NFCSS, Details of the Modeling

NFCSS Material Flow Model

Overall material flow for a nuclear fuel cycle can be sketched by tracking the nuclear materials in each of the processes in the nuclear fuel cycle. NFCSS is capable of simulating different nuclear fuel cycle models with different reactor types and fuel types including non-existing fuel types (fuels with MA content) with the introduction of accurate libraries and data. Since commercially existing nuclear fuel cycle options in bulk amount are once through fuel cycle and U and Pu recycling in some reactor types, these two option is illustrated in below figure.

This is a fuel cycle model with two fuel types. The first fuel type in the model is Uranium fuel from natural material whereas the second fuel type is the fuel using reprocessed material. The second fuel type in the system is mostly Mixed Oxide (U+Pu) fuel type since it is the only commercially available fuel from reprocessed material. Other fuel types such as fuels containing thorium or fuels with Minor Actinide content could also be used to investigate the future options.

Illustration of material flow simulated in NFCSS (UOX + MOX Fuel use case).


The heavy metal starts flow from its natural location to the its end location which is spent fuel storage or HLW storage in NFCSS modelling. NFCSS does not include final disposal of spent fuel in its model. In this flow the heavy metal spends some time in each of the processes or in betweeb the processes. This is due to the technical and physical requirements of the handling of heavy metals.

Below table gives typical waiting and process times for a thermal reactor cycle.

Products or Services Lead Times
NatU Procurement 2 years before loading
Conversion to UF6 1.5 years before loading
Enrichment 1 year before loading
UO2 fabrication 0.5 year before loading
Spent fuel storage in the reactor pool before transport 2 years after unloading
Spent UO2 or URE(*) storage before reprocessing 5 years after unloading
Spent MOX storage before reprocessing 5 years after unloading
Reprocessing (Pu and RepU availability) 1 year
MOX fuel fabrication 1 year
URE(*) fuel fabrication 0.5 year

(*) URE is UO2 fuel using reprocessed Uranium.

(*) For Thorium fuel cycle please refer IAEA-TECDOC-1864 which is available in ‘References’ tab.  This is to be added as shown below

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