6.63. When assessing the impact of human intrusion, consideration should be given to the volumes of waste that might be affected by the different types of intrusion and to the heterogeneity of the waste. Potentially significant heterogeneities (‘hot spots’) may occur and their impacts need to be assessed. On a large scale, such differences in activity concentrations of the waste may result from a number of factors, including changing waste acceptance criteria with time or different waste emplacement campaigns being dominated by specific waste streams. On a smaller scale, some waste packages may contain particular items that have significantly greater activity concentration (e.g. disused sealed sources) than the average for all waste packages. Heterogeneities in the waste should be assessed by performing a range of calculations that take due account of the possible range of activities and compositions of waste. The volumes of waste that might be affected in the event of intrusion should also be assessed.