  The Spent Fuel and Waste Science and Technology (SFWST) Campaign of the U.S.
Department of Energy Office of Nuclear Energy (DOE-NE), Office of Spent Fuel
and Waste Disposition is conducting research and development (R&D) on geologic
disposal of spent nuclear fuel (SNF) and high-level nuclear waste (HLW). This
work includes the Geologic Disposal Safety Assessment (GDSA) program which is
charged with development of generic deep geologic repository concepts and
system performance assessment models. One part of the GDSA framework is the
development of a biosphere model capable of assessing dose to potential
receptors exposed to radionuclides released via groundwater from geologic
disposal sites. This work includes the development of a biosphere model capable
of estimating doses to potential receptors living in the biosphere and exposed
to radionuclides released from a hypothetical geologic disposal site.
  The GDSA biosphere model is being developed so that it is compatible with the
GDSA framework including PFLOTRAN, the massively parallel subsurface flow and
reactive transport code. PFLOTRAN is a subsurface flow and reactive transport
code that solves a system of partial differential equations for multiphase flow
and transport of components in porous materials such as shale formation.
PFLOTRAN simultaneously simulates energy and mass flow with fluid properties as
function of pressure and temperature through equations of state. PFLOTRAN also
solves the mass conservation and transport equations of multicomponent
formulations of aqueous chemical species, gases, and minerals reactive
transport. It contains a waste form process model that simulates the
radionuclide inventory under potential failures in a geological repository.
PFLOTRAN can thus calculate the source term of radionuclides in ground water
which can then be used as the GDSA biosphere model input.
