Measuring the relevance of factors in the occurrences of events

A new way to compare the relevance of the different factors intervening in the occurrences of an event is presented and developed in this paper. The idea behind the method comes from cooperative game theory but the focus is slightly different because factors are not necessarily rational decision-makers and because the only data available are obtained by repetition of the event. The concept of relevance measure for a factor in a set of data is introduced, some significant examples are given and the main properties of relevance measures are defined and studied. One of these measures, the fair measure, is proved to have interesting properties which characterize it. Two real world situations, one about traffic accidents and the other one about mining accidents, both of them with real data, are used to show the use of relevance measures to compare factors in each one of these events.     

The determination of 134Cs and 22Na diffusion profiles in granodiorite using gamma spectroscopy

Spent nuclear fuel repository safety evaluation today requires both laboratory and in situ field work in order to assess the parameters affecting the sorption and diffusion of radionuclides. Recent investigations at the Grimsel test site suggest that non-conservative errors in transport properties derived from laboratory scale experiments can lead to over-conservative estimates of matrix diffusion depths. As a result, the geosphere’s capability to retain radionuclides may be underestimated. In this study the in situ diffusion and the sorption of ¹³⁴Cs and ²²Na into granodiorite were determined using gamma spectroscopy. Autoradiography was used to reveal the minerals into which the radionuclides were sorbed. A rock sample was obtained from the Grimsel underground in situ diffusion test site in Switzerland. In the in situ test, a solution containing several different radionuclides was circulated continuously in a packed-off injection hole for two years and three months in order to study diffusion of the radionuclides into the surrounding bedrock. The gamma measurements show that in the course of the experiment ¹³⁴Cs diffused 2.5 cm and ²²Na 10 cm into the rock matrix, respectively. Caesium was found to have sorbed on mafic minerals biotite and chlorite. Results of this study were used in order to calculate an in situ effective diffusion coefficient for caesium and sodium in Grimsel granodiorite.