The HSE said the contractors are unlikely to suffer long-term effects
The operators of Sellafield are to be prosecuted after two contractors received a "higher than anticipated" dose of radiation.
The workers were refurbishing a floor at the site's plutonium finishing and storage plant in July 2007 when they were exposed to airborne contamination.
Sellafield Ltd is accused of failing to discharge its duty under Section 3 (1) of the Health and Safety Act 1974.
The case will be heard at Whitehaven Magistrates' Court on 24 July.
A spokeswoman for the Health and Safety Executive (HSE) said: "The two contractors were exposed during the decontamination of an area of concrete floor.
"As a result of this exposure the two contractor employees received an internal dose of radiation."
She added: "As far as we know the contractors have not shown any illness arising out of this incident. The level of dose received would indicate that the likelihood of adverse long-term effects is low."
Sellafield Ltd confirmed the incident took place, but said it would not comment further while a legal case was active.
Earlier this month, the company revealed that a low-level radioactive leak at the nuclear reprocessing plant had gone undetected for 14 months.
In that instance, no-one was contaminated.