Minoru Tanigaki

Construction of FFAG Accelerators in Kurri for ADS Study

Kumatori Accelerator driven Reactor Test project (KART) has been started at Kyoto University Research Reactor Institute (KURRI) from the fiscal year of 2002, aiming to demonstrate the basic feasibility of Accelerator Driven Sub-critical Reactor system (ADSR) and to develop an 150 MeV proton Fixed Field Alternating Gradi ent (FFAG) accelerator complex as a neutron production driver. This FFAG complex will be connected with our Kyoto University Critical Assembly (KUCA) by the end of March 2006 for the basic ADSR experiments.

Measurement of air dose rates over a wide area around the Fukushima Dai-ichi Nuclear Power Plant through a series of car-borne surveys

A series of car-borne surveys using the Kyoto University RAdiation MApping (KURAMA) and KURAMA-II survey systems has been conducted over a wide area in eastern Japan since June 2011 to evaluate the distribution of air dose rates around the Fukushima Dai-ichi Nuclear Power Plant and to evaluate the time-dependent trend of decrease in air dose rates. An automated data processing system for the KURAMA-II system was established, which enabled rapid analysis of large amounts of data obtained using about 100 KURAMA-II units. The initial data used for evaluating the migration status of radioactive cesium were obtained in the first survey, followed by other car-borne surveys conducted over more extensive and wider measurement ranges. By comparing the measured air dose rates obtained in each survey (until December 2012), the decreasing trend of air dose rates measured through car-borne surveys was found to be more pronounced than those expected on the basis of the physical decay of radioactive cesium and of the air dose rates measured using NaI (Tl) survey meters in the areas surrounding the roadways. In addition, it was found that the extent of decrease in air dose rates depended on land use, wherein it decreased faster for land used as building sites than for forested areas.

Research Project on Accelerator-driven Subcritical System Using FFAG Accelerator and Kyoto University Critical Assembly

The Research Reactor Institute of Kyoto University started the KART (Kumatori Accelerator-driven Reactor Test facility) project in fiscal year 2002 under the Contract with the Ministry of Education, Culture, Sports, Science and Technology of Japan. The purpose of this research project is to demonstrate the basic feasibility of accelerator-driven system (ADS), studying the effect of incident neutron energy on the effective multiplication factor in a subcritical nuclear fuel system. For this purpose, a variable-energy FFAG (Fixed Field Alternating Gradient) accelerator complex is constructed and coupled with the Kyoto University Critical Assembly (KUCA). This paper presents the present status of the project and some of the results from the task performed up to Fiscal Year 2005.

Behavior of Boron Implanted in Semiconductor Si

Using β-NMR with 12B nuclei the temperature dependence of the lattice locations of boron implanted in Si is studied. At low temperature almost 100% of the implanted B is in either substitutional site or nonsubstitutional site. Above 260 K, the nonsubstitutional B rapidly becomes undetectable and disappears at a temperature higher than 325 K due to the fast spin-lattice relaxation. Above 450 K, the fraction of substitutional B increases to 100%. These experimental results are consistently explained by the thermal atomic jump and the dissociation of the defect associated with the nonsubstitutional B.

Studies of interaction between He and elements with mass number 140 in Fe by time-differential perturbed-angular-correlation measurements

Room-temperature time-differential perturbed-angular-correlation (TDPAC) spectra of 140Ce arising through 140Ba-140La from 140Cs in He-doped Fe, unannealed and annealed in vacuum at various temperatures, were obtained in order to examine whether Ce (or rather, La and Ba) and He form complexes having a definite geometrical structure in Fe, as suggested by first-principles density-functional theory calculations. No clear signal of such complexes was observed in the TDPAC spectra. However, the TDPAC spectra indicate that Ce and He form complexes having a variety of geometrical structures. Comparison with reported TDPAC results on 111Cd arising from 111In in He-doped stainless steel shows that the parent atoms (La and Ba) of 140Ce trap He atoms more efficiently than In atoms do, indicating stronger bonding of He to the former atoms, while different from the present case, 111Cd (In)–He complexes form a unique geometrical structure.

Development of a Carborne Survey System, KURAMA

A carborne survey system named KURAMA (Kyoto University RAdiation MApping system) has been developed for the establishment of air dose rate maps in Fukushima and the surrounding area as a response to the nuclear accident at the TEPCO Fukushima Daiichi Nuclear Power Plant. KURAMA is a γ-ray survey system with Global Positioning System (GPS) and up-to-date network technologies developed for the primary use of carborne surveys. The monitoring data tagged by GPS location data are shared with remote servers over the cloud network, then processed by servers for a real-time plot on Google Earth and other various purposes. Based on the success of KURAMA, KURAMA-II, an improved version of KURAMA with better handling and ruggedness, was developed for autonomous operation in public vehicles. About 200 KURAMA-II systems now serve for continuous monitoring in living areas by local buses as well as the periodic monitoring in Eastern Japan by the Japanese government. The outline and present status of KURAMA and KURAMA-II are introduced.

Large hyperfine anomaly between Y 91 and Y 91 m in Fe

Nuclear magnetic resonance on oriented nuclei was carried out using a sample of dilute

NMR-ON studies on the magnetic hyperfine field at 140La in Fe

^{91}\mathrm{Y}

Development and Operation of a Carborne Survey System, KURAMA

and

Construction of a FFAG Complex for ADS Research in KURRI

^{91m}\mathrm{Y}