The evaluated criticality safety benchmark data in the 2021 edition are presented in nine volumes. These volumes span approximately 80 000 pages and contain 587 evaluations with benchmark specifications for 5 121 critical, near-critical or subcritical configurations, 45 criticality alarm placement/shielding configurations with multiple dose points for each, and 237 configurations which have been categorised as fundamental physics measurements that are relevant to criticality safety applications.

New to the 2021 edition of the handbook are experiments from the Kilopower Reactor Using Stirling Technology (KRUSTY) – shown on the front cover – and Thermal/Epithermal eXperiments (TEX) programs performed at the National Critical Experiments Research Center (NCERC) in the United States; highly enriched uranium experiments with Lucite at NCERC; pitch variation experiments at Sandia National Laboratory in the United States; and structural material experiments at the Valduc facility in France.