In 1986, the world's worst nuclear disaster occurred at the Chernobyl power station. Soviet authorities established a 30km 'Exclusion Zone' around this nuclear wasteland, but in 2006 a second explosion rocked the stricken reactor, obliterating all living things and causing the Zone's boundaries to ripple outwards. From this epicenter came waves of mutated creatures, deadly radiation, and a strange, anomalous energy. The Zone was cordoned off by the military, who would shoot on sight anyone foolish enough to brave the horrors within.
A repost of Doom's Mod Merge for SoC; since the Rasputinator domain died I haven't been able to find a DL mirror, so I'm uploading for posterity. Authorship credit goes to Sgt. Doom of Facepunch, additional credits and installation instructions are listed in the various readmes of the archive.
For the unaware, Doom's Mod Merge combines Total Freeplay with the LURK 1.1 weapons and number of small gameplay fixes/changes, allowing the player to start as a member of any faction, do quests for them, or just go innawoods and live off the land. The mod contains absolutely no graphical enhancements, shaders, etc. and so should be compatible with just about any FX mod.