June 23 (Reuters) - Retail bellwether Walmart ( WMT ) has signed a long-term nuclear power purchase agreement with Constellation Energy ( CEG ), the companies said on Tuesday.

Under the agreement, Constellation Energy ( CEG ) will supply nuclear power from its Dresden Clean Energy Center in Illinois to Walmart's ( WMT ) previously announced "high-tech" perishable distribution center, currently in development in Belvidere, Illinois.

-- Walmart ( WMT ) will buy about 176 megawatts of electricity, including 30 megawatts of additional output from planned upgrades, under two 15-year contracts starting in 2029 and 2030.

-- The agreement is among the first between a major U.S. retailer and a nuclear energy provider and underscores growing corporate interest in baseload clean power, which can provide electricity around the clock.

-- The deal would support investment in efficiency upgrades, or uprates, at the Dresden Clean Energy Center, allowing the plant to increase output without building new generation capacity.

-- Dresden, one of Constellation's largest nuclear plants, is licensed to operate through 2049 and 2051.