And of course, there is always the ever popular "why?" question that comes up whenever these sort of "make X country have a bigger military" questions come up.
Canada is in a unique position; it's only neighbor, the US, is strong enough that challenging them would be suicide, but also strong enough to protect Canada from everyone else. This combination means Canada can effectively free-ride on American defense spending; spending less on defense and more on other things (like healthcare, education, infrastructure, tax cuts, etc.). Yes, Canada maintains a respectable military, but not one that would conceivably slug it out alone with a superpower. But at the same time, there is nothing inherently stopping Canada from being like Costa Rica and eliminating its military entirely.
So, we return to the question of: what would Canada have to give up to afford a nuclear navy, and why would they want to do so? Being able to rely on the American umbrella is great for Canada (less so for the US); let the US pay for any expensive nuclear warships they want.