Production has stopped at a newly opened nuclear medicine facility at Sydney's Lucas Heights after workers there were exposed to an unsafe dose of radiation.

Key points: Contamination was detected outside a container holding Molybdenum-99 (Mo-99)

Contamination was detected outside a container holding Molybdenum-99 (Mo-99) ANSTO says the exposure is equivalent to a conventional radiation therapy treatment

ANSTO says the exposure is equivalent to a conventional radiation therapy treatment It comes less than two weeks after the facility was granted a licence to produce Mo-99

The Australian Nuclear Science and Technology Organisation (ANSTO) said three workers were "attended to by radiation protection personnel" after contamination was detected on the outside of a container holding 42 millilitres of Molybdenum-99 (Mo-99) on Friday morning.

"Initial indications are that two of these workers received a radiation dose above the statutory limit," a spokesperson said.

"Early calculations indicate that the radiation dose received by two of the workers involved in medicine processing, was equivalent to that of a conventional radiation therapy treatment."

The spokesperson said manufacturing of Mo-99 ceased on Friday morning and an investigation was underway.

He said the workers were receiving ongoing support from ANSTO, including medical observation from an occupational physician.

The spokesperson said supplies of Mo-99 were being provided by alternative facilities at ANSTO while the investigation was underway.

The incident comes less than two weeks after ANSTO received a licence to begin supplying Mo-99 — the parent isotope of technetium-99m, used in 85 per cent of all Australian nuclear medicine.

It also follows a series of contaminations scares at the Lucas Heights facility in recent years — including one just two months ago in which three workers were exposed a chemical spill.

In August 2017 a worker was left with blisters on his hands and a higher risk of developing cancer after he dropped a vial of radioactive material and was contaminated through two pairs of gloves.

The event was deemed the most serious in the world in 2017, according to the International Nuclear Event Scale — the global grading system for nuclear incidents.

An independent review of the facility in October 2018 found it failed modern nuclear safety standards and should be replaced.

In the same week ANSTO confirmed five workers had received a dose of radiation at the facility, but that the amount of radiation was "less than a chest x-ray".