Design study on sodium-cooled reactor. Results of the studies in 2004

In Phase I of the 'Feasibility Studies on Commercialized Fast Reactor Cycle Systems (F/S)', an advanced loop type reactor has been selected as a promising concept of sodium-cooled reactor, which has a possibility to fulfill the design requirements of the F/S. In Phase II, design improvements for further cost reduction and the establishment of the plant concept have been performed. In the present study, the reactor core design and large-scale plant design have been performed by adopting a modified fuel assembly with an inner duct structure and double-wall straight tube steam generators (SG). These concepts were discussed at the interim review of FY2003. For the SG, safety logics have been studied and the structural concept has been established. And the plant designs improving the in-service inspection (ISI) and repair capability have been performed. Furthermore, an elaborate confirmation of the design has been performed reflecting the development of elemental technology, and back-up concepts have been proposed. Besides, cost reduction measures have been studied by reduction of reactor grade materials, introduction of autonomous standardizations, simplification of the design due to deregulation and adoption of systematized standards for BOP and NSSS. In the next step, reflecting the results of elemental experiments, in-depth design studies and examination of critical issues will be carried out and the plant concept will be accomplished in preparation for the final evaluation in Phase II. (author)