Nuclear safeguards inspectors view historical trends on a regular basis to reassure themselves that a plant is operating as declared. Other types of inspector are likely to perform similar activities. Nuclear safeguards are founded on materials accountancy, and hence nuclear safeguards inspectors often want to relate what they see to laws of mass conservation. The interfaces discussed in this paper facilitate a synergy between qualitative reasoning regarding trends with quantitative reasoning about simple models that are driven by forcing functions, which describe materials flows through a plant. The focus in the paper is on the assessment of data trends that pertain to a standard 3-tank arrangement in a nuclear fuel reprocessing plant, and on how inspectors might wish to interact with evaluations performed. (C) 2012 Elsevier Ltd. All rights reserved.