Within the EC project EVIDOS, 17 different mixed neutron-photon workplace fields at nuclear facilities (boiling water reactor, pressurised water reactor, research reactor, fuel processing, storage of spent fuel) were characterised using conventional Bonner sphere spectrometry and newly developed direction spectrometers. The results of the analysis, using Bayesian parameter estimation methods and different unfolding codes, some of them especially adapted to simultaneously unfold energy and direction distributions of the neutron fluence, showed that neutron spectra differed strongly at the different places, both in energy and direction distribution. The implication of the results for the determination of reference values for radiation protection quantities (ambient dose equivalent, personal dose equivalent and effective dose) and the related uncertainties are discussed.
Bibliographical noteFunding Information:
This research is partly funded by the European Commission under the auspices of the Euratom 5th Framework Programme: Nuclear Energy, 1998– 2002, Contract No. FIKR-CT-2001-00175.
The EVIDOS project funded by the European Commission within its fifth Framework Programme has been one of the largest projects in the last decade in the field of dosimetry and spectrometry of mixed neutron–photon workplace fields at nuclear facilities. It has been a cooperation of partners from seven institutions and seven countries within Europe. The name EVIDOS stands for ‘EValuation of Individual DOSimetry in mixed neutron and photon radiation fields’. In order to evaluate the readings of radiation protection instruments—ambient dose-meters, passive personal dosemeters and new active electronic dosemeters—the reference values for radiation protection quantities needed to be determined by spectrometry.