Tritium is also used as a source of radiation in various products utilizing tritium illumination. Tritiated water contains the radioactive hydrogen isotope tritium. "Neutron blankets" Deuterium and tritium fusion generates neutrons. Fusion boosting is achieved by introducing tritium and deuterium gas. As an isotope of hydrogen, tritium (T) frequently binds to oxygen and forms TO. This has been used to decontaminate humans who are internally contaminated with tritiated water (tritium). In some CANDU reactors the tritium is periodically extracted. Likewise, removing an electron from a tritium atom produces a triton. The incident was discovered when employees began leaving bioassay urine samples with elevated tritium levels. Additional integrated features include interchangeable visible or infrared laser and tritium light source. Trace amounts are also produced by the beta decay of tritium. Tritium illuminated night sights are also available. It was then recycled after removal of tritium decay products. Caesium-137 has been used in hydrologic studies analogous to those with tritium. Current ITER designs are investigating total containment facilities for any tritium.