Radioactivity production around the surface of a cooling water pipe in a D-T fusion reactor by sequential charged particle reactions

Around the surface of a cooling pipe in a D-T fusion reactor, it is expected that the radioactivity production via what is known as ‘Sequential Charged Particle Reaction (SCPR)’ would be enhanced by recoiled proton from hydrogen in cooling water. In order to simulate the circumstances, several sheets of foil with a thickness of 50–250 μm were laminated on a polyethylene board for six fusion materials (Fe, Cu, V, Ti, W, Pb). The laminated samples were irradiated with intense D-T neutrons at the fusion neutronics source facility in JAERI. After irradiation, the decay gamma rays emitted from the sequential reaction products (56Co, 65Zn, 51Cr, 48V, 184Re, 206Bi) were measured and the effective cross-sections for producing those were obtained at several positions. The present results indicated that the sequential reaction rate increases prominently as the location becomes closer to hydrogen compounds.