Storage and disposal of radwaste and spent nuclear fuel

Storage and disposal of low- and medium -level radwaste

   
STORAGE OF RADWASTE
Storage of low-level and medium-level radwaste is now carried out normally. Not only radwaste from nuclear power plants, but also institutional radwaste is usually stored in the place of its origin, or in facilities designed especially for this purpose. During a temporary storage (up to a few tens years), radioactivity of waste is decreasing which facilitates its later handling. The non-negligible advantage of storing is that radwaste is situated on one place which simplifies its continual transport to permanent repository. During the time period of storing, more advanced methods of treatment and disposal of radwaste can be developed which makes it possible to carry out these activities at a higher level than at the time of the generation of this radwaste. 
   

  
DISPOSAL OF RADWASTE
Following the storage and processing of radwaste, the phase of its disposal comes. Various designs of permanent repositories exist that are divided into three main categories - surface, near surface, and deep underground repositories.
    

Surface repositories are designed for permanent storage of low- and medium-level radwaste during the time period enabling to assume that records about the site and its use will be still maintained. This is important because surface repositories are easily accessible and the repository site itself should be ultimately released for unlimited use. Repository has always several safety barriers and monitoring systems. Two groups of surface repositories are known: without engineering barriers, and with engineering barriers. In surface repositories without engineering barriers, radwaste is laid directly into excavations or onto properly adjusted surfaces. Radwaste can be possibly laid also covered as a protection against water, rain, wind, and so one. It is obvious that such repositories are suitable only for certain low-level waste (contaminated earth) while it is necessary to realize that the term "repository without engineering barriers" is a questionable one. It means that for the storage of radwaste, suitable surfaces are used with a minimum adjustment, without building special construction structures and without special technological equipment. Surface repositories with engineering barriers are more common in the world and the trend is to increase the level of engineering barriers in the construction of new repositories. The reason is the permanent efforts to improve safety and protection of the population and the environment.    

  
The lifetime of engineering barriers is counted in hundreds years. Examples of surface repositories without engineering barriers are repositories in operation in Sweden (repository for Forsmark and repository of the nuclear research center Studwik), in the USA (repository Barnwell), in the United Kingdom (repository Drigg), and so on. Surface repositories with engineering barriers are in operation for example in France (Centre de la Manche), in India (repository Tarapur), Japan (repository Rokkasho). The concept of such a repository will be described in details on the example of the Republic Repository in Mochovce in the last section of this chapter. 

   
Near surface repositories represent objects on the boundary within a direct reach of biosphere. Deserted and adjusted mining areas used for the disposal of radwaste, and also some especially built constructions (Richard mine in the Czech Republic) belong into this group.
    

  
The use of deep underground repositories is expected mainly for high-level radwaste, but also for low- and medium-level radwaste. The same criteria are valid for them as for deep underground repositories of spent nuclear fuel and high-level active radwaste, of course with regard to the fact that low- and medium-level waste has a significantly shorter time period of danger and do not produce residual heat. As examples of deep underground repositories for low- and medium-level waste, the following operated and designed facilities in Germany (repositories Asse, Morsleben and Konrad), in the USA (WIPP facility), in Sweden (repository Forsmark) and in Finland (repository Olkiluoto) can be shown. An interesting solution was implemented in case of the Swedish repository Forsmark that was build below sea bottom.

   
For completeness' sake, it is necessary to add other methods of radwaste disposal. In the past, some countries used to dispose low-level radwaste into sea. Radwaste was thus disposed in selected places in Northern Atlantic during the period 1949 to 1982. Since 1983, a moratorium on the disposal of radwaste into sea is in effect. Also other possibilities for the disposal of radwaste and spent nuclear fuel are studied, such as disposal below sea bottom, disposal into sulfur, and so on.
Institutional radwaste (mainly open and used sources) is selected at the point of its generation and following the phase of storage, it is disposed mainly into surface repositories in suitable packages (except certain closed sources).