Are all the nuclear warheads turning into lead ?
And they’re mostly not directly turning into lead, but turning into other things which will turn into yet other things and so on before eventually reaching lead.
Also, lead is only the final result for three of the four major decay chains: The fourth will end up as bismuth-209, which is almost stable, and then eventually, after billions of years, as thallium-205.
It should be noted that the isotopes used as the fissile material for nuclear weapons are enriched and purified in order to make them as stable as possible, not only to reduce the radiation from normal decay but also to ensure that when activated the reaction occurs at the appropriate rate and doesn’t go too fast or releasing a lot of neutron-absorbing isotopes (‘poisons’) which would cause a weapon to fissile. Even then, subtle phase changes and interlattice defects can cause unsuspected problems which is why the nuclear weapons arsenal requires a very expensive aging surveillance program to ensure that nuclear materials continue to function appropriately and aging trends in other non-nuclear components are well characterized. The limiting factor in most modern nuclear weapon systems isn’t either the natural decay of [SUP]239[/SUP]Pu or [SUP]235[SUP]U but the decay of tritium ([SUP]3[/SUP]H) which is used as an initiator and booster to increase neutron yields in the Primary phase. Since tritium has a half-life of ~12.3 years, it has to be replenished regularly in order for the weapon to operate reliably.
Stranger
About surveillance of breakdown:
Clearly many things are unpredictable, but isn’t the decay rate itself entirely predictable by the physics/math? I mean, not even “simulation” aging is necessary for that, right?
The simulations aren’t to determine how much decay has happened. That is, as you note, quite easily calculated. They’re to determine how well the warheads will work, given that amount of decay.
(Bolding mine)
In this context, “fissile” is good and “fizzle” is bad.
I’ve never heard of anyone complaining that their chain reaction was proceeding too quickly when referring to a weapon…
I thought the half-life of bismuth was something like 1.9 x 10^19 years, which makes billions of years look like the blink of an eye.
And don’t Plutonium and U-235 also have half-lives so long that they won’t turn to lead during our species lifetime?
PU-239 has a half-life of 24,000 years, which is not all that long.
U-235 is 700 Million years, which is short enough that natural reactors are not possible any more.
That only seems longer than a PBS pledge drive.
The rate of decay is stochastic (randomly distributed on a distribution) and can be determined in the aggregate; however, the effects on the integrity of the fissile material and other surrounding materials are often difficult to determine. For instance, in the 1957 Windscale fire, the buildup of energy in the graphite moderator (ironically due to attempts at annealing the moderator to prevent the development of dislocations due to Wigner energy) and burst of an isotope cartridge resulted in combustion. Phase changes in the fissile material of a nuclear weapon can cause local variations in the fission rate that can detrimentally impact yield, as discovered with several early thermonuclear devices.
Yes, that was a typo. A fizzle (a weapon that fails to achieve the expected energetic yield) is generally the result of producing neutron-absorbing isotopes at a higher than expected rate, which again was seen in a number of early weapon tests using boosted fission or fusion.
For a nuclear weapon to operate efficiently (achieve maximum yield from the minimum of material) it has to follow a budget of energy release. Too much energy released too soon will blow the weapon apart, resulting in a substantially decreased yield (another cause of fizzles). With multistage thermonuclear weapons, the initial energy release is dedicated to producing tritium from lithium deuteride via neutron bombardment, which is then heated by x-rays to fusion temperatures hence, “thermonuclear fusion”. The resulting fusion products are a careful balance of neutrons to increase the fission rate of fissile material and x-rays which provide the thermal yield that heats the atmosphere to create the thermal pulse and blast effects we associate with nuclear weapons. (Actual weapon designers will no doubt cringe at this abrieviated explanation of the complex processes occuring within the core but it will serve for the purposes of discussion.) The management of this energy budget is one of the key factors in weapon design, and is carefully assesses in aging surveillance programs, albeit almost entirely by simulation although the National Ignition Facility is designed to reproduce some of these processes in a controlled test.
Stranger
Right, my mistake. I’m not quite sure precisely how I misread the number, but I obviously did.
Well, I got both plutonium and U235 wrong. I only memorize the outliers.