In the context of nuclear waste disposal, the possibility of incorporating selectively plutonium and cesium in a mono-silicate neodymium-fluoroapatite Ca9Nd(SiO4)(PO4)(5)F-2 (britholite) is investigated. For this purpose, a force field for the modeling of fluoroapatite Ca-10(PO4)(6)F-2 is established based upon the experimental data of crystallographic parameters and elastic constants. To test further the validity of the potentials, the constant pressure specific heat for Ca-10(PO4)(6)F-2 is measured and compared to the calculated values, Neodymium ions and silicate groups are introduced in the fluoroapatite structure using transferable potentials to obtain the neodymium-britholites Ca10-yNdy(SiO4)(y)(PO4)(6-y)F-2. The force field accuracy is tested by comparing the calculated and experimental values for the lattice parameters and volumes with respect to y(1 less than or equal to y less than or equal to 6), Plutonium and cesium are introduced separately in Ca9Nd(SiO4)(PO4)(5)F-2 also using transferable potentials, The bulk modulus B and the specific heats, C-P and C-V, of the resulting structures are calculated. The cases of trivalent and tetravalent plutonium have been studied by considering, respectively, the following compositions: Ca9Nd1-x(Pu3+)(x)(SiO4)(PO4)(5)F-2 and Ca-9.25(Pu4+)(0.25)Nd-0.5(SiO4)(PO4)(5)F-2. In both cases plutonium is found to substitute for calcium Ca(2), which is seven coordinated, by six oxygen ions and a fluorine, Conversely, cesium, which is introduced in the following structure Ca9.5Cs0.5Nd0.5(SiO4)(PO4)(5)F-2, will substitute for Ca(1) as well as for Ca(2), with a slight preference for Ca(1) which is nine oxygen coordinated. The activation energies for the lattice migration of Pu and Cs are also calculated in the presence of calcium vacancies.