The B61, like all modern nuclear weapons, has two components that have a limited lifespan and are replaced on a regular basis (neutron generators and gas transfer systems). However, NNSA's plans for the B61 go well beyond these limited-life components and involve replacing thousands of other non-nuclear parts, such as switches, foams, and cables, as well as the bomb's uranium secondary. The bomb's plutonium "pit" would not be changed.
These parts are continually assessed by the stockpile surveillance program, run by Sandia National Lab, which inspects 11 warheads of each type in the U.S. arsenal each year to look for problems. Yes, the warhead parts are getting older, but there is no evidence that they are about to fail. B61s have no moving parts and components do not "wear out." Besides the limited-life parts, it is not clear why the B61 LEP must be completed by 2022.
Bob Peurifoy, a former director of weapons development at Sandia, said in a Nov. 15 interview that, aside from the limited-life parts, the B61 "should be left alone until the stockpile surveillance process finds a problem."
In addition to extending the service life of the B61, NNSA and the Pentagon considered many new concepts to increase the weapon's safety against accidental detonation and security against unauthorized access and use, known together as "surety." But after conducting cost-benefit analyses, major surety upgrades were found to be not worth the price. For example, the rebuilt B61 bomb would not have multi-point safety, a fire-resistant pit, or an optical initiator. The B61 already has many of the most modern surety features, including insensitive high explosives, and the LEP would not add major new ones.
Tactical versions of the B61 stored in Europe, which can be delivered on U.S. and NATO fighter jets, are potentially more vulnerable to theft than the strategic B61 bombs based in the United States. NNSA has proposed to address this concern, in part, by folding four of the B61 versions into a new one, the B61-12, whose design would be based on that of the B61-4. The B61-4 has the lowest maximum yield of the B61 series, meaning it has the smallest amount of fissile material.
The planned B61-12 would be used as both a tactical and strategic bomb, and it would have to meet the military specifications of the higher-yield B61-7 strategic bomb. To do that, the Pentagon proposes to make the B61-12 more accurate than the B61-4 by replacing the parachute with an $800 million guided tail kit for ground detonation.
But rather than pursue this complicated and expensive consolidation, the physical security of forward-deployed B61s could be addressed in other ways, such as by providing more secure storage in Europe, or by stationing these bombs in the United States.
The Pentagon has time to explore alternatives to a $10 billion B61 life extension. One option would be to scale-back the program by replacing only the parts that are known to be at the end of their lives and only for the weapons that are likely to still be deployed a decade from now. For example, NNSA could only upgrade the strategic B61-7, of which there are an estimated 120 in service, and replace only the limited-life parts and possibly the radar (which is an old model that still uses vacuum tubes). The B61-7 already had significant upgrades in 2009. As for the roughly 180 tactical bombs based in Europe, such limited upgrades could be made only for the number planned to be deployed ten years from now.
This scaled-back approach to the B61 LEP would save billions of dollars. If the Pentagon does not go for it, Congress could require a public, independent program review to explore viable alternatives before it makes a $500 million down payment on the program next year.
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