Thermal neutron activation: Sample preparation utilizing graphite as a diluent

1973 ◽  
Vol 14 (2) ◽  
pp. 395-400 ◽  
Author(s):  
N. D. Stalnaker ◽  
B. T. Kenna ◽  
M. Kahn
2015 ◽  
Vol 84 (3) ◽  
Author(s):  
Klemen Stražar ◽  
Matjaž Kavčič ◽  
Žiga Šmit ◽  
Jure Simčič ◽  
Radojko Jaćimović ◽  
...  

IntroductionThe influence of polyacetal wear particles on aseptic loosening of non-cemented isoelastic femoral stems with polyacetal coating remains unclear. The aim of our study was to use nuclear methods to prove the presence of polyacetal wear particles, to determine their morphology and to check their distribution in the tissues around loosend hip prosthetic components.MethodsTissue samples obtained during retrieval of 4 aseptic loosened primary hip prostheses with isoelastic stems made of polyacetal were subjected to nuclear analyses. Proton microbrobe method (mikro-PIXE) was used to prove the presence of polyacetal wear particles and to check for their morphology by detection of barium, which is molecularly in BaSO4 embedded in polyacetal. Thermal neutron activation was used to determine distribution pattern of polyacetal wear in the peri-prosthetic tissues.ResultsAgainst expectations, polyacetal wear particles were found rather rare, larger than 100 µm and present in pseudo-membrane samples around the loosened stem, but virtually absent in tissues away from their origin. Concentration of BaSO4 in polyacetal wear particles in pseudo-membrane samples was similar to the one in polyacetal coating (conc. Ba = 14217 µg/g and 14800 µg/g, respectively).ConclusionAccording to the results, the primary cause of the loosening of the isoelastic stems with polyacetal coating is most probably mechanical restlessness, which is responsible for local production of the large polyacetal wear particles responsible to accelerate the process of loosening. PIXE method and thermal neutron activation are sensitive quantitative nuclear methods suitable for direct or indirect detection of wear particles in the tissue around loosened prostheses and to determine morphology of wear particles and their distribution in the tissues.


2018 ◽  
Vol 106 (7) ◽  
pp. 535-547 ◽  
Author(s):  
Holger Dorrer ◽  
Katerina Chrysalidis ◽  
Thomas Day Goodacre ◽  
Christoph E. Düllmann ◽  
Klaus Eberhardt ◽  
...  

Abstract Several experiments on the study of the electron neutrino mass are based on high-statistics measurements of the energy spectrum following electron capture of the radionuclide 163Ho. They rely on the availability of large, radiochemically pure samples of 163Ho. Here, we describe the production, separation, characterization, and sample production within the Electron Capture in Holmium-163 (ECHo) project. 163Ho has been produced by thermal neutron activation of enriched, prepurified 162Er targets in the high flux reactor of the Institut Laue-Langevin, Grenoble, France, in irradiations lasting up to 54 days. Irradiated targets were chemically processed by means of extraction chromatography, which allowed separating the formed Ho from the 162Er target-material and from the main byproducts 170Tm and 171Tm, which are co-produced in GBq amounts. Decontamination factors of >500 for Er and of >105 for Tm and yields of 3.6·1016 and 1.2·1018 atoms of 163Ho were obtained, corresponding to a recovery yield of 95 % of Ho in the chemical separation. The Ho-fraction was characterized by means of γ-ray spectrometry, Inductively-Coupled-Plasma Mass Spectrometry (ICP-MS), Resonance Ionization Mass Spectrometry (RIMS) and Neutron Activation Analysis (NAA). In this process, the thermal neutron capture cross section of 163Ho was measured to σHo-163 to Ho-164m= (23±3) b and σHo-163 to Ho-164g= (156±9) b for the formation of the two isomers of 164Ho. Specific samples were produced for further purification by mass separation to isolate 163Ho from the Ho-isotope mixture, as needed for obtaining the energy spectrum within ECHo. The partial efficiency for this second separation step is (32±5) %.


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