Key factors in imprecision in radiological emergency response assessments using the NAME model

Abstract

In the very early stages of response to an accidental release of radioactivity leading to environmental contamination, it is likely that only limited measurements of radioactivity in the local environment will be available on which to base decisions concerning protection measures and radiation monitoring activities. Model predictions will be used to aid understanding of the radiological situation and to form a basis for emergency health protection decisions. This paper presents an analysis of the relative importance of contributors to the imprecision associated with emergency response calculations based on a few off-site measurements, using predictions from the UK Met Office's NAME III (Numerical Atmospheric dispersion Modelling Environment version 5.2) dispersion model. The results presented extend those from a previous study in which a simple Gaussian plume model was used and confirm the key parameters contributing to imprecision. The potential extent of the sheltering countermeasure resulting from a hypothetical release in real weather conditions occurring in 2007 and 2008 is also presented.

A method for displaying imprecision in early radiological emergency assessments

“…The inputs into an emergency assessment tool will often not be well defined in the early stages of an emergency. The key categories of these sources of imprecision, as identified in Haywood et al (2010) can be summarised as:…”

“…Previous articles (Haywood 2008, Haywood et al 2010 have identified the key contributors to the imprecision in model predictions of local dispersion and doses following an accidental release of radioactivity to atmosphere, considering the early stages of an accident. Both the R91 Gaussian model (Clarke 1979) and the UK Met Office's NAME (Numerical Atmospheric dispersion Modelling Environment version 5.2) dispersion model (Jones et al 2007) were used, and the key parameters were found to be essentially the same, namely uncertainty in the weather (in particular the rainfall rate and the wind direction and fluctuations), the release duration and the dry deposition velocity for those radionuclides for which deposition contributes significantly to dose.…”

Different types of uncertainty in nuclear emergency management

“…However, these are only some of the uncertainties faced by emergency managers and recovery teams in responding to a nuclear accident. The modelling and analysis of dose, while reducing some of the uncertainties, introduces further ones related to the model choices and the computation (Haywood, 2010;Haywood et al, 2010). Then there are ambiguities and value uncertainties that arise when the managers try to contextualise emergency plans with their imperatives to minimise the risk to "human health" or some such objective to the specifics of the accident and those affected (French et al, 2016).…”