Deuterium oxydatum = Schweres Wasser
= D2O/mit Proton + Neutron/entsteht durch mehrfaches destillieren/= leicht giftig/= leicht radioaktiv/verursacht Untergewicht/hemmt Zellteilung (Magen)/gebraucht in Atomreaktoren/kommt
1 : 7000 vor in Wasser. Quelle: remedia.at (= Deuterium oxydatum/= Water-d2/= Heavy water/= Dideuterium oxide).
Vergleich: Siehe: Aquae allgemein
Experiments in mice, rats, and dogs have shown that 25% deuteration causes (sometimes irreversible) sterility, because neither gametes nor zygotes can develop. High concentrations of heavy
water (90%) rapidly kill fish, tadpoles, flatworms, and Drosophila. Mammals, such as rats, given heavy water to drink die after a week, at a time when their body water approaches about
50% deuteration. The mode of death appears to be the same as that in cytotoxic poisoning (such as chemotherapy) or in acute radiation syndrome (though deuterium is not radioactive), and is due
to deuterium's action in generally inhibiting cell division. It is more toxic to malignant cells than normal cells but the concentrations needed are too high for regular use. As in chemotherapy,
deuterium-poisoned mammals die of a failure of bone marrow (bleeding and infection) and intestinal-barrier functions (diarrhea and fluid loss).
Not withstanding the problems of plants and animals in living with too much deuterium, prokaryotic organisms such as bacteria, which do not have the mitotic problems induced by deuterium,
may be grown and propagated in fully deuterated conditions, resulting in replacement of all hydrogen atoms in the bacterial proteins and DNA with the deuterium isotope.
Full replacement with heavy atom isotopes can be accomplished in higher organisms with other non-radioactive heavy isotopes (such as carbon-13, nitrogen-15, and oxygen-18), but this cannot be
done for the stable heavy isotope of hydrogen.
Deuterium oxide is used to enhance boron neutron capture therapy, but this effect does not rely on the biological effects of deuterium per se, but instead on deuterium's ability to moderate (slow)
neutrons without capturing them.
Toxicity in humans
Because it would take a very large amount of heavy water to replace 25% to 50% of a human being's body water (water being in turn 50% - 75% of body weight) with heavy water, accidental
or intentional poisoning with heavy water is unlikely to the point of practical disregard. Poisoning would require that the victim ingest large amounts of heavy water without significant normal water
intake for many days to produce any noticeable toxic effects.
Oral doses of heavy water in the range of several grams, as well as heavy oxygen 18O, are routinely used in human metabolic experiments. See doubly labeled water testing. Since one in about every
6400 hydrogen atoms is deuterium, a 50 kg human containing 32 kg of body water would normally contain enough deuterium (about 1.1 gram) to make 5.5 grams of pure heavy water, so roughly
this dose is required to double the amount of deuterium in the body.
The American patent U.S. Patent 5,223,269 is for the use of heavy water to treat hypertension (high blood pressure). A loss of blood pressure may partially explain the reported incidence of dizziness
upon ingestion of heavy water. However, it is more likely that this symptom can be attributed to altered vestibular function.
Heavy water radiation contamination confusion
Although many people associate heavy water primarily with its use in nuclear reactors, pure heavy water is not radioactive. Commercial-grade heavy water is slightly radioactive due to the presence
of minute traces of natural tritium, but the same is true of ordinary water. Heavy water that has been used as a coolant in nuclear power plants contains substantially more tritium as a result of neutron
bombardment of the deuterium in the heavy water (tritium is a health risk when ingested in large quantities).
In 1990, a disgruntled employee at the Point Lepreau Nuclear Generating Station in Canada obtained a sample (estimated as about a "half cup") of heavy water from the primary heat transport loop
of the nuclear reactor, and loaded it into a cafeteria drink dispenser. Eight employees drank some of the contaminated water. The incident was discovered when employees began leaving bioassay
urine samples with elevated tritium levels. The quantity of heavy water involved was far below levels that could induce heavy water toxicity, but several employees received elevated radiation doses
from tritium and neutron-activated chemicals in the water. This was not an incident of heavy water poisoning, but rather radiation poisoning from other isotopes in the heavy water. Some news services
were not careful to distinguish these points, and some of the public were left with the impression that heavy water is normally radioactive and more severely toxic than it is. Even if pure heavy water
had been used in the water cooler indefinitely, it is not likely the incident would have been detected or caused harm, since no employee would be expected to get much more than 25% of their daily
drinking water from such a source.
On Earth, deuterated water, HDO, occurs naturally in regular water at a proportion of about 1 molecule in 3200. This means that 1 in 6400 hydrogen atoms is deuterium, which is 1 part in 3200 by
weight (hydrogen weight). The HDO may be separated from regular water by distillation or electrolysis and also by various chemical exchange processes, all of which exploit a kinetic isotope effect.
(For more information about the isotopic distribution of deuterium in water, see Vienna Standard Mean Ocean Water.) In theory, deuterium for heavy water could be created in a nuclear reactor,
but separation from ordinary water is the cheapest bulk production process.
The difference in mass between the two hydrogen isotopes translates into a difference in the zero-point energy and thus into a slight difference in the speed at which the reaction proceeds.
Once HDO becomes a significant fraction of the water, heavy water becomes more prevalent as water molecules trade hydrogen atoms very frequently. Production of pure heavy water by distillation
or electrolysis requires a large cascade of stills or electrolysis chambers and consumes large amounts of power, so the chemical methods are generally preferred. The most important chemical method is
the Girdler sulfide process.
An alternative process, patented by Graham M. Keyser, uses lasers to selectively dissociate deuterated hydrofluorocarbons to form deuterium fluoride, which can then be separated by physical means.
Although the energy consumption for this process is much less than for the Girdler sulfide process, this method is currently uneconomical due to the expense of procuring the necessary hydrofluorocarbons.
As noted, modern commercial heavy water is almost universally referred to, and sold as, deuterium oxide. It is most often sold in various grades of purity, from 98% enrichment to 99.75 - 99.98%
deuterium enrichment (nuclear reactor grade) and occasionally even higher isotopic purity.