NBN ISO 21391:2020

This document provides guidance, requirements and recommendations related to determination of limits on subcriticality dimensions and to their compliance with:
— geometrical dimensions specified in the design (design dimensions), or,
— actual dimensions. This document is applicable to nuclear facilities containing fissile materials, except nuclear power reactor cores. This document can also be applied to the transport of fissile materials outside the boundaries of nuclear establishments. Subcriticality dimension control based on dimensions and layout of fuel assembly, fuel rods and fuel pellets are not covered by this document.
This document does not specify requirements related to the control of fissile and non-fissile material compositions. The Quality Assurance associated with the fabrication and layout of the unit based on specifications (e.g. drawings elaborated during design) is a prerequisite of this document.
The Quality Assurance is important to ensure the consistency between the unit geometry, its general purpose and its intended function.