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Upcoming Release Notes
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.. currentmodule:: scarabee

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New Features
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- A new nodal diffusion solver based on the nodal CMFD method with 2-node current
  calculations has been added. This new solver, called :class:`NEM4DiffusionDriver` is
  approximately 10 times faster than the previous :class:`NEMDiffusionDriver` solver
  which was based on the method of interface currents. It has an identical interface to
  the previous solver (with a few added elements), and should work as a drop in
  replacement. As such, the previous :class:`NEMDiffusionDriver` has been deprecated. The
  motivation behind this new solver is not purely the better run time performance, but it
  is written in such a way that is will be drastically easier to add other nodal methods
  in the future, such as the Semi-Analytical Nodal Method and the Analytical Nodal Method.

- A new finite-difference diffusion solver, based on the new CMFD nodal kernel method
  above, has been added. This new solver is called :class:`FDNodalDiffusionDriver`.
  Currently, there are no plans to deprecate the previous :class:`FDDiffusionDriver`
  class, as that solver yields superior performance for finite-difference calculations.

- A new Semi-Analytical Nodal Method solver, called :class:`SANMDiffusionDriver` has been
  added, based on the new nodal diffusion solver shell. This solver uses a flux expansion
  based on a quadratic and hyperbolic functions.

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Bug Fixes
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- There was a bug where copying a DiffusionData instance in Python did not include the
  LeakageCorrections which may be present. This resulted in the copies not having a
  LeakageCorrections instance and gave incorrect results in nodal diffusion calculations.