A PACE analysis is a complex process and has been divided into a number of stages.
The source term tool allows you to select radionuclides from a database and arrange them into release phases. Phases can be rearranged and scaled. The tool will allow you to perform a preliminary dose assessment to help determine which radionuclides make the greatest contribution and eliminate insignificant radionuclides from the analysis.
The preprocessor allows you to specify a nested calculation grid over the area of interest. The PACE utilises spatial data describing population, agricultural production and economic activity and the pre-processor will resample this data into the calculation grid.
The heart of a Level-3 probabilistic safety analysis is the repetitive consequence calculation for different weather sequences drawn by sampling from an historical meteorological database. In this way the ranges of possible consequences can be ascertained. PACE has been designed to use the UK Met Office model NAMEIII which is a sophisticated lagrangian particle model that can use either 3-D numerical weather prediction (NWP) or single site meteorological data. Alternatively PACE incorporates a simple Gaussian dispersion model.
For each grid square PACE calculates such consequences as:
Consequences can be mitigated by countermeasures and PACE allows you to consider the following protective measures:
Results of calculations are stored for each grid square within an ArcGIS(TM) database and can be queried and plotted on maps.
The final stage is to summarise and aggregate the data into a form suitable for decision makers. PACE contains two tools to assist with this.
The analysis tool is supplied with a set of default calculations to allow you to estimate numbers of people and areas affected by emergency countermeasures, numbers of health effects and other common PSA requirements. As well as providing a default set of calculations, the analysis tool allows you to set up custom calculations (for example the number of people exposed to a given dose or above, the area of land to be evacuated) and store them as a file. The tool runs through each meteorological sequence and each grid square and applies the calculations and aggregates them over each met sequence. It can then present statistical results for example the minimum, maximum, mean or xth percentile number of people exposed to a threshold dose or area to be evacuated. The tool also indicates the meteorological sequence associated with each statistic so for example you can identify why a particular set of weather conditions gave rise to such a large exposed population or large area of evacuation.
This tool exploits the mapping capability of ArcGIS(TM). It allows you to present probabilistic results as a map. For example you could colour code each grid square to indicate the probability of exceeding a given number of fatalities or economic cost in that square. Alternatively you could plot a given percentile in each grid square, for example the 95th percentile incidents of solid cancers or numbers of people to be evacuated.