RIEMF in MgO and Al2O3 insulated MI cable ITER magnetic diagnostic coils

Radiation induced currents and voltages, generally termed RIEMF, have recently been the object of discussion due to inconsistent results. The problem is due to a possible RIEMF generated along the centre conductor of a coil in a radiation field. To address this, two representative ITER coils have been made from 1 mm diameter MI cable with copper and stainless steel inner conductors. Measurements were made of the radiation induced voltage and current between the centre and outer sheath, as well as the voltage across the two ends of the centre conductor during 60Co gamma irradiation at 10 Gy/s. While putting an upper limit on the radiation-induced part, it has been demonstrated that, within the measurement capability, no significant RIEMF is produced along the central conductor. However, the measurements have highlighted other potential problems due to temperature and pressure gradients for the use of MI cable magnetic coils in ITER.