Tritium

• About Deuterium
• Super Heavy hydrogen
• Hydrogen 3
• TripAdvisor lodges (deprecated)

Colorless gas

• 6.032099 g · mol -1 ( mol T-T)
• 3.0160495 u (T- atom )

Gaseous

-252.5 ° C

-248.1 ° C

215.98 hPa ( at the melting point )

Template: Infobox chemical / molecular formula search is not possible

Tritium (from Greek τρίτος tritos the third party ' ) is a natural isotope of hydrogen. Its nuclear core is also called Triton, it is composed of one proton and two neutrons (3H). Tritium is known because of its mass as " About Heavy " or "super heavy " hydrogen.

The other two isotopes of hydrogen are protium (1H) and deuterium (2H ).

Independent names and symbols for isotopes of an element is unique to deuterium (symbol D instead 2H) and tritium ( T symbol instead 3H), because the mass ratio between protium and its isotopes is relatively large (deuterium and tritium 1:2 1:3 ) and this results in significant differences in the chemical behavior. ( In comparison, the next largest isotopes 3He and 4He pair is 1:1,33; 235U and 238U at only 1:1,013 ).

Formation

Natural origin

Tritium is formed in a natural way, mainly in the stratosphere. Fast protons of cosmic rays formed by spallation in part, directly tritium, but especially secondary neutrons that form in the stratosphere and upper troposphere in reactions with nitrogen tritium:

Or

The tritium is formed first HT (tritium hydrogen ) diffuses (if in the stratosphere caused ) the tropopause is oxidized in the troposphere with a time constant of 6.5 years by photochemical reactions to HTO (T -containing water ) and then a shower of comparatively quickly. From education and radioactive decay to a steady state sets, which are constantly in the biosphere 3.5 kg tritium from natural production to 99% in the near-surface layers of the oceans.

By-product of nuclear fission

In heavy water moderated reactors ( see, eg, CANDU ) falls tritium in an amount of about 1 kg per 5 GWa (gigawatt -year ) - which is about 158.4 PJ generated electrical energy - as an unavoidable by-product and can be made of the cooling water to be extracted.

Tritium is also less frequent by-product of nuclear fission of 235U, 233U and 239Pu and created this with a frequency of approximately one per 10,000 tritium nucleus splits. This means that the release of tritium must be taken into account in the operation of nuclear reactors, particularly in the reprocessing of nuclear fuels and storage of spent fuel assemblies, since tritium may not be retained. The tritium production reactor operation is not intended, but a side effect.

The tritium produced in 7% of ternary decays, so if the parent nuclide is split into three rather than two fragments.

Production of lithium

Tritium can be produced by reaction of 6Li with neutrons:

Therefore, the high neutron flux is in nuclear reactors. In the same way also the need for the use of nuclear fusion energy tritium in the blanket to be bred by nuclear fusion reactors.

Properties

The symbol is 3H; For reasons of simplicity, in the formula and T notation is often used.

While in the nucleus of the hydrogen atom (1H) in addition to the proton is not a neutron and deuterium (2H or D) a neutron, there are two tritium. In contrast to 1H and 2H of the atomic nucleus is unstable and decays with a half-life of 12.32 years, while emitting an electron and an antineutrino in the helium isotope 3He ( beta decay ):

In this decay has an energy of 18.6 keV is total release:

.

Of these, the electron receives keV kinetic energy on average 5.7. Compared to other beta emitters, the radiation is very soft. In water it is stopped after a few microns; it can not penetrate the upper skin layers. The radioactivity of tritium is therefore dangerous especially in the ingestion or inhalation.

Tritium oxide ( about heavy water) T2O has a boiling point of 101.51 ° C and a melting temperature of 4.48 ° C.

Use

Among other things in biology, chemistry and medicine tritium is used as a so-called tracer for labeling of certain substances.

In tritium gas light sources ( long-life fluorescent ) of gaseous tritium is used together with a phosphor used in sealed borosilicate glass. The beta radiation of tritium excites the phosphor coating on the inside of the glass tube on a weak lighting ( fluorescent ). This " cold lights " have a theoretical life of several decades and are available in various colors.

The aforementioned tritium gas light sources are also used as light source to watch dials and pointers of certain watch models for the application.

Ionization smoke detectors work partially with tritium gas vial as ionizer. During the production and storage of large amounts of radioactivity, however, because there are health risks. Therefore, by phosphorescent light source, like for example, replaces Superluminova. In smoke detectors can take Tritium also 241Am ( americium ) are used.

Tritium has partnered with deuterium the most favorable properties as a fuel for fusion energy: a high energy yield, a relatively large cross section, the smallest possible for this to be overcome Coulomb (only an electric charge per atom ) and thus a relatively low fusion temperature. It is about 150 million Kelvin, compared to 400 million Kelvin at the next suitable in this respect deuterium -deuterium reaction. Therefore, no other fuel mixture for nuclear fusion on a large scale in discussion or even testing. It is thus also for ITER, W7- X and future fusion power plants provided. However, sufficient quantities of tritium would be only through the breeding of lithium -6 produced in the reactor itself for its continuous operation.

Tritium is also an essential part of certain nuclear weapons. When small quantities of around two to three grams of gaseous tritium introduced into fission weapons, it can effect their explosive increase by a factor of two, also called " boosting ". For neutron bomb tritium is even essential for the function required; Here, however, larger amounts of up to 20 grams per tritium warhead is required. In hydrogen bomb tritium is used only as a booster and to adjust the explosive force of Fissionstufe, in the fusion stage, however, comes Lithiumdeuterid used.

As described above occurs selectively 3He from tritium by beta decay. Because of the rarity and elaborate production of pure 3He from natural sources of this isotope is expensive and is used virtually exclusively in basic research.

Safety

The outgoing tritium chemical risks have with those of hydrogen identical, but comparatively negligible compared to the radioactive hazards as gaseous beta emitter that also require a completely different handling instructions. The marking of hydrogen according to Annex I to Directive 67/548/EEC or GHS, dealing only with the risks associated with the chemical hazards would work here rather euphemistically and have therefore been omitted, since tritium only for professionally qualified laboratories and only is handled in small amounts.

Tritium is not highly radiotoxic, but can be stored and implemented in the form of water in the body. A Franco -Belgian 2008 study concludes that its radiological effects have been underestimated: it can store, for example, in the DNA ( genetic material ), which can be problematic in the case of pregnancy. Even another study concludes that the effects might have been underestimated so far by a factor of 1000-5000.

Proof

The detection of tritium occurs inter alia by means of liquid scintillation counters or ionization chambers open.