1The assessment time frame is the time period used in the calculations for the post-closure performance assessment.

2A barrier in this context is a physical obstruction that prevents or inhibits the movement of radionuclides, or provides shielding against radiation. There are two types of barrier: engineered barriers and natural barriers. In this context, a barrier is a physical entity that provides, or contributes to, safety.

3The waste package is defined as the product of conditioning that includes the waste form and any container(s) and internal barriers (e.g. absorbing materials and liner), as prepared in accordance with requirements for handling, transport, storage and/ or disposal. This includes an outer container and, if included, an encapsulation matrix that fills the void space within the container. The waste form is the combination of waste and waste encapsulant.