Reply #1: Tritium, besides keeping nuclear weapons working is an essential

[NNadir]

tracer material in research.

It is worth noting that there are quite literally millions of persons on the planet today who would be dead without the the technological availability of tritium.

Many people fantasize about an age of fusion power. Without access to tritium, such even discussing such an age would be impossible.

Like all technological materials, including, say gasoline, tritium has its positive uses and its negative uses. Sane people do not advocate the construction of nuclear weapons; but on the other hand neither would sane and moral people demand that tritium be banned.

Like Carbon-14, tritium is a naturally occurring material, resulting from the interaction of cosmic rays with the upper atmosphere. The total amount of tritium existing from natural sources is roughly 7 kilograms. Roughly 5.5% of tritium decays each year, meaning that in order to maintain tritium inventories, about 400 grams must be produced each year in the atmosphere.

http://www.physics.isu.edu/radinf/tritium.htm

Less than 1% of the Tritium now found on earth was formed naturally. Most of the tritium now existent formed in the super high neutron fluxes found in nuclear explosions (including underground nuclear explosions), the manufacture of hydrogen bombs and the operation of nuclear reactors, especially those moderated by heavy water, like the CANDU. The tritium formed in the latter case is unfortunately not recoverable since its concentration is extremely low relative to deuterium, it's mother isotope. (Deuterium has a very low neutron capture cross section which is why it is used in these types of reactors.)


Commercially tritium is made from Li-6 by placing it in a neutron flux. The nuclear reaction by which it is created commercially is the Li-6(n,alpha)H-3 reaction. This reaction is often performed in university research reactors.

Interestingly, the major toxicity associated with tritium has very little to do with its radioactivity. Organisms containing large amounts of tritium die because of the profound isotope effect associated with tritium. This is because the ratio of masses for tritium and ordinary hydrogen-1 is the highest for any two isotopes of the same element known. Because hydrogen bonding, hydride transfer, and proton transfers are essential to life, the slowing of these reactions due to isotope effects is often fatal. (This same effect is possible using ordinary heavy water, deuterium oxide, but it is nowhere near as pronounced.)

Even increased by a ration of 99:1 with respect to its natural occurrence, the radioactivity associated with all the tritium is completely trivial when compared with naturally occurring radiation. The radioactivity of the ocean associated with the natural occurrence of potassium-40 in seawater for instance is roughly 500 billion curies (2 X 10^22 Beq). Normal operation of nuclear power plants worldwide produce about 4.0 X 10^15 Beq of Tritium (4 hundred thousand curies) or 1/20 millionth of this activity on a decay basis. Since however the energy of tritium decay is much lower than the far more dangerous K-40 however, the total dose equivalent for tritium is extremely trivial.

It is estimated that the total exposure to tritium from all sources, weapons testing, nuclear power production, tritium in medical testing and tracer studies, and nuclear weapons production accounts for an absorbed dose of 2.6 X 10^-8 Gray per year. Since a fatal dose of radiation is about 300 gray (LD50) this means that the total exposure is about 1 ten billionth of a fatal dose. For beta decaying isotopes like tritium, the conversion between grays and Sieverts is unity. The background radiation that most people experience is about 3.6 X 10-3 Sieverts = (for tritium) 3.6 X 10^-3 Gray. This means that the total dose equivalent radioactivity for tritium of all sources is (2.6 X 10-8)/(3.6 X 10-3) = 7 X 10^-6 or 1 seven millionth of total background from natural sources. (For people who live in Denver or other places at high altitude, or who fly alot on airplanes, background radiation is much higher than this figure.)

http://www.inchem.org/documents/ehc/ehc/ehc25.htm#PartNumber:4

http://www.lbl.gov/abc/wallchart/teachersguide/pdf/Chap15.pdf

Thus concern about tritium exposure is a tempest in a very tiny teapot.

The amount of tritium in nuclear weapons, while classified, is not huge. In fact most thermonuclear weapons generate much of their tritium for fusion reactions in situ, from the lithium in lithium deuteride, which forms tritium with the high neutron flux available in nuclear explosions. Here is a somewhat detailed description of a thermonuclear weapon. Note the presence of a small amount of tritium and deuterium gas at the core of the primary.

http://nuclearweaponarchive.org/Usa/Weapons/W87.html

One important research use for tritium is to obtain its decay product, Helium-3, which is not available on earth by any natural process and is best obtained by collecting the decay product of tritium. (This takes some patience since the half-life of tritium is about 12.26 years.) The properties of Helium-3 have lead to new understandings of the properties of matter. Liquid helium-3 has essentially zero viscosity and will actually flow up the walls of containers in which it is kept. Formerly helium-3 was very important in extremely low temperature cryogenic work, although magnetic cooling techniques have rendered this use somewhat less important than it once was.