UN talks will begin in 15 June 2017 on the recently released draft text of the Convention on the Prohibition of Nuclear Weapons. The nuclear weapon states have chosen not to join the talks.
The draft text proposes that, when the weapon states are ready to do so, one way they could fulfill their obligations to achieve nuclear disarmament is by agreeing "provisions for the verified and irreversible elimination of any remaining nuclear weapon programmes under strict and effective international control" that could take the form of "additional protocols" to the treaty. It is unforeseeable at present when any of the weapon states would join the ban treaty.
It is likely that when weapon states decide to join the ban treaty, the "provisions for the verified and irreversible elimination" of the weapons will have to be agreed on a case by case basis, including the timeline for elimination. It may still be useful to have a sense how quickly they could eliminate arsenals of their current sizes.
The greatest challenge may be for the United States and Russia, which each hold about 7000 warheads (as of 2017), including almost 3000 warheads each already awaiting dismantlement.
In the early 1990s, Russia was dismantling an estimated 2000 warheads per year. It has been estimated that the dismantlement rate in Russia currently is about 300-500 warheads a year. Russia currently has two operating nuclear weapon assembly/disassembly plants that together handle all steps of the disassembly cycle: Lesnoy (formerly Sverdlovsk-45) and Trekhgorny (Zlatoust-36).
The United States has declared that from fiscal years 1994 through 2016, it dismantled 10,681 nuclear warheads. This is done at the Pantex warhead assembly and disassembly plant in Texas.
A rate of over 1000 disassemblies in one year was achieved in 1994, 1995, 1996 and 1998. The current rate is below 300 warhead disassemblies per year. At the current rate, it will take about a decade to dismantle the 2,800 warheads currently in the queue for elimination. The low rate of current US dismantlement is due to the US using most of the work space at Pantex for warhead life extension. Were the United States to join the ban, there would be no more life extension activities.
The United States and Russia may have eliminated most of the warheads currently awaiting dismantlement if they decide the ban treaty decade from now. This would leave them with stockpiles of roughly 5000 warheads each to eliminate.
The past level of warhead dismantlement suggest that if the US and Russia were to focus on dismantling warheads, and operating at the same levels as they did in the 1990s, it would take Russia about 3-5 years and the United States about 4-6 years to dismantle all their nuclear weapons. Since the earlier high rates of dismantlement took place without international monitoring, the actual timeline for verified elimination of the 5000 remaining warheads may be somewhat longer. This does not include the time that would be required if the ban included an obligation to eliminate dedicated nuclear-warhead delivery vehicles - specifically, intercontinental and submarine launched ballistic missiles.
One indication of the speed at which such warhead delivery systems can be verifiably eliminated is offered by the US Cooperative Threat Reduction programs that between 1994 and 2013 helped Russia eliminate 914 ICBMs and 695 SLBMs and 155 bombers.
The number of delivery systems eliminated over this twenty year period is more than twice the current number of such systems deployed by the United States and Russia. As of March 2017, under the New Start treaty counting rules, Russia has 523 deployed ICBMs, SLBMs, and heavy bombers, while the United States has 673 such deployed systems.
It would appear that in agreeing "provisions for the verified and irreversible elimination of any remaining nuclear weapon programmes under strict and effective international control" Russia and the United States could be encouraged to set a deadline of no longer than 10 years to eliminate their weapon stockpiles.