It was designed to withstand the shock wave from a nuclear blast but was cancelled as they didn't want to be seen as provoking the west.

Now the tank may be able to withstand the shockwave but I'm not sure abut the crew also I don't know how the tank would stand up to the the debris that tend to come with a nuclear explsion. The remains of a towerblock hitting it at a couple of 100mph will do more then scratch the paintwork.