An irradiation facility of

137

Cs gamma source

has been established in 1981 in Hangchow and functioned normally since then. The intensity of

137

Cs gamma source used is 50 kCi. The source is composed of a cast cylinder of

137

Cs chloride

doubly encapsulated in high integrity stainless steel casting filled with helium and sealed by welding. The dimensions of the cylinder were 52 mm in outer diameter and 480 mm in length

having characteristics of a single line source. The pool is 5 m in depth under the floor locating at the center of the cave. The source is arranged on the elevator frame. The top end of the source was kepted 3 m under water level

so that it can meet the need of safty requirement of 2.68 m under the water level. The irradiation cave was shielded with concrets wall of 1.56 m for the sake of residents safety nearby. The roof of the cave was designed in arched form.

This pool type designs

in comparing with dry-well type is more simple

safe

and-easy to operate and repair etc.