I've explained it before but gonna do it again. The cherbobyl event generated significant localized Fallout in the immediate vicinity of the plant. This Fallout was not normal either. It was literally the ash of an open, burning nuclear reactor. That ash will emit lethal radiation for the next 300 years, minimum. Thankfully for humanity, it's not hard Gamma radiation that can go through everything but the much more easy to manage beta wave type radiation which is easily blocked and has an ionizing range of around 1 meter.
Beta Waves can be blocked by any sort of barrier. Clothing, cloth mask, or dirt. It was the latter that the liquidators used to neutralize the Fallout. Literally flipping over hundreds of square kilometers in order to bury the Fallout. The closer you are to the plant however the greater concentration and in the case of the Red Forest, which was immediately down wind of Reactor 4, it was not possible to go in and bury the Fallout which means it's still active at the surface level, though by now buried under a thin layer of natural accumulation.
If those soldiers went into that area, with no protection and started digging? Then they literally inhaled the remains of a burning nuclear reactor into their lungs. They are going to die at best. At worst, they won't die.