I believe NNSA Deputy Administrator for Defense Programs Don Cook has provided the first open-source confirmation of rumors that the W78 warhead has a pit corrosion problem.

For some time, I have wondered why the Obama Administration wants to replace both the W88 and the W78 with a common warhead, utilizing newly manufactured W88 pits.  The statement of work for the W78 LEP isn’t all that helpful.

Stephen Young has previously noted rumors of pit corrosion problems with the W78.  The Jasons themselves noted that the 100 year estimate was only for “most” or “predominant” pit types.  There were other pit types for which NNSA was undertaking or considering “mitigation paths.”

Cook, in answer to a question by Senator Feinstein about why the Administration wants to produce between 50-80 pits per year appeared to confirm those rumors by describing how the decay of plastics and other materials may corrode the pit and then confirming “we’re seeing those kinds of problems” in some pit types.

MR. COOK: Again, I think this is a very good question. Let me try to give a quick technical answer.

JASON determined that the lifetime of the plutonium parts in pits are good for 100 years or 80 was their conclusion. Due to plutonium decay which is by alpha — that’s helium that interstitially causes a potential problem. The actual problems that we have go well beyond that.

We have the plutonium pits in the midst of the chemistry of high explosives with binders that decompose just like plastics in cars exposed to the sun. The plutonium is radioactive. The decay goes on. That degrades all of the plastics, all of the cushions, all of the things that are around the pit. And it also causes corrosion in the pit.

So on the one hand, JASON is absolutely correct about what they said. But the difficulty is that, as weapons get older, much of the chemistry in a radiolytic environment starts to take over. And that has been the problem, and we’ve invested many of the people and time in surveillance to actually pin down in which weapons systems we’re seeing those kinds of problems. And we can predict how long they’re good for.

Those are not good for 100 years.

That would seem to confirm the rumors about the W78, which is set to receive a W88 pit in the lifetime extension program.  Indeed, NNSA Administrator Tom D’Agostino jumped in to make clear that “what we are planning on doing is manufacturing a pit design that we currently have in the stockpile [the W88] that will allow us to potentially consolidate the number of different types of warheads” –  a reference to replacing the pits in the W78.

Of course, there may be other, less adventurous, mitigation strategies than a FrankenLEP.  But it does appear, reading between the lines, that Cook and D’Agostino confirmed that concerns about pit corrosion in the W78 are driving the common lifetime extension program.