J. Yamada

M. Shimo

T. Kawano

T. Uda

National Institute for Fusion Science (NIFS-Repository)

Effect of Electromagnetic Field in Fusion Facility on Electronic Personal Dosimeter Kawano, T.  Yamada, J. (Tokyo Metropolitan Univ.) Uda, T. Shimo, M. (Fujita Health Univ.)  Work environment in a nuclear fusion facility is surrounded by, along with radiation field, electromagnetic field generated by many devices like a superconductive coils system (around 0.4?3T ), a motor generator (60Hz), and heating systems, which include a neutral beam injection (NBI),?an ion cyclotron range of frequency (ICRF, 25-100 MHz) and an electron cyclotron resonance heating (ECH, 77-168GHz). So, personal dosimeters used to evaluate exposed radiation dose is possibly also exposed to such electromagnetic field. The effect of electromagnetic field on electronic personal dosimeters in a nuclear fusion facility was examined in a magnetic resonance imaging?MRI; 64MHz, 0.5?3T?examination room instead of a nuclear fusion facility, assuming an electromagnetic environment in a nuclear fusion facility is similar to that in a MRI examination room1).    Three types of electronic personal dosimeters (PDM-111,  112 and 117), were used as typical ones (Fig.1).  The electromagnetic field distribution was surveyed and dosimeters were placed at locations with various strengths of magnetic field (??? in Fig.2). The natural radiation dose was measured for about one week.  It was found that while dosimeters were not affected by the electric field1), they were affected by the magnetic one as shown in Fig.3. Figure 3 shows that the dosimeters detected radiation levels less sensitively as the magnetic field strength was increased up to 150 mT. The dosimeters underestimated the environmental radiation dose rates by about 10 – 30 % when the magnetic field strength was larger than 150 mT. It is concluded that the strength of the magnetic field needs to be carefully considered when an electronic personal dosimeter is used for monitoring both personal and area dose in a nuclear fusion facility. 1)Yamada, J. et al.: Jpn. J. Health Phys., 45(2010)56.   a : PDM1110.40.60.81.01.20 200 400 600Static magnetic field (mT)Relative doseequivalent ratesb : PDM1120.40.60.81.01.20 200 400 600Static magnetic field (mT)Relative doseequivalent ratesc : PDM1170.40.60.81.01.20 200 400 600Static magnetic field (mT)Relative doseequivalent ratesFig.3 Effect of magnetic field strength on environmental radiation dose measured with electronic personal dosimeters. Relative dose equivalent rates were normalized to the dose rates at 0.08mT. Fig.1 Electronic personnel dosimeters and performance.PDM-117 PDM-112 PDM-111  Type     Radiation      Energy        Detection  limit  PDM111    �-ray    60 keV or higher    0.01�Sv PDM112    �-ray    40 keV or higher       1�Sv PDM117    X-ray    20 keV or higher       1�Sv  ? Reception Operation room MRIdCenter Bed Locker  room MRI examination room Window 1.5 ? Door Console ? ? ? ? ? ? ? ? ? 2.5 m ? ?        730 ?        244 ??        103 ?? ?       40 ?         6.3 ?         4.5 ?         1.9 ?? ?       0.4 ?         0.2 ?         0.1 Static magnetic field ?mT?Position No. Fig.2? Magnetic field dispersion in the MRI examination room.? (????Measurement  positions).  482§18. Effect of Electromag etic Field in FusionFacility on Electronic Personal DosimeterKawano, T.,  Yamada, J. (Tokyo Metropolitan Univ.),  Uda, T.,  Shimo, M. (Fujita Health Univ.)

Effect of Electromagnetic Field in Fusion Facility on Electronic Personal Dosimeter

Abstract

Similar works

Full text

Available Versions

National Institute for Fusion Science (NIFS-Repository)