Inductance control rod position detector for nuclear heating reactor

The ultrasonic wave control rod position detector (CRPD) used in the 5 MW Nuclear Heating Test Reactor (NHR-5) and the coils coding CRPD used extensively in water reactors have some defects. Three new kinds of CRPDs are described in this paper. This first is the GRAY code rod position detector; it consists of 5 grouped secondary coils and one coding bar. As the control rod (CR) is withdrawn, the coding bar passes the coils and changes their output signals. By picking up and processing the signals, 5 bits binary GRAY code which is related to the rod position is obtained. The second is the self-encoding rod position detector; it consists of 8 secondary coils and a coding bar. As the CR moves, 8 output signals indicating the rod position will be changed. The third is the digital-analog rod position detector; it consists of two long opposite and two short secondary coils arranged on the longitudinal axis of the rod housing and a coding bar. While the bar passes the coils, their outputs which indicated the rod position will be changed. The comparison of the four kinds of CRPDs illustrates that the new kinds are simpler in structure, more reliable in operation and lower manufactures cost. The manufacture process of all the new kinds of detectors are the same as that of the coils coding CRPD, and the latter is a ripe technology. So they can be used in NHRs and other water reactors. (author)