A Jerusalem Magistrates Court judge sentenced nuclear whistleblower Mordechai Vanunu to six months in prison after he was convicted of violating the terms of his release from prison in April 2004.
Vanunu also received a suspended three-year suspended sentence.
Last April Vanunu was convicted of breaching 15 clauses of an IDF Central Command order prohibiting him from contacting foreign journalists and leaving the country.
"This is not a defendant who made a mistake, was negligent or didn't understand what was stated in the order," Judge Yoel Zur wrote in the verdict, "He understood it perfectly well, but did not agree with the order's prohibitions.
"It is not easy to rule on active prison time for Vanunu's repeated offenses, especially since he sat a long prison term in the past, most of which was in solitary confinement, but it seems that the defendant has shown complete contempt of the orders."
Vanunu returns to prison after over three years (photo: Gil Yohanan)
The original indictment included 22 different violations of the order, but during the trial the State Prosecutor's Office submitted an amended indictment, and he was eventually charged with 19 violations and was acquitted of four.
According to the indictment, Vanunu held conversations with foreign journalists and provided them with news and details on Israel's nuclear reactor.
He was acquitted of speaking to foreign nationals on the internet and via video and voice chats.
Vanunu was sentenced to 18 years behind bars in 1986 after giving an unauthorised interview to a British newspaper about his work at Israel's Dimona reactor. The disclosures all but blew away the secrecy around an assumed Israeli atomic arsenal.
Since his release Vanunu has campaigned for the Jewish state to be disarmed while denying Israeli officials' charges that he has more secrets that he could divulge if allowed to emigrate.