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The IRSN Neutron facilities for radiation protection.



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J.L. Pochat, B. Asselineau, V. Gressier, J-F. Guerre-Chaley, V. Lacoste, L. Lebreton,
A. Martin, H. Muller, G. Pelcot, L. Van-Ryckeghem, IRPA, 24-28/05/2004, Madrid, Spain.



The laboratory of metroloy and neutron dosimetry (LMDN) of the Institute for radiological protection and nuclear safety (IRSN) performs evaluation and R&D on external dose assessments to the ionising radiations of which mostly considered are photons and neutrons. The LMDN, as an associated laboratory to the Bureau  National de Métrologie (BNM), is strongly involved in the reference establishment and in the traceability for neutron fields for calibration purposes and owns, at the Cadarache center several facilities dedicated to the ‘neutron dosimetry’.

The first facility consists in 241Am-Be and 252Cf sources delivering wide reference neutron energy distributions according to the ISO standards and dedicated to the calibration of survey instruments and  personal dosemeters. To fulfil the need of calibration in neutron field similar to some of those encountered in workplaces, IRSN has developed the “CANEL” assembly. This assembly, is a modular moderator duct delivering fission-like neutron energy distribution created from 3.3 MeV or 14 MeV neutron impinging an uranium shell. IRSN is currently contributing to the definition and preparation of a new ISO standard describing the fundamentals of characterization of these kinds of “realistic radiation fields”.

From an ideal point of view, the response of neutron devices placed in a wide energy neutron field is more reliable than when its response is known as a function of the neutron energy .

To determine the response function of neutron spectrometers or dosemeters, IRSN already uses two ‘SAMES’ accelerators to produce 3.3 MeV and 14 MeV neutron beams.

The ‘SIGMA’ assembly is a graphite moderated 241Am-Be facility, which allows to determine the response of the devices to “thermal” neutron energies.

A new facility named ‘AMANDE’, dedicated to monoenergetic neutron production allowing to determine response function of all type of neutron dosemeters will provide in 2005 a complete set of monoenergetic neutron beams dedicated to research in dosimetry from few keV up to 19 MeV.

IRSN existing reference facilities are being characterized by means of Monte Carlo simulation and spectrometry and dosimetry measurements. The characteristics of these facilities allowing tests and calibrations of neutron dosemeters will be presented.

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