Half life means half of it would have decayed by that length of time. In other words, this stuff would remain potent for a long long time. To answer your question, yes.
"Potency" and "half-life" are opposing notions. Potency being the amount of radiation released per unit of time. There is a limited number of atoms to decay in a given mass. If the half life is long, that means that a given atom isn't likely to spontaneously decay.
Isotopes with short half lives are "hot" naturally. Isotopes with long half-lives can be brought to a critical mass and caused to decay "prematurely." This is what is referred to as thermonuclear fission, aka "kaboom" of "make electricity" if controlled.
"Contamination" is also a relative term, as we are bombarded by natural radiation.
http://www.uic.com.au/nip17.htm <- Homework reading