, the larger deformation of time distribution of neutron counts is observed, which in turn resulted to the detection of the nuclear material. In addition to its features of low cost and portability, this method is capable of detecting uranium that emits very few spontaneous fission neutrons. We presented the fundamental principle of this method and its effectiveness for detecting nuclear materials through the experimental verifications. The results of this study have been published in the Annals of Nuclear Energy entitled as “First demonstration experiment of the neutron rotation method for detecting nuclear material”.

JAEA HP Press release (Japanese only)

Development of accurate nuclear reaction calculation method accelerating new neutron applications – Release of calculated database contributing neutron applications in the science and medical fields – 

2021.02.12

NSEC, Kyushu University, and Osaka University developed a calculation method predicting accurately the amount of neutrons generated from the nuclear reactions induced by deuterons. In addition, based on the results calculated with the method, the nuclear reaction database JENDL/DEU-2020 was produced and released for the design studies of accelerator-based neutron sources.

In the research fields such as experimental nuclear physics, medicine, and fusion reactor development, intensive neutron beams with high energies above 10 MeV are required. However, conventional neutron sources such as nuclear reactors cannot satisfy these requirements. Under these circumstances, new neutron sources using the nuclear reactions induced by deuterons have been proposed.

In order to design such neutron sources, it is necessary to accurately predict the amount of neutrons generated from the nuclear reactions by deuterons under various conditions such as incident deuteron energies, target nuclei, and so on. However, conventional calculation methods cannot make reliable prediction for those conditions spread over wide range. This is because the quantum mechanical "wave" properties of deuterons are not taken into account appropriately.

In this study, we developed a new calculation method by integrating the several theoretical models taking quantum mechanical effects into consideration. From the comparison with the measured data, it was confirmed that the prediction accuracy of the present method is four times better than that of the conventional one. Furthermore, the calculated results were compiled into a database applicable to the simulation software employed in the design studies of neutron sources, and it was released as JENDL/DEU-2020.

By using JENDL/DEU-2020, the reliability of the simulation is greatly improved and that makes easier to design various neutron sources suitable for their purposes. It is expected to promote the use of neutrons in a broad range of the fields such as basic science, material development, medicine, and so on.

JENDL/DEU-2020 has been available from the following URL link since February 10th, 2021.
https://wwwndc.jaea.go.jp/index.html

The study was published in Journal of Nuclear Science and Technology on February 10th, 2021.

JAEA HP Press release (Japanese only)

Development of individual dosimetry system for targeted alpha therapy based on PHITS

2021.01.16

An individual dosimetry system is essential for the evaluation of precise doses in nuclear medicine. We therefore developed an individual dosimetry system dedicated to nuclear medicine particularly to targeted alpha therapy based on Particle and Heavy Ion Transport code System PHITS, under collaboration between Nuclear Science and Engineering Center of JAEA and Osaka University. It calculates not only absorbed doses but also biological doses from the PET-CT images, considering the dose dependence of relative biological effectiveness, the dose-rate effect, and the dose heterogeneity. The developed system has been implemented in the latest version of PHITS, which is freely available by submitting an application form to us via PHITS website. The results of this study have been published in an open-access journal “EJNMMI Physics” entitled as “Individual dosimetry system for targeted alpha therapy based on PHITS coupled with microdosimetric kinetic model”.

JAEA HP Press release (Japanese only)