| 摘要 |
PURPOSE:To prevent decrease of plateau region caused by bending in thermal expansion under high temperature and to enable accurate measurement of ion current, by a method wherein a filament of Na ionization detector is made coil- shaped and arranged on axis of a cylindrical collector. CONSTITUTION:Na ionization detector for detecting leakage of Na from a plant of high-speed breader reactor comprises an ionization sensor 1, Pt filament 2 of high temperature for performing Na ionization of the sensor 1, and a collector 3 for collecting Na ions. The filament is made coil-shaped so as to absorb the thermal expansion of the filament 2 by variation of the coil pitch l. In this constitution, distance between the filament 2 and the collector 3 does not vary, and surface area of the filament becomes large hence the ion current increases, therefore the same filament temperature as that of a linear filament is obtained in self heating by smaller current than in the linear filament. Thus sensitivity and accuracy can be improved. |
