Tritium boosting (more correctly deuterium-tritium boosting) is a technique for increasing aspects of the efficiency of fission devices. It is not a full fusion reaction, although a tritium-boosted fission Primary will be more effective in initiating a fusion Secondary. While boosting itself produces only a slight additional amount of blast, it has a major effect on the neutrons produced by the Primary, and indeed may increase explosive yield of other parts of the Primary.
When it became apparent that the more neutrons became available from the first fission, however, the idea arose that injecting a small amount of tritium into the fission Primary would not appreciably increase the explosive yield but would greatly increase both the number and speed of neutrons. 
Tritium boosting has a number of significant technical and military advantages, which explain why it is used in essentially all militarized nuclear weapons, including in India, Pakistan, and North Korea. While it is sometimes described as easy to implement, other reports suggest that the tritium boosting mechanism failed in early Indian and North Korean tests. These advantages comprise:
- high efficiency with relatively low compression and thin reflector/tamper;
- low weight and small size;
- intrinsic safety capability (zero or negligible yield when the tritium is not in the weapon
- Boosted Weapons, Globalsecurity
- Andre Gsponer, Independent Scientific Research Institute, Geneva, Switzerland (2 February 2006), Fourth Generation Nuclear Weapons: Military effectiveness and collateral effects, pp. 5-6