, city (1990 pop. 202,141), Ibaraki prefecture, E central Honshu, Japan, on the Kashima Sea. The city is a leading producer of Japan's electrical equipment. It is also the site of one of Japan's largest copper mines, and of the largest commercial port in the prefecture. A nuclear fuel plant in Tokaimura, 15 mi (24 km) southwest of Hitachi, was the site of an accident involving an uncontrolled chain reaction in 1999.