Defining the Populations Playlists

The workspace also has an All Playlist for Populations, which is currently selected for both Run Rows.

Follow the same procedure as described above for the Models Playlists to create separate Day and Night Playlists for populations, with only the appropriate folder of populations selected for each Playlist.

You have now completed all of the input settings for the risk calculations, and you should save the workspace before proceeding to run the calculations.

Running the risk calculations and viewing the results

To run the calculations, move to the Input Supertab, expand the Run Row Selector, select the All Run Rows node at the top of the list, and click on Run. The calculation should run quickly, i.e. in one or two minutes.

Comparing the Multi-Level Risk Contour Plots for Day and Night

The quickest way of viewing the Multi-Level risk contour plot for a particular Run Row is to right-click on the Run Row in the Run Row Selector and select Multi-Level from the list of Risk Results. The Results Selection Wizard dialog will have that Run Row already selected, with all available risk levels and the Outdoor vulnerability also already selected. These settings for risk levels and vulnerability are suitable for the tutorial, so with this method you can immediately click on Finish in the Wizard dialog to view the plot.

Use this method to view the Multi-Level contour plot for Day, and then the Multi-Level contour plot for Night.

If you “drag” the tab header for the Night plot downwards, you can move it to a separate pane below the Day plot, and compare the two plots side-by- side as shown.

For a full description of how to rearrange results views in this way, enter “Views” in the

Search tab of the Help Window to see the topic on “Options for working with Views”.

You can see that the risk contours are larger for night than for day, even though the Day Run Row has additional Scenarios selected. The weather conditions defined for night are more stable than for

day, and include the very stable 1.5 m/s F condition that is not modelled for day. Dispersion distances are longer in stable conditions, and this has a noticeable effect on the size of the risk contours.

You can see that the risk contours are centred on the chlorine sphere, although there is a small contour centred on the propane sphere.

Viewing the individual risk ranking results for the school

This section is not relevant to Safeti Lite because the risk ranking results are not available in Safeti Lite.

The school is only inhabited during the day, so you will view the results for the Day Run Row only. To view the results, take the following steps:

1.Right-click on the Day row in the Run Row Selector and select the IR Ranking Grid results.

2.Move through all of the screens in the Results Selection Wizard dialog, taking the default selection in all screens except two:

In the Risk ranking point selection screen, deselect the Nearest houses point. In the Vulnerabilities selection screen, deselect the Indoor vulnerability.

3.Click on Finish in the final screen to view the results.

4.Expand the grid down to the fourth level, which shows the contributions from individual Scenarios as shown.

These results show that 99.98% of the individual risk at the school comes from the rupture of the chlorine sphere.

The rest of the risk comes from ruptures of the chlorine tank wagon, with different levels of contribution from different locations along the route (identified by the Location Index).