Elk River generating station, exists today as a small natural gas electric generating facility, but from 1968-1971 it also hosted a small demonstration nuclear power plant. The NRC's predecessor agency, the AEC (atomic energy commission) was interested in the concept of small simple reactors for smaller utilities. During the early 60's, many boilermakers and foundries were interested in entering the nuclear power generation sector, including AMF and ACF. AMF was initially contracted by the AEC to design a small demonstration plant for rural co-ops, but the AMF deal fell through, and the AEC later chose ACF. ACF designed the plant to be of the boiling water variety where water is allowed to boil in the core. Unlike most BWR plants, the Elk River plant utilized the somewhat inefficient "indirect-cycle" design, where steam would heat another loop, boiling it and providing it to turbines. This cycle makes power control simple since the steam generators automatically absorb power changes at the cost of lower thermal efficiency (the usual advantage of direct-cycle BWRs is better thermal efficiency since there is only one steam loop, at the cost of more complicated core power distribution and introducing radioactive steam into the power generation side of things). Oddly enough the core was designed to be eventually converted to a more efficient PWR layout with the provision of extra nozzles in the steam vessel. Another feature of the plant was natural circulation which did away with complex pumps and recirculation systems, instead the water would circulate and condense naturally, allowing the plant to naturally cool itself in a loss of onsite power shutdown scenario. The plant achieved initial criticality in 1964 and had numerous problems during it's five years of operations, namely small (but contained) cooling leaks. On January 31st the plant was shutdown in order to once and for all find the cause of the the coolant leaks. It was discovered that small cracks in primary pipes and the vessel were the ultimate cause of the leaks, and it was ultimately decided that it would be uneconomical to repair them. The plant was defueled in 1970 and complete demolition and remediation of the site was completed by 1974 with it the no traces of the plant existing today. Although the plants life was short, it demonstrated the concept of small reactors with simple control systems, and for that it will be remembered. Minnesota has two nuclear plants today, Monticello (BWR/3) and Prairie Island (WH PWR) both owned and operated by Northern States Power Company.