DEVELOPMENT OF CONTROL SYSTEM FOR THE FLOW RATE/PASSAGE OF TRITIUM WITH BREMSSTRAHLUNG COUNTING METHOD.

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For tritium process in thermonuclear fusion reactors as well as a heavy water type reactor and the nuclear fuel reprocessing, it is indispensable to control the flow rate/passage of tritium according to the concentration of tritium. Especially, for the process of high level tritium, the development of precise control system for tritium is of a great importance from viewing point of safety. The applicability of a bremsstrahlung counting method to the insitu measurement of high level tritium has been examined so far. Since the penetration range of bremsstrahlung X-rays is remarkably greater than that of beta-rays, it is possible to measure directly the amount of tritium in a container attached with an appropriate window by the bremsstrahlung counting method. This method, therefore, will be a promising one to control the flow rate/passage of tritium.As a first step, to improve the sensitivity of bremsstrahlung counting method, the effect of a gold evaporated window on the intensity of bremsstrahlung X-rays has been examined. The window plays important roles of the confinement of tritium and the emission of the bremsstrahlung X-rays. By using the gold coating window, it was seen that the detection limit was extended toward lower tritium concentration of about 0.1 muCi/cm^3. In addition to the above examination, some preliminary experiments were carried out using an apparatus constructed to test the applicability of bremsstrahlung counting method to the control system. As a result, it was seen from the preliminary tests that two control valves attached to the present apparatus precisely operated at a given concentration irrespective to the flow rate in the range from 7 to 54 cm^3/min. From those results, it was revealed that it was possible to develop a tritium control system based on the bremsstrahlung counting method.