TEPCO and its network of partner companies at Fukushima Daiichi have yet to identify the location and condition of melted fuel in the three most seriously damaged reactors. Removing it safely represents a challenge unprecedented in the history of nuclear power. Quantities of melted fuel are believed to have accumulated at the bottom of the damaged reactors’ containment vessels, but dangerously high radiation has prevented engineers from accurately gauging the state of the fuel deposits.
TEPCO is now worried that the scorpion robot will not be able to reach the space beneath the pressure vessel, and like its predecessor, will not be able to work for very long in the damaged plant (the scorpion is designed to handle 1,000 total sieverts). The high level of radiation may force TEPCO, a nationally-owned company, to rethink its robot-based strategy for locating the molten fuel. The firm is currently in the early stages of a cleanup that’s expected to last decades. Until TEPCO knows the precise location of the melted fuel, and until it’s able to ascertain the structural damage in each of the three reactors affected, the company won’t be able to decommission the plant and remove the fuel.