retention

in nuclear chemistry
https://doi.org/10.1351/goldbook.R05357
Of atoms undergoing a nuclear transformation, that fraction which remains in or reverts to its initial chemical form.
Source:
PAC, 1982, 54, 1533. 'Glossary of terms used in nuclear analytical chemistry (Provisional)' on page 1551 (https://doi.org/10.1351/pac198254081533)