The Monte Carlo particle transport code of CEA
In order to assess the reliability of the simulation results obtained for the CP-1 model, we have performed an extensive sensitivity analysis, covering both the effect of the nuclear data library and the impact of the technological uncertainties. Furthermore, we have quantified the temperature effect.
Sensitivity to technological data
In order to substantiate our analysis, we have also somputed the sensitivity coefficients corresponding to variations in the density of the main materials used in CP-1, encompassing the fuel, the moderator and other structural materials (graphite in the pier and wood in the scaffold and in the filler). The methods used in TRIPOLI64 to compute first-order sensitivities is based on the IFP technique. The results are reported in the following table.
Sensitivity coefficients for density variations of several materials of CP-1, including fuel, moderator, and structures.
During the operation of CP-1, the temperature effect was measured by opening a window and letting the pile cool down by about 10 degrees. The adjustment of the control rod position, based on the calibration of the control rod worth that had been estimated close to the critical point, gave an estimate of about -3 pcm/K. We have computed the temperature effect with TRIPOLI-4 and we have obtained the values reported in the following table. The overall effect for the whole reactor is in good agreement with the experimental measurement.
Temperature effect for the pile components and for the whole reactor, as estimated by TRIPOLI-4.
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