Re-determination and re-evaluation of the f and α parameters in channels Y4 and S84 of the BR1 reactor, for use in k0-NAA at DSM Research

Since the introduction of k0-based NAA as an analytical tool in 1989, all irradiations by DSM Research are done in channels Y4 and S84 of the BR1 reactor in Mol (Belgium). The last determination of f and α-values for these channels was performed in 1993. Although the configuration of the reactor did not change over all these years and therefore no change in f and α was to be expected, DSM Research decided to re-determine both parameters in both channels. Having much experience in this field, the INW k0-group was asked by DSM Research to perform this re-determination, in co-operation with the SCK, Mol. As the flux in channel Y4 is not constant during the start up and the scramming of the reactor, a numerical integration method was applied. This is a new approach in comparison with all previous reported data from DSM Research, where this change in flux was not taken into account. For the work presented here, use was made of the most recent nuclear data available in the literature.