Can you provide a citation for the $500B? Because Carney has mentioned federal money in that amount for projects Canada-wide that include "energy" generally, but not nuclear specifically.
I did find this (potential?) $100B number on Ontario nuclear energy:
but if you take that number and 'ammortize' it over the average 40-year life span of reactors, it comes to $2.5B/year (in capex), which is about ~1% of the provincial budget. I'm not sure how much raw GW capacity that would add, or how many GWh would be generated annually, to do the math on the per-kWh (capex?) cost.
The article goes over the pros and cons of various points in the energy mix debate.
