What if an airplane crashes?

Written by  Martin Arnold

Radioactive waste is too hot to be disposed of, which is why it has to be stored temporarily for decades to cool down. The interim storage facility (Zwilag) in Switzerland is located in Würenlingen in the canton of Aargau.


Since 2001, the Zwilag interim storage facility, located in the shadow of the well-known Paul Scherrer Institute, has been storing packed fuel elements. The entrance is well secured: a double gate and hydraulic roadblock form the first obstacle, while the reception is operated by security personnel. The atmosphere of a high-security prison is noticeable. And with good reason: 40 casks with high-level radioactive, spent fuel elements and waste from reprocessing are stored here. The cylindrical casks emit heat for 40 years through their outer walls, acting like a heater 20 years on when you touch it. Disposal can only begin when they have cooled down to ambient temperature. A concrete roof soars 20 metres above, allowing the heat to escape. Calculations show that 200 casks could be stored here. What if an airplane crashes? "It would break through the roof, but the casks can withstand an airplane crash," says Walter Heep, director of Zwilag. The six-metre high casks are stored here for 40 years. It is a colourful cast, and even includes the first Castor casks. Established in 1980, Zwilag is an completely normal public limited company and is owned by the nuclear power plant operators. It is financed by a fund out of which the nuclear power plant operators pay for the management of radioactive waste.
Alongside the high-level radioactive waste in the Castors, barrels with medium- and low-level radioactive contents are also stored at Zwilag. Between the individual parts of the facility runs a conveyor system, which works like a roundhouse with its rotating system. In this way, the 200-litre barrels with the low-level radioactive waste can be transported unmanned. They, too, are strictly controlled, and a barcode provides information about their contents.
No more than once or twice per year, high- or medium-level radioactive waste arrive from a Swiss nuclear power plant or the reprocessing facility in La Hague, which Switzerland is obliged to take back after the waste has been reprocessed in France.

20,000 degrees hot
Zwilag undertakes other tasks besides storage. For instance, components from nuclear power plants that are slightly radioactive on the surface are cleaned, contaminated and recycled here. It is possible to do this with over 80 per cent of the objects. A so-called conditioning plant is used for decontamination, allowing staff to mostly treat the structural components of nuclear power plants so they can be disposed of or recycled as conventional waste. The station uses chemical or electrolytic processes, but objects are sometimes also sprayed with a water pressure of up to 2,000 bar. The remaining radioactive residues are melted in the plasma plant at a temperature of up to 20,000 degrees. While this procedure, the only of its kind in the world, cannot eliminate the radioactivity, it does reduce the material volume by up to 80 per cent. It also destroys organic substances, preventing them from forming gases when they are later disposed of. With the help of an admixture of glass, the waste from the plasma plant is moulded into repository-grade material.
Once there are no more nuclear power plants operating in Switzerland, then –based on an operating term of 50 years – around 100,000 cubic metres of radioactive waste will have to be disposed of. Ten per cent of this will be highly radioactive, i.e. extremely dangerous, and will have to be safely buried for more than 200,000 years. Because underground storage is so expensive, the current goal is to keep the amount of waste small. An interim storage facility also includes a hot cell. Storage casks can be checked and repaired in the hot cell, which has been built to withstand a falling airplane. The hot cell is also for unloading spent fuel elements. The high-level radioactive waste can also be repacked here in transport or storage casks, which will one day be required in the repository. Zwilag's business object is only then achieved when the last cask is buried deep underground – something that will take decades because, according to the current plans, Switerzland is only expected to proceed with a deep repository in 2050.

Cutting of the Documentary "Into Eternity" (2010)