Stoppers is a truncated conical piece of rubber or cork used to close off a glass tube, piece of laboratory glassware, a wine bottle or barrel and containers with orifices. A rubber stopper is also called a rubber bung, and a cork stopper is called cork. Ground glass stoppers are commonly used with laboratory glassware, mainly because of their nonreactivity. They come in many forms such as cork, rubber and plastic film that stretches over the opening.
The storage containers are designed to prevent the deterioration of the plutonium, the formation of plutonium hydrides and oxides. Therefore, the existence of these compounds will alert us that the containers are failing in some way. These compounds are also indicators that pyrophoric plutonium compounds may be forming. Because it is extremely important to avoid fires in the storage vault and the spread of fine plutonium powders formed during a fire, the detection of the hydrides and oxides is crucial. Fortunately, the hydrides and oxides are very easy to detect radio graphically because they are powders with about 60% the density of plutonium.