Charles Harvey Eccleston was sentenced Monday in Washington's federal court.
He pleaded guilty in February to attempting to insert a virus onto an Energy Department computer network.
Prosecutors say Eccleston, who was fired from the NRC in 2010, was a disgruntled ex-employee who attracted FBI attention after entering a foreign country's embassy in the Philippines and offering to sell email account information for U.S. government employees.
He later met with undercover FBI employees as part of a plot to deliver the computer virus. But prosecutors say the link he thought contained the virus was actually developed as part of the undercover operation and was inert.