Monticello Nuclear Generating Plant

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The Monticello Nuclear Generating Plant is a nuclear power plant located in Monticello, Minnesota along the Mississippi River. The site, which began operating in 1971, has a single nuclear reactor ( boiling water reactor) of the General Electric BWR-3 design generating 613 megawatts, but studies are ongoing to uprate it to 700 MWe. Currently the plant is both owned and operated by Northern States Power Company (NSP), an Xcel Energy operating utility. The reactor was originally licensed to operate until 2010, however on November 8, 2006, it was extended to operate until 2030. The plant has had a solid operating history and is one of only two plants in the United States to never have received an Enforcement Action from the Nuclear Regulatory Commission, the other facility is North Anna Nuclear Generating Station. Roughly 1300 gallons of radioactive water accidentally leaked from the plant into the Mississippi River in an incident in 1982.

In January 2007 a 13-ton control box fell eight to twelve inches and caused an unexpected shutdown. This control box was located in the condenser room of the turbine building and contained valves which controlled steam pressure. Emergency response teams at the station deemed that the event was likely caused by inadequate welds at the time of installation and fatigue due to vibrations over the life of the plant. Construction of the on-site independent spent fuel storage installation (ISFSI) pad began in June 2007. The target date for the completion of the pads is December 2007 with insertion of the first ten dry storage containers (holding spent fuel assemblies) into horizontal storage modules (HSMs) in mid-2008. Initially, 12 HSMs will be placed on the storage pad. Each HSM " a thick, reinforced, pre-cast concrete structure about the size of a single car garage " Each HSM has the capacity to hold 61 fuel bundles. On September 11, 2008, a cable fault tripped the transformer which supplied power to the site. This resulted in a loss of off-site power and the plant automatically shut down. On September 17, 2008, an employee for a rental equipment company was electrocuted by one phase of the 115-kV power line outside of the plant due to a lack of situational awareness. The plant was offline at the time due to the forced outage described above. In February 2011, the site's plant officials determined that four control rod blades could be affected by a potentially substantial safety hazard. Vice President Tim O'Connor indicated that the blades would be replaced in March.

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