The safety features and power backups built into third-generation reactors should shut them down safely even without electrical power.
Links:
[1] http://admin.indiaenvironmentportal.org.in/feature-article/how-newer-reactors-would-have-survived-fukushima
[2] http://admin.indiaenvironmentportal.org.in/category/author/paul-marks
[3] http://admin.indiaenvironmentportal.org.in/category/journal/new-scientist
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/nuclear-power
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/nuclear-power-plants
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/japan
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/nuclear-safety
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/nuclear-accidents
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/radiation
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/energy