A study of some characteristics for the reactor filtered beam of 0.186 keV, 24.4 keV and 144 keV

The quasi-monoenergetic neutron beam of 186 keV, 24.4 keV and 144 keV are obtained at the tangential channel of the swimming pool reactor by use of 238U, 56Fe and 28Si filter, respectively. Some characteristics, such as beam purity and neutron fluence rate on the axis direction, are determined. The results show that the beam purity is nearly independent of the axial distance, the fluence rate descreases as the distance increases and the trend of the fluence rate attenuation follows approximately the inverse square law of a point source. The position of the equivalent point source is far away from the reactor core. The conclusion can be used to explain the phenomenon, that is the purity of 24.4 keV neutron beam varies with the Fe filter position, observed by Kond-aiah et al