Atsushi Kaminaga

Development of Flexible Neutron-Shielding Resin as an Additional Shielding Material

A soft-type neutron-shielding resin has been developed by improving an existing hard-type neutronshielding material using the epoxy-based resin as an additional shielding material. A flexible heat-resistant neutron-shielding material has been developed, which consists of a new polymer-based resin with boron. The neutron shielding performance of the developed flexible heat-resistant resin with the 252Cf neutron source is almost the same as that of polyethylene. The outgases of H, H2, NH4, H2O, CO, O2, C4H10, and CO2 from the developed resin have been measured at high temperature (up to 250°C) by thermal desorption spectroscopy methods. The soft-type resin and the newly developed heat-resistant resin will be applied to prevent the effects of neutron streaming and to control the movement of a vibrated pipe as the seal material around the plumbing in the future fast reactor and innovative fission reactor.

Fuelling characteristics of supersonic molecular beam injection in JT-60U

Supersonic molecular beam injection (SMBI) was successfully operated in JT-60U after improving the performance of the vacuum seal used inside the injector head. Frequent density jumps were clearly observed in the main plasma against the SMBI pulses with filling gas pressures (PFG) of 0.2–0.6 MPa. The fuelling efficiency exhibited a weak dependence on PFG and the injection direction (high- and low-field-side injections). The amount of fuelling necessary for achieving the same density level is much smaller for SMBI than for gas puffing. It is comparable for SMBI and pellet injection even with shallower penetration of SMBI as discussed. The SMBI ionization area was estimated based on emission measured using a fast TV camera with a time resolution of 0.167 ms. The estimations indicated a similar penetration position for PFG = 0.6 and 0.2 MPa, although the ionization area was larger for 0.6 MPa. This result supports the weak PFG dependence of the fuelling efficiency. The front of the ionization area moved between the first and second frames of the fast TV camera and it reached just inside the separatrix in the second frame. The ionization area was significantly expanded even in the first frame from the expected SMB size and the expansion was enhanced in the second frame. These relatively slow changes between the two frames suggest that the interaction between the SMB and the plasma significantly influences the fuelling characteristics.

Neutron Tranamission Experiment of Boron-doped Resin for the JT-60SC Neutron Shield using 2.45 Mev Neutron Source

The neutron shielding design has been carried out for the JT-60 superconducting modification using the boron-doped resin. For the boron doped resin with 0.8 and 2 wt % boron, the neutron transmission experiment with 2.45 MeV neutron source has been performed. The shielding performance of the boron-doped resin for the fast neutron flux does not depend on the boron density in the range of 0.8-2 wt% boron. On the other hand, for the thermal neutron flux the shielding performance of 2 wt% boron is superior to that of 0.8 wt% boron. Most of the reaction rates by DOT3.5 and MCNP calculations agree with the experiment results within 20 %.