On a global scale, disposal of spent nuclear fuel from nuclear power plants foresees creation of constant depositories. They shall comprehensively ensure spent nuclear fuel storage during several thousand years: during this time the fuel loses its residual radioactivity. But for today, none of the countries in the world has a full-scope permanent depository, though the work on their creation is underway. This situation forced specialists to start search for different options of spent nuclear fuel storage for the period till permanent depositories are created and in operation.
Design decisions for nuclear power plants with WWER-1000 reactor types foresaw removal of spent nuclear fuel (after 3 years in the spent fuel ponds) to stationary depositories (Russia). However, even back during USSR times it became clear that due to limited possibilities of the depository and impossibility of its extension, and impossibility to build a plant on spent fuel processing in the near future, there would be problems with maintaining of NPP operability with strict safe operation assurance.
In 1992, search of a possibility to radically change the current situation for the largest Ukrainian nuclear power plant – Zaporizhzhya NPP – started because according to specialists’ forecasts, ZNPP power units would have had to be stopped by 1998 due to the lack of free cells in the spent fuel pools, this cutting off electrical power from one fourth of the Ukrainian population and companies.
Upon agreement with State Nuclear Supervision Body "Goscomatom", Zaporozhye NPP announced and international contest for the best project for temporary storage of spent nuclear fuel. After thorough investigation, the plant selected a project based on dry ventilated cask storage, of Sierra Nuclear Corporation and Duke Engineering and Services (DЕ&S) technologies.
DЕ&S technology was recognized as the ecologically safest, most practical, effective, cost-effective and most fully satisfying ZNPP needs:
The essence of the project
During spent fuel storage in the SFP during 3-5 years, residual heat emission and fuel radioactivity significantly decrease. This fuel can be safely stored dry in special casks ensuring effective heat removal from the fuel assemblies and sufficient biological protection from radiation impact on the NPP personnel and environment. This interim storage type is widely used in the international practices of NPP operation.
Based on comparative analysis of possible ways of spent nuclear fuel storage, conducted by Kharkiv institute "Energoproject", a system of interim storage of spent fuel in ventilated concrete casks installed on concrete site was selected for Zaporizhzhya NPP (VCC-VVER). This system is a direct modification of an interim storage system used in the USA and having a NRC license. At present 6 of the USA nuclear power plants have dry cask storage systems and not less than 6 more are establishing such storage systems on their sites. Canada, Germany, Switzerland, Great Britain and Lithuania belong to the countries with well-established practices of dry spent fuel storage.
Companies participating in SFDS construction and operation
Zaporizhzhya NPP bears full responsibility for development, construction, tests and operation of SFDS. ZNPP is responsible for implementation of all activities related to the project and for submittal of all the required information and financing required for obtaining license for SFDS construction and operation.
All construction works in the frames of the project, as well as implementation of quality assurance program shall be under ZNPP control.
Contractor companies participating in the design, construction, tests and operation of SFDS are: Kharkiv "Energoproject" Institute (KhIEP), Duke Engineering & Services (DE&S) и Sierra Nuclear Corporation (SNC).
KhiEP is the general consultant on SFDS design and construction. KhiEP is also responsible for development of the environmental protection report, maintaining of design input data for development of technical safety case and for development of the working design of SFDS construction, including the required reconstruction of the existing systems and structures.
DE&S is a contractor company responsible for overall coordination of the following activities: project development, design analysis, project logistics, construction oversight, licensing, quality assurance, start-adjustment activities and operation of the systems and equipment.
The chief DE&S subcontractor and lead contractor company on design of the VCC-VVR system is SNC. SNC is also the equipment supplier for the SFDS technological systems; together with DE&S, this company is responsible fort the design and manufacture of these systems for ZNPP.
Additional ZNPP contractors in Ukraine participating in both SFDS construction and operation, and in equipment manufacture, material and equipment supplies shall be identified at the stage of SFDS construction.