Geometrically frustrated pyrochlore oxides of the type A2B2O7 (where A=Rare Earth, B=Ti or Zr) have been the subject of extensive investigations because of their interesting and rather unconventional magnetic properties. We propose to investigate the crystal structure of crystals of the zirconate pyrochlores A2Zr2O7 (A=Pr, Nd) using the SXD instrument. Our aim is to establish the exact A/Zr ratio, due to its strong correlation with the magnetic properties and ground states of these pyrochlore oxides. The single-crystal neutron diffraction measurements are significant for the understanding of the structural and magnetic study of the zirconate pyrochlore oxides currently being carried out at Warwick. This study opens up the possibility for a wide range of research experiments on this new class of geometrically frustrated pyrochlores.