Patent ID: 8735804

Claim:
A device for online measurement of a flow of fast and epithermal neutrons φ 1 (t n ) at instants t n over an energy interval [E min , E max ], comprising: a fast neutron detector (DNR) containing material suitable for detecting principally fast neutrons; a thermal neutron detector (DNT) containing material suitable for detecting principally thermal neutrons; a first electronic circuit (C 1 ) which delivers, at instants t n , a digital signal VR(t n ) from a detection signal delivered by the fast neutron detector; a second electronic circuit (C 2 ) which delivers, at instants t n , a second digital signal VT(t n ) from a detection signal delivered by the thermal neutron detector; means (PMM, CE) able to determine, at instants t n , the isotopic composition of the fast neutron detecting material and the isotopic composition of the thermal neutron detecting material; means (PMM, CE) able to determine, at instants t n , from the said isotopic compositions, the progressive sensitivity to the fast neutrons I 11 (t n ) of the fast neutron detector, the progressive sensitivity to the thermal neutrons I 12 (t n ) of the fast neutron detector, the progressive sensitivity to the thermal neutrons I 21 (t n ) of the thermal neutron detector and the progressive sensitivity to the fast neutrons I 22 (t n ) of the thermal neutrons detector, means for computation (CALC), at instants t n , of the flow of fast and epithermal neutrons φ1(t n ) and of a flow of thermal neutrons φ2(t n ), from the following system of equations: VR ( t n )= KR×I 11 ( t n )×φ1( t n )+ KR×I 12 ( t n )×φ2( t n ), and VT ( t n )= KT×I 21 ( t n )×φ1( t n )+ KT×I 22 ( t n )×φ2( t n ) where KR and KT are, respectively, a coefficient for calibration of the fast neutron detector and a coefficient for calibration of the thermal neutron detector.