This op-ed originally appeared in The Hill , Nov. 14, 2018. With much of the world’s attention trained on nuclear risks from North Korea, Iran, and Russia, the unfinished work of keeping nuclear materials and know-how from criminals and terrorists cannot be ignored. As the White House emphasizes state-based threats, Congress must take up a greater leadership role to prevent a nuclear or radiological 9/11. Effective congressional oversight of this issue has been constrained in recent years by numerous obstacles, including limited institutional knowledge, misunderstanding of the subject,...