After a nuclear power plant accident, researchers found radioactive isotopes of iodine, tellurium, and cesium-but no heavy isotopes-in the atmosphere downwind  This material came either from spent fuel rods or from the plant' s core  Spent fuel rods never contain significant quantities of tellurium isotopes  Radioactive material ejected into the atmosphere directly from the core would include heavy isotopes  After the accident, steam, which may have been in contact with the core, was released from the plant
The core contains iodine, tellurium, and cesium isotopes, which are easily dissolved by steam
The researchers found some radioactive material from spent fuel rods as well as some material that was ejected into the atmosphere directly from the plant's core.