Neutron spectrometry system for radiation protection: measurements at work places and in calibration fields

There is a real need to improve the knowledge of the fields to which workers in the nuclear industry could be exposed, and to define new calibration fields. A sufficient accuracy in the characterisation of these two types of radiation field would be reached only if detector systems with spectrometric properties are employed. This paper presents an operational spectrometry system used for measurements of the spectral fluence both in working areas and in calibration fields. It describes two different techniques to cover the whole possible energy range: proton recoil detectors from 100 keV to 20 MeV and the multisphere technique for the lower energy range down to thermal neutron energies. The detectors and their main characteristics are briefly described, with the different unfolding codes. The dosimetric quantities are calculated from the measured spectrum. The improvement and comparison of the two techniques are presented and discussed for two ISO reference fields: Am-Be and 252Cf. The whole spectrometry system is finally put in practice with measurements in: two radiation protection situations (source manufacturing work station, and irradiated fuel transport container, and a 'simulated realistic' neutron spectrum). This work is part of a larger European research project which has to gather measurements in working areas and finally provides, in the laboratory, neutron calibration fields close to those met in radiation protection practice. (author)