Thoria rods and a water moderator are arranged in a simple rectangular geometry in a multilayered configuration to produce 233U by bombardment with 14-MeV neutrons. The 233U production rate is measured by measuring the 312-keV gamma activity associated with 233Pa. Detailed neutronic calculations have been made using the versatile MCNP Monte Carlo code and the BMCCS2 cross-section library. There is very good agreement between the experimental measurements of 233U production and the corresponding calculations.