DONA Detector: Further Improvements and Evaluation for Field Applications

The DONA neutron spectrometer concept is based on the measurement of neutron induced activity in a series of small metal disks that have been exposed to a neutron field. The induced activity is measured and the neutron spectrum is calculated using and unfolding technique, based on environmental neutron spectra. The novelty of the approach lies in the concept as such, including usage of carefully selected metal disks arranged in a holder, high performance gamma-ray spectrometry and spectrum unfolding using a library of environmental neutron spectra. This report covers the IRMM exploratory research prolongation project for 2006 and now environmental neutron fields with considerably lower neutron fluence rates are used. The result shows that after further refinement of the detector device and the data evaluation program the detector can very well be used for environmental neutron fluence measurements. Tests were done at PTB, Germany, using their calibrated neutron source and at the MOX fuel fabrication plant Belgonuclearire in Mol, Belgium.JRC.D.4-Isotope measurement

Neutron Fluence Spectrometry Using Disk Activation

A simple and robust detector for spectrometry of environmental neutrons has been developed. The technique is based on neutron activation, i.e. the activation of a series of different metal disks followed by gamma-ray spectrometry of the activated disks and subsequent neutron spectrum unfolding. It is a technique similar to the foil activation but now applied to low neutron fluence rates. The detector has been tested in quasi mono-energetic neutron fields where the obtained spectra showed good agreement with spectra measured using a Bonner sphere spectrometer. The detector has also been tested by means of an AmBe source and, again, a good agreement with the assumed spectrum was achieved. Low-level and ultra-low level gamma spectrometry allowed for the measurements of very low neutron fluences with detection limits for fast neutrons in the order of 10 s-1 cm-2.JRC.D.5-Neutron physic