Boron-lined neutron detectors with gamma discrimination for reactor applications

Neutron sensitive detectors capable of discriminating against gamma backgro und have been indigenously developed for reactor applications. A boron-10 l ined proportional counter with 3.5 cps/nv counting sensitivity and a boron- 10 lined gamma compensated neutron ion chamber with a current sensitivity o f 11fA/nv have been developed for the reactor start up and intermediate ran ge instrumentation, respectively. The detectors have all-welded high-purity aluminium construction and integral mineral-insulated cable assembly. Expl osion-welded SS-aluminium clad material has been used as interface between the aluminium body of the detector and the ceramic-metal insulators. The co unter has gas filling of argon and carbon dioxide at 20 cm Hg. It has 190 m g of enriched boron-10 coating and can be used over a neutron flux range of 0.1 nv to 10(5) nv. The gamma compensated ion chamber has hydrogen filling at 10 psi pressure. Performance tests in typical neutron and gamma fields show that the chambers can tolerate gamma background up to 1000 r/h and ove r 100 degrees C of ambient temperature.