Heavy water reactor
The heavy water reactor (Heavy Water Reactor, HWR) is a type of nuclear reactor , wherein heavy water (D 2 O) as the moderator - and usually also as a coolant is used -. Heavy water is water that contains the heavier hydrogen isotope deuterium (D or 2 H) with the mass number 2 instead of the ordinary hydrogen ( 1 H) with the mass number 1 .
Heavy water absorbs neutrons less strongly than ordinary water. Therefore, in contrast to light water reactors , this type of reactor can be operated as a natural uranium reactor , so that no uranium enrichment is necessary. One disadvantage is that the extraction of the heavy water is associated with costs. In addition, there are higher costs due to the larger dimensions and the associated higher material requirements of such reactors.
The difference in neutron absorption is exploited in the event of danger (e.g. a cooling leak or failure of the control rod system ): The reactor vessel is flooded with ordinary water H 2 O ( light water ) from the reserve cooling water basin. The stronger neutron absorption of the light water reduces the reactivity , the previously critical reactor becomes subcritical and the chain reaction stops. The reactor cannot be restarted without heavy water.
In heavy water reactors, the deuterium in the heavy water is converted into the hydrogen isotope tritium by neutron capture , which in turn can be used to manufacture certain nuclear weapons .
Technical development
On May 15, 1944, Chicago Pile 3 became critical as part of the Manhattan Project , making it the world's first functioning heavy water reactor. The German research reactor Haigerloch - which never reached criticality - also used heavy water as a moderator.
Heavy water reactors are mainly operated by countries with their own uranium deposits that do not (yet) have a uranium enrichment facility. Of the various reactor types, the CANDU reactor ( pressure tube reactor ) developed in Canada has prevailed. The heavy boiling water reactor proved to be economically disadvantageous ; this line of development did not prevail.
Of the over 400 nuclear reactors worldwide, only 49 are moderated with heavy water. There are numerous pressurized heavy water reactors in India . In the plans to develop so-called fourth generation reactors , heavy water is no longer provided as a moderator.
Heavy water reactors in Germany
The only two heavy water reactors used in Germany to generate electricity were
- the multi-purpose research reactor Karlsruhe (52 MW net, 57 MW gross), which was in operation from 1966 to 1984 and
- the Niederaichbach nuclear power plant (100 MW net, 106 MW gross), which was in operation from 1973 to 1974.
supporting documents
- ↑ International Atomic Energy Agency: Operational & Long-Term Shutdown Reactors. August 3, 2014, accessed August 4, 2014 .
- ↑ Statistics of the IAEA , accessed on December 22, 2013 (English).
literature
- Hans Michaelis: Manual of nuclear energy. Original edition March 1982, Deutscher Taschenbuchverlag, Munich.