Decrease in the activity of irradiated graphite and liquid radioactive waste

Abstract

Nowadays, the problem of nuclear waste deactivation is very urgent. The method proposed consists of exposing the aqueous solution of radionuclide to powerful nanosecond electromagnetic pulses by placing the treated solution between two electrodes connected to the outlets of the generator. Single-pole current pulses with a length of 1 ns, an amplitude of more than 5 kV, and a repetition frequency of 1 kHz are used. Such pulses can be obtained from the generator units with an amplitude of 5 kV to 15 kV. They have a pulse capacity of 1 to 4 MW, and the mains capacity is below 50 W. The pulse action leads to radiolysis of water and accelerated decay of radionuclides. As a result of radiolysis, hydrated electrons, hydrogen atoms, and various radicals are formed that causes precipitation of radionuclides, such as 137Cs and 90Sr. The description of several experiments and results of experimental investigations of the influence of powerful nanosecond electromagnetic pulses on the properties of water solutions with radioactive nuclides 137Cs and 90Sr and on items of irradiated graphite is presented. Under the influence of pulses on real liquid waste and aqueous solutions, radioactive nuclides in water are reduced by 5 to 50 times during 15 minutes. The effect described is preserved for 20 days. The reduction of beta activity twice during 25 min is observed in big blocks of the irradiated graphite. Flow-through unit for processing of liquid waste is developed, tested, and patented (RU 2726145. MPK G21F 9/28, July 7, 2020). This technology can be used to treat emergency solutions with tritium at Fukushima NPP. of the irradiated graphite.