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2023.06.07
Nuclear Science and Engineering Center (NSEC) has developed a method to estimate the terrestrial soft error rates (SERs) based on simulation coupled with one-time neutron irradiation testing which can be applied to various kinds of neutron sources as the member of the consortium of Quantum Innovation for Safe and Smart Society (QiSS) and in cooperation with Kyoto University, Kyoto Institute of Technology, Kyushu University, Osaka University, Socionext Inc., High-Reliability Engineering and Components Corporation and Hitachi, Ltd..
The reliability of semiconductor devices become more important in the highly computerized society. Soft errors caused by secondary cosmic-ray neutrons are a reliability problem for semiconductor devices in the terrestrial environment. Since the shielding of neutrons is difficult, evaluations of SERs are necessary to assure the reliability of devices. Acceleration tests using spallation neutron beams with the energy spectrum being similar to that of the terrestrial neutrons provides realistic SERs. However, only a few facilities can provide neutron beams with suitable spectra. Therefore, there is a shortage of beam time to live up to vast demands for SER evaluations.
Therefore, we developed an estimation method of SER in the terrestrial environment associating any single measured data with a Monte Carlo Simulation. Specifically, the dependence of SER on neutron energy and critical charge is calculated by simulation, and the critical charge is determined by a single measured data. We also demonstrated the effectiveness of our proposed method by using measured data using various neutron beams with different energy spectrum and radiation transport analysis code PHITS. Our proposed method enables to use various kinds of neutron sources for terrestrial SER estimation.
This work was supported by Japan Science and Technology Agency (JST) through the Program on Open Innovation Platform with Enterprises, Research Institute and Academia (OPERA) under Grant JPMJOP1721. The results of this study have been published in IEEE Transactions on Nuclear Science (https://doi.org/10.1109/TNS.2023.3280190) on May 31, 2023.
JAEA HP Press release (Japanese only)
2023.02.15
Nuclear Science and Engineering Research Center of Japan Atomic Energy Agency (JAEA), in collaboration with Hirosaki University and Hokkaido University, has succeeded for the first time in the world in developing a prediction model enabling simultaneously reproducing in vitro cell-killing effects and the clinical curative effects.
Therapeutic effects of radiotherapy on cancer can be evaluated by both using a model for predicting cellular responses, which was developed based on biological experiments with cultured cells and estimating the relationship between the dose and the cell killing effects (cell death). However, while in general basic cell experiments handle homogeneous cell populations, the tumor treated in clinical practice is composed of heterogeneous cell populations, so it has not been possible to reproduce clinical curative effects based on the model parameters determined by cell experiments. Here, focusing on cancer stem-like cells that are the cause of heterogeneity, we developed an integrated microdosimetric-kinetic (IMK) model that considers the abundance ratio of cancer stem-like, and successfully reproduced cell-killing effects of cancer cells measured by cell experiments and the clinical curative effects. In this study, we examined the curative effects of radiotherapy on lung cancer. In the future, applying the present model to various types of tumors, we expect to develop custom-made treatments for patients with different percentages of cancer stem-like cells.
The finding of this study will be published in Radiotherapy and Oncology (impact factor 6.901) on February 15, 2023.
JAEA HP Press release (Japanese only)
2023.02.02
Nuclear Science and Engineering Center (NSEC), in collaboration with Kyoto University, has succeeded in overcoming the oxygen-induced low-temperature embrittlement of titanium by ultrafine-grained processing.
Interstitial oxygen (O) has long been considered as a double-edged sword in titanium (Ti) and its alloys. It can significantly increase the strength, but severely deteriorate the ductility on the other hand, which in turn drives the increased cost to purify Ti through removing O during industrial productions. For example, the addition of oxygen interstitials by merely 0.3 wt.% (corresponding to ~1.0 at.%) will render titanium totally brittle at 77 K. Here, we propose a new and fundamental strategy to overcome this dilemma in titanium via grain refinement. It is demonstrated in an ultrafine-grained (UFG) (d ~ 2.0 µm) titanium containing 0.3 wt.% oxygen that an ultrahigh strength (~1250 MPa) and large uniform elongation (~14%) can be simultaneously achieved at 77 K, a significant alteration in properties that points towards a straightforward route for decreasing the cost of Ti structural alloys.
The research results were published online in the international scientific journal Nature Communications (https://10.0.4.14/s41467-023-36030-0) on February 1, 2023. This research was supported by JST/CREST [Nanomechanics] Elucidation of macroscale mechanical properties based on understanding nanoscale dynamics for innovative mechanical materials (JPMJCR1994), JST-PRESTO [Nanomechanics] Nanoengineering on Mechanical Functions of Materials (JPMJPR1998), and Elementary Strategy Initiative for Structural Materials (ESISM) of the Ministry of Education, Culture, Sports, Science and Technology (MEXT).
JAEA HP Press release (Japanese only)
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