LONDON (Reuters) - Britain’s Sellafield Ltd, which reprocesses nuclear fuel, is to be prosecuted after an employee was contaminated, the country’s nuclear regulator said on Friday.

The incident occurred in February at a facility handling special nuclear materials, the Office for Nuclear Regulation (ONR) said.

It said it will prosecute over the incident under the Health and Safety at Work Act.

“For legal reasons we are unable to comment further on the details of the case which is now the subject of active court proceedings,” the ONR said in a statement.

A spokesman for Sellafield also declined to comment due to the court case.

Sellafield Ltd manages Britain’s nuclear reprocessing plant in Cumbria, northwest England, and employs around 11,500 people.

Sellafield was once the site of the world’s first major nuclear plant. In 1957 it saw Britain’s worst ever nuclear accident when a fire led to a radioactive leak.

Another radioactive leak in 2005 prompted a fine of 500,000 pounds ($678,000) for its operator.

The plant is currently going through a massive decommissioning program, which includes dismantling infrastructure and decontaminating nuclear waste.

The cost of the work has been estimated at more than 70 billion pounds and is expected to take another 100 years to complete.($1 = 0.7374 pounds)