Alkali metal from the Chernobyl accident. Caesium-137 undergoes high-energy beta decay and eventually becomes stable barium-137. It is a strong emitter of gamma radiation. Caesium-137 has a very low rate of neutron capture and cannot be feasibly disposed of in this way, but must be allowed to decay. Caesium-137 has been used as a tracer in hydrologic studies, analogous to the use of tritium. Small amounts of caesium-134 and caesium-137 were released into the environment during nearly all nuclear weapon tests and some nuclear accidents, most notably the Goiânia accident and the Chernobyl disaster. As of 2005, caesium-137 is the principal source
Effects of the Chernobyl disaster most soils because it binds to the clay minerals. Tests (c. 1997) showed that caesium-137 levels in trees of the area were continuing to rise. It is unknown if this is still the case. There is some evidence that contamination is migrating into underground aquifers and closed bodies of water such as lakes and ponds (2001, Germenchuk). The main source of elimination is predicted to be natural decay of caesium-137 to stable barium-137, since runoff by rain and groundwater has been demonstrated to be negligible. An increased incidence of thyroid cancer was observed for about 4 years after the accident