TEPCO began using a "spray-shower" technique to disseminate water into the No. 3 reactor at its troubled Fukushima No. 1 nuclear power plant on Sept. 1.
TEPCO began using a "spray-shower" technique to disseminate water into the No. 3 reactor at its troubled Fukushima No. 1 nuclear power plant on Sept. 1.
The method consists of spraying coolant water like a shower above the fuel rods so that water will fall evenly on all fuel rods and cool them efficiently.
Until Sept. 1, Tokyo Electric Power Co. has been using a method in which coolant water trickles down the inner walls of the pressure vessels at the No. 1 through No. 3 reactors. The No. 3 reactor, however, did not cool down as efficiently as did the No. 1 and No. 2 reactors. TEPCO officials have hinted at the possibility that part of the melted fuel in the No. 3 reactor did not fall through to the bottom, but remains on the grid-like core support plate beyond the reach of the trickling water.
In the new injection method, water is sprayed inside the shroud, a major component covering the core.
TEPCO has also begun considering a review of its plan to remove all highly radioactive water at the Fukushima No. 1 plant by the end of this year. Once the quantity of radioactive water has been reduced to such levels that heavy rains would not cause an overflow, the rate of water treatment will be adjusted to minimize the amount of waste generated.