James Birch and Martin Tolson received the average annual dosage of plutonium for a member of the public in a "matter of a few seconds".
Magistrates in Newbury, Berkshire, fined AWE and the site licensee Hunting Brae after the firms admitted liability for the accident, which happened on December 15 last year as contaminated pipework was being dismantled. The pair were prosecuted by the Health and Safety Executive.
AWE admitted failure to ensure the health and safety of its employees and was fined pounds 14,000 with pounds 375 costs. Hunting Brae admitted failure to ensure that work was done under the control of qualified personnel, and was fined pounds 4,000.
The firm also admitted that it undertook ionising radiation work without taking the necessary steps to restrict the two workers from being exposed.
Collingwood Thompson, for the prosecution, said: "In a matter of a few seconds, two workers received the annual average dose of background radiation for an average member of the public in this country."
Mr Thompson told the hearing the accident happened as a worker dismantled and removed redundant equipment.
Mr Thompson further explained that the man was not affected by the radiation as he had on a protective suit, but that Mr Birch and Mr Tolson - who were in the room at the time - breathed in some radioactive particles. "It is an incident which should never have occurred in the first place."
Marion Egan, for the defence, told the hearing that since the accident steps had been taken by the companies to make sure such an incident would not happen again.
In a statement read after the hearing, AWE and Hunting Brae said: "We regret that two of our workers were subjected to contamination.
"However, we would like to point out that no radioactive material was released outside the laboratory, and there was no risk to other employees or to the public.
"This was an isolated incident. We treated this incident extremely seriously and took immediate action to strengthen our safety systems.
"Notwithstanding this event, the company does have an excellent safety record and, as part of our commitment to safety, we are continually reviewing and improving our procedures."
Peter Gardner, a superintendent inspector with the HSE, said: "The main message for operators is that people who hold the site licences must be in day-to-day control of the activities that pose risks."Reuse content