Russian forces blindfolded and detained the head of Europe’s largest nuclear plant, Ukraine’s nuclear power provider said Saturday, reigniting long-simmering fears over the plant’s security. The alleged kidnapping on Friday apparently took place shortly after Russian President Vladimir Putin escalated his war in Ukraine and pushed it into a new, dangerous phase by annexing four Ukrainian regions that Moscow fully or partially controls and heightening threats of nuclear force. In a possible attempt to secure Moscow’s hold on the newly annexed territory, Russian forces seized the director-genera…