Molecular dynamics (MD) simulations are used to examine irradiation damage accumulation in bulk body-centered cubic (BCC) tungsten under repeated, spatially overlapping collision cascades. A periodic 100a × 100a × 100a cell is equilibrated at 400 K and then exposed to 30 sequential 30 keV primary knock-on atoms (PKAs) initiated within a confined central volume to encourage overlap. Defects are quantified by Wigner-Seitz analysis and loop character is determined with the dislocation extraction algorithm. The total surviving defect population grows strongly sublinearly with cascade count. Relative to a linear estimate obtained by summing single-cascade production using an arc-dpa-based prediction [1], cascade overlap markedly reduces retained defects via cascade–defect recombination [2]. The surviving defect count falls to roughly 50% of the linear expectation after five PKAs and to about 30% after 30 PKAs, indicating that damage retention is progressively suppressed as pre-existing defects interact with subsequent cascades. Beyond the reduction in defect numbers, cumulative irradiation alters defect morphology and loop character. Early cascades primarily leave isolated Frenkel pairs, whereas continued irradiation drives clustering and loop formation. Interstitial clustering predominantly results in stable 1/2<111> interstitial loops. Vacancies, in contrast, accumulate in cascade cores and follow a distinct pathway: <100> vacancy platelets form as stable precursors and, upon exceeding a critical size, collapse into <100> vacancy loops, explaining the prevalence of <100> vacancy loops. Additional accelerated MD in vacancy-rich environments further suggests that sustained vacancy absorption can transform a <100> vacancy loop into a 1/2<111> loop, providing an atomistic route for loop-character evolution observed in experiments [3]. REFERENCES [1] Nordlund, Kai, et al. "Improving atomic displacement and replacement calculations with physically realistic damage models." Nature communications 9.1 (2018): 1084. [2] Granberg, F., J. Byggmästar, and K. Nordlund. "Molecular dynamics simulations of high-dose damage production and defect evolution in tungsten." Journal of Nuclear Materials 556 (2021): 153158. [3] Yi, X., et al. "In situ study of self-ion irradiation damage in W and W–5Re at 500 C." Philosophical Magazine 93.14 (2013): 1715-1738.