Investigation of development condition with new nuclear emulsion for neutron measurement under high gamma-ray background

Ishihara, Kohei*; Kawarabayashi, Jun*; Tomita, Hideki*; Naka, Tatsuhiro*; Asada, Takashi*; Morishima, Kunihiro*; Nakamura, Mitsuhiro*; Maeda, Shigetaka; Iguchi, Tetsuo*

Progress in Nuclear Science and Technology (Internet), 4, p.661 - 664, 2014/04

https://doi.org/10.15669/pnst.4.661

Spent fuel emits not only neutrons but also lots of -rays by its included fission products (for example, neutron/ ratio is in the order of 10). For its safety handling, it is important to investigate the neutron characteristics such as an emission rate, emission profile and energy spectrum. But it is difficult to measure the neutron characteristics with high precision because of lots of -rays. So the neutron characteristics are estimated by an evaluation based on its burning history. It is necessary to measure them for estimate of adequacy of the simulated result. Also, a direct measurement of the neutron characteristics is essential in the case that each spent fuel has different burning history and is mixed (for example the accident of the Fukushima Dai-ichi Nuclear Power Plant). Therefore, we develop a new nuclear emulsion in order to measure neutrons under high -rays field in our study.

Fusion materials development program in the Broader Approach activities

Nishitani, Takeo; Tanigawa, Hiroyasu; Jitsukawa, Shiro; Nozawa, Takashi; Hayashi, Kimio; Yamanishi, Toshihiko; Tsuchiya, Kunihiko; Mslang, A.*; Baluc, N.*; Pizzuto, A.*; et al.

Journal of Nuclear Materials, 386-388, p.405 - 410, 2009/04

https://doi.org/10.1016/j.jnucmat.2008.12.146

The establishment of the breeding blanket technology is one of the most important engineering issues on the DEMO development. For the DEMO blanket, developments of the structural materials and functional materials such as tritium breeder and neutron multiplier. Which should be used under the savior circumstance such as high neutron fluence, high temperature and strong magnetic field, are urgent issues. In the Broader Approach activities initiated by EU and Japan, developments of reduced activation ferritic martensitic steels as a DEMO blanket structural material, SiC/SiC composites, advanced tritium breeders and neutron multiplier for DEMO blankets, are planed as common interest issues of EU and Japan. This paper describes the overview of the development program.

Examination results on reaction of lithium

Asada, Takashi; Kawai, Masataka *

JNC TN9410 2001-001, 153 Pages, 2000/12

JNC-TN9410-2001-001.pdf:11.14MB

Before the material corrosion tests in lithium, the reactions of lithium with air and ammonia that will be used for lithium cleaning were examined, and the results were as follows. (1)When lithium put into air, surface of lithium changes to black first but soon to white, and the white layer becomes gradually thick. The first black of lithium surface is nitride (LiN) and it changes to white lithium hydroxide (LiOH) by reaction with water in air, and it grows. The growth rate of the lithium hydroxide is about 1/10 in the desiccator (humidity of about 10%) compare with in air. (2)When lithium put into nitrogen, surface of lithium changes to black, and soon changes to brown and cracks at surface. At the same time with this cracking, weight of lithium piece increases and nitridation progresses respectively rapidly. This nitridation completed during 1-2days on lithium rod of 10mm in diameter, and increase in weight stopped. (3)Lithium melts in liquid ammonia and its melting rate is about 2-3 hour to lithium of 1g. The liquid ammonia after lithium melting showed dark brown.

Sensitivity control of nuclear emulsion using AgBr nano-grains

Ishihara, Kohei*; Takagi, Keisuke*; Kawarabayashi, Jun*; Tomita, Hideki*; Naka, Tatsuhiro*; Asada, Takashi*; Morishima, Kunihiro*; Nakamura, Mitsuhiro*; Kuge, Kenichi*; Maeda, Shigetaka; et al.

no journal, , 

The nuclear emulsion with AgBr nano-grains has been developed for neutron detection under high -ray background. It has been demonstrated that the detection sensitivity of -rays can be well suppressed compared to that of neutrons by adjusting the size of AgBr nano-grains to deposit the energy of the secondary electrons produced by -rays below a certain threshold which can create Ag latent images.

Development of automatic readout and recognition of nuclear emulsion for fast neutron measurement

Sakai, Yosuke*; Minato, Haruna*; Ishihara, Kohei*; Tomita, Hideki*; Kawarabayashi, Jun*; Iguchi, Tetsuo*; Naka, Tatsuhiro*; Asada, Takashi*; Morishima, Kunihiro*; Nakano, Toshiyuki*; et al.

no journal, , 

In order to measure a neutron-spectrum under high ray environment, a new nuclear emulsion and its data-processing method are developed. In fast neutron measurement using the nuclear emulsion which can record the three-dimensional track of a charged particle, incidence neutron energy spectrum can be obtained by analyzing the track of the recoil proton generated by the elastic scattering of a neutron. The high-speed automatic analytic method of the recoil proton track in a nuclear plate is developed. It checked that the recoil proton track length distribution obtained by viewing and automatic analysis was in agreement with a model calculation result about by the basic experiment using 14 MeV neutron.

Temperature dependence of -ray and neutron sensitivities of nuclear emulsion with AgBr nano-grains

Ishihara, Kohei*; Kawarabayashi, Jun*; Tomita, Hideki*; Naka, Tatsuhiro*; Asada, Takashi*; Morishima, Kunihiro*; Nakamura, Mitsuhiro*; Maeda, Shigetaka; Iguchi, Tetsuo*

no journal, , 

In order to establish a neutron spectrum measurement in high field such as spent nuclear fuel storage, advanced nuclear emulsion based on non-sensitized OPERA film with AgBr grain size of 60 nm has been developed. A nuclear emulsion has the feature of being easy to cause latent image degradation in the high temperature condition. In this study, the experiment estimated the temperature dependency of the sensitivity to the ray and neutron of a new nuclear emulsion. It is confirmed that the detection efficiency for a neutron and fell in more than 30 C environment.