In a brief press release last month, the US Department of Energy’s National Nuclear Security Administration (NNSA) announced it had completed, on time and within budget, the manufacturing of a key replacement component for submarine-launched nuclear warheads. What the release didn’t say is how the new device reportedly dramatically increases the capability of refurbished weapons to reliably destroy missile silos or other hardened underground targets. That could violate current policy, stated in the Obama administration’s 2010 Nuclear Posture Review, that “the US will not support new military missions or provide for new military capabilities” in its nuclear weapons. The NNSA maintains that the new component—known as an arming, fuzing, and firing subsystem, or fuze—does not provide the warhead with new military capabilities.
The fuze upgrade is part of a broader refurbishment program to extend the life of W76-1 warheads until 2040 or later. The 100-kiloton W76 is the most numerous nuclear weapon in the nation’s arsenal. Around 500 of the 890 warheads deployed on US ballistic missile submarines are W76s, according to a March article in the Bulletin of the Atomic Scientists. The remainder are more modern, higher-yield W88 warheads.
The fuze is an electromechanical assembly that combines the systems that disable the warhead safing mechanisms, determine the timing of the detonation, and send the electrical signals needed to initiate the implosion. It determines the exact altitude at which the warhead will detonate; in the original version of the W76-1, that value was fixed in advance of the missile’s launch. That in-flight adaptability, the Bulletin article says, enables the fuze to adjust the height of the airburst to compensate for what would otherwise be near misses of the target. The result is an improved probability that detonation will occur within the kill zone of a missile silo or other underground target built to withstand all but the most precise nuclear strike.
Although an NNSA spokesperson declined to comment on the Bulletin article, the new fuze was alluded to in fiscal year 2016 Department of Defense budget documents as adding “an efficient hard target kill capability” to sea-launched ballistic missiles. And in 1997, during W76-1 life-extension planning, George Nanos, the former director of Los Alamos National Laboratory, explained in an article in the Submarine Review that the original warhead lacked a fuze “capable of placing the burst at the right height to hold other than urban industrial targets at risk.” The combination of the then recently deployed D5 missile’s improved accuracy and the new fuze, he said, would bestow a reliable hardened target capability on the revamped W76.
An NNSA fact sheet says the W76-1 life extension “is fully consistent with the US commitment to not develop new nuclear warheads” and “does not provide new military capabilities.” An NNSA source says the agency stands by the assertion.
The UK Ministry of Defence referred to the arming, fuzing, and firing system in a June 2016 blog post, saying it replaced one that was “becoming obsolete” on its sea-launched reentry vehicles. The ministry also declared that the refitted warhead’s destructive power was unchanged.
With the new fuze and completion of the W76-1 refurbishment program in 2019, all US submarine-launched missiles will be considered precise enough to use against hardened military targets, according to the Bulletin. Ten years ago, before the NNSA began delivery of refurbished W76-1s with the new fuzes, only the W88 warheads could offer such assured capability. The last of an estimated total of 1600 life-extended W76-1s are scheduled to be in service by 2019.
The newly capable W76-1 may cause concern among Russian military planners that the US is improving its capacity for a preemptive strike to take out Russian intercontinental ballistic missiles in their silos, according to the Bulletin. The new threat could further heighten the alert status of Russian nuclear forces.
