Field of Science

Demolishing the 'vacuous' argument for the RRW

The Reliable Replacement Warhead program (RRW) is a long-standing and controversial proposal that aims to replace aging plutonium pits and other parts in nukes to modernize the current US nuclear arsenal. Proponents of the RRW say that having nuclear weapons of dubious function and quality will defeat the basic purpose of a deterrent and therefore modernizing the arsenal and replacing worn out parts is essential for its very existence. In addition, Russia has indicated that it is modernizing its nuclear arsenal and this fact has put further pressure on implementation of the RRW. Opponents of the RRW say that by modernizing the arsenal the US will send out the wrong signals to the rest of the world, indicating that nuclear deterrence and weapons development is still an important part of US defense strategy. In any case, very recently the top government advisory group JASON which among others included Freeman Dyson) did a study on the central plutonium 'pits' in the nuclear weapons and concluded that these would last for at least half a decade if not more. Since then several arguments have continued to float around for the RRW.

In the latest issue of The Bulletin, Jeffrey Lewis and Kingston Reif do a neat and clean job in demolishing the latest argument made by a General Chilton who, of all possible reasons, bases his argument on vacuum tubes, the point being that outdated vacuum tubes in nukes necessitate replacement. The last line is priceless and is not exactly BAS-like
Firstly, vacuum tubes are not used in the physics package of a single nuclear weapon design. Vacuum tubes are used only in the radar-fuse, which tells the firing system when the bomb is at the correct altitude for detonation, in some modifications (mods) of one warhead design, the B61 gravity bomb. In total, the B61 bombs that have vacuum tubes in their radar-fuses account for only about one in ten operationally deployed warheads. (Vacuum tubes are used in the radars of three B61 mods: 3, 4, and 7. Mods 10 and 11 have newer radars that use solid-state electronics.) The fuses in these weapons are old, but perfectly functional. To reiterate, vacuum tubes are not in use in any other warhead design, including the W76 warhead, a portion of which would be replaced by the first RRW warhead, the WR1, if it ever were funded and developed.

Secondly, the Energy Department has routinely replaced radars without nuclear testing or redesigning the physics package. In fact, during the 1990s, Sandia National Laboratories scientists developed the MC4033 common radar, which uses solid-state electronics, for planned refurbishments of the B61 and B83 gravity bombs. All B83 bombs now use the common radar, though similar plans to fit a new radar on all B61s have been repeatedly deferred.

Most recently, in 2006, Sandia planned to replace the remaining B61 vacuum tube radars as part of ALT 364/365/366. The National Nuclear Security Administration, which overseas the nuclear weapons complex, canceled these latest ALTs, which would have resulted in the removal of the last vacuum tubes from the U.S. nuclear stockpile, because the U.S. Air Force preferred replacement to life extension. Due to this absurd twist, one could say that vacuum tubes remain in the U.S. nuclear arsenal in part because of the RRW, contrary to Chilton's insistence that the RRW is needed to get rid of them.

The bottom line is that vacuum tubes are used only sparingly in the U.S. nuclear arsenal and can be replaced on short notice if the need arises, independent of whether Congress funds the RRW Program. Of the many reasons that Defense and Energy officials have put forth to justify the RRW Program, the need to replace vacuum tubes is the worst and has no place in the debate about the RRW or modernizing the nuclear stockpile. General Chilton can stick that prop in his, um, pocket.


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