This paper briefly describes the material characterization of the WWER-1000 RPVs that operate in Ukraine and the RPV material degradation monitoring program using surveillance specimens. The research is aimed at the surveillance database collection for the following characteristics of the WWER-1000 RPV beltline welds—transition temperature, yield stress, and master-curve reference temperature—followed by statistical treatment and analysis of these databases. This paper publishes yield stress and master-curve reference temperature data for the first time. The main goal of the paper is the identification of the chemical factor influence on radiation embrittlement and radiation hardening for welds from the RPV core region. It is found that silicon and nickel have the greatest impact on the transition temperature shift. The yield stress shift and master-curve reference temperature shift are most affected by nickel, silicon, and chromium. It is also shown that nickel and manganese have a synergetic effect for both radiation embrittlement and hardening. Based on the results of the statistical analysis a simple general form for the embrittlement trend equations for the transition temperature and master-curve reference temperature as well as hardening are proposed.