Development of an innovative neutron flux mapping system

Abstract

An innovative in-core flux mapping system has been developed and applied successfully for service in commercial pressurized water reactors. With the benefit of double indexing path selector mechanism, the reliability of the detector drive system has been improved five times higher than that of a conventional system. The problems caused by strong friction generated between the detector cable and guide tubes have been resolved by the double indexing path selector architecture enabling the detector guide tubes to have smaller curvature and shorter length in nature. The system normally exerts two-thirds of force to make the detector reach the top of the fuel position, compared with conventional ones. In addition, simple and fast maintenance is realized by optimizing the number of components in the detector drive system and providing easy access to the components, thereby guaranteeing minimum radiation exposure to maintenance personnel. The programmable logic controller-based digital controller with Windows ®-based operator console provides fully automated and user-friendly operation and maintenance support means. The developed in-core flux mapping systems have been deployed at the Kori nuclear units 1–4.