Study of Leakage Electromagnetic Field Monitoring with a Wide Frequency Range on Safety Management in a Magnetic Fusion Facility

Abstract

With respect to considerations of nuclear fusion systems, since the electromagnetic field in the wide frequency range from the static magnetic field to extremely high frequency was utilized for the plasma confinement, heating at the magnetic confinement fusion facilities, not only ionizing radiation but also non-ionizing radiation should be investigated and discussed in terms of occupational protection as one of the issues in fusion facilities. To clarify the behavior of non-ionizing radiation, leakage from electric and magnetic fields has been observed at the Large Helical Device (LHD), because a strong magnetic field generated by large superconducting magnet coils for plasma confinement, in addition to high-frequency and high-power oscillators for ion cyclotron range of frequencies (ICRF) and electron cyclotron resonance heating (ECRH) for plasma heating, are used. In the LHD experiments, magnetic field leakage has been observed at extremely low frequencies (ELFs) around a power supply system for superconducting magnet coils. The magnetic field outside the experimental hall and the intensity of electric field leakage from the oscillators for ICRF and ECRH are significantly below the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines and radio frequency exposure protection standards in Japan (RCR-STD38). The ICNIRP and RCR-STD38 provide guidelines for limiting exposure to electric and magnetic fields to protect against established adverse health effects. The guidelines for safety management to protect the working people in fusion facilities should be made clearer with respect to occupational protection from non-ionizing radiation.