[en] The internal parts of reactor DR 3 - the top shield ring, the reactor tank, the graphite reflector and the inner and outer steel tanks - contain about 1 TBq of ⁶⁰Co at the beginning of 2012. The dismantling of these components requires a detailed planning in order to reduce the exposure of the involved dismantling staff to be as low as reasonable achievable. Radiation fields from the internal components have been calculated with the Monte Carlo code MCNP5. The order of dismantling the internal parts of DR 3 is dictated by the construction of the reactor; therefore, the following sequence of dismantling is more or less fixed: (1) top shield plug, (2) top shield ring, (3) reactor tank, (4) graphite reflector and (5) steel tanks with a lead shield between the tanks. The Monte Carlo calculations of the radiation fields are based on measured and calculated activity concentrations in the different construction parts. The uncertainty of these estimates is considerable and determines the major uncertainty on the calculated radiation fields around the construction parts. The report contains the results of the MCNP5-calculations of the radiation fields that have been used in the planning of an optimal dismantling of the internal parts of reactor DR 3. (Author)