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ORIGEN Family of Modules 
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This section describes how to perform the calculations and evaluations
described in :numref:`origen-theory` using the ORIGEN family of modules in SCALE.
These modules are summarized briefly below.

1. The ARP module creates a new ORIGEN library by interpolating a set of existing
   libraries. ORIGEN libraries organized for this purpose are called ORIGEN
   Reactor libraries. Those distributed with SCALE are described in 
   :numref:`sec-origen_rx`.

2. The ORIGEN module is used to solve depletion, decay, activation, and
   feed problems described by :eq:`eq-origen-odes`, as well as the decay 
   emission calculations described by :eq:`eq-origen-decay`. For spent fuel 
   calculations using the ARP interpolation methodology, it may be more 
   convenient to use ORIGAMI, as described in the :ref:`ORIGAMI chapter <sec-origami>`.

3. The OPUS module is used to perform post processing and analysis on
   ORIGEN results contained in ORIGEN concentrations files, including
   sorting, ranking, and unit conversion.

Two types of files are an integral part of the ORIGEN family of modules:
the library file and the concentrations files.

-  The library file is a binary file, usually either with the complete
   filename “ft33f001” or with extension “.f33,” and it contains a
   collection of transition matrices **A**\ *,* usually corresponding to
   different burnups. It is typically called an “ORIGEN library,”
   “ft33,” or “f33” file.

-  The concentrations file is also a binary file, usually either with
   the complete filename “ft71f001” or with extension “.f71.” The f71 is
   a solution archive containing isotopics vectors
   :math:`{\overrightarrow{N}}_{\ }` corresponding to different
   materials or different points in time.

.. note:: 

   A fundamental cability to create ORIGEN libraries within the ORIGEN 
   sequence has been added to SCALE 6.3, effectively deprecating the 
   stand-alone COUPLE module.