Cyclopts Theory¶
Resource Exchange Problem Family¶
Cyclus is a nuclear fuel cycle simulator, and the primary consumer of fuel in such cycles are nuclear reactors. Used fuel eventually leaves reactors and can be stored or processed.
The mechanism by which these decisions are made in Cyclus is called a Resource Exchange. Actors in the exchange can request resources (e.g. fuel) and others bid on those requests to provide the given resource. Actors are also allowed to place an arbitrary number of custom constraints on collections of their requests and bids. For example, a reactor could request two types of fuel, and constrain their requests such that they receive only a certain quantity of fuel (i.e., any combination of fuel types is acceptable).
Reactors are the drivers of any fuel cycle. The types and number of each type of reactor determine the possible resource flows. A critical property of the formulation used in the Cyclus resource exchange model is that it can be separated into two exchanges: one in which reactors request fuel and another in which reactors supply used fuel. This holds true in all cases except when
- repositories and reactors actively compete for the same processed fuel source (e.g., if MOX is produced by a fuel production plant, and repositories and reactors both actively request that fuel)
- if a reactor has the same input and output fuel commodity and bids on its own requests (i.e., it is self recycling)
In reality, neither situation occurs exactly as stated. In fuel cycle modeling practice, both cases can be achieved by modeling them slightly differently. The second example can be modeled as facility compound with a reactor, reprocessing facility, and fuel fabrication facility each with a high affinity for trade with the other. The first example can be avoided by the bidding facility delineating between mox fuel for reactors and byproducts for storage.
Formulation Effects¶
Each parameter has a theoretical basis in the real-life problem that is being modeled and an effect on the underlying formulation. This section describes the underlying formulation for each problem type and describes which parameters relate to that effect.
Any given formulation is comprised of, nominally, five prime characteristics:
- the number of request nodes (unodes)
- the number of supply nodes (vnodes)
- the number of arcs
- the number of exclusive arcs
- the number of constraints
Reactor Request¶
Number of Request Nodes¶
- number of requesters
- assemblies per request
- multicommodity zone fraction
- commodities in multicommodity zone
Number of Supply Nodes¶
- number of suppliers
- fraction of multi-commodities suppliers
- number of commodities per supplier
Number of Arcs¶
- number of request nodes
- number of supply nodes
- connection probability
Number of Exclusive Arcs¶
- exclusion probability
Number of Constraints¶
- number of supply constraints
- number of suppliers
- number of demand constraints
- number of requesters
Reactor Supply¶
Number of Request Nodes¶
- number of requesters
- fraction of multicommodity requesters
- number of commodities per requester
Number of Supply Nodes¶
- number of suppliers
- assemblies per supplier
Number of Arcs¶
- number of request nodes
- number of supply nodes
- connection probability
Number of Exclusive Arcs¶
- exclusion probability
Number of Constraints¶
- number of assemblies
- number of requesters
- number of request constraints
Performance¶
Both formulation’s performance will be functions of:
- number of commodities
- number of arcs
- number of exclusive arcs
- number of constraints
- unit capacity/demand coefficients
- supply constraint values
- demand constraint values
- preference coefficient values
Resource Exchange Species¶
In order to generate random cases of resource exchanges, a parameter space must be defined. Given a full set of selected parameters, classes of resource exchanges that fit those parameters can be generated. The parameter space depends on the exchange being generated:
