4. METHOD OF SOLUTION
Organ dose equivalents are approximated in two ways, depending on the exposure type. For external exposures, energy specific organ-to-skin-surface dose conversion ratios are used to approximate dose equivalents to specific organs from doses calculated to a point on the skin surface. The organ-to-skin ratios are incorporated in organ- and nuclide-specific dose rate factors, which are used to approximate doses during immersion in contaminated air. For internal exposures, 50 year dose equivalents are calculated using organ- and nuclide-specific, 50 year dose conversion factors. Doses from direct, external exposures are calculated using the energy-specific dose conversion ratios, user supplied exposure conditions, and photon flux approximations for eleven source geometries. Available source geometries include: point, shielded and unshielded; line, shielded and unshielded; disk, shielded and unshielded; cylindrical surface, unshielded; uniform, semi-infinite volume, shielded and unshielded; uniform, infinite slab, shielded and unshielded; uniform, nonabsorbing cylindrical volume, unshielded; and uniform, nonabsorbing spherical volume, unshielded; and uniform, self-absorbing cylindrical volume, shielded and unshielded.
External doses from immersion in contaminated air are calculated using the organ- and nuclide-specific dose rate conversion factors, user supplied exposure conditions, and an infinite to finite air volume correction formula. External doses are calculated using the appropriate inhalation or ingestion, 50 year, organ- and nuclide- specific dose conversion factors and user supplied exposure conditions.