Gentilly is near identical to the 660MW unit at Point Lepreau in NB. It needed a refurbishment after 28 years of operation. The estimate for the project was $1.5B and 18 months. It ended up taking $2.5B ($3.1B in today's money) and close to 4 years to complete (2008-2012). Just for reference, original construction costs were $3.8B in today's money.

With a ~70% lifetime capacity factor, it's been more of a liability for NBPower than anything.

When Gentilly was due for refurbishment, Hydro Quebec decided to decommission rather than going through the expense of refurbishment. Costs to put it back into service at this point are going to be very high. They already have solid baseload, so they'd be better off looking at more wind/solar.