40-year-old bad math could delay the opening of the Fort Calhoun nuclear reactor even further. Omaha Public Power officials discovered that supports for heavy equipment in the plant's containment building might not withstand extreme stress. The Fort Calhoun plant has been closed since 2011. Critics say OPPD should consider shutting down the reactor for good because of the mounting costs. The utility believes that Fort Calhoun is worth salvaging because significant improvements have already been made and it's the only power plant it owns that produces electricity without greenhouse gases.