Determination of the235U concentration in the aqueous coolant of the first circuit of a nuclear reactor

Conclusions A technique was developed for determining the²³⁵U concentration in the aqueous coolant of the first circuit of a nuclear reactor: detection limit 3·10^–12 g/cm³. Using the method in the IVV-2M reactor has shown that with this technique, an operational monitoring of the uranium concentration in the coolant and in the fluids washed from the surface of the first circuit, as well as monitoring other qqueous samples, is possible.Lavsan, which is directly irradiated in a liquid sample and electrochemically etched, can be recommended as a detector. The optimal conditions of etching 180-m-thick lavsan (after irradiation with thermal neutrons to a flux of (1–2)·10¹⁶ cm^–2) are: 30% aqueous KOH solution, a temperature of (70±0.2)°C, an electric field strength of 20 kV/cm, a frequency of 4 kHz, and an etching time of 100 min.Translated from Atomnaya Énergiya, Vol. 61, No. 5, pp. 334–338, November, 1986.