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Lightning-production of antimatter clouds


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.
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JAEA HP Press release (Japanese only)
Kyoto University HP press release (Japanese only)

Discovery of self-healing capability of ceramics under radiation environment


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.
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JAEA HP Press release (Japanese only)

Development of an emergency assessment system of the marine environmental radioactivity


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.
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JAEA HP Press release (Japanese only)

First determination of palladium-107 in spent nuclear fuel


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.
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JAEA HP Press release (Japanese only)

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


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


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


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


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


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


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.


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.


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)