Senior Tepco engineers were aware of design flaws at five of its Fukushima Dai-ichi reactors for decades, but complacency and cost-consciousness prevented the company from fixing those problems, reports the Wall Street Journal. While newer reactors have backup diesel generators and electrical switchers placed securely in the well-protected reactor building, the first five reactors had kitchen-table-sized switchers placed in less secure turbine buildings, which the water from the tsunami easily overwhelmed.
Once flooded by the tsunami, the electrical switchers were useless, shutting down the vital cooling system in the reactors and causing the radioactive meltdowns. "There's no doubt Tepco should have applied new designs," says an 88-year-old former top executive. Although Tepco improved safety at the plants several times over the years, including improving placement of the backup generators, it never secured the electrical switchers in the turbine buildings. "Once water gets in there, the whole thing is kaput," says a former Tepco VP.