A valve malfunctioned in the liquid-oxygen tank on the Atlas booster.

About 75 gallons of fuel were dumped on the runway when a valve in the wing tank malfunctioned, a Northwest spokesman said.

He was having lunch at a school cafeteria, and a valve malfunctioned and caused a water heater to explode.

On Sept. 1, a different valve connected to the steam generator malfunctioned, and the plant was taken off line for two days.

"I've been studying the maintenance reports of deck 31," he muttered, pointing to the screen, "and I can't understand how a seal or a valve could have malfunctioned so badly."

Officials said that a valve malfunctioned during the loading, causing the spill.

The mitral valve was malfunctioning.

Neither Mr. Mako nor officials in the Environmental Protection Department said why the valve had malfunctioned.

There was the occasion in 1979 when a valve malfunctioned and was ingeniously fixed up with a handy piece of angle iron.

The regulators believe operators may have waited too long to shut down the reactor after discovering that a valve had malfunctioned.