Nuclear (fission) generation is more expensive - but you have to compare apples-to-apples. Electricity production will be a mix of sources. Renewable / Sustainable tends to be variable - think solar, wind, and even hydroelectric to some degree. Exotic technologies like geothermal (land or sea based) may help with this, but we are a long way from having substantial production capability. Base load generation today largely consists of creating heat, boiling water, and spinning a turbine. We have decided that creating heat by burning carbon-based fuels has unacceptable externalities.

Given that, doesn't research and development into making fission safer and more affordable make sense?