scholarly journals Conceptual design report for immobilized high-level waste interim storage facility (Phase 1)

1998 ◽  
Author(s):  
K.C. Burgard

Author(s):  
Udo Sach ◽  
Goswin Schreck ◽  
Max Ritter ◽  
Jean-Pierre Wenger

Abstract At present, Switzerland has no final repository for radioactive wastes. Very early, the Swiss nuclear power plant operators were aware of the necessity to expand interim storage capacity for spent fuel elements and operational wastes. Already in 1991, Nordostschweizerische Kraftwerke AG (NOK) therefore started building a reactor-site interim storage facility (ZWIBEZ) at its Beznau power plant site. Moreover, as early as in 1990, “ZWILAG Zwischenlager Würenlingen AG”, a company established by the nuclear power plant operators had initiated the licensing procedure for a central interim storage facility in Switzerland. This central interim storage facility is designed for the storage of all categories of radioactive wastes and includes a conditioning facility for low-level and medium-level waste. Eleven years later, in July 2001, the first transport and storage cask loaded with irradiated fuel elements was stored in this facility. For both of the stores the concept of dry interim storage in suitable storage casks in a storage hall was chosen for the storage of irradiated fuel elements and vitrified high-level wastes from reprocessing. Cooling is established through natural circulation. Leaktightness of the casks is continuously monitored by means of a cask monitoring system. The other wastes arising from nuclear power plant operation and reprocessing are stored in a ventilated storage hall which provides shielding and — depending on the radioactive inventory — protection against external impact. The conditioned radioactive wastes, packaged in drums, are placed into open storage containers with identical base and having the same sling points as ISO containers. These containers are stacked up in free-standing stacks up to a height of 16 m. The storage concept varies, depending on the radioactive inventory; for the ZWIBEZ reactor-site interim store, a storage hall for low-level waste has been built without partition walls, whereas the store for the medium and high-level waste in the central interim store ZWILAG has been designed with partition walls dividing the hall into several storage shafts which are closed by shielding slabs. By including a hot cell into the ZWILAG facility, the purpose of this facility has been expanded beyond interim storage of radioactive waste to cover also the visual inspection of fuel elements and vitrified waste canisters as well as the reloading of fuel elements and canisters from smaller transport casks into combined transport and storage casks. Furthermore, the hot cell enables inspection and/or repair work to be performed in the cask lid area of loaded transport and storage casks, the replacement of the lid seals of storage casks and the conditioning of medium-level waste.





Author(s):  
H. Geiser ◽  
J. Schro¨der

The idea of using casks for interim storage of spent fuel arose at GNS after a very controversial political discussion in 1978, when total passive safety features (including aircraft crash conditions) were required for an above ground spent fuel storage facility. In the meantime, GNS has loaded more than 1000 casks at 25 different storage sites in Germany. GNS cask technology is used in 13 countries. Spent fuel assemblies of PWR, BWR, VVER, RBMK, MTR and THTR as well as vitrified high level waste containers are stored in full metal casks of the CASTOR® type. Also MOX fuel of PWR and BWR has been stored. More than two decades of storage have shown that the basic requirements (safe confinement, criticality safety, sufficient shielding and appropriate heat transfer) have been fulfilled in any case — during normal operation and in case of severe accidents, including aircraft crash. There is no indication of problems arising in the future. Of course, the experience of more than 20 years has resulted in improvements of the cask design. The CASTOR® casks have been thoroughly investigated by many experiments. There have been approx. 50 full and half scale drop tests and a significant number of fire tests, simulations of aircraft crash, investigations with anti tank weapons, and an explosion of a railway tank with liquid gas neighbouring a loaded CASTOR® cask. According to customer and site specific demands, different types of storage facilities are realized in Germany. Firstly, there are facilities for long-term storage, such as large ventilated central storage buildings away from reactor or ventilated storage buildings at the reactor site, ventilated underground tunnels or concrete platforms outside a building. Secondly, there are facilities for temporary storage, where casks have been positioned in horizontal orientation under a ventilated shielding cover outside a building.



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