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Tesi etd-07012016-115646

Tipo di tesi
Tesi di laurea magistrale
Calibration of a new spectrometry setup for in vivo lung monitoring
Corso di studi
relatore Ing. Ciolini, Riccardo
relatore Prof. Lebacq, Anne Laure
Parole chiave
  • Semiconductor detectors
  • Gamma spectrometry
Data inizio appello
Riassunto analitico
The Anthropogammametry Laboratory of SCK-CEN has the objective to screen workers of nuclear facilities (SCK-CEN and other companies) for internal contamination, because they can be contaminated from inhaling or swallowing radioactive material.
Routine measurements, carried out daily, are whole body counting and lung monitoring.
In lung monitoring, the objective is to screen if plutonium has been inhaled from the people and, to do this, 241Am peak energy (59 keV) is searched by using three germanium detectors, which are chosen for their high resolution, especially at low energy. To increase the measurement efficiency a new set of bigger Germaniun detectors were mounted in the SCK-CEN antropogammametry laboratory.
The objective of this study was to calibrate and optimize a new setup for in-vivo lung monitoring in the Antropogammametry Laboratory at SCK-CEN. This new setup, made of two HPGe, had to be more efficient and more comfortable for the people doing measurements than the actual setup used (two LEGe detectors).
To reach these goals, some background measurements of the bunker and studies of the best position of the detectors had to be done. MCNP code was the tool used to simulate the performances of the detectors in different position to find the one that would give the best efficiency for the measurements.
After that, efficiency curves depending on the CWT were established through multiple measurements and it is possible to see a really improved efficiency for the energy of interest, almost doubled.
As the calibration was done with a phantom, also the uncertainties in these curves had to be taken into account , because a person is really different from a phantom, either for the composition either because he can move during the measurements (50 minutes). It has been found that the sum of the uncertainties is about 16% (k=1).Other studies of uncertainties were done with MCNP, using an anthropomorphic phantom model.
With this new setup what we expect is a decrease of MDA and then improved performances.