An extensive series of measurements has been made in the Demonstration Reactor benchmark, the Zero Power Plutonium Reactor (ZPPR) Assembly 2, to provide physics data necessary for LMFBR design. An important objective of the program was to test the applicability of data obtained in the plate-fueled critical to a power reactor design with a more homogeneous composition. Sufficient, fuel inventory was obtained in the form of rods which were used, within sodium-filled calandria, to build large zones in which direct comparisons of parameters could be made with those in the plate zones. A variety of quantities worth of Compared in the two environments. In addition to the direct reactivity worth of rod-for-plate substitution, comparisons are given for small sample and rates,reaction Worths’ neutron spectrum, reaction rate ratios, in-cell reaction rates, reaction rate scans, sodium-void coefficient, and 238U Doppler coefficient. The experiments are Compared With calculations using the ARC system and NDFB/Version-I data. It is found that many parameters of interest can be adequately studied in the plate geometry and that the calculation methods, in genidentified a good representation of the heterogeneity effects. Some areas are identified in which further experimental and analytical study is needed.