Radiometric instrumentation at the Sellafield reprocessing complex

The safe handling and routing of radioactive materials in an operational reprocessing facility requires the provision of monitoring instrumentation capable of detecting and quantifying the activities of specific radioisotopes and/or fissile contents. Such instrumentation is required for a number of purposes: safeguards to ensure that the `nuclear material´ inventory of the plant is properly accounted for; quality checking of used fuel fed to the reprocessing plant, to ensure conformation to the envelope of allowable initial enrichment, irradiation and cooling time; process and criticality control during all phases of the reprocessing operations; and ensuring that both product and waste streams comply with the appropriate transport and storage/disposal regulations. BNFL have developed many such monitoring instruments, for situations where no commercial systems are available, the emphasis being on the cost effective achievement of accurate and reliable measurement. This work describes some of the radiometric techniques which have been utilised in such instrumentation. A number of examples are given