My suspicion is that modern armour would be relatively effective as brief-exposure radiation shielding - three inches of (extremely dense, potentially DU) armour plate against a single burst of radiation will stop essentially all alpha and beta radiation, while gamma is attentuated at low energies by about 10% by steel compared to lead shielding and at high energies by approximately the same, although overall far less attentuation.

Shielding in most applications is about stopping long term cumulative exposure to people there every day; against a single, intense exposure (and assuming NBC filtering, no exposure to fallout products, and generally the tank being buttoned up tight) I would not expect an explosion that the crew physically survived, to irradiate them enough that they would die of radiation exposure.