Design of a package for encapsulation, transport and final disposal of discarded radium needles

This paper describes the development work aiming at designing and building a package for radium needles. These needles comes mainly from hospitals where they were used in radiotherapy, but industrial sources may be stored in this package. It was previously defined that the package should be in a form which is acceptable in final disposal site, and also conform the type A - non-special form, of the 'Regulations for the safe transport of radioactive materials', safety series n. 6, 1985 Edition, published by the IAEA. As the final disposal site has not yet been defined, there is not a list of requirements to be fulfilled by the package. Hence the adopted criterion was to keep the source in a non readily dispersible form. The development work was undertaken to select packaging materials as shieldings, structural and absorbing materials, to define package geometries and encapsulation process. As this waste will be temporally stored before transport to the final disposal site additional requirement was considered: radon leakage from the package should be limited. To find out a figure for the maximum leakage rate, an interim storage scenario was defined. The incurred doses on operating personnel from the radon leakage shpould not exceed maximun permissible doses for workers. The package has an inner stainless steel cilindrical capsule, with two cubic decimeter in volume, in which the radium needles are enclosed with charcoal as an inert absorbing material. The shielding materials are a 0.5 cm thick lead layer inside a concrete shell 23 cm thick. The outer package is a 200 liters drum. Pertinent type A package tests were performed. This include integrity of containment system and shielding. (Author)