The FAMILY-21 code is a stand-alone simulation code developed to quantitatively indicate reactor systems and nuclear fuel cycle systems adaptable to future uncertain nuclear needs. This code has made it possible to examine and evaluate the path from the current thermal reactor system to a future system with less resource constraints and better environmental compatibility from various viewpoints.

The FAMILY-21 code has been used in the activities of the JAEA’s Fast Reactor Cycle Technology Development Project, Japanese New Nuclear Policy-planning Council (Japan Atomic Energy Commission), IAEA/GAINS project.

FAMILY-21 consists of an input tool, a solver, a graphic tool, and a post-processor to simulate the mass balance of the entire nuclear fuel cycle or parts of it over 300 years. In addition, the code can simultaneously calculate up to 23 reactor types (LWR x 14, HWR x 4, and FR x 5), allowing users to use any combination of coolants and fuels by manipulating the input tools.

The solver, modularized into front-end, reactor, and back-end, plays a key role in FAMILY-21's simulation capabilities, providing time change (amount, composition) of uranium and transuranium elements in nuclear fuel cycles and reactors. In addition, this solver can calculate the material balance and isotope composition for a period of 300 years in about 1 minute, so it is possible to efficiently conduct case studies of various scenarios and parameters. A graphical tool programmed by Spreadsheet and Microsoft Visual Basic 2017 (Japanese version) generates about 100 patterns of graphs from the data in the output file created by the solver to assist our analysis. Graphs and data tables from this graphical tool can be freely edited using Microsoft Excel. In addition, by using a post-processor to calculate the high-level radioactive waste treatment process and the final disposal site located downstream of the reprocessing process, the calculation time of the nuclear fuel cycle by the solver can be shortened.

Note that this FAMILY-21 code system is created with Microsoft Visual Basic 2017 (Japanese version) and is still under development, so it has not been released to the public.