In OPAL, those tasks - moderation and reflection - are performed by the cooling water flowing through fuel assemblies in the core and heavy water (D 2 0) contained in the reflector vessel surrounding the core. Core and fuel. The compact core of the reactor is a notable feature. read more
Opal is a non-crystalline form of the mineral silica and is formed from amorphous "balls" or "lumps" of silica. So the opal is a very unique gem compared with others, like diamonds or a ruby which is formed crystalline. read more