[en] Calculated irradiation hardening revealed that stabilized depleted zones control hardening of pressure-vessel steels for Light Water Reactor (LWR) irradiation conditions. Stabilized zones were predicted when zones had no bias for interstitials, when vacancy formation energies were high and during growth of interstitial loops. The calculated dependence of irradiation hardening as a function temperature, dose and dose rate were in qualitative agreement with experimentally observed dependencies. Depleted zones assumed to be unbiased microvoids resulted in much greater predicted hardening than when depleted zones were assumed to be biased vacancy loops. The effect of alloy composition on hardening was attributed to effects on interstitial loop growth, depleted zone bias and vacancy formation energy