New digital position indicator for control rod

The digital position indicator for control rod (DRPI) has a characteristic of reducing wire cable tube penetrating into a reactor vessel by placing a signal processing board in the vessel. However, on renewal from analogue to digital system in the previous plant, a case without sufficient securing of space to establish an air-conditioning apparatus for a signal board and arrangement of its temperature environment in the vessel can be supposed. And, an instrumentation control apparatus in the nuclear plant is at present promoted on general digitalisation aiming at upgrading of functionality, economics and maintenance, and then a function capable of adequately conducting interface with the digital instrumentation apparatus is required. In order to overcome these subjects, the Mitsubishi Electric Co., Ltd. Developed a new digital position indicator for control rod realizing thinning of cables and miniaturization of connectors, miniaturization of control card due to adoption of hybrid IC, reduction of temperature increase in the board due to review of the board structure design, and processing of position indication operation and accident diagnosis due to a microprocessor. Here were described on a technology for realization of miniaturization and no-air conditioning, apparatus constitution and characteristics of the new system, and abstract on verification test results. (G.K.)