AbstractAround 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.
D-T核融合炉における冷却管表面付近では、冷却水中の水素からの反跳陽子により、「逐次荷電粒子反応（SCPR）」を介した放射能生成が促進されると予想される。この状況を模擬するため、6種類の核融合材料（Fe、Cu、Ti、V、W、Pb）の箔を厚さ50～250μmでポリエチレン板上に積層した。積層試料は、JAERIの核融合中性子源施設において強力なD-T中性子で照射された。照射後、逐次反応生成物（⁵⁶Co、⁶⁵Zn、⁵¹Cr、⁴⁸V、¹⁸⁴Re、²⁰⁶Bi）から放出される崩壊ガンマ線を測定し、それらの生成に対する実効断面積を各位置で求めた。その結果、逐次反応率は水素化合物に近い位置ほど顕著に増大することが明らかになった。