NUCLEAR, BIOLOGICAL AND CHEMICALWEAPONS
February 8, 2006: The U.S. is designing a new generation of nuclear weapons that are unique in the history of weapons. The new nukes will not be tested. Most nations abide by a 1992 treaty that prohibits any nuclear weapons testing, even underground. That means you cannot test a new nuclear weapon design.
The current arsenal of American nukes is getting old (most are at least 25 years old), and being rebuilt, so to speak, as components wear out. This process could go on indefinitely, but it is believed that new technologies make it possible to design more reliable, and easier to maintain warheads. Ah, but the testing problem. Well, technically, it's not that big a problem. The new designs would follow closely, the essential operations the warhead must perform to create a nuclear explosion, based on how current warheads do it. Most importantly, simulation software is much more powerful, reliable and accurate than it was only a decade ago. But still, with something like nuclear weapons, you want to be really, really sure that they will work when needed.
The U.S. currently has 5,700 nuclear warheads that are ready for use, plus another 4,200 that are "out-of-service," but held in storage, just in case. Plans will apparently be made to have some of the older, and proven (via live testing) warheads kept in service for a long time. Keeping these older weapons around for decades is not unreasonable, as by replacing worn out components, the warheads can be kept in working order. The warheads have many electronic parts that don't age well, as well as other components that degrade with constant exposure to radiation. So constant replacement of components is required to keep the weapons working.
There are also some radioactive components (like tritium or Polonium-210), that lose their radioactivity relatively quickly. A common component found in nuclear weapons is the neutron pulse tube trigger. This device accelerates microscopic amounts of Tritium or Deuterium into each other, producing neutrons at a carefully controlled rate, and this in turn starts the chain reaction (the big explosion.) Less sophisticated designs use a Polonium-Beryllium trigger. This version is easier to build, but the Polonium-210 used in the trigger has a short half life (140 days) and has to be replaced every two years, otherwise the trigger won't work. The more modern designs use radioactive materials that last longer, but still have to be replaced or refreshed every 5-10 years.
The "untested" designs will be subject to continuous simulated testing, as newer, and more powerful, software comes on line. Meanwhile, most of what is in these warheads can be tested, with the radioactive material removed. These warhead tests are extensively recorded (by high speed video and many other sensors), but, still, you never know, without a test that produces an actual nuclear explosion.