# The Impact of Tritium in the Environment
## 2 Artificial Sources
### Fusion  
The only technology known today that would allow for such a \"technological breakthrough\" is fusion. The International Thermonuclear Experimental Reactor (ITER) project has shown that such a machine can be built at the current level of technological development and will be able to conduct the physical and nuclear technological tests necessary to create the first experimental fusion power plant.  
First-generation fusion reactors (TOKAMAK, STELLARATOR) will likely be powered by a mixture of deuterium and tritium. This is the most technically simple fusion reaction and is accompanied by the formation of a helium nucleus (alpha particle):  
\[{}^{2}_{1}H+{}^{3}_{1}H\rightarrow{}^{4}_{2}He+{}^{1}_{0}n+17.6\ \mathrm{MeV} \tag{3}\]  
The disadvantage of this reaction is the production of a high-energy neutron. The high rate of this reaction and relatively high energy release (17.6 MeV) makes equal-component mixtures of deuterium and tritium the most promising for controlled fusion. The first of the  
Figure 7: The global share of Nuclear Electricity Generation (NEG). The trend interpolation function (NEG, % = 18.3e\({}^{-0.029}\), R\({}^{2}\) = 0.91) was calculated according to the IAEA database [13].  
two components involved in the D-T reaction, deuterium, is a stable, widespread isotope of hydrogen. Ordinary water contains approximately 0.015% heavy water, D\({}_{2}\)O. To ensure the operation of a fusion reactor that uses tritium as the nuclear fuel, it is necessary to provide for the possibility of its reproduction. For this purpose, the reactor core can be surrounded by a layer of light lithium isotopes, where the following reactions will take place:  
\[{}^{6}_{3}Li\,\vec{\tau}+\,^{1}_{0}n\,\vec{\tau}\rightarrow\,^{3}_{1}H+\,^{4}_ {2}He+4.8\text{ MeV} \tag{4}\]  
\[{}^{7}_{3}Li\,\vec{\tau}+\,^{1}_{0}n\,\vec{\tau}\rightarrow\,^{3}_{1}H+\,^{4}_ {2}He+\,^{1}_{0}n-2.47\text{ MeV} \tag{5}\]  
For a 2 GWe fusion reactor, a tritium mass flow rate of 0.32 kg/day must be ensured. At the same time, its burnup rate is estimated at 0.3%, which means that the total tritium inventory in the reactor should reach several dozens of kilograms. Due to technological improvements, the total initial amount of tritium will be 3.0-3.3 kg and will double every 6.8-12.8 years [30]. Therefore, after 20 years of operation, the tritium inventory inside the reactor will be about 25 kg.  
Assuming that current nuclear power capacity is replaced by fusion reactors within the next 20 years, the amount of tritium in the biosphere could reach 500 kg, which corresponds to the amount released into the atmosphere during the period of active nuclear testing and exceeds the natural background by more than two orders of magnitude.  
Concerning fusion reactors, the main systems producing tritium are the tritium injection, collection, and purification systems, the blanket breeder, and the tritium extraction system from the blanket. This reactor uses about 1 \(\times\) 10\({}^{18}\) Bq of tritium [31]. According to [32], the total tritium content in a 517 MW nuclear fusion facility is 28.75 kg/y (1.0 \(\times\) 10\({}^{19}\) Bq). This corresponds to its modern content in the biosphere, both from natural and artificial sources, and annual tritium losses may reach 4.5-6.18 g (1.6-2.2) \(\times\) 10\({}^{15}\) Bq, which is 2-3 orders of magnitude exceeding the amount released from fission reactors. Expected losses to the environment are 1.6-2.2%\({}_{\circ}\), which is in good agreement with several model assessments (between 0.0057 and 7.0; on average, 1.4%\({}_{\circ}\)[23]). Meeting current global energy needs (161,000 TWh) through fusion alone would increase the tritium inventory in the biosphere to 10\({}^{27}\) Bq and would involve annual tritium emissions of 10\({}^{23}\) Bq. This evaluation could change if the production or breeder of tritium is for the continuous use of fusion energy.