The initial design and the subsequent changes shall be carried out in accor­dance with established codes, standards, requirements and design bases.

The adequacy of design shall be verified and validated, before the imple­mentation, by additional individuals or groups. Design changes should be justified and submitted to controls commensurate with the original design.

21.1.4 Procurement

Suppliers shall be evaluated and selected on the basis of specified criteria and periodically assessed. The procured items or services shall meet estab­lished requirements.

Suppliers of services acting on site should be subject to control and supervision commensurate with the safety relevance of the task performed.