With rising fuel prices, pending international limits on sulfur emissions, and concerns about greenhouse gas emissions in mind, the British shipping consultancyLloyd's Registry has launched a study of whether oil tankers should be nuclear-powered. At present, reactors have been used almost exclusively to power military ships, starting with the famous U.S.S. Nautilus submarine (above). In civilian shipping, with the exception of one Russian container boat, nuclear propulsion is used only for icebreakers. Vince Jenkins, global marine risk adviser at Lloyds, clients of the firm are showing interest in alternative propulsion technologies that would cut carbon emissions. "Nuclear power is the only technology that can replace carbon emissions entirely," Jenkins told the Financial Times.