A Hanford worker was seriously injured when he fell through an access door to a catwalk 50 feet above the ground Wednesday morning inside a building at the Hanford 300 Area just north of Richland.

He hit the rail of a ladder halfway down, and then fell the rest of the way to the ground, said Todd Nelson, spokesman for Washington Closure Hanford. The railing kept him from hitting the floor with full force, according to DOE.

The Washington Closure worker was taken to Kadlec Regional Medical Center in Richland by ambulance with "very serious but non-life-threatening injuries, including to his leg," said Dave Brockman, manager of the Department of Energy Hanford Richland Operations Office, in a memo sent to all Hanford employees Wednesday evening. The worker's name was not released.

The accident follows a series of safety events that the Defense Nuclear Facilities Safety Board said appeared to be increasing in recent months in a newly released May report.

The man was described as an experienced Hanford worker who was preparing a crane for the demolition of the 336 Building, also called the High Bay Test Facility, which was built in 1969. He is a "D4 worker," an employee who does deactivation, decommissioning, decontamination and demolition tasks on unneeded buildings.

Work stopped immediately at the 336 Building when the man was injured and work at all Washington Closure Hanford projects did not resume after the lunch break. Washington Closure does cleanup work at the nuclear reservation along the Columbia River and operates the Environmental Restoration Disposal Facility for low-level radioactive waste in central Hanford. About 1,100 people work for the company and its subcontractors.

Washington Closure workers have today off for the Fourth of July holiday and do not work Fridays, so work will not resume until at least Monday.

In addition, work at high elevations at Washington Closure has been stopped until investigations into the accident are completed and any needed action is taken to increase safety, according to Brockman.

Washington Closure began an investigation Wednesday and a corporate team from its parent company, URS, is expected to arrive Monday to help. DOE also will launch a formal investigation, said DOE spokesman Geoff Tyree.

"There will be a lot of review and questioning and work on improvements in the days and weeks to come," Brockman told employees. "For today, I ask that each and every one of you consider this serious incident a call to redouble your own commitment to safety of yourself and those around you on the job."

He also wished the worker a rapid and full recovery.

Washington Closure recognized potential safety incidents earlier this year and made a concerted effort to increase worker safety, Nelson said. Two weeks ago, it started a new safety awareness program called Safety Ownership that focuses on workers thoroughly understanding their job tasks, following instructions and focusing on their jobs without distractions.

Site representatives for the Defense Nuclear Facilities Safety Board wrote in their weekly report for May 22 that two decommissioning workers at Washington Closure had skin contamination from radioactive material that week and that a fire alarm was inadvertently tripped during work to clean up and tear down buildings.

"The frequency of similar events appears to be increasing in recent months," the report said.

It noted that in the 327 Building in March a waste storage box "contacted" a nuclear chemical operator as it was being moved by an overhead gantry crane. The load was not centered under the crane hook. When the box was lifted it rotated unexpectedly and cornered the worker between the box and a hot cell wall, according to a safety board report.

The worker was not injured. Washington Closure retrained its rigging workers afterward, the report said.

Also in March, a worker entered a high-radiation area in the basement of the 327 Building without the required dosimeter, which was not noticed by the high-radiation area guard, according to a safety board report.

Various levels of supervision and management took actions, including bringing the electronic dosimeter to the worker and notifying the supervisor of the high-radiation area. However, the worker was allowed to continue work even though the total amount of radiation he was exposed to could not be determined, the report said.

The most serious accident at Hanford in recent years was a 6-foot fall in 2004 that killed a nongovernment-contract worker who hit his head.