Measurement of Neutron Spectrum Parameters of Miniature Neutron Source Reactor

The neutron spectrum parameters of the miniature neutron source reactor（MNSR） in China Institute of Atomic Energy were measured by bare monitor method using Au， Zr and Fe as monitors. The measured values of α（a parameter accounting for the nonideality of the 1/E epithermal neutron fluence rate distribution）， f (thermal / epithermal neutron fluence rate) and f_F (thermal / fast neutron fluence rate) in the inner irradiation site are －0.007±0.003， 20.8±0.4， and 5.5±0.2， respectively. The value of φ_th measured by this method is agreed with that measured by 4πβ-γ method within 2%. Compared with SLOWPOKE, MNSR had higher values of αand f_F. The comparison with the previous measurements indicates that MNSR has a quite constant neutron spectrum. The fluence rate monitors are not needed when k₀ NAA is performed by using MNSR as neutron source， and with occasional check, the comparator data from one measurement may be used as a standard for subsequent analyses over a period of time.