Bestimmung der Aktivitaet der Thoriumisotope "2"2"8Th, "2"3"0Th und "2"3"2Th in thoriumhaltigen Materialien mittels Alphaspektrometrie

Different materials containing thorium are investigated in the Physikalisch-Technische Bundesanstalt with respect to their activity of thorium isotopes ("2"2"8Th, "2"3"0Th and "2"3"2Th). In this report, after compiling the main decay data of these isotopes as well as those of "2"2"9Th used as tracer, the procedures applied in the investigations are described (complete dissolution, chemical separation, electrolysis, alpha spectrometry). Details are given for two special samples (a welding electrode and a gas incandescent mantle). The present investigations show that it is possible to determine separately the activities due to the thorium isotopes "2"2"8Th, "2"3"0Th and "2"3"2Th in materials containing thorium with a relative measuring uncertainty of the order of 5% (2#sigma#) using alpha spectrometry. The radiochemical analysis of the welding electrode yielded the following specific activities: 54,7 Bq/g "2"3"2Th, 22,3 Bq/g "2"2"8Th and 6,7 Bq/g "2"3"0Th. This corresponds to a content of 1,5% ThO_2 in the investigated electrode. The radiochemical analysis of the incandescent mantle yielded 439 Bq/g "2"3"2Th, 194 Bq/g "2"2"8Th and 58 Bq/g "2"3"0Th. (orig.)SIGLEAvailable from TIB Hannover: RA 3143(36) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman