| 摘要 |
<p>938,994. Detecting neutrons. ATOMIC ENERGY OF CANADA Ltd. Feb. 23, 1961 [April 15, 1960], No. 6705/61. Class 39 (4). Apparatus for detecting thermal neutrons comprises a thermal neutron detector positioned to receive substantially no direct radiation and a hydrogenous scatterer positioned and adapted to scatter thermal neutrons. The apparatus may be used for measuring the thermal neutron flux of a nuclear reactor to give a measure of its power. As shown in Fig. 1 a path 10 for radiation may be provided in the concrete shield 11 of the reactor and may be lined with a steel liner 12 and with a boron-aluminium lining 13 which absorbs thermal neutrons and prevents activation of the steel and concrete. The scatterer 14 comprises two sheets of polystyrene arranged at 45 degrees to the path of radiation and the thermal neutron detectors 20, 21 are situated in recesses to the side of the path; lead gamma ray shields 22, 23 are arranged in front of the detectors and polythene reflectors 24, 25 are arranged behind the detectors. Thus thermal neutrons from path 10 are reflected into the detectors whilst fast neutrons and gamma rays pass through the scatterer 14 into a beam catcher chamber 17 designed to minimize reflection of radiation. The scatterer may be of other hydrogenous material such as polythene, water, hydrocarbon substances, or ice.</p> |
