Development of hybrid real time wide-band electronic radiation dosimeter for a mobile robot

Abstract

� Abstract— The electronics of a robot working in a nuclear power plant needs to survive in the radiation environment. To know how much radiation the robot has encountered to replace sensitive electronic parts, a dosimeter to measure the total accumulated dose is necessary. Among many radiation dosimeters or detectors, semiconductor radiation sensors have advantages in terms of power requirements and their sizes over conventional detectors. Among such sensors, a metal oxide field effect transistor (MOSFET) can be used as a dosimeter that measures the total accumulated radiation dose for a measurement period and a diode as a dose-rate sensor for radiation survey. This paper describes the use of the radiation-induced threshold voltage change of a commercial power pMOSFET as an accumulated radiation dose monitoring mean and that of the photo-current of a commercial SiC Diode as a dose-rate measurement mean. Commercial p-type power MOSFETs and SiC Diodes were tested in Co-60 gamma irradiation facilities to see their capabilities as radiation sensors. We found an inexpensive commercial power pMOSFET that shows good linearity in their threshold voltage shift with the radiation dose and a SiC diode that shows good linearity in its photo-current change with dose-rate. According to these findings, a radiation hardened hybrid electronic radiation dosimeter for nuclear robots has been developed for the first time. This small hybrid dosimeter also has an advantage in terms of reliability improvement by using a diversity concept. No such small and simple semiconductor electronic dosimeters with this extended range of dose (~ 100 krad) and dose-rate (50 rad/hr ~ 8 krad/hr) capability and with these levels of redundancy and diversity has ever been found. Keywords—Dosimetry, Hybrid, MOSFETs, SiC, radiation detectors