Justification, optimization, and the application of dose limits are three fundamental principles of radiation protection in the ICRP system. This is detailed in its latest General/Basic Recommendations (known as 2007 Recommendations) in ICRP Publication 103, which can be downloaded freely from
Justification, dose limitation and optimization are the three basic principles of radiation protection. The question has rather wide scope. ICRP issued lots of recommendation on protection of non-human species, representative persons, diagnostic levels in medical imaging, dose coefficients etc. What is your actual point of interest?