Glass mold
As the glass blocks in which is nuclear engineering a mold referred to with glazed high-level radioactive waste from the reprocessing is filled. It is often referred to as "HAW-Kokille" or "HAW-Glaskokille", HAW is the abbreviation for High Active Waste . In general, a mold is understood to be a mold for casting metallic materials. It is used for transport and storage.
Manufacturing
Glass canisters contain the fission products from spent nuclear fuel elements that cannot be recycled during reprocessing and are produced in vitrification plants that are attached to the reprocessing plants (e.g. La Hague , Sellafield , Tscheljabinsk , Tokai-mura , Karlsruhe ). There, for conditioning, the borosilicate glass mixed with the highly radioactive liquid waste (see HAW glazing ) is filled into cylindrical stainless steel containers and solidifies as it cools. The mold is then welded to a stainless steel lid and externally decontaminated .
Depending on the type, the cylindrical mold has a diameter of 43 centimeters and a height of 1.34 meters. It can hold around 400 kilograms (150 liters) of glass product. This corresponds to the amount of fission products from three to four reprocessed pressurized water reactor fuel elements. The glass canisters returned to Germany from the French reprocessing plant in La Hague as part of the contractual obligations are around 1.50 meters high and contain around 180 liters of glass. The vitrification process in Sellafield builds on the French process. The glass canisters also have almost the same dimensions.
Transport and Storage
In the coming years, a total of 3556 glass canisters with waste from German nuclear power plants will be transported back from France with nuclear waste ; about 1092 glass canisters are expected from Sellafield.
The glass canisters are initially temporarily stored in the reprocessing plant because of their high decay heat output . Then they were usually placed in transport and storage containers for transport to Germany and brought to the Gorleben transport container warehouse . When they are transported back, the highly radioactive glass canisters still have a temperature of 150 to 180 ° C on the surface. Inside it is even more than 400 ° C. They should subside in the transport containers for another 20 to 30 years in the interim storage facility. For eventual final storage , provision is made to remove the glass canisters again from the transport containers and repackage them in storage containers.
Two container types were used up to 2006: CASTOR HAW20 / 28CG and TS28V. These two transport and storage containers can hold 20 or 28 glass canisters, depending on the heat output of the waste.
The glass canisters to be returned from La Hague after 2006 have a higher thermal output of up to 2 kW due to higher burn-up of the reprocessed fuel elements. For this reason, only 20 molds could have been placed in the containers previously used. Compared to loading with 28 molds, the number of containers required would have increased considerably and at least two additional return transports would have been necessary. To avoid this, new containers with the designation TN 85 were developed in France , which are designed for a maximum heat output of 56 kW.
With the nuclear waste transport in November 2008, eleven containers of the new type TN 85, each with 28 molds, were transported from La Hague to Gorleben. For the subsequent transport in November 2010, ten CASTOR HAW28M containers and one TN 85 type with 28 canisters each were used.
safety
Doubts have been raised about the safety of glass canisters. The glass canisters could burst if water enters. Corresponding attempts to precisely measure the risks when the molds come into contact with water have not yet been published.
Recovery
A utilization of the energy output of the glass canisters, for example for low-temperature heat exchangers, has not yet been investigated.
Web links
Individual evidence
- ↑ a b SPIEGEL: A cylinder that shines forever , March 22, 2001.
- ^ NDR.de: "The nuclear waste interim storage facility in Gorleben" ( Memento from September 11, 2010 in the Internet Archive )
- ↑ SPIEGEL : Doubts about the concept: Researchers argue about the long-term safety of nuclear waste storage , February 2, 2010.
- ↑ Shuao Wang, Evgeny V. Alekseev and a .: Neptunium Diverges Sharply from Uranium and Plutonium in Crystalline Borate Matrixes: Insights into the Complex Behavior of the Early Actinides Relevant to Nuclear Waste Storage. In: Angewandte Chemie. 122, 2010, pp. 1285-1288, doi : 10.1002 / anie.200906127 .