Iowa’s only nuclear power plant is offline. The management company that operates the Duane Arnold Energy Center says it’s been taken down to replace a relief valve. Wisconsin-based Nuclear Management Company says nothing about any problems in its news release, just states that the part in the main steam system at the plant in Palo is being replaced now as a preemptive maintenance move, to ensure reliability through the high-demand summer months. The plant ten miles northwest of Cedar Rapids generates 580 megawatts of electricity, enough to serve about 432-thousand homes. The Duane Arnold Energy Center’s owned by Alliant, Central Iowa Power Cooperative and the Corn Belt Power Coop.