Tokyo Electric Power Co. (TEPCO) said Wednesday that its new estimate shows that all the fuel rods in reactor 3 at the Fukushima No. 1 nuclear power plant apparently melted down and fell onto the bottom of the containment vessel.
In November 2011, the company had said it believed only about 63 percent of reactor 3′s fuel core had melted.
The new estimates are based on when the High Pressure Coolant Injection (HPCI) system stopped providing cooling water to the crippled reactor:
The revised estimate is based on the finding that an emergency cooling system, known as HPCI, of reactor 3 stopped working six hour earlier than previously thought, and that the meltdown had also started more than five hours earlier.
Tepco had previously said that the HPCI had shut down at 2:42 a.m. on March 13, 2011. But further investigation over the past year determined that the HPCI appeared to have lost its cooling function about at 8:00 p.m. on March 12.
The new report also indicates that all the fuel in reactor 3 melted through the pressure vessel and penetrated more than two feet into the containment structure:
According to the new estimate, all the melted fuel penetrated the pressure vessel, fell onto the bottom of the containment vessel and melted about 68 cm (27 inches) into the concrete.