## Concept: Regions & Institutions¶

Cyclus establishes a hierarchy of agents: Facility agents are managed by Institution agents that exist within a Region agent. This series of ownership allow for control of the interaction behavior between agents. For example, two facilities may not be allowed to trade if they are in two different regions.

Every Cyclus simulation needs at least one Region and one Institution, and in this case, we’ll use the simplest options:

• a Null Institution (NullInst) that holds a set of facilities that are deployed at the start of a simulation.
• a Null Region (NullRegion) that holds a set of Institutions.

Defining these is done in the archetypes section of the code. This is done in a similar manner as the other archetypes previously defined, except regions and insitutions used in this tutorial come from the agents library, rather than the cycamore library.

Using the template and table below, properly fill the template with the variables listed in the table below. In the template, the dots represent the archetypes already defined in the simulation.

Variable Value Purpose
lib6 agents Library of the archetype
arch6 NullRegion Name of archetype
lib7 agents Library of the archetype
arch7 NullInst Name of archetype

Once complete, your agent Archetypes block should be:

Since these are all archetypes, no matter what library they’re from, we must append these twospec blocks into the the arechtype block that we already have. This results in the full archetype block:

<archetypes>
<spec>
<lib>cycamore</lib>
<name>Enrichment</name>
</spec>
<spec>
<lib>cycamore</lib>
<name>Reactor</name>
</spec>
<spec>
<lib>cycamore</lib>
<name>Source</name>
</spec>
<spec>
<lib>cycamore</lib>
<name>Sink</name>
</spec>
<spec>
<lib>agents</lib>
<name>NullRegion</name>
</spec>
<spec>
<lib>agents</lib>
<name>NullInst</name>
</spec>
</archetypes>


## Concept: Regions¶

Regions tie together a fuel cycle as they designate what facilities are in the region’s fuel cycle. Regions may apply preferences to each potential request-bid pairing based on the proposed resource transfer. The basic structure of a region is:

<region>
<name>Region_name</name>
<config>
<NullRegion/>
</config>
<institution>
...
...
</institution>

</region>


Where:

• name: name of the region
• config: Region archetype to use

In between the two dotted lines is where the institution and facility information goes.

## Concept: Institution¶

In Cyclus input files, each institution block defines an agent that acts as an institution in the simulation. An institution block can only appear within a region block. Each institution block has the following sections in any order:

• name (required, once) - a name for the prototype
• lifetime (optional, once) - a non-negative integer indicating the number of time steps that this region agent will be active in the simulation
• config (required, once) - the archetype-specific configuration
• initialfacilitylist (optional, may appear multiple times) - a list of facility agents operating at the beginning of the simulation

Each initialfacilitylist block contains one or more entry blocks that each contain the following sections, in the following order:

• prototype - the name of a facility prototype defined elsewhere in the input file
• number - the number of such facilities that are operating at the beginning of the simulation

Put together, the institution block is the form:

<institution>
<initialfacilitylist>
<entry>
<prototype>Prototype_name</prototype>
<number>number_of_prototype_names</number>
</entry>
</initialfacilitylist>
<name>Inst_name</name>
<config>
<NullInst/>
</config>
</institution>


There can be multiple entry blocks within the same institution.

The example below introduces two institution agents (the region section that encloses them is not shown). The first institution has the name SingleInstitution, and is configured from the archetype with the name NullInst. The NullInst has no defined archetype-specific data. This institution begins the simulation with two facility agents, one based on the FacilityA prototype and another based on the FacilityB prototype. The second institution has the name AnotherInstitution, is also configured from the archetype with the name (or alias) NullInst. This institution has no initial facilities.

<institution>
<initialfacilitylist>
<entry>
<prototype>FacilityA</prototype>
<number>1</number>
</entry>
<entry>
<prototype>FacilityB</prototype>
<number>1</number>
</entry>
</initialfacilitylist>
<name>SingleInstitution</name>
<config>
<NullInst/>
</config>
</institution>

<institution>
<name>AnotherInstitution</name>
<config>
<NullInst/>
</config>
</institution>


Putting it all together, a complete region template is of the form:

<region>
<name>Region_name</name>
<config>
<NullRegion/>
</config>
<institution>
<initialfacilitylist>
<entry>
<prototype>Prototype_name</prototype>
<number>number_of_prototype_names</number>
</entry>
</initialfacilitylist>
<name>Inst_name</name>
<config>
<NullInst/>
</config>
</institution>
</region>


## Activity: Write the Region template¶

Using the template below, let’s create the region section of our input file.

<region>
<name>[VALUE]</name>
<config>
<NullRegion/>
</config>
<institution>
<initialfacilitylist>
<entry>
<prototype>[VALUE]</prototype>
<number>[VALUE]</number>
</entry>
</initialfacilitylist>
<name>[VALUE]</name>
<config>
<NullInst/>
</config>
</institution>
</region>


Now the next part of the region template is the other facilities in the region’s fuel cycle. In our example, these facilities are UraniumMine, EnrichmentPlant, and NuclearRepository. Using the above exercise and the table below, fill out the rest of the region template.

Variable Name Amount
prototype UraniumMine 1
prototype EnrichmentPlant 1
prototype NuclearRepository 1
name United States Nuclear 1

### Check: Complete Region block¶

<region>
<name>region1</name>
<config>
<NullRegion/>
</config>
<institution>
<initialfacilitylist>
<entry>
<prototype>UraniumMine</prototype>
<number>1</number>
</entry>
<entry>
<prototype>EnrichmentPlant</prototype>
<number>1</number>
</entry>
<entry>
<prototype>NuclearRepository</prototype>
<number>1</number>
</entry>
</initialfacilitylist>
<name>United States Nuclear</name>
<config>
<NullInst/>
</config>
</institution>
</region>


## Activity: Save your input file¶

Save your input file as cyclus_intro_file.xml

## Activity: Add an extra insitution into the Region¶

Having multiple insitutions help organize facilities and their affiliation. Let’s create region, USA, that contains two institutions, Exelon and United States Nuclear. Exelon is the institution that holds the 1178MWe BRAIDWOOD-1 reactor and United States Nuclear holds the UraniumMine, EnrichmentPlant, and NuclearRepository.

Using the template above and the table below, let’s build the region.

1. Since there are two institutions, Exelon and United States Nuclear, we will split the region into two parts. Let’s first build the Exelon institution. This institution has one 1178MWe BRAIDWOOD-1 prototype. Using this information we can write this institution as:

<region>
<name>USA</name>
<config>
<NullRegion/>
</config>
<institution>
<initialfacilitylist>
<entry>
<prototype>1178MWe BRAIDWOOD-1</prototype>
<number>1</number>
</entry>
</initialfacilitylist>
<name>Exelon</name>
<config>
<NullInst/>
</config>
</institution>

1. Now let’s build the second institution, United States Nuclear. This institution has one UraniumMine prototype, EnrichmentPlant prototype, and one NuclearRepository prototype. Using this information we can write this institution as:
<institution>
<initialfacilitylist>
<entry>
<prototype>UraniumMine</prototype>
<number>1</number>
</entry>
<entry>
<prototype>EnrichmentPlant</prototype>
<number>1</number>
</entry>
<entry>
<prototype>NuclearRepository</prototype>
<number>1</number>
</entry>
</initialfacilitylist>
<name>United States Nuclear</name>
<config>
<NullInst/>
</config>
</institution>

1. We will close the region section by appending the two sections together and appending a </region> tag to the end of the section. Once complete, your region prototype should look like:
<region>
<name>USA</name>
<config>
<NullRegion/>
</config>
<institution>
<initialfacilitylist>
<entry>
<prototype>1178MWe BRAIDWOOD-1</prototype>
<number>1</number>
</entry>
</initialfacilitylist>
<name>Exelon</name>
<config>
<NullInst/>
</config>
</institution>

<institution>
<initialfacilitylist>
<entry>
<prototype>UraniumMine</prototype>
<number>1</number>
</entry>
<entry>
<prototype>EnrichmentPlant</prototype>
<number>1</number>
</entry>
<entry>
<prototype>NuclearRepository</prototype>
<number>1</number>
</entry>
</initialfacilitylist>
<name>United States Nuclear</name>
<config>
<NullInst/>
</config>
</institution>
</region>


## Activity: Save your Input File¶

You are now ready to generate a full Cyclus input file.

1. Save your input file as ‘cyclus_intro_file.xml’

Full input file