12 years is quite short as half-lives go for radioactive waste. Also, if ingested as water (THO or T2O), tritium is not as bad as it's high activity shows. Other forms can accumulate in the body and are very dangerous (in older days, clock industry workers were applying phosphorescent paint on numbers, that was tritium-enhanced, with a paint brush they used to lick to keep the hair straight, and they had terrible cancers... may be the clock bloggers could dig more detailed stories).
But water in the body actually has a pretty high turnover so it only remains for a few days and concentrates in no particular organs. I was surprised to see in biology labs, that tritium as a tracer is classed rather low in the danger/confinement scale compared to many industrial chemicals used to voluntarily damage DNA in experiments.

Pierre