sentences:  Though the Russians claim to have improved their operations, they continue to use the same borehole, which has already been contaminated with kerosene.According to the head of Russian Antarctic Expeditions, Valery Lukin, new equipment was developed by researchers at the Petersburg Nuclear Physics Institute that would ensure the lake remains uncontaminated upon intrusion.Lukin has repeatedly reassured other signatory nations to the Antarctic Treaty System that the drilling will not affect the lake, arguing that on breakthrough, water will rush up the borehole, freeze, and seal the other fluids out.