The U.S. Nuclear Regulatory Commission has announced stricter security requirements for the nation’s 33 research and test reactors, most of which are located at universities.

Under the new rules, anyone seeking unescorted access to a research reactor must be fingerprinted and undergo a criminal background check by the Federal Bureau of Investigation.

The new requirements come eight months after the commission announced that people with access to sensitive “safeguards information” — such as the details of a research reactor’s security plans or procedures — would have to undergo a similar review.

In the past, the fingerprinting and background-check requirements applied only to people with access to reactors used for power generation. Congress broadened the law to cover research reactors in a 2005 energy bill, though it allowed the commission to exempt some people from the requirements. So far, the commission has chosen not to do so. —Kelly Field