Nuclear transmutation effect by thermal neutron on degradation in superconductivity of ReBCO tapes

Abstract Rare earth barium copper oxide (ReBCO) tapes of GdBCO, EuBCO and YBCO have been neutron-irradiated in Japan Research Reactor #3 and isotopes produced during the irradiation were investigated by a Ge detector along with superconductivity tests at high magnetic field. The maximum thermal and fast neutron was 8.29 x 10 22 n/m 2 and 1.46 x 10 21 n/m 2 , respectively. As the results 153 Gd, 152 Eu and 155 Eu were detected and nuclear transmutation was confirmed. No isotopes of Y were found. Since the cross section of Gd for {n,γ} reaction is very large in thermal neutron region, the nuclear transmutation of Gd occurs by the capture of thermal neutrons. Eu transmutation occurs by the same mechanism. These facts suggest that the thermal neutrons have dominant effect on the degradation in superconductivity of GdBCO and EuBCO tapes. The possible mechanisms on the degradation, a Gd/Eu recoil model, an oxygen deficiency model and an electron exchange model, are discussed.