6.32 Safety functions are fulfilled by elements of a disposal facility, such as a physical or chemical property of part of the disposal system, or a process or combination of processes, that contribute to containment and isolation of the waste (e.g. low hydraulic conductivity, slow corrosion rates, slow dissolution of the waste matrix, low radionuclide leaching rates, low radionuclide solubility, high sorption). Active controls, such as the prevention of human intrusion or monitoring, can also provide safety functions or contribute to confidence in natural and engineered barriers and safety functions, although limitations in the timescales over which credit can be taken for such controls should be observed (see paras 6.66-6.73 on institutional control).