Neutron-Proportional Tube Performance In High Gamma-Ray Environments

A new 3He neutron proportional tube design has been developed to extend the operability of 3He tubes for neutron counting in mixed neutron/gamma-ray radiation fields. The new tube design uses a thin 10B lining in conjunction with standard 3He tube operation to increase the intrinsic efficiency and to decrease y-ray interactions compared t previous designs. This design change, in conjunction with previous materials materials studies, has greatly enhanced the performance of 3He neutron proportional counters in high gamma-radiation environments. Neutron coincidence counting y-ray doses beyond 100 rad/h gamma per active foot of tube length is now possible. Totals neutron counting in gamma radiation fields as high as 200 rad/h gamma per active foot is also possible. the dependence of y-ray pile up on the energy of the incident y-rays has also been examined. The data indicate that 3He tubes exhibit less pileup pulses from low-energy y-ray sources than form high-energy y-ray sources at a given dose rate.