Kinetic isotope effect approximation that reduced masses are approximately equal to the masses of the hydrogen, deuterium, or tritium was used. In addition, the vibrational motion was assumed to be approximated by a harmonic oscillator, so that formula_19 (X = H, D, or T). The subscript ""s"" refers to these "semi-classical" kinetic isotope effects, which disregard quantum tunneling. Tunneling contributions must be treated separately as a correction factor. For isotope effects involving elements other than hydrogen, many of these simplifications are not valid, and the magnitude of the isotope effect may depend strongly on some or all of the neglected factors. Thus, kinetic
Tritium in small quantities by some nuclear power plants. In January 2014 it was made public that a total of 875 TBq (2.45 g) of tritium are on the site of Fukushima Daiichi, and the amount of tritium contained in the contaminated water is increasing by approximately 230 TBq (0.64 g) per year. According to a report by Tepco ""Tritium could be separated theoretically, but there is no practical separation technology on an industrial scale"." Tritium's decay product helium-3 has a very large cross section for reacting with thermal neutrons, expelling a proton, hence it is rapidly converted back to tritium