Hanford union workers tell NBC Right Now there was an explosion at the plutonium finishing plant cleanup site weeks ago, but the event wasn't shared with the public. The Hanford union representative says it happened when workers were cutting some pipe as part of the demolition of the Plutonium Finishing Plant. The union representative wants to remain anonymous and says workers are concerned management isn't putting worker safety first. Having a pipe explode at probably the most contaminated facility in the United States. This is one of the most hazardous buildings in the U.S." said the Union representative. PFP is where the plutonium was manufactured for one of the atomic bombs dropped in World War II. Workers describe the explosion as a spark then flames that shot out of a pipe and a loud bang that vibrated the pipe and the worker. "Management continues to call it a small pop even though the workers say no this thing was a big, loud bang like a shot gun blast," said the union representative. Workers say they think the contractor is playing down the explosion and possible safety concerns to protect themselves from fines and work delays. The union representative says if the pipe broke, workers would have inhaled plutonium particles that could have possibly deadly health effects.