Decades of scientific study at the sites of the world's two worst nuclear disasters — Chernobyl (1986, Ukraine) and Fukushima Daiichi (2011, Japan) — have shown that radioactive contamination follows predictable patterns that can be tracked, mapped and managed. Key radionuclides such as cesium and strontium entered soil, water and food chains, moving from grass into livestock and from seawater into marine life, though monitoring found that levels in seafood and coastal waters generally declined over time and remained within safe limits at greater distances from the disaster sites. Researchers now use a combination of ground sensors, three-dimensional mapping systems and computer models to guide cleanup efforts — which range from removing and storing contaminated topsoil to applying potassium fertilisers to reduce crop absorption of radioactive cesium — with the overarching finding that radiation risk, while real and long-lasting, is measurable and controllable.