In the context of creating Plutonium at the Hanford Site, effluent refers to the cooling water that is discharged from a nuclear reactor that may or may not be radioactive. General Name, Symbol, Number Plutonium, Pu, 94 Chemical series Actinides Period, Block 7, f Density, Hardness 19816 kg/m3, no data Appearance silvery white metal Atomic properties Atomic weight 244. ... Hanford Site during the Manhattan Project. ... Nuclear power station at Leibstadt, Switzerland. ...