More than 100 cold-war era research reactors run on uranium pure enough to be used in a nuclear weapon. But switching to safer fuel isn't easy.
Links:
[1] http://admin.indiaenvironmentportal.org.in/feature-article/nuclear-exchange
[2] http://admin.indiaenvironmentportal.org.in/category/author/geoff-brumfiel
[3] http://admin.indiaenvironmentportal.org.in/category/journal/nature
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/uranium
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/nuclear-fuel
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/poland
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/russia
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/nuclear-weapons
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/nuclear-proliferation
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/nuclear-power-plants
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/nuclear-research
[12] http://admin.indiaenvironmentportal.org.in/category/thesaurus/united-states-america-us