For accurate activation analysis, it is necessary to understand the neutron and gamma-ray environment experienced by a sample
during irradiation. A new irradiation position was recently installed in the RT2 thimble of the NIST reactor. Modeling by
MCNP was used to select the radial location in the reflector thimble and the size of the D2O shielding tank. After installation, the new rabbit was characterized for thermal, epithermal, and fast fluence rates, spectral
parameters f and α, temporal stability, axial and radial flux gradients, and temperature.