After 16 years of irregular service, the plant was closed permanently in 1992 by its operator, Portland General Electric (PGE),[3] after cracks were discovered in the steam-generator tubing.

The Trojan Powder Company had formerly manufactured gunpowder and dynamite on a 634-acre (2.57 km2) site on the banks of the Columbia River, four miles (6.5 km) from the town of Rainier, Oregon.

At the time, the single 1,130 megawatt unit at Trojan was the world's largest pressurized water reactor; it cost $460 million to build the plant.

[11] In 1978, the plant went offline on March 17 for routine refueling and was idle for nine months while modifications were made to improve its resistance to earthquakes.

[25] A week after the election, the Trojan plant suffered another steam generator tube leak of radioactive water, and was shut down.

In December 1992, documents were leaked from the U.S. Nuclear Regulatory Commission showing that staff scientists believed that Trojan might be unsafe to operate.

[30] In 2005, the reactor vessel and other radioactive equipment were removed from the Trojan plant, encased in concrete foam, shrink-wrapped, and transported intact by barge along the Columbia River to Hanford Nuclear Reservation in Washington, where it was buried in a pit and covered with 45 feet (14 m) of gravel, which made it the first commercial reactor to be moved and buried whole.

[32] The iconic 499-foot-tall (152 m) cooling tower, visible from Interstate 5 in Washington and U.S. Route 30 in Oregon, was demolished in 2006 via dynamite implosion at 7:00 a.m. PDT on Sunday, May 21.

[citation needed] A number of the civil defence sirens that were originally installed within a 10-mile (16 km) radius of Trojan, to warn of an incident at the plant that could endanger the general public, continue to stand in the Washington cities of Longview, Kelso, and Kalama.