In the case of a radiological emergency it is of utmost importance that we can rapidly quantify theradionuclide content of a person or population to ensure that the right precautions or treatmentsare taken. In this project we investigate how well the Palmer geometry works to quantify the Cs-137 content of a test population. The aim is to find if this geometry could replace the currentmeasuring geometry. To begin with, we investigate the full energy peak efficiencies in the Palmer geometry formeasurements of whole body content of radioactive nuclides using Detective-X, a spectrometricgamma radiation detector produced by ORTEC. First, we perform an empirical efficiency cali-bration based on measurements with the phantom IRINA using both Cs-137 and Eu-152 to cover arange of energies. We employ two configurations of the IRINA phantom to represent the bodyof the average woman and man in Sweden. The detector is directed towards the abdomen of the phantom, which is in a crouched seated position, to emulate the Palmer geometry. Additionally, we construct a detector model in Monte-Carlo N-particle transport code (MCNP).To validate this model we calibrate the detector with a Cs-137 point source at various angles of in-cidence to determine its angular dependence, performing the measurements along two axes ofrotation. We find that the efficiency in the final MCNP model agree well with the empiricalcalibration. The detector model is then used alongside the MCNP models of two IRINA configurations to compare the simulated and empirical calibrations. We observe that the detector model agree well with our empirical calibrations. Finally, we measure the whole body content of Cs-137 in a group of residents around Umeå,Sweden. In these measurements, the Palmer geometry is employed, where the test person sitswith the detector in their lap, having the top cap against their stomach, and crouches over it. These measurement are compared to those taken in a low background setup (mobile whole body counter), where the test person lays down on their back in a lead cradle and have their legs and head above their chest and abdomen. We find that the signal in the Palmer geometry has a higherbackground level, preventing detection of low activities. Additionally, the Palmer setup tends to underestimate the activity compared to the current setup. More test subjects with higher activity is needed to test the setup, as the current data is not sufficient for definite conclusions. In conclusion, the simulation model is sufficient for future simulations of the Palmer geometry. The tests of the Palmer geometry are not sufficient to sufficiently prove if the geometry will be a good method to determine the whole body content of radionuclides. To test it further a larger test population with a higher activity is needed. The calibrations should also be done with other configurations of IRINA and activity distribution to better emulate an adult human.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:umu-226681 |
| Date | January 2024 |
| Creators | Sundin, Marcus |
| Publisher | Umeå universitet, Institutionen för fysik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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