A glass bottle of plutonium powder that probably cracked when a federal employee tapped it up against a piece of marble later fell apart, releasing the radioactive material into a Boulder, Colo., lab, according to a new federal report on the June 9 spill.

The report on the accident at the National Institute of Standards and Technology campus also confirmed the substance that makes up a key component of a nuclear bomb trigger was obtained without managers' approval, and the worker on the project when the powder spilled then washed his hands at a sink connected to the municipal sewer system and left the lab, spreading the contamination.

Plutonium, which is produced in reactors from the absorption of neutrons by uranium, has 15 isotopes – all radioactive. It poses the most significant hazards in research settings from internal contamination by inhalation or ingestion, the report said, because the alpha particles from the radioactive decay inside the body are in direct contact with human tissue. In short, it causes cancer. ...