Experience of creating an in situ biogeochemical barrier in contaminated groundwater at nuclear fuel cycle facilities. part 1

Background: The operation of radioactive waste (RAW) pools is associated with potential environmental risks. Remediation of adjacent territories represents a priority in the Strategy for Environmental Safety of the Russian Federation.

Aim: To determine the characteristics of a biogeochemical anti-migration barrier created for the remediation of aquifers with complex contamination, as well as to assess the effectiveness of this barrier.

Materials and methods: The elemental composition of samples was determined by inductively coupled plasma mass spectrometry (ICP-MS); the method of capillary gel electrophoresis (CGE) was used to determine the ion concentration.

Results and discussion: Maximum concentrations of ammonium, sulfates, uranium, and nitrates in RAW filtration zones are 448, 1800, 4.9, and 10,000 mg/L, respectively. As a result of bioremediation, iron partially passes into sulfide phases, while the remained iron re-precipitates into hydroxide phases during bio- or reoxidation. Purification yielded a chemically active mineral sediment preventing the spread of U, Np, Pu, and Tc redox-sensitive radionuclides, as well as Sr and Am.

Conclusion: An effective and economically feasible approach to the purification of groundwater near nuclear fuel cycle facilities during their operation and post-mothballing periods has been tested. The tested method involves the in situ intensification of microbial processes by introducing soluble sources of organic carbon and phosphorus.