Modelling precipitation-induced excursion of the ambient dose equivalent rate

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This study investigates the influence of precipitation on the ambient dose equivalent rate, focusing on gamma radiation levels. Utilising data from the TELERAD network and locally sourced precipitation data from the SCK CEN site, an experimental study is conducted to evaluate a reference model and the improvements of an expanded model to predict these excursions caused by rainfall. The reference model is developed based on basic rate equations and properties of radionuclides, focusing on the progeny of Rn-222, Pb-214 and Bi-214 that are deposited onto the surface by precipitation and emit ground shine. This reference model linearly correlates rain intensity with increases in radiation levels, which are presented as the ambient dose equivalent rate in this study. Subsequently, this model is expanded to include different scavenging effects, namely in-cloud and below-cloud scavenging, which are processes by which airborne particles, in this case radioactive particles, are captured from the atmosphere by precipitation and later deposited on the surface. These scavenging effects are parametrised and represented by a sublinear relation between the radiation levels and the rain intensity. Both models are implemented using MATLAB and validated with experimental data. The implementation requires a divide into separate rain events and a description of the background radiation for every event. The free variable in the reference model, the ratio of initial activities ξ = A0_Bi/A0_Pb, is evaluated within its predetermined range, [0.55 – 3.82]. A lower value within this range is preferred to yield the best results, indicating a slower decay to be more in line with reality. When implementing the expanded model, this parameter is optimised for every event, to limit uncertainties. Results of the expanded model demonstrate that incorporating scavenging parameters significantly improves the predictions of the model. However, the expanded model still possesses shortcomings. Inconsistencies within one rain event cannot be explained with the current expanded model, indicating the need for additional effects, such as a variable radon concentration throughout an event, to be considered to improve the model.
Original languageEnglish
QualificationCivil Engineer
Awarding Institution
  • KU Leuven
  • Frankemölle, Jens Peter, SCK CEN Mentor
  • Meyers, Johan, Supervisor, External person
  • Camps, Johan, SCK CEN Mentor
  • Van Leuven, Stijn, SCK CEN Mentor
Date of Award27 Jun 2024
StatePublished - 27 Jun 2024

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