Emergency response in U.S.S.R. at the time of the accident of Chernobyl nuclear power plant

The report outlines the emergency measures taken by the Soviet authorities following the accident at the Chernobyl nuclear power plant that occurred on April 26, 1986. About 10 percent, or 250 tons, of the graphite moderator dissipated in the accident and fire took place in 30 places due to hightemperature materials released by the explosion. Water was used at first for cooling, but was soon found ineffective. Then such materials as silver (2,400 t), soil/clay (1,800 t), boron carbide (40 t) and dolomite (800 t) were dropped from helicopters onto the reactor core. This served rather effectively to cool the core. Two divers carried out the removal of water from the upper and lower pools. A tunnel was excavated from a trench near the No. 3 unit to the lower pool, which was then consolidated with concrete, while various sensors were installed in the upper pool. Nitrogen was supplied to eliminate oxygen from the bottom of the core. Afterwards, the degree of contamination and radiation level were analyzed and the position and stability of the core debris were determined. Various measures, including fixation of radioactivity, decontamination, and river protection, were taken to prevent the expansion of contamination. (Nogami, K.)