Predicting Induced Activity in the Havar Foils of the 18F Production Targets of a PET Cyclotron and Derived Radiological Risk
| Autor: | J. Javier Martinez-Serrano, Antonio Díez de los Ríos |
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| Rok vydání: | 2014 |
| Předmět: |
Risk
Alternative methods Fluorine Radioisotopes Radiochemistry Materials science Epidemiology Health Toxicology and Mutagenesis Cyclotron Cyclotrons Radiation Dosage Effective dose (radiation) Dual beam law.invention Activation product law Positron-Emission Tomography Alloys Radiology Nuclear Medicine and imaging Neutron Irradiation Radiology FOIL method |
| Zdroj: | Health Physics. 107:103-110 |
| ISSN: | 0017-9078 |
| DOI: | 10.1097/hp.0000000000000064 |
| Popis: | The PET cyclotron at the Centre of Molecular Imaging of the Universidad de Malaga (CIMES) is a 16.5 MeV GE PETtrace cyclotron working at dual beam (40 μA beam). The cyclotron is dedicated mainly to F production. The F target has two thin circular foils composed of a metal alloy (Havar), that are highly activated by the proton beam and secondary neutrons. The main purpose of this study is to assess induced activity radiological risk derived from the Havar foils activation. Induced activity in Havar foils was estimated by two procedures. One consisted in estimating neutron and proton fluxes with MCNPX and using them as inputs in the activation code ACAB. Alternatively, given the regular periodicity of the irradiation cycles, an analytical expression was derived to estimate activity concentrations of activation products using production rates calculated with MCNPX. Large differences were found in the induced foil activities predicted by the two procedures. Therefore, an irradiated vacuum foil was measured with a Ge detector to analyze activity levels. Cobalt-58 (Co) and Co activities calculated with ACAB match well with measurements. Cobalt-60 (Co) activity estimated with the alternative method agrees acceptably with the measured activity, and Co activity is slightly overestimated. Cobalt-57 (Co) is the activation product of concern in the long term. The vacuum and window foils will be exempted in 3.3 y and 5.5 y, respectively, after replacement. Calculated effective dose with MCNPX and ICRP reference HML phantoms in the foils replacement operation is 0.34 mSv, and annual effective dose would be 2.1 mSv, which is below the annual limits. |
| Databáze: | OpenAIRE |
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