Abstract: A method of manufacturing, as a length of mineral insulated cable, a self-powered neutron flux detector, a lead cable therefor or both, with the detector, the lead cable or both having predetermined .gamma.-ray sensitivity in a high radiation environment, is provided wherein metal bands are provided around the detector core wire, the lead cable core wire or both, inside the sheath to control the .gamma.-ray sensitivity. The metal bands, and sleeves of a frangible insulation, are assembled in an oversize sleeve which is then reduced in diameter to pulverize the frangible sleeves, each metal band being in electrical contact with either the core wire or sheath. The metal bands incorporated in the lead cable predetermine the .gamma.-ray (and hence the dynamic response) of the lead cable, the metal bands incorporated in the detector predetermine the .gamma.-ray response (and hence the dynamic response) of the detector.

Abstract: A prompt responding, coaxial, self-powered neutron flux detector assembly is provided wherein the emitter electrode is at least of the order of 0.9 mm in diameter and is of metal selected from iron, nickel, titanium, chromium or alloys based on these elements so that at least 90% of the total electrical current induced in the detector is prompt and will be derived from (n,.gamma.,e) interactions in said metal, the tubular collector electrode is of one of these materials with zirconium or zirconium alloys included in the group and in use these electrodes are connected directly to the measuring instrument or are connected to the measuring instrument via a lead cable. When a lead is used having conductors of similar metals to the detector electrodes, then for(i) a coaxial lead cable the emitter electrode diameter is .gtorsim.

Abstract: A self-powered neutron and gamma-ray flux detector is provided wherein the emitter comprises an emitter core of at least one material selected from nickel, iron, titanium and alloys based on these metals, and an emitter outer layer around the core which has a thickness in the range of the order of 0.03 mm to of the order of 0.062 mm and which is of at least one material selected from platinum, tantalum, osmium, molybdenum and cerium. With this construction, by increasing the emitter diameter beyond the optimum for a solid platinum emitter, the ratio of neutron to gamma-ray sensitivity, and hence the prompt response fraction, is increased while an acceptably small burnup rate is maintained. Larger diameter emitters of this construction have response characteristics that closely match those required for a fuel power detector in, for example, heavy-water-moderated, natural-uranium power reactors. The emitter core is preferably of Inconel (Trademark) and the emitter jacket is preferably of platinum.