Remote Measurement of Coolant and Effluent Parameters in Operating Nuclear Power Plants

A measurement system to determine reactor coolant and containment atmosphere parameters under remote control in order to provide capabilities described in NUREG-0578 and subsequent regulatory documents has been developed and installed in an operating nuclear power plant. The design was based on an extension of concepts used earlier to support automation of routine radioisotope measurement in CANDU¿ reactors. The compound system of fixed and movable collimators configured with multiple sample lines was described in detail earlier. Extensive thicknesses of lead and tungsten, with multiple aperture sizes and sample geometries were utilized to allow a range of isotope measurements from routine coolant concentrations to post-accident levels of ten curies per cubic centimeter, as indicated in Table 1. Temperature and pressure sensors were included to allow verification of sample flow and to provide sample volume corrections. The system was implemented in modular fashion to meet the constraints of power plant backfit installations. The sensor and detector unit was designed to be located in a hostile environment in an inaccessible part of the plant. Performance tests in a high radiation field in a hot cell facility indicated that measurements could be made in fields exceeding 100 rads per hour. A separate module contained signal conditioning electronics and relay controls for valve operation and collimator motion. The computer for data analysis and operator interaction can be located at any distance from the sensors.