Thursday, November 15, 2007
HOW TASTY IS TRITIUM?
Hint: The watch shown above costs $15,000.
The real deal is that Tritium itself is pretty harmless.
Paying $15,000 for a watch that could harm you would not make much sense.
The tiny radiation from Tritium, can't penetrate the watch face, or even a sheet of toilet paper. It cannot penetrate human skin. Its travel path is well under 1/100 of an inch.
Tritium occurs naturally in the environment. The world's oceans are filled with Tritium. It is used commercially in products such as luminous dials and exit signs. Tritium is a radioactive isotope of hydrogen that is produced naturally by the interaction of cosmic rays with the earth's atmosphere. Tritium enters groundwater by way of rainfall at a concentration of approximately 16 picocuries/liter With the onset of atmospheric nuclear testing in 1953, the tritium concentration in rainfall began to increase. At Ocala, Florida, the tritium concentration in rainfall increased to as high as 2200 picocuries/liter in 1963. The Environmental Protection Agency, which monitors water quality, allows water with anything less than 20,000 picocuries per liter to be used as drinking water. Tritium is naturally present in surface waters at about 10 to 30 picocuries per liter (pCi/L).
(T, or 3H), the isotope of hydrogen with atomic weight of approximately 3. Its nucleus, consisting of one proton and two neutrons, has triple the mass of the nucleus of ordinary hydrogen. Tritium is a radioactive species having a half-life of 12.32 years; it occurs in natural water with an abundance of 10-18 of that of natural hydrogen. Tritium was discovered in 1934 by the physicists "Ernest Rutherford, M.L. "Oliphant, and Paul Harteck, who bombarded deuterium (D, the hydrogen isotope of mass number 2) with high-energy deuterons (nuclei of deuterium atoms) according to the equation D + D ® H + T. "Willard Frank Libby and Aristid V. Grosse showed that tritium is present in natural water, produced by the action of cosmic rays on atmospheric nitrogen.
The amount of water on Earth is 326,000,000,000,000,000,000 gallons , or 1.3 x 1018 m3
1 Becquerel (1 Bq) is one radioactive decay per second.
The radioactive half-life of tritium is 12.35 years, thus, about 5.6% of whatever is left from the previous year decays away each year.
A Tritium Unit (TU) is 1 atom of tritium per 10^18 atoms of hydrogen, or 0.118 Bq per L , or 3.2 pCi per L , or 7.1 disintegrations per minute per liter.
The average archaic background level of tritium before the nuclear age was about one tritium breakdown every 3 or 4 seconds per liter of surface water, and one thousandth as much in deep water. The actual modern level globally for fresh water has been found as high as 50 Bq per liter. In the United States the permissible tritium standard for drinking water is 20,000 picoCuries per liter equal to 740 breakdowns per second per liter, or 740 Becquerel per liter. Tritium decays by simultaneous beta and anti-neutrino emission. The beta particle is expelled from the nucleus at about 0.45 X 10^10 cm per second, for a 6 KeV particle. At 20 KeV, a beta particle's speed is about 0.8 X 10^10 cm per second. Tritium's average beta decay energy is 5.685 KeV. Tritium's beta decay particle's maximum decay energy is 18.6 KeV. Tritium's decay particle's average track in water is about 0.006 mm, or 0.0006 cm, or 3/10,000th of an inch or 0.56 micrometers.
Commercial tritium demand is 400 grams/year . The current U.S. arsenal of 10,000 warheads requires approximately 2200 grams/year (at four grams of tritium/warhead) to offset decay.
The specific activity of 3H (Tritium) is 28.8 Ci/milliatom, or 9650 Curies per gram, or 357 Tera-Becquerels per gram, or as 28.7 Ci/mmol (Curies per millimole). Pure tritium gas (T2) has a specific activity just over 57,000 Curies/mol.
One Curie of tritium weighs about 0.0001036 grams. One Curie of tritium contains approximately 20,811,069,238,989,819,449 atoms = about 2.08 X 10^19 atoms. One atom of tritium weighs about 4.979 X 10^-24 grams (0.000 000 000 000 000 000 000 004 979 grams). Whether in the form of gaseous hydrogen or as water vapor, 1.85 x 10^12 Bq (50 Ci) of tritium occupies a volume of about 1/6 of a cup. One gram of T2 gas has a radioactivity of 3.59 X 10^14 Bq (9.7 X 10^3 Curies). There are about 359,000,000,000,000 (359 trillion) decays per second in one gram of tritium gas (T2).
Tritium glows.The amount of tritium found in a typical illuminated rifle sight is between about 0.012 Curies and 0.200 Curies. Illuminated handgun sights often use even more tritium. Tritium is also used in watch dials, and in exit signs in theaters and office buildings. Airport runway lights can use from 30 to 165 Curies of tritium per light, which could add up to as much as 100,000 Curies per runway.
For radiological purposes, the "Quality Factor" (aka "Relative Biological Effectiveness" or "RBE") for tritium has generally been set at about 1.8.
98% of the tritium from nuclear reactors is released in the oxidized form of tritiated water , mainly in the form of HTO., along with some DTO (Deuterium-Tritium-Oxygen) and even a little T2O). The rest is released in the "elemental" form (mostly HT, along with a little DT and T2).
According to Gordon Wozniak, senior scientist at Lawrence Berkeley National Laboratory and vice chair of the American Chemical Society's Nuclear Chemistry and Technology Division , the average person has about 40 billion atoms of tritium in their body at any one time. Dr. Wozniak is not worried about that amount. Interestingly, 1.7 Bq/Kg the amount the established authorities give for the average amount of tritium in the human body corresponds to a somewhat higher total amount -- 1.7 times 80 kilograms, for example, equals about 135 breakdowns per second, compared to the 71 per second which would come from Wozniak's 40 billion tritium atoms, and would thus indicate about twice as many tritium atoms in the human body. These are global averages. Local values may be lower, or higher. The EPA limit for tritium in drinking water is about 416 times higher than Wozniak's figure for tritium in the human body.
As part of the 1958 United States - United Kingdom Mutual Defense Agreement, there have been three barter agreements, based on what resources the two countries had, and wanted, at various times. The United States received plutonium totaling 5,366 kilograms from the United Kingdom under the Barter A, B, and C Agreements during the period 1960 - 1979. The United States gave the United Kingdom 6.7 kilograms of tritium and 7,500 kilograms of highly enriched uranium for the plutonium.
Global inventory of tritium is about 53 X 10^18 Bq, which is about 50 times greater than tritium levels due to natural sources alone. However, much of this tritium is deposited in the deep ocean where it is unavailable to the circulating waters of the Earth. Okada and Momoshima estimate that current levels of tritium in surface, ground and rain water are in the range 0.1 to 8 Bq/L. Based on these concentrations they estimate that current tritium levels in humans are 1.7 Bq/kg and result in an annual dose of 0.05 microGray to gamma-equivalent doses in microSieverts ... The United Nations Scientific Committee on the Effects of Atomic Radiation reports a global average dose of 0.01 microGray per year for the human population The 2400 microSv total background dose for all sources of radioactivity per year corresponds to a population risk of 10 fatal cancers per million people per year and an individual risk of 7 in ten thousand per lifetime. 0.03 microGray tritium background dose corresponds to a population risk of 0.003 fatal cancers per million people per year and an individual risk on the order of 2 in ten million per lifetime.
According to an Idaho State University fact sheet, the worldwide production of tritium from natural sources is 4 x 10^6 Curies per year with a steady state inventory of about 70 x 10^6 Curies. Total Natural Sources Steady State Global Inventory: 1.3 X 10^18 Bq (corresponds to an annual production of 0.062 X 10^18 Bq/year).
Average concentration of tritium in the earth's waters is 0.00000027 Ci per cubic meter (or 10 Bq per liter).
Posted by 22a-rbZD.007 at 5:27 AM