Recently, Butcher (1987) and Morell et al. (1991) used the abundance of the long lived isotope 232Th (half life 14 Gyrs), compared to that of a stable element neodymium, to determine an upper limit for the age of the Galaxy. However, this method suffers from the fact that neodymium is partly s-process and partly r-process whereas thorium is pure r-process. Europium which is pure r-process may be used to avoid this problem. This poster presents new measurements of the thorium and europium abundances in halo stars.