Israel has attacked Iran’s Arak heavy water reactor, Iranian state television said Thursday, adding that there was 'no radiation danger whatsoever”

Israel’s attacks on Iran’s atomic facilities have increased risks of nuclear and chemical contamination, experts say.

Uranium ore that miners dig up is relatively harmless. But it contains tiny amounts of a rare radioactive isotope, Uranium 235, that can be used to power nuclear reactors at low levels of enrichment, and to fuel atom bombs at higher levels. The percentage of U-235 in mined uranium is less than 1 percent.