The Nuclear Fuel Cycle Simulation System (NFCSS) is a scenario based computer simulation tool, implemented in a web based platform, for studying various options of nuclear fuel cycle for nuclear power plants (NPPs). The NFCSS is used to develop illustrative scenarios in support of policy making on nuclear fuel cycles and to assist educational and research activities. It provides answers to questions related to various scenarios of nuclear fuel cycle for periods ranging from a few years to 200 years maximum. The NFCSS is very efficient and reasonably accurate in answering questions such as: the nuclear mineral resources and technical infrastructure needed at each stage of the front end of the nuclear fuel cycle; the amounts of used fuel, actinide nuclides and high level waste generated from a given reactor fleet; and the impact of introducing recycling of used fuel on mineral resource savings and waste minimization.

A new simulation system, named VISTA (the precursor to the NFCSS), was developed in 1996 to fulfil the need for making quick and simple calculations. It was then intensively used to quantify the different scenarios fixed by the working groups of the conference. The NFCSS was initially designed as a standalone spreadsheet tool that could be implemented on computers running Microsoft Office. With the expansion of various web based information services by the IAEA, a web accessible version of the NFCSS was launched in 2003, and from 2005 it was made freely available to Member States and public through the IAEA website. Reference IAEA-TECDOC-1535 in 2007.

The NFCSS has also been used internally by the IAEA for estimating spent fuel discharges from civilian reactors worldwide, plutonium and minor actinides (MAs) accumulation in the discharged spent fuel and in the high level waste (HLW). Since NFCSS model requires isotopic composition of spent nuclear fuel as inputs to make estimates of various material accumulations from nuclear reactor operation, a simplified fuel depletion module called Calculation of Actinide Inventory (CAIN) was developed. The CAIN requires a small number of input parameters and gives results in a very short time. Unlike more sophisticated fuel depletion codes like ORIGEN1 and others, CAIN’s computational resource requirement is very minimal and suitable for implementation using various web based platforms. Despite its simplicity and minimalistic approach, the CAIN is very effective and reasonably accurate in estimating isotopic composition of spent fuel discharged from various reactor types. The NFCSS has been used for carrying out fuel cycle assessments for two main commercial nuclear fuels, namely, UO2 fuel and Pu-doped uranium dioxide (MOX) fuel, and for 7 types of NPPs that compose the global nuclear reactor fleet, i.e. pressurized water reactors (PWRs), boiling water reactors (BWRs), pressurized heavy water reactors (PHWRs), high power channel-type reactors (RBMKs), advanced gas-cooled reactors (AGRs), gas cooled reactors (GCRs) and water-water energetic reactors (WWERs). Recently, the NFCSS has been extended for application to thorium fuel cycles for light water reactors (LWRs). It also has been demonstrated that in principle the NFCSS is capable of modelling fuel cycles of fast reactors (FRs).

The NFCSS can calculate the actinide inventory such as uranium (U), plutonium (Pu), MA (e.g. Np, Am and Cm) entrained in spent fuels using the CAIN fuel depletion model. For a given nuclear programme size, the NFCSS can provide estimates of material flows and various fuel cycle requirements such as natural uranium resources, enrichment services in separative work unit (SWU), volume of fuel fabrication, volume of spent fuels, accumulation of Pu and MAs, reprocessing volumes and so on. A unique feature of the NFCSS is that it does not need specific reactor core design codes or other proprietary information. This flexibility allows the NFCSS to simulate future uranium needs and other fuel cycle requirements for a reactor park, country, region, or the entire world. The NFCSS is recognized for its speed, accuracy and ease of use by a wide range of professionals in academia, research and policy institutions of Member States.