Nuclear Resources
======================

Estimates of available uranium resources in the literature vary considerably, which could become relevant if advanced nuclear fuel cycles (e.g., the plutonium cycle including fast breeder 
reactors, the thorium cycle) are not available. In MESSAGE advanced nuclear cycles such as the plutonium cycle and nuclear fuel reprocessing are in principle represented, but their 
availability varies following the scenario narrative. :numref:`fig-uran` below shows the levels of uranium resources assumed available in the MESSAGE SSP scenarios, building upon earlier work 
developed in the Global Energy Assessment (see Riahi et al., 2012 :cite:`riahi_chapter_2012`). These span a considerable range of the estimates in the literature, but at the same time none of 
them fall at the extreme ends of the spectrum (see Rogner et al., 2012 :cite:`rogner_chapter_2012`, Section 7.5.2 for a more detailed discussion of uranium resources). Nuclear resources 
and fuel cycle are modeled at the global level. 

.. _fig-uran:
.. figure:: /_static/nuclear_resources.png
   :width: 600px

   Global uranium resources in the MESSAGE interpretation of the SSPs compared to seven supply curves from a literature review (Schneider and Sailor, 2008 :cite:`schneider_long-term_2008`). 
   Conservative Crustal and Optimistic Crustal refer to simple crustal models of uranium distribution in the crust and the of extraction costs on the concentration. Pure-KCR refers to a fit 
   of a simple crustal model to known conventional resources (KCR) as estimated by the Red Book 2003 (OECD/NEA, 2004 :cite:`oecd_uranium_2004`). PPM-Cost over the simple crustal models 
   include a relationship between uranium grade and extraction costs. FCCCG(1) and (2) as well as DANESS refer to estimats from more complicated models of the dependency of extraction costs on
   uranium concentration (and therefore resource grade).