"This reactor remained operative for 30 years and must be closed down," said Vanunu on Monday.
"It is dangerous and could cause a catastrophe like the one at Chernobyl if it continued to operate under the present conditions," he added.
"It might cause a catastrophe for Jordan and for the whole Middle East."
"I think Jordan has the right to enquire about what Israel is doing since it [the reactor] is very close to the Israeli borders [with Jordan]," he told Aljazeera.
Vanunu was jailed in 1986 for treason by an Israeli court after disclosing information to Britain's Sunday Times which led analysts to conclude that Israel had produced nuclear warheads.
Negev desert inhabitants display
pills to combat radiation effects
The 49-year technician said on the day of his release in April he was "kidnapped by Israeli spies in an apartment in Italy in September 1986, drugged and then kept on a yacht for seven days, chained to a bed", before being brought to Israel, where he was imprisoned in October that year.
Israel has never acknowledged having a nuclear arsenal, but foreign experts are convinced that the country has clandestinely produced between 100 and 200 nuclear warheads.
The Chernobyl disaster - the world's worst nuclear power accident - occured in April 1986 at Chernobyl in the former Soviet Union, now Ukraine. It killed more than 30 people instantly and the high radiation in the surrounding 30km radius caused 135,00 people to be evacuated. Many continue to suffer the effects of that radiation.