NFCSS Material Flow Calculation Model

NFCSS material flow calculation model is based on the material flow model which is described in Modeling section of the NFCSS web site.

The NFCSS web site is planned to provide the advanced version of the software in the future. The advanced version will enable the visitors to make calculations for a period of time with the selection of input and output parameters from a database. The visitors will be able to add their inputs to the database in structured MS Excel form.

Development of a CD version of the software is also planned with the full features. But the dissemination time is not decided yet.

Below list gives the input and output parameters for the basic calculation tool (UOX + MOX fuel use case).

Input Parameters:

• Reactor Type : There are currently 7 reactor types selectable in NFCSS basic calculation web site. Those are PWR, BWR, PHWR, RBMK, AGR, GCR, WWER.
• Fuel Types: In basic internet version of NFCSS, PWR and BWR reactor types are assumed the only reactor types that can burn the fuel from reprocessed material. All the other types has only one fuel type which is UOX type. For PWR and BWR types the two fuel types can be selected, UOX and MOX.
  
  MOX fuel is assumed to be fabricated with proper mixture of depleted uranium (enrichment tails) and reprocessed Plutonium from the spent UOX fuel with 3.3% initial enrichment, 33 GWD/t discharge burnup after 5 years of cooling.
• Nuclear Power: Gross electric power capacity in MWe.
• Load Factor
• Thermal Efficiency
• Discharge Burnup
• Initial U235 Enrichment (or Pu content) for each fuel type
• Tails Assay
• Share of Fuel Type 2 in the reactor
• Reprocessing Ratio for each fuel type
• Uranium Source for Fuel Type 2
• Use of Reprocessed Uranium

Output Parameters:

• Natural Uranium Requirement
• Conversion Requirement
• Enrichment Service Requirement .
• Depleted Uranium Arising
• Depleted Uranium Use for MOX fuel
• Fuel Fabrication Requirements (for two fuel types)
• Electricity Production
• Spent Fuel Discharge (for two fuel types)
• Spent Fuel Storage (for two fuel types)
• Spent Fuel Reprocessing (for two fuel types)
• Reprocessed Pu amount
• Amount of used Reprocessed Pu in MOX fuel
• Reprocessed U amount
• Amount of used Reprocessed U
• MA amount in Reprocessing Waste
• FP amount in Reprocessing Waste

The basic calculation model, which is given here, is to calculate annual service and material requirements as well as the arisings for an equilibrium core. So that the loading of initial core of a reactor, or discharge during the refuelling period or at the end of reactor life is not considered. It is also assumed that all mass reduction in heavy metal (U, Pu, Th, MA, etc) amount is considered as fission product accumulation. This is not true in reality since there is some mass loss during the operation of the reactor, but for the purpose of the NFCSS, this is an acceptable assumption.

Calculation starts from the reactor. Then two parallel calculation series are performed. In the first serie, simulation runs for the front end of the nuclear fuel cycle. The second serie performs the calculation for the back end of the nuclear fuel cycle.

In the front end of the cycle, annual fresh fuel requirements, annual enrichment service requirements, annual depleted uranium amount, annual conversion requirements and annual natural uranium requirements are calculated. The only interface between the first and second series of the calculations is the introduction of reprocessed material from the back end to the front end.

In the back end of the cycle, annual spent fuel discharge amount, annual spent fuel reprocessing amount, annual spent fuel storage amount, annual reprocessed material amount (U or Pu), annual other material arisings such as MAs, annual Fission Products arisings and annual HLW arisings are calculated.