Mordechai Vanunu, who served 18 years in prison for leaking Israel's nuclear secrets, began to serve a three-month prison sentence on Sunday.Vanunu, who was released in 2004, returned to prison after refusing to perform community service for contacting a foreigner without authorization, a violation of his parole. He was arrested last December on suspicion that he had met with a Norwegian national at a hotel lobby. Vanunu's attorney had stressed then that the man's ties with the Norwegian woman had nothing whatsoever to do with espionage."I survived 18 years [in prison] - I could survive [even] another six," Vanunu shouted outside the Jerusalem District Court on Sunday. "Are you trying to discipline me? You cannot take my freedom of expression away ... I'm not an animal," he stated.A panel of Supreme Court justices decided last Tuesday to return Vanunu to prison after the former technician at the alleged Dimona nuclear plant was denied his request to serve his community service in Arab-dominated east Jerusalem. He told the judges that he was worried about being attacked in west Jerusalem by angry Israelis.Vanunu was jailed in Israel for discussing details of his work as a Dimona technician with the British Sunday Times. He reportedly revealed Israeli nuclear secrets and gave the newspaper photographs of the plant's operation.Under the terms of his parole, Vanunu also is prohibited from leaving the country or approaching foreign embassies.