Patent Number: 
Section: claims

1. A process for producing a daughter radionuclide from a parent radionuclide comprising the steps of:loading the parent radionuclide on a first solid medium contained in a generator and onto which the parent radionuclide is retained and whereby the daughter radionuclide is formed by radioactive decay of the parent radionuclide;eluting the first solid medium with a A0 solution so as to recover a A1 solution comprising the daughter radionuclide;loading the A1 solution or a A1′ solution onto a head of a second solid medium contained in a chromatography column, the A1′ solution being formed by adjusting a pH of the A1 solution;first washing the second solid medium with a A2 solution;second washing the second solid medium with a A2′ solution;eluting the daughter radionuclide with a A3 solution,wherein in the chromatography column the first washing step is conducted from head to tail of the column and the second washing step and the second eluting step are conducted from tail to head of the column. 2. The process according to claim 1 wherein the daughter radionuclide is lead 212. 3. The process according to claim 1 wherein the parent radionuclide is chosen from radium 224, thorium 228 and their mixtures. 4. The process according to claim 1 wherein the parent radionuclide is radium 224. 5. The process according to claim 1 further comprising air-flushing the second solid medium. 6. The process according to claim 1 wherein the A2 and A2′ solutions, identical or different are chosen among solutions having an acidity corresponding to that of an aqueous solution of a strong acid of concentration ranging from 0.1 to 0.5 mole/L. 7. The process according to claim 6 wherein the A2 and A2′ solutions, identical or different are chosen among solutions having an acidity corresponding to that of an aqueous solution of a strong acid of concentration equal to 0.5 mole/L. 8. The process according to claim 1 wherein the A2 and A2′ solutions are chosen from HCl or nitric acid solutions. 9. The process according to claim 1 wherein the A3 solution is a solution having a pH ranging from 5 to 9. 10. The process according to claim 9 wherein the A3 solution is an ammonium acetate solution. 11. The process according to claim 1 further comprising the following steps:loading radium 224 on a cation exchange resin contained in a generator;eluting with a 2 N hydrochloric acid solution so as to recover a A1 solution comprising lead 212;loading the A1 solution on the stationary phase of a liquid chromatography column;washing the column from head to tail with a A2 solution of 0.1 N hydrochloric acid;washing from the tail to head of the column with the same A2 solution;eluting from the tail to the head of the column with a A3 solution of 0.4 N ammonium acetate; andair flushing. 12. The process according to claim 1 further comprising a preliminary step of generating the parent radionuclide from a source radionuclide in a generator from which the parent radionuclide is eluted. 13. The process according to claim 2, wherein the source radionuclide is thorium 228, the parent radionuclide is radium 224 and the daughter radionuclide is lead 212.