Characterization of Bonner sphere systems at monoenergetic and thermal neutron fields

Abstract

The Institute for Radiological Protection and Nuclear Safety (IRSN) and the GFR, Universitat Autónoma de Barcelona (UAB) use Bonner spheres (BS) for neutron spectrometry at workplaces. The two systems, equipped with similar cylindrical 3He proportional counters, were simulated with the MCNP Monte-Carlo code to determine the response to neutrons of different energies for each polyethylene sphere. The BS systems were characterized at monoenergetic and thermal neutron fields. Measurements were performed at the Physikalisch-Technische Bundesanstalt (PTB) and at the National Physical Laboratory (NPL) standard laboratories, and with the newly characterized IRSN 'SIGMA' thermal neutron facility. The energy distribution of the reference neutron fluence was folded with the response functions for comparison purposes with the experimental data. In almost all cases related to monoenergetic neutrons, a good agreement between the experimental and the calculated count rates was found, and some discrepancies of a few per cent were observed in the thermal region.

Evaluation of individual monitoring in mixed neutron/photon fields: mid-term results from the EVIDOS project

“…Reference field spectrometry is primarily performed with a Bonner-sphere system (3) for the entire energy range. The measurements of the doubledifferential (energy and direction) neutron fluence are performed with novel instruments based on SDD-spectrometers (4) and Si-diodes (5) .…”

“…It consists of a 3 He filled proportional counter and 12 polyethylene spheres. The five smallest spheres are used bare and also with a cadmium shield.…”

Robust Design of Artificial Neural Networks Methodology in Neutron Spectrometry

“…[39] Spectral information must generally be obtained from passive detectors which respond to different ranges of neutron energies such as the multispheres Bonner system or Bonner spheres system (BSS). [40][41][42] BSS system, has been used to unfold the neutron spectra mainly because it has an almost isotropic response, can cover the energy range from thermal to GeV neutrons, and is easy to operate. However, the weight, time consuming procedure, the need to use an unfolding procedure and the low resolution spectrum are some of the BSS drawbacks.…”

Evolutionary Artificial Neural Networks in Neutron Spectrometry

“…Equation 1 is an ill-conditioned problem wich has an infinite amount of solutions Although there is a wide range of different devices used for neutron spectrometry, the majority of the instruments can be grouped together into a small number of broad categories, each one based on a common underlying technique (Matzke, 2003;McDonald et al, 2002;Thomas, 2004). Among the many available neutron spectrometry techniques, the multisphere or Bonner sphere spectrometer (BSS) system is the most used for radiation protection purposes (El Messaoudi et al, 2004;Lacoste et al, 2004;Vylet, 2002), due to advantageous characteristics as wide energy range (from thermal to GeV neutrons), large variety of active or passive thermal sensors allowing adapting the sensitivity to the specific workplace, good photon discrimination and simple signal management. Disadvantages are the poor energy resolution, which does not allow appreciating fine structures as narrow peaks, the weight, and the need to sequentially irradiate the spheres, requiring, in general, long exposure periods (Bedogni et al, 2007).…”