The reactor at Ukraine's Zaporizhzhia nuclear plant which was set ablaze on Friday is inside a very solid concrete containment vessel designed to protect it from rocket fire, says Andrew Stuchbery, head of the Department of Nuclear Physics at the Australian National University. Russian troops attacked Europe's largest nuclear power plant on Friday, setting part of the Ukrainian facility ablaze. Local authorities said no immediate radiation rise was detected and "essential" equipment was unaffected by the fire, but it remained unclear what the invading forces planned next. SOUNDBITES