Press Release

HOME > Press Release

Back Number

How much radioactive waste is converted to what? - Elucidation of the mechanism of transmutation induced by deuteron -

2018.10.12

NSEC and Kyushu University have developed a theoretical method to accurately predict isotopic production cross sections of residual nuclei in the deuteron-induced spallation reactions.

Among radionuclides produced in a nuclear reactor, those with long half-lives require long-term management and hence it is strongly desired to convert them into stable or short-lived ones. Spallation reaction is one of the candidates especially for transmutation of long-lived fission products (LLFPs). In recent years, it has been suggested that the use of deuteron as incident particles improves the efficiency of transmutation compared to other charged particles such as proton.

In the design study of a transmutation system using a deuteron primary beam, accurate cross section data of deuteron-induced reactions on LLFPs are indispensable. Isotopic production cross sections of residual nuclei are especially important. However, conventional theoretical methods are not necessarily adequate for deuteron-induced ones. This is because, although the deuteron is a weakly bound nucleus and easily breaks up by the interaction with a target nucleus, this effect is not considered sufficiently in the conventional methods.

In the present study, we have developed a theoretical method to calculate deuteron-induced spallation reactions taking into account the breakup processes explicitly. The calculated cross sections reproduced the experimental data well over a wide mass number range of residual nuclei.

Research and development on a transmutation system using a deuteron primary beam will make great progress by the present work. In addition, the result of the present work is expected to make a large contribution to various fields related to deuteron-induced reactions, such as production of medical radioisotopes, radioactivity evaluation in deuteron accelerator, and so on.

The study was published in Physical Review C on October 11th, 2018.

JAEA HP Press release (Japanese only)
Kyushu University HP (Japanese only)
JST HP (Japanese only)

Clarification of the mechanism which determines scintillation detector light output - Toward accurate measurement of protons and heavy ions in accelerators, space, and medical treatment -

2018.8.30

NSEC, JAEA and Takasaki Advanced Radiation Research Institute, QST have clarified the mechanism which determines the light output of scintillation detectors to accurately estimate scintillation light output owing to incidence of protons and heavy ions.

Owing to its high efficiency and low price, scintillators are widely used for measurement of gamma-rays, neutrons, etc. However, theoretical background of the relationship between the light output and the energy deposition by protons and heavy ions has been debated for a long time. Clarification of the light emission mechanism and the mechanism-based prediction of light yield have been desired.

In this study, we developed a numerical model composed of 3 phases; 1: radiation transport calculation to simulate microscopic energy deposition, 2: mechanism to transfer deposited energy between molecules, and 3: the mechanism to dissipate the energy by particular transition without emitting light. This model succeeded in reproducing the light yield of scintillators in irradiation by gamma-rays, beta-rays, alpha-rays, protons and heavy ions. In particular, this model accurately predicted the light yield by protons and heavy ions giving an insight into the mechanism which determines the light yield.

The result of this study can contribute to development of new scintillation detectors for radiation measurement in various environments such as accelerator, and space. The study was published in PLOS ONE on August 30th, 2018.

JAEA HP Press release (Japanese only)
QST HP Press release (Japanese only)

Development of the new numerical simulation code ‘JUPITER’ for estimating core meltdown behavior

2018.3.26

NSEC developed a numerical simulation code ‘JUPITER’ which estimates the accumulation and distribution of fuel debris in severe accidents (SAs). By using JUPTIER, simulation of the relocation of the fuel debris into the lower part of the primary containment vessel (PCV) become possible. We confirmed that core meltdown behavior in SAs can be evaluated.

In the SAs, it is considered that the high temperature fuels and structures melt and relocate to the inside of the PCV. However, estimation of the composition and distribution of fuel debris, release of fission products from fuel debris and a possibility of re-criticality are difficult and items in evaluations of behavior of the SAs.

In this research, we developed the new numerical simulation code ‘JUPITER’ based on state of the art computational fluid dynamics technique and without artificial assumptions. By JUPITER, we performed melt relocation simulation from the reactor pressure vessel to the lower part of the pedestal, and obtained the following results;


These results, which have more detailed information in results by conventional SA codes, are to be able to contribute the safer and more reasonable decommissioning.

We will improve JUPITER to perform more realistic simulation, which consider chemical reactions and so on. This research and its results will be published in research journal of the Atomic Energy Society of Japan. Animation of the corium spreading behavior.

JAEA HP Press release (Japanese only)

Elucidation of a significant role of extremely low energy electrons in the formation of complex DNA damage

2018.2.16

NSEC, QST and TAT elucidated a new process about modification of the genetic information in DNA due to the irradiation, which causes mutation induction or carcinogenesis, by a computer simulation.

Although most of the radiation damage to genomic DNA could be rendered harmless by repair enzymes in a living cell, it is thought that the localized damage within a few nm (clustered damage) is persistent, resulting in modification of genetic information. However, the precise three-dimensional structure and formation process have still not been fully elucidated for the chemical modification of clustered damage produced by actual irradiation. Therefore, a prediction by a computer simulation was craved.

In this study, we focus on interactions of electrons produced by irradiation in living system. We developed the calculation code that can simulate electron irradiation to a DNA molecule in the nanometer level and succeeded the simulation of the electron behavior which led to clustered damage. From the analysis of those results, we revealed that the clustered damage, which was generated by the electrons, was converted to the double strand breaks of DNA when base excision enzymes process the isolated base lesions induced by the extremely low energy electron. In addition, the termini of the double strand breaks may have some DNA base lesions. This result indicates that a low energy secondary electron is involved in modification of genetic information in the living system and will be significant to understand initial factor of mutation induction or carcinogenesis by radiations.

We will expand our study to quantitative evaluation of the production fraction of complex DNA damage formed by irradiations. This research and its results are published in Physical Chemistry Chemical Physics, edited by the Royal Society of Chemistry.

JAEA HP Press release (Japanese only)

Development of a Model for Estimating the Therapeutic Effect of Boron Neutron Capture Therapy (BNCT) Considering Intra- and Intercellular Heterogeneity in 10B Distribution

2018.2.5

NSEC, JAEA succeeded in developing a model for estimating the therapeutic Effect of Boron Neutron Capture Therapy (BNCT) considering intra- and intercellular heterogeneity in 10B distribution, under collaboration with Kyoto University, Tsukuba University, and Central Research Institute of Electric Power Industry (CRIEPI). The new model was developed from our previously established stochastic microdosimetric kinetic (SMK) model that determines the surviving fraction of cells irradiated with any radiations. In the model, the probability density of the absorbed doses in microscopic scales is the fundamental physical index for characterizing the radiation fields. A new computational method was established to determine the probability density for application to BNCT using the Particle and Heavy Ion Transport code System PHITS. The parameters used in the model were determined from the measured surviving fraction of tumor cells administrated with two kinds of 10B compounds. The model quantitatively highlighted the indispensable need to consider the synergetic effect and the dose dependence of the biological effectiveness in the estimate of the therapeutic effect of BNCT. The model can predict the biological effectiveness of newly developed 10B compounds based on their intra- and intercellular distributions, and thus, it can play important roles not only in treatment planning but also in drug discovery research for future BNCT. The details of this study are described in T. Sato et al. Sci. Rep. 8: 988, 2018.

JAEA HP Press release (Japanese only)

Chemical stabilization of nuclear fuel by incorporation of zirconium from the fuel cladding

2017.12.25

NSEC, JAEA has clarified that uranium dioxide (UO2) become chemically stable by forming solid solution containing zirconium (Zr). The stabilization by Zr indicates that the molten fuel debris in TEPCO Fukushima Dai-ichi Nuclear Power Plants (1F) would be stable against dissolution by chemical reactions and remain in the reactors until the oncoming retrieval.

Spent nuclear fuel emits intense ionizing radiation and decomposes water into hydrogen peroxide (H2O2). In the case of direct contact of the fuel with water, H2O2 consequently reacts with the fuel and the reaction induces dissolution of uranium from the fuel. This sequence of chemical reactions is expected to occur for the fuel debris in 1F. However, little is known about the chemical behavior of fuel debris in water, because the composition of fuel debris is far different from the usual UO2 fuel due to the melting with the materials in the reactor core.

We have performed experiments regarding the dissolution of U by H2O2, and elucidated that incorporation of Zr significantly affects the dissolution of U. The U oxide containing Zr was used as simulated fuel debris, because the fuel debris is expected to contain Zr from the fuel cladding. When the simulated debris containing 50 % of Zr in atomic ratio was exposed to aqueous H2O2 solution, the amount of dissolved U from the simulated debris was only 4 % of that from UO2. This inhibited dissolution was resulted from the effect of Zr to promote H2O2 decomposition on the surface of simulated fuel debris.

We are going to further investigate basic chemistry of molten fuel, in order to support the research and development for the safe retrieval and management of the fuel debris in 1F.

Linked URL: https://doi.org/10.1016/j.jnucmat.2017.10.050
JAEA HP Press release (Japanese only)

Lightning-production of antimatter clouds

2017.11.24

NSEC, JAEA, has revealed that lightning triggers an atmospheric nuclear reaction, which is called a photonuclear reaction, together with a research team including Kyoto University, RIKEN and the University of Tokyo.

Intense lightning-produced gamma-ray emission, which is called a short burst, was observed at Kashiwazaki, Niigata Pref. on 2017 February 6, by detector systems that the research team developed for thunderstorm-radiation measurement. Furthermore, detections of 0.511-MeV gamma rays were successfully made around 35s after the short-burst occurrence, suggesting that electron-positron annihilations took place when the thundercloud floated over the detectors.

Both the short burst and the subsequent 0.511-MeV gamma rays provide conclusive evidence of lightning-induced photonuclear reactions that have been theoretically predicted until now. This is because those signals are thought to originate from neutrons and unstable radioactive nitrogen isotopes that are generated by photonuclear reactions between high-energy gamma rays derived from lightning and atmospheric nitrogen nuclei.

This work also implies that radioactive carbon-14 (14C) is produced by lightning. As well known, 14C is used for radioactive dating in a wide variety of research fields. Therefore, this implication of the 14C production associated with lightning may give a great impact on science community. This work was published in “Nature” on November 23, 2017.

Linked URL: https://www.nature.com/articles/nature24630
JAEA HP Press release (Japanese only)
Kyoto University HP press release (Japanese only)

Discovery of self-healing capability of ceramics under radiation environment

2017.11.13

NSEC, JAEA and Takasaki Advanced Radiation Research Institute, QST has developed a novel method to observe nanometer-sized superfine structures created in ceramics irradiated with high-energy heavy particles. The objective of this development is to elucidate the reason why specific ceramics have exceptionally high resistance against radiation.

By using the method, the interior of the superfine structure was analyzed. As a result, it has been found that the ceramics can be categorized into two groups; 1) the ceramics where the interior of the superfine structure is disordered and damaged and 2) the ceramics where the damaged region is healed by recrystallization. The result indicates that the latter ceramics have self-healing capability which enables them to restructure their atomic arrangement quickly after the damaging process.

It is expected that revealing the mechanism of self-healing capability of ceramics leads to a wide use of ceramics under intense radiation environments such as in space and nuclear reactors.

Linked URL: http://iopscience.iop.org/article/10.1088/1361-6528/aa8778/meta
JAEA HP Press release (Japanese only)

Development of an emergency assessment system of the marine environmental radioactivity

2017.03.10

NSEC, JAEA has developed the Short-Term Emergency Assessment system of Marine Environmental Radioactivity (STEAMER) to immediately predict the radionuclide concentration around Japan in case of a nuclear accident. STEAMER forecasts the radionuclide concentration of ocean and sea bottom sediment for 30 days by a particle random-walk model, SEA-GEARN developed by NSEC, JAEA by using online forecast data of oceanic flow fields by Japan Meteorological Agency and information of radionuclides release into the ocean. It is possible to estimate the distribution of radionuclides after the release from nuclear sites in East Asian countries including Japan and any sea region around Japan. Coupling the STEAMER with the emergency atmospheric dispersion prediction system, such as Worldwide version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI), enables comprehensive environmental pollution predictions both in the air and ocean. The stability and robustness of the system has been validated by test operation since September 2014.

It is possible to use STEAMER for the design of oceanic emergency countermeasures against a nuclear accident and detailed post-accident assessment such as, setting up an emergency ocean monitoring area based on the predicted pollution distribution, estimating the source term of oceanic release from a facility through the reverse analysis from ocean monitoring data, and prohibiting fishing and sailing from the detailed assessment.

Linked URL: http://www.tandfonline.com/doi/full/10.1080/00223131.2017.1286272
JAEA HP Press release (Japanese only)

First determination of palladium-107 in spent nuclear fuel

2017.02.03

NSEC, JAEA and Takasaki Advanced Radiation Research Institute, QST have determined for the first time at Palladium-107 content in spent nuclear fuel. The radiation from 107Pd has a long-term risk of health problem associated with its long half-life of 6.5 million years. Thus, the accurate information on 107Pd content is essential for evaluating such radiation effects. However, no reliable analytical method for 107Pd has been established so far. Due to the absence of the measured content of 107Pd, theoretical values provided by calculation have been employed as the substitute. A separation technique developed by our research team has achieved highly selective recovery of Pd with the purity above 99.9%, resulting in the first determination of 107Pd. In this technique, Pd is recovered as precipitate, which is formed through remote activation by laser irradiation. The developed technique can be applied to various samples, such as damaged nuclear fuel and high level radioactive wastes.

Linked URL:http://pubs.acs.org/doi/abs/10.1021/acs.analchem.6b03286.
JAEA HP Press release (Japanese only)

Evaluation of World Population-Weighted Effective Dose due to Cosmic Ray Exposure

2016.09.29

We evaluated the population-weighted annual effective doses and their probability densities for the entire world as well as for 230 individual nations, using a sophisticated cosmic-ray flux calculation model in tandem with detailed grid population and elevation databases. The resulting world population-weighted annual effective dose was determined to be 0.32 mSv, which is smaller than the UNSCEAR's evaluation by 16%. These data improve our understanding of cosmic-ray radiation exposures to populations globally, and they were published in Scientific Reports on Sep. 21, 2016.

JAEA HP Press release (Japanese only)

Major step forward the practical use of medical isotope 99mTc produced by using accelerator neutrons

2015.07.17

The special group for RI generation technology using accelerator neutrons has succeeded to obtain the distribution of 99mTc-radiopharmaceutical for bone scanning in mouse with single photon emission tomography (SPECT) for the first time using 99mTc, which was separated by thermochromatography from 99Mo produced by using accelerator neutrons. Radionuclidic purity and radiochemical purity of the separated 99mTc and its aluminum concentration met the United States Pharmacopeia regulatory requirements for 99mTc from the fission product 99Mo. The SPECT image was comparable with that obtained from a fission product 99Mo. These results provide important evidence that 99mTc radiopharmaceutical formulated using 99Mo can be a promising substitute for the fission product 99Mo.

JAEA HP Press release (Japanese only)

Completion of "JAEA CHART OF THE NUCLIDES 2014" covering nuclear decay data

2015.04.01

The distribution of "JAEA CHART OF THE NUCLIDES 2014", produced by Nuclear Data Center, Research Group for Reactions Involving Heavy Nuclei, Nagaoka University of Technology and Waseda University, began on March 12, 2015. The chart of the nuclides lists 3,150 nuclides which are observed in experiments and 2,916 of them give the half-lives from evaluation. In addition, 1,578 nuclides" half-lives are not measured yet but are provided theoretically. In this chart, 23 kinds of decay schemes are newly added. The chart is expected to be used by researchers to comprehend up-to-date nuclear data easily. It can also be used as a material in lecture for the public, including high school students, to understand the productions and the transmutations of radioactive nuclei, and also the origin of matters in the universe, and so on. It is expected to widely use the chart of the nuclides in various purposes in the world.

JAEA HP Press release (Japanese only)

Practical use of WAZA-ARIv2 for set up of CT examination condition in medical institution

2015.03.03

Practical use of WAZA-ARIv2 began on January 30, 2015 at the web server in the National Institute of Radiological Sciences (NIRS). WAZA-ARIv2 has been developed under the collaboration research project among the research group for radiation protection of JAEA, NIRS and Oita University of Nursing and Health Sciences. In WAZA-ARIv2, new functions, e.g. taking into account both age and physique for a patient in dose calculation, are added to WAZA-ARI, which had been operated in trial. Then, WAZA-ARIv2 enables medical service workers to reduce and manage radiation dose for the patient at their medical institution.

JAEA HP Press release (Japanese only)

New method for elemental analysis at J-PARC

2015.01.13

Nuclear Science and Engineering Center (NSEC) developed a new elemental analytical method that combines two non-destructive techniques by using an intense pulsed neutron beam at the Japan Proton Accelerator Research Complex (J-PARC). The combined method provides significant synergy. Specifically, it can be used to quantify elemental concentrations in the sample, to which neither of these methods can be applied independently.

JAEA HP Press release (Japanese only)

Development of new technology of more than tenfold processing speed and less than one fifth cost for radioactive waste solution treatment

2014.06.09

Nuclear Science and Engineering Center (NSEC) developed a new technology for radioactive waste solution treatment with more than tenfold processing speed and less than one fifth cost relative to conventional techniques, in cooperation with Ningyo-toge Environmental Engineering Center (NEEC). This technology is based on uniquely invented "emulsion flow method" (Patent No.5305382, Japan) where simplicity, low cost, and high efficiency go together. NSEC and NEEC have succeeded in selectively removing uranium down to the concentration of uranium lower than its effluent standard (0.0022 Bq/ml) from decontamination waste solutions by using a half-size testing apparatus.

JAEA HP Press release (Japanese only)

Demonstration of NDA technique for determining uranium mass in drums stuffed with dismantling waste of nuclear facilities.

2014.06.09

Nuclear Science and Engineering Center (NSEC) designed a NDA system using Fast Neutron Direct Interrogation (FNDI) method for determining uranium mass in drums stuffed with dismantling waste of nuclear facilities. Ningyo-toge Environmental Engineering Center (NEEC) manufactured the NDA system and installed in the site. NSEC and NEEC have conducted the demonstration tests and experimentally proved that a small amount of uranium fissile contained in the waste drum could be quantified in a short time.

JAEA HP Press release (Japanese only)

Assessment of radiation dose reduction in various buildings for gamma-rays emitted from radioactive cesium.

2014.03.31

Research Group for Radiation Protection has developed useful computational simulation techniques to assess radiation dose reduction in various buildings for gamma rays from radioactive cesium that was released into environment due to the TEPCO Fukushima-Dai-ichi Nuclear Power Plant accident. By the developed techniques, influential factors on the radiation dose reduction were analyzed for each type of building where residents stay in daily life.

JAEA HP Press release & Report (Japanese only)