Oswald, S. (Corresponding Author)MLZ*

2014

Abstract: Technetium-99m, the metastable isomer of technetium-99, is the most common radionucli-de used in nuclear medicine for tumor diagnosis and for monitoring the function of organs.It is produced from the decay of molybdenum-99, which can be produced most efficient-ly in research reactors by nuclear fission of uranium in dedicated targets irradiated byneutrons. For the subsequent extraction of molybdenum from the irradiated target, analternative dry-chemical method using fluorine is being tested since higher yield and lessradioactive waste are expected. In order to test this method safely, a substitute, a so-calledfission product surrogate, is prepared and tested, which has similar properties and can behandled more easily due to the reduced radioactivity.At first, the necessary theoretical background is presented. After a short introduction onnuclear fission, the expected amount of molybdenum in an irradiated target is calculatedand then compared with the results of a detailled irradiation simulation. By consideringthe chemical aspects of the extraction with fluorine, it is also reviewed whether more fissionproducts should be included in the surrogate.Further, the relevant material properties of molybdenum and uranium are evaluated forthe experimental procedure before the samples are alloyed in an arc furnace. For the subse-quent investigations, the samples are prepared using an optimized preparation procedure.In particular, the homogeneity, the purity and the composition of the samples are ofimportance for the produced fission product surrogate. Through the combined applicationof optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy,differential scanning calorimetry, and mass spectrometry, each of these aspects can beexamined at its best. Also, the suitability and accuracy of the individual examinationmethods are compared precisely.Applying multi-stage dilution series, it turns out that the expected required molybdenumconcentration can be obtained. Using optical microscopy, the homogeneity of the alloyis evaluated, while the differential scanning calorimetry is suitable for estimating a ge-neral trend of the molybdenum concentration. An accurate result for the molybdenumconcentration in the fission product surrogate is only possible with the elaborate massspectrometry.

Keyword(s): Others (1st) ; Materials Science (2nd) ; Unveröffentlichte Hochschulschrift

1. RPHYSICS (RPHYSICS)
2. DOMUSER (DOMUSER)
3. MATSCI (MATSCI)
4. EDV (EDV)

1. HEU-MEU: Brennstoffentwicklung