![proton](http://sfa-fuzija.splet.arnes.si/files/2015/02/proton.jpg)
The nucleus of hydrogen is a proton.
![deuterium](http://sfa-fuzija.splet.arnes.si/files/2015/02/deuterium.jpg)
The nucleus of deuterium consists of a proton and a neutron.
![tritium](http://sfa-fuzija.splet.arnes.si/files/2015/02/tritium.jpg)
The nucleus of tritium consists of a proton and two neutrons.
Tritium will be produced by nuclear reaction with lithium in the blanket of the fusion reactor.