The Pentagon is sending a?Boeing Co. (BA)?plane, equipped to detect radioactive “clouds” from nuclear tests, to sample air for radiation from the damaged Fukushima nuclear plant in?Japan.

The WC-135W Constant Phoenix, a modified Boeing C-135, has equipment designed to collect particulates and whole-air samples, according to the U.S.?Air Force. The craft, similar in size to a Boeing 707 airliner, usually is used for monitoring required by the 1963 Limited Nuclear Test Ban Treaty, which prohibits above-ground nuclear weapons testing.

“I can confirm the WC-135 has deployed to the Pacific region,” said Major Chad Steffey, a spokesman for the Air Force, in an e-mail yesterday.

The deployment steps up the U.S. military’s humanitarian and technical assistance to Japan after the March 11 earthquake, tsunami and the worst nuclear accident since Chernobyl. The Defense Department has deployed more than a dozen ships and their aircraft for humanitarian relief as well as equipment and personnel to help with the nuclear crisis.

A?Northrop Grumman Corp. (NOC)?Global Hawk drone also flew over the 40-year-old power station at Fukushima, about 135 miles (220 kilometers) north of Tokyo, to collect data. Air Force Secretary Michael Donley said after a congressional hearing in?Washington?yesterday that it won’t be the last mission.

Water Cannons

Water cannons may have had some success in cooling one reactor at the damaged Fukushima plant, owned by Tokyo Electric Power Co. The United Nations nuclear agency said the situation remained “very serious.”

The existence of the WC-135W stems from orders given by General Dwight D. Eisenhower, who commissioned a program in 1947 for detecting atomic explosions. A WB-29 flying between Alaska and Japan in September 1949 detected nuclear debris from?Russia’s first atomic test, according to the Air Force.

WB-50s were first converted in 1950 for air-sampling missions, and the WC-135W replaced the WB-50 in 1965.

The WC-135W’s cockpit crew is from the 45th Reconnaissance Squadron at Offutt Air Force Base in Nebraska. The personnel operating the equipment are from the Air Force Technical Applications Center at the base.