GB616544A - Apparatus for measurements employing neutron radiation - Google Patents

Abstract

616,544. Determination of hydrogen atom concentration. SHELL DEVELOPMENT CO. Feb. 25, 1946, No. 5839. Convention date, April 10, 1945. [Class 40 (i)] [Also in Group XXXVI] In an apparatus for determining hydrogen atom concentration in a substance, fast neutrons are discharged into the specimen where they are scattered, and converted by collision with hydrogen atoms into slow neutrons, which fall on a test member the material of which is partially converted by impact of the slow neutrons into an unstable isotope, which subsequently disintegrates and emits ionising particles which are detected and counted, the number emitted in a given time being proportional to the slow neutron emission and to the hydrogen atom concentration in the specimen. In Fig. 1, a hydrogen-containing fluid is circulated through a metal pressure barrel 3 containing a porous core 1 whose degree of saturation is to be measured. A source of fast neutrons 9 (which may be a radium-beryllium mixture) in a lead container irradiates the core and the fast neutrons are scattered and converted by collision with hydrogen atoms of the fluid to slow neutrons. These bombard a test member (which may be of rhodium, indium, silver, manganese, dysposium) partially converting it to an unstable isotope. The test member comprises the cathode 15 of a radiation detector 17 of the Geiger counter or ionisation chamber type having anode 19, and the counter output is applied through switch 35 to an amplifier having recording and indicating units 25, 26. After irradiation of the core and test member for a prescribed time with switch 35 open, the fast neutron source is removed to a distance and switch is closed. Beta particles emanated by the disintegrating isotope in the test member ionise the radiation detector causing current pulses to pass between the electrodes. The pulses are amplified and counted, the number registered in a predetermined time being proportional to the slow neutron production, which is a function of the hydrogen atom concentration in the core, and consequently of the degree of saturation of the core with the hydrogen-containing fluid. In a modification (Figs. 2, 3, not shown), the test member may take the form of a plate placed adjacent to the core, which after receiving the emergent slow neutrons may be removed to a distance and placed in proximity to a radiation detector with amplifier and indicator. The detector wall may have a window of beta-ray permeable material such as mica supported on a metal lattice. The device may be used for measurements of gas pressure, liquid-level, concentration of a substance in a mixture, presence of moisture, determination of hydrogen in metals, in which hydrogen-containing substances are involved.