While experts worry that loosely guarded nuclear materials in foreign countries might fall into the hands of terrorists, six civilian research reactors at American universities continue to use weapons-grade uranium that could go a long way toward making a nuclear bomb. Although the reactors may not be particularly tempting targets for terrorists or criminals, they are disturbingly accessible ones – their security is far less rigorous than that imposed by the government for its own bomb-grade uranium stockpiles. It is time for the Energy Department to accelerate the universities’ conversion to less dangerous fuels.