Glory
What could be more glorious than protecting the country from bad guys walking around with stolen nuclear material? Okay, there's probably not an attempted robbery on nuclear trucks every day, but maybe that's because the couriers are so good at preventing them in the first place.
You're not just ensuring that the nuclear materials don't get into the wrong hands; you're also making sure that the nuclear materials arrive safely to labs or factories. This is super important, because nuclear plants provide 20% of the nation's electricity—so we all need those materials to arrive safely (source). Someone's got to make sure that the nation can keep on truckin', right?