"When TSHTF, if you are not already living on a working, sustainable farm that is defensible and hard to find, you are probably going to die." I would say that time is now.
The actual nuclear winter will only last a few years, of more concern is the 450 + nuclear reactors in operation.
When the end happens, the grid will go down and then the backup generators at the nuke stations will cut in. Most have enough fuel for several weeks, but eventually that's gonna run out and they will stop, assuming the EMP didn't kill them outright. And the pulse is real. I personally saw it from the French Nuke tests in the Pacific on my electrometer, so be prepared with backup solar gear, inverters, comms radios and so on in your EMP safe. You have got one haven't you ?
When a nuke reactor is shut down, even at 100 %, shutoff, there is still between 10% and 50 % of latent heat to dispose of, hence the reason for the backup generators running the cooling systems.
What happens after the fuel runs out depends on the design. Some might just melt down internally, but most will melt down and the cooling systems will be compromised, causing a steam explosion, releasing radioactivity into the atmosphere. 400 + Chernobyl's all going off within a small space of time.
No where in the world will be spared as it spreads worldwide, crossing the equator. The really bad radio nuclides have relatively short 1/2 lives, except plutonium, and will decay away quite quickly. That said, you wont want to be within 200 km of a nuke plant, preferably as far away as possible, like the Moon or Mars !
After about a million years, it will be safe enough to locate yourself near to the site as the radio activity will have mostly decayed to lead.
Why prep then ? Well some will be left, possibly with massive chromosomal damage and grotesque cancers, but I suppose that's survival.
Joe average doesn't have a clue what's gonna happen WTSHTF, ignorance is bliss I suppose. All they want is pizza and the latest gossip from the net, along with cheap electric. Maybe a movement can be started to encourage people to go it alone with electric, thereby negating the usefulness of nuke power stations ? We are already totally off grid (for over 20 years now), and independent in water, electrikery, waste disposal and fuel (wood gas), so it can be done, why are you not doing it ? Money is no object as the Govt turds are spending billions on wars that don't concern us.
On the ignorance is bliss theme, Joe average has no idea what it takes to grow food, and I suspect some preppers don't either. Most think they can throw some seeds out and in a few days have food, with no preparation of the soil, fertiliser, weed and pest control etc. Perhaps they will be the lucky ones to die quickly.
Money, cash, bitcoin etc will be worthless, knowledge will be power, and .22 LR rounds the new gold standard. Stock up now.
Someone once said we get the leaders we deserve....