Modelling in support of the decommissioning of the 40 MeV Medical Cyclotron of VUB (Brussels)
The 40 MeV cyclotron of VUB, which was mainly used for the production of isotopes for medical diagnostics, has reached its end of life. Its operation scheme is based on the survey of 35 years of operation with a multi particle and energy that changed on a daily or even hourly basis. During the operation of the cyclotron, the concrete bunker, the cyclotron itself and structural materials in the main cyclotron room and irradiation rooms were activated as a consequence of beam particle interactions with the materials. A detailed knowledge of the radiological inventory of the cyclotron installation is an important factor in elaborating future decommissioning strategies.
Radionuclide inventories and the associated activities can be determined by activation calculations and by measurements. The non-destructive activation calculations have the advantage that they can occur prior to time consuming dismantling activities. However, due to the heterogeneity of the cyclotron with multi-particle and multi-energy irradiations, simulation of the actual workload is impractical and also time consuming. A simplified approach for the workload has to be developed together with the fine-tuning of the geometric model. The calculation models and methodology can then be validated by the several measurements already performed in the concrete bunker and the magnet. Finally, the concept of waste clearance [1] has to be applied for the investigated materials during this study.
Objectives
- Perform a literature study on decommissioning of cyclotrons, with the focus on radionuclide inventory and strategies for material evacuation.
- Assemble and review the available information of the 40 MeV CGR Cyclotron VUB
- Material composition,
- Geometry of the components (magnets, beam line, Cyclotron bunker, etc.),
- Beam source distribution (beam current, energy, and spatial distribution),
- Irradiation history of the facility.
- Improve the current MCNP input with the information above.
- Perform source term calculations with the ALEPH2 code in order to demonstrate the potential added value of non-destructive activation calculations for the decommissioning of the facility.
References
[1] IAEA Safety Report Series No.95, Methodologies for Assessing the Induced Activation Source Term for Use in Decommissioning Applications, 2019.
Het vereiste minimumdiploma van de kandidaat
- Academic bachelor
De vereiste achtergrondkennis van de kandidaat
- Physics