Irradiation effects are one of typical environmental issues in nuclear power plants, space crafts and so on. Microstructural evolutions and phase transitions are introduced under irradiations, which deteriorate materials properties. We investigate the radiation-induced phenomena by means of microstructural observations, chemical analysis and mechanical properties. Examples of recent projects are on stainless steel, zircaloy, ZrO2, CeO2, and nuclear fuel. The typical experimental equipment is ion accelerators, TEM, SEM, AFM, positrons, EELS, EDS, Raman, FT-IR, micro-indentation and others.

    Fullerene is one of the promising materials for synthesizing wide variety of dimensionalities and shape with large space for enclosing foreign elements. In this study we investigate interactions of fullerene with foreign elements and radiation effects by experimental and theoretical techniques; ion accelerators, TEM, SEM, EDS, Raman, FT-IR, TG-DTA, Chromatography and others.

    Our lab circumstance is open-minded and people are so motivated scientifically. People can learn as much techniques as they want. They enjoy technical assistance at first, and finally become independent scientists with excellent technical skills and abilities. Students are encouraged to present their progress at conferences (domestic and international) and publishing research papers. We are good relation to Sekimura Lab and Katsumura Lab not only with scientific corporations but also recreations.

>> Page Top

1. Radiation effects in structural materials and fuel materials for LWR, advanced reactors and fusion reactors
   1. Fundamental study of formation and stability of defect clusters under ion irradiation

      Energetic particles introduce dense atomic displacements so called cascades. We developed a new technique related to transmission electron microscopy (TEM), and have found mobile and unstable defect clusters associated with cascades, invisible by conventional TEM.

      •H. Abe, N. Sekimura, Y. Yang, Journal of Nuclear Materials 323 (2003) 220–228, Stability and mobility of defect clusters in copper under displacement cascade conditions.

      •Z.C. Li, H. Abe and N. Sekimura, Journal of Nuclear Materials (2007) in press, Detection of point defects upon ion irradiation by means of precipitate coherency.

   2. Radiation embrittlement in iron-based alloy

      Degradation of pressure vessel steels in nuclear power plants is thought to be induced by Cu, Mn, Ni, Si clusters invisible by TEM. We developed positron beam system interfaced with an ion accelerator so as to detect vacancies and their diffusion process simultaneously.

      •T. Iwai, Y. Ito and M. Koshimizu, Journal of Nuclear Materials 329-333 (2004) 963-966, Vacancy-type defect production in iron under ion beam irradiation investigated with positron beam Doppler broadening technique.

   3. Other research projects

      •Development of fuel cladding materials for supercritical light water reactor (SCWR)

      •Dual-beam irradiation effects for simulation of degradation of fusion reactor materials

      •Ion irradiation effects in fluorite-type crystals for simulation of high burn-up microstructure in nuclear fuels

2. Radiation induced surface activation effect and its application to advanced nuclear technology

   One of the approaches for increasing the power of nuclear plants is to enlarge the critical heat flux of fuel claddings by improving the wettability for light water. The hydrophilic oxide thin films on metal substrates were achieved by the dosage of gamma ray irradiation. Experimental and theoretical approaches have done to clarify its mechanism and evaluate efficiency in the practical environment.

   •M. Kariyazaki, H. Abe, A. Sayano,　F. Kano, Y. Katano, T. Onitsuka and N. Sekimura, J. Japan Inst. Metals 71 (2007) in press (Japanese), Ray Type Dependence of Radiation Induced Surface Activation Phenomenon.

3. Radiation effects on carbon-based materials

   Structural characteristics of fullerene, such as large surface and enclosed space, are expected to have efficient absorption of foreign elements. Radiation effects have studied to clarify the stability of fullerene by means of Raman spectroscopy.

   •N. Sakaguchi, H. Abe, N. Sekimura1 and Y. Katano, J. Japan Inst. Metals 71 (2007) in press (Japanese), Defect Formation in C60 Molecules under Irradiation with Electrons and γ-ray.

4. Microparticle acceleration and its application to cosmic dust detector

   Cosmic dust is energetic microparticles consisting with billions of atoms. Its density, energy and other information are clues to understand the origin of the solar system and the universe. Microparticle acceleration technique was developed and applied to test real-time dust detectors. One of the detectors is scheduled to be loaded on Bepi Colombo, Mercury orbiter being launched on 2013.

   T. Miyachi, M. Fujii, N. Hasebe, M.N. Kobayashi, G. Kuraza, A. Nagashima, Y. Nakamura, K. Nogami, T. Iwai, S. Sasaki, H. Ohashi, S. Hasegawa, H. Yano, H. Shibata, Advances in Space Research 35　(2005) 1263-1269, Velocity Dependent Response of a Piezoelectric material to Hypervelocity Microparticles.

>> Page Top