Abstract: A method of molding a plastic lens, in which: a pair of upper and lower molds are arranged to form a gap, corresponding to the thickness of the lens, therebetween; an adhesive tape is applied around the molds to define a cavity between the molds; and a plastic material is injected into the cavity. Optical axes of the molds are centered at respective positions of the molds. After the centering step, each of the molds is held with the centered optical axis. A height of each mold held is measured referring to a reference height. Displacements of the molds are determined on the basis of the measured heights of the molds and the reference height. The molds held are horizontally moved with the centered optical axes for axial alignment. The molds held are axially moved to form a predetermined mold gap between the molds on the basis of the determined displacements of the molds. Then, the adhesive tape is applied around the molds to define the cavity.

Abstract: An improved process for treating waste gas from a nuclear power plant to recover radioactive rare gases such as Kr and Xe therefrom. The waste gas is treated with titanium, zirconium or alloys thereof to remove oxygen present in the waste gas.