Aerial view of Diablo Canyon Nuclear Power Plant which uses seawater from the Pacific Ocean for cooling and is constructed directly over one fault line and near a second one. PG&E's application to relicense the Diablo Canyon plant is currently being scrutinized in response to growing concern arising from Japan's Fukushima Daiichi nuclear power plant disaster. The plant was upgraded to withstand a magnitude 7.5 earthquake after the discovery of the nearby Hosgri fault which generated a 7.1 magnitude earthquake in 1927. It has two Westinghouse designed pressurized water nuclear reactors. Issues concerning the use of seawater for cooling include the possible ingestion of kelp (the plant is throttled back during storms to mitigate this problem) and the possible ingestion of sea life (in 2008 one of the two units was taken off line because of a rapid influx of jellyfish at the water intake). The plant has been the subject to several legal challenges and protests, and in 1981 1900 activists were arrested at the plant during two weeks--the the largest number of arrests in the history of the United States anti nuclear movement. The nuclear power plant is located at Avila Beach, San Luis Obisopo County, California.