Near the Russian city of Ozersk, about 80 miles south of Yekaterinburg, stands a warehouse like no other.

The Fissile Material Storage Facility, with walls 23 feet thick, is a hangar-sized vault to protect fissile materials – highly enriched uranium and plutonium – that could be used for nuclear weapons.

The facility was built at a cost of $309 million by the United States in a period of cooperation with Russia to prevent the spread of nuclear weapons materials.

That period has ended, Russia informed U.S. officials in December that it wants to end nuclear security cooperation with the United States. Although anticipated for some time, the decision marks an unfortunate conclusion to an remarkable effort. Created by Congress in 1991 as the Soviet Union was falling apart and championed by then-Sens. Sam Nunn, D-Ga., and Richard Lugar, R-Ind., the program extended the hand of the United States to Russia.

Despite decades of mistrust during the Cold War, the Nunn-Lugar program involved cooperation on the most sensitive of projects. Overall, the program reflected a sense of magnanimity, bipartisanship and purpose in U.S. foreign policy.

There is no question that the $1.6 billion a year or so spent for this goal has been a bargain.

Two decades of operational experience in Nunn-Lugar may also prove valuable should another nuclear-armed nation suddenly collapse. Russia may be withdrawing, but the potential threats aren’t going away.