Leaded Glass for Shields
One possible problem associated with shielding a gamma ray source is the difficulty in seeing what is on the other side of the shield. This can be a significant issue if the source of the radiation has to be manipulated. One solution has been to use a video camera and monitor. Another approach is to observe the source via one or more mirrors. The most common solution however is to employ a leaded glass window in the shield. Leaded glass, just like lead crystal glassware, is clear and colorless. The piece to the left in the photo is approximately 60 % lead (by weight).
Unfortunately a prolonged exposure to radiation turns leaded glass a dark amber-brown color. Eventually it can become impossible to see through. The piece of lead glass in the center of the photo was irradiated with gamma rays from cobalt-60.
The darkening of lead glass as a result of an exposure to radiation can be prevented by adding small amounts of cerium (the piece to the right in the photo). Although the presence of the cerium adds a yellowish color to the glass, it makes the glass resistant to radiation induced darkening. Besides, the yellow color looks cool.
Donated by Phil Rudolph.