Globally, the storage of spent nuclear fuel from nuclear power plants provides for the development of permanent long-term storage facilities. They must ensure complete storage of spent nuclear fuel for several thousand years: during the mentioned time period the fuel will lose its residual radioactivity. But today there is not any state in the world having a fully-featured permanent repository, although the activities on their development are underway. This circumstance forced the search for storage options for spent fuel to begin until the completion of construction of permanent storage facilities.
The design solutions of the nuclear power plants with WWER-1000 provided for the transportation of spent nuclear fuel (after 3-5 years of storage in the cooling ponds) to a stationary storage facility (the Russian Federation). However, in the times of the USSR it became clear that due to the limited storage facilities, the lack of the possibility of its expansion, as well as the lack of opportunities for the near future to build a plant for the reprocessing of spent nuclear fuel, the problems would arise in maintaining the viability of nuclear power plants while ensuring safe operation.
In 1992, the search began for a radical change in the current situation for the largest Ukrainian nuclear power plant, Zaporizhzhia NPP, as according to experts, due to the shortage of free cells in the cooling ponds, by 1998, the ZNPPs would have had to decommission the power units of ZNPP and would leave without electricity a quarter of the population and enterprises of Ukraine.
With the approval of the Nuclear Power State Committee of Ukraine (Goskomatom), Zaporizhzhia NPP announced an international contest for the best design of spent fuel temporary storage, and after careful analysis, the design based on the dry ventilated container storage technology of Sierra Nuclear Corporation (SNC) and Duke Engineering and Services (DE&S) was chosen.
DE&S technology was recognized as the most environmentally safe, practical, efficient, cost-effective and best suited to the specific needs of Zaporizhzhia NPP, namely:
Key point of the design
When storing SFAs in the cooling pond for more than 5 years, the residual heat release and the radioactivity of the fuel are significantly reduced. Such fuel can be safely stored by dry method in special containers, which ensure efficient heat removal from the SFAs and sufficient biological protection against radiation effects on the NPP personnel and environment. This method of intermediate storage of SFAs is widely used in the international practice of operating nuclear power plants.
Based on a comparative analysis of potential methods for SFAs storage, carried out by the Kharkov Institute “Energoproekt” (KhIEP), a system for intermediate storage of SFAs in ventilated concrete containers installed on a concrete site (VSC-WWER system) was selected for Zaporizhzhia NPP. This system is a direct modification of an interim storage system that is licensed by the United States Supervisory Authorities (NRC) and used at the US nuclear power plants. Currently, several US nuclear power plants have dry container storage facilities, and a number of others are actively implementing plans to create such storage facilities on their territory. Canada, Germany, Switzerland, Great Britain and Lithuania also belong to the countries with already established practice of dry container storage of spent nuclear fuel.
Organizations involved in the construction and operation of the DSFSF
Zaporizhzhia NPP is fully responsible for the development, construction, testing and operation of the DSFSF. ZNPP was responsible for the implementation of all the activities related to this project, as well as for the provision of all the necessary documentation and funding required to obtain a license for the construction and operation of the DSFSF.
All construction works within the framework of this project, as well as the implementation of the quality control program at the facility were under the control of ZNPP.
The contracting organizations involved in the design, construction, testing and operation of the DSFSF at Zaporizhzhia NPP were Kharkov Institute “Energoproekt” (KhIEP), Duke Engineering & Services (DE&S) and Sierra Nuclear Corporation (SNC).
KhIEP acted as a general consultant for the design and construction of the DSFSF. KhIEP was also responsible for the development of a report on environmental protection, the provision of design input data for the development of a technical safety report, as well as the development of a detail design for the construction of the DSFSF, including the necessary reconstruction of existing systems and structures.
DE&S was the contracting organization responsible for the overall coordination of the following works: design development, design analysis, design logistics, construction supervision, licensing, quality assurance, personnel training, pre-commissioning procedures and operation of systems and equipment.
The main subcontractor of DE&S and the leading contracting organization for the design of the VSC-WWER system was SNC.