NTI, a Washington-based group, has released a report ranking 32 countries on nuclear security.

The survey was conducted by the Nuclear Threat Initiative, co-chaired by former Sen. Sam Nunn (D-Ga.), and was based largely on publicly available data. The purpose, organizers said, was to provide governments with a tool to determine how better to secure their nuclear materials. 

The least-secure nations with “weapons-usable” nuclear materials: North Korea, Pakistan and Iran. The most secure: Australia, Hungary and the Czech Republic. 

The United States comes in 13th place, tied with Belgium. It would have ranked second, the authors of the index noted, but for the sheer number of its nuclear sites. 

The report is available at www.ntiindex.org