Answer to Question 1
An excess of material is necessary in the transfer chamber to insure that the cavities are filled. If too little material is present or even if just the right amount of material is present, the force on the material in the mold cavity may not be sufficient to give good mold filling. Therefore, excess material is always used. This excess material is the cull.
Answer to Question 2
The radiation from radioactive cobalt is -particles. The high penetration of these particles, when compared with electrons in an electron beam, is due to the high energy of the -particles.