French surface disposal experience. The disposal of large waste

More than 90 percent of the volume of radioactive waste that are generated in France can be managed in surface disposal facilities. Two facilities are presently operated by ANDRA: the Centre de l'Aube disposal facility that is dedicated to low and intermediate short lived waste and the Morvilliers facility for very low level waste. The Centre de l'Aube facility was designed at the end of the years 1980 to replace the Centre de la Manche facility that ended operation in 1994. In order to achieve as low external exposure as possible for workers it was decided to use remote handling systems as much as possible. Therefore it was necessary to standardize the types of waste containers. But taking into account the fact that these waste were conditioned in existing facilities, it was not possible to change a major part of existing packages. As a consequence, 6 mobile roofs were constructed to handle 12 different types of waste packages in the disposal vaults. The scope of Centre de l'Aube was mainly to dispose operational waste. However some packages, as 5 or 10 m3 metallic boxes, could be used for larger waste generated by decommissioning activities. The corresponding flow was supposed to be small. After the first years of operations, it appeared interesting to develop special procedures to dispose specific large waste in order to avoid external exposure costly cutting works in the generating facilities. A 40 m3 box and a large remote handling device were disposed in vaults that were currently used for other types of packages. Such a technique could not be used for the disposal of vessel heads that were replaced in 55 pressurised water power reactors. The duration of disposal and conditioning operation was not compatible with the flow of standard packages that were delivered in the vaults. Therefore a specific type of vault was designed, including handling and conditioning equipment. The first pressure vessel head was delivered on the 29 of July 2004, 6 heads have been delivered at the end of June 2005 and the 55 vessel heads should be disposed by 2013. The safety approach of the facility was adapted to take into account the disposal of such large waste. This methodology and the disposal technique can be generalised to receive large waste from decommissioning activities for which cutting works and conditioning in standard packages would not be relevant. For instance this option is investigated for steam generators and could be helpful to manage waste from the important decommissioning program that is starting up in France in particular for the first generation power reactors. This decommissioning program also motivated the implementation of a facility for the disposal very low level waste, in agreement with French regulation for the management of waste in nuclear facilities. It is located in Morvilliers village, close to Centre de l'Aube facility. Disposal is performed in trenches in clay that are protected from rainwater by removable roofs. Standard packages were developed even if handling techniques are more 'rustic' due to very low dose rate. First deliveries were done in October 2003. Since start up large waste, as concrete blocks or heat exchangers, have been disposed. For very heavy waste, the interest of dedicated disposal cells is investigated. (authors)