Radiochemical Determination of Long-Lived Radionuclides in Proton-Irradiated Heavy-Metal Targets: Part I—Tantalum

Abstract

In this study, distillation, precipitation, and ion-exchange methods were chosen for the separation of the long-lived β-emitters I,Cl and the α-emitters Dy,Gd, Gd, andSm from Ta targets irradiated with protons up to 2.6 GeV to determine their production cross sections. Measurements of I/I and Cl/Cl ratios were performed with accelerator mass spectrometry. After separation of the lanthanides, the molecular plating technique was applied to prepare thin samples to obtain highly resolved α-spectra. Autoradiography and focused ion beam/scanning electron microscopy techniques were used to characterize the lanthanide deposited layer. Experimental cross-section data are compared with theoretical predictions obtained with INCL++ and ABLA07 code, and a satisfactory agreement is observed.

Separation and recovery of exotic radiolanthanides from irradiated tantalum targets for half-life measurements

“…Due to the long time elapsed after irradiation of the Ta samples (i.e., 17 years) short-lived reaction products were already decayed. Exemplificative γ-spectra of the LnF 3 precipitate and the supernatant after fluoride precipitation are shown in Fig 5. As in [43], an average 98% Lns separation yield from the Ta matrix was here obtained. The detection of 133 Ba and 178m2 Hf radionuclides in the LnF 3 precipitate (Fig 5A) is due to the sorption of Hf and Ba cations on the negatively charged surface of the LuF 3 carrier, that ultimately leads to the co-precipitation of Hf and Ba in the form of fluoride complexes [46].…”

“…As in [ 43 ], an average 98% Lns separation yield from the Ta matrix was here obtained. The detection of 133 Ba and 178m2 Hf radionuclides in the LnF 3 precipitate ( Fig 5A ) is due to the sorption of Hf and Ba cations on the negatively charged surface of the LuF 3 carrier, that ultimately leads to the co-precipitation of Hf and Ba in the form of fluoride complexes [ 46 ].…”

“…The procedure for the dissolution of the Ta samples and the precipitation of the Lns fluorides is described in detail in [ 43 ]. The dissolution of the “Tensile” type specimen was carried out in 4 mL 10 M HNO 3 and 4 mL conc.…”

“…However, in those studies (mostly involving amounts of Lns in the order of milligrams), the separation efficiency for each Lns was not stated, and furthermore, the applied procedures required an extensive use of organic solvents. Recently, a method for the extraction of ppb amounts of Dy, Gd, and Sm nuclides from proton irradiated Ta targets was reported for cross section measurements [43]. The separated Dy fraction contained traces of Ho and Tb, while the Sm fraction included small amounts of Eu and Pm.…”

High precision half-life measurement of the extinct radio-lanthanide Dysprosium-154

“…The Dy fraction containing 154 Dy was obtained from the reprocessing of four Ta samples from the STIP-II project. The procedure for the dissolution of the Ta samples is described in detail in 37 . Successively, a series of ion-exchange separation processes allowed us to obtain a purified Dy fraction in 1 M HNO 3 .…”