BS ISO 21391:2019,Nuclear criticality safety — Geometrical dimensions for subcriticality control — Equipment and layout.BS ISO 21391:2019 pdf free download.
BS ISO 21391:2019 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.
BS ISO 21391:2019 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.
Nuclear criticality safety is achieved by methods of control in accordance with ISO 1709. The applicatio of some of these methods of control (such as geometry, interaction) can lead to requirement(s) on geometrical dimension limits. This document covers subcriticality control based on geometrical dimensions, called subcriticality dimensions, related to equipment and layout.
Stages presented in this document are summarized in the flow diagram in Annex A and an example of this standard application is presented in Annex B.
2 Normative references
ISO 11311, Nuclear criticality safety-Critical values for homogeneous plutonium-uranium oxide fuel mixtures outside of reactor;
ISO 12749-3, Nuclear energy,nuclear technologies, and radiological protection -Vocabulary- Part 3:Nuclear fuel cycle;
4 Subcriticality dimensions
4.1 In the nuclear criticality safety assessment, the unit geometry is defined by;
—dimensions of items containing fissile media;
—dimensions of materials surrounding fissile items;
—layout dimensions;
—dimensions and layout of mobile items;
4.2 Some of these dimensions or distances can be required to be subcriticality dimensions. Accordingly, subcriticality dimensions shall be identified and controlled. The compliance of the actual dimension
with the subcriticality limits shall be verified to ensure subcriticality of a unit according to Clause 7. The determination of subcriticality limits is presented in Clause 6.