Access to accurate and reliable information is of prime importance in all nuclear energy applications. This is especially true in the area of nuclear criticality safety for the front- and back-end of the fuel cycle, including transport and storage of spent fuel. The data needed in this area comprises reference values for minimum critical mass, concentration and geometry, as well as the maximum critical moderation of well-defined systems. The accuracy of such data influences both the safety and economy of the fuel cycle.
In 1999, the NEA Working Party on Nuclear Criticality Safety (WPNCS) established an expert group to study the status of nuclear criticality safety reference values (minimum and maximum critical values), following the detection of large deviations in existing reference values between different criticality safety handbooks and guidelines.
The present report represents the outcome of the NEA study and contains a compilation and evaluation of nuclear criticality safety reference values from various sources. Some of the values were taken from published reports, while others were calculated specifically for this study. Many discrepancies have been identified and resolved, thus reinforcing the importance of data verification and validation as essential tools in this field.