Boron-10 lined proportional counters for reactor instrumentation

B-10 lined proportional counters for thermal neutron flux monitoring at the nuclear reactors have been developed. Design details of the counters with thermal neutron sensitivity of 20 cps/nv and 1 cps/nv are described. Systematic tests carried out on the detectors establish the usefulness for the reactor applications. The gas constants for the boron counter gas mixture 95% A + 5% CO2 have been evaluated. These values are extremely useful in estimation of the amplification factor for the boron lined counters at various operating parameters. The gamma tolerances of the detectors have been estimated experimentally. (author)