放射線防護の3原則で最初に示される。残りの2つは最適化と線量限度。（もともとjustificationはThe justification of practiceであり、）放射線利用は受ける不利益よりも利益の方が大きくなければならないというもの。放射線診療でも重要な原則だと考えられている。
ただし、2007年勧告からは、3つの全ての被ばく状況に適用するとしており、防護が正当であることも問われることになっているが、あまりにも合理主義的な表現になっていると受け止められかねないのではないだろうか（皆様はどう思われますか（IAEA GSR part3はより限定的に記述されており、現存被ばく状況での対策で、対策を講じることでの不利益が大きすぎないようすべきとしています）？）。
The Recommendations evolve from the previous process-based protection approach using practices and interventions by moving to an approach based on the exposure situation. They recognise planned, emergency, and existing exposure situations, and apply the fundamental principles of justification and optimisation of protection to all of these situations.
Principle 4: Justification of facilities and activities
Facilities and activities that give rise to radiation risks must yield an overall benefit.
Principle 10: Protective actions to reduce existing or unregulated radiation risks
Protective actions to reduce existing or unregulated radiation risks must be justified and optimized.
1.14. The application of the justification principle to medical exposures requires a special approach. As an overarching justification of medical exposures, it is accepted that the use of radiation in medicine does more good than harm. However, at the next level, there is a need for generic justification, to be carried out by the health authority in conjunction with appropriate professional bodies, of a given radiological procedure. This applies to the justification of new technologies and techniques as they evolve. For the final level of justification, the application of the radiological procedure to a given individual has to be considered. The specific objectives of the exposure, the clinical circumstances and the characteristics of the individual involved have to be taken into account
by means of referral guidelines developed by professional bodies and the health authority.
Requirement 10: Justification of practices
The government or the regulatory body shall ensure that only justified practices are authorized.
3.16. The government or the regulatory body, as appropriate, shall ensure that provision is made for the justification of any type of practice and for review of the justification, as necessary, and shall ensure that only justified practices are authorized.
Requirement 48: Justification for protective actions and optimization of protection and safety
The government and the regulatory body or other relevant authority shall ensure that remedial actions and protective actions are justified and that protection and safety is optimized.
5.7. The government and the regulatory body or other relevant authority shall ensure that the protection strategy for the management of existing exposure situations, established in accordance with paras 5.2 and 5.4, is commensurate with the radiation risks associated with the existing exposure situation; and that remedial actions or protective actions are expected to yield sufficient benefits to outweigh the detriments associated with taking them, including detriments in the form of radiation risks.
Requirement 49: Responsibilities for remediation of areas with residual radioactive material
The government shall ensure that provision is made for identifying those persons or organizations responsible for areas with residual radioactive material; for establishing and implementing remediation programmes and post-remediation control measures, if appropriate; and for putting in place an appropriate strategy for radioactive waste management.
- Action plan needs to be developed by the contractor and approved by the regulatory body
- Radiation doses received by workers are controlled as in a planned exposure situation
- Additional doses received by members of the public need to be justified
- Ongoing monitoring programme needs to be established
- A public information plan must be in place
- A mechanism must exist for ‘interested parties’ to be involved in the planning, implementation and verification of the remedial actions