Plutonium Biokinetics in Human Body A. Luciani - Kit-Bibliothek - FZK

• the necessity of performing measurements with both detecting systems and under different
geometry configurations for which the efficiency factors are known;
• the necessity of limiting the measurement time in order to minimize the time that the
subject was obliged to remain in the shielded room;
• the statistical significance of impulse counted by each detector in the region of interest of
Americium.
A measurement time of 2000 seconds seemed to satisfy all the aforementioned
requirements. In order to decrease the whole time necessary for carrying out the series of
measurements with both detecting systems and for different geometry, when possible
simultaneous acquisitions from both detecting systems were carried out. Yet, as the trolleys
supporting the detecting systems move on the same track, not all the combinations in the
measurement positions were possible to simultaneously perform with both detecting systems.
Typically measurements of activity on lung with HPGe detecting system and on knee with
phoswich detecting system were simultaneously performed. Similarly measurements of
activity on lung with phoswich detecting system and on knee with HPGe detecting system
were simultaneously performed too. As the phoswich detecting system has a better geometric
efficiency, the measurement time was reduced to 1500 seconds, when measurements with
HPGe detectors were not simultaneously carried out.
Unfortunately some days before performing measurements on the contaminated
subject one of the HPGe detectors was damaged. Therefore in the following part the results of
the measurements performed with the other three germanium crystals are presented. This had
a limited implication on the final evaluation of subject's organs burden activity.
The measurements with phoswich were carried out in normal way.
2.3.3 RESULTS OF THE MEASUREMENTS
Examples of the spectra acquired from the subject with HPGe and phoswich systems
positioned on the lung region are shown in Figure 2.3.11 and Figure 2.3.12, respectively.
counts
0 59.5
Figure 2.3.11 The spectrum acquired with the HPGe detecting system positioned on the lung
(measurement position 1) of the contaminated subject. The full energy peak is
given by 241 Am (59.5 keV).
68
energy [keV]