The Great East Japan Earthquake and Its Nuclear Consequences

Disclaimer: The interpretation of the events at the Fukushima Nuclear Power Plant is preliminary and based on public information that was available approximately one month after the earthquake. Opinions expressed in this paper are those of the authors alone.IntroductionOn March 11, 2011, at 2:46 p.m. local time a 9.0 magnitude earthquake struck off the coast of Japan at a depth of 32 km (19.9 miles) approximately 129 km (80 miles) east of Sendai, 177 km (109 miles) east northeast of Fukushima, and 373 km (231 miles) northeast of Tokyo.1 This magnitude places the earthquake as the fourth largest in the world since 1900 and the largest in Japan since modern instrumental recordings began 130 years ago. The impacts of the earthquake and the resulting tsunami up and down the northeast coast of Japan is currently estimated to result in a tragic loss of more than 20,000 lives,2 extensive damage, and destruction of the infrastructure (including water, electricity, gas, buildings, and roads).Within seconds after the earthquake started, the nuclear reactors 1, 2, and 3 of the Fukushima Nuclear Power Plant went into a controlled, orderly, automatic shut down with the insertion of the control rods into the cores at each reactor and thenuclear chain reaction at each reactor stopped. As designed, the cooling system at each nuclear power plant remained in operation to carry away the residual heat, which is about 7 percent of the full power heat load. Reactors 4, 5, and 6 at Fukushima were undergoing routine maintenance and were not operating at thetime of the earthquake.