The 12/13 configuration of the ORNL PCA was replicated in the ASPIS facility at AEE Winfrith in 1983 in order to utilize the accurately characterized fission plate source of ASPIS. The restricted lateral dimensions of the PCA and REPLICA configurations (68.5by 68.5 cm) are not well suited to solution using one- and two-dimensional codes. Accordingly further studies have been performed in which the lateral extent of the radial shield components has been increased to 183 by 191 cm. The fission plate of the REPLICA studies had a cross section of 40.2 by 63.5 cm. which was identical to the projection of the core source onto the first shield member of the PCA. For the new configuration, measurements have been made using both the fission plate of the REPLICA studies and a fission plate of 56 cm radius.Measurements in all configurations have been performed using activation foils. An analysis of the measurements is presented.