The police seized records Wednesday from the company that runs the fuel-reprocessing plant where Japan's worst nuclear accident occurred last week. Prime Minister Keizo Obuchi, vowing to make his country "once again feel secure," visited the site later. As he has done before, Obuchi acknowledged his government's slow response to the accident on Thursday in Tokaimura, 80 miles northeast of Tokyo. More than 50 people were exposed to radiation in the accident, in which workers who were violating standard operating procedures set off a chain reaction.