Location and sizing of a plant stack: Design study using CFD

摘要

The effect of the presence of a stack on the ground level concentration of emissions near the plant is to significantly decrease the concentrations (in practical cases of interest, by a factor of 5-10), while the presence of nearby plant buildings is to partly eliminate this beneficial effect due to the effect of the building wake. The author of this paper believes that the practical methods currently used for the evaluation of ground concentrations in these cases deserve some improvement. One line of development here suggested is the use of Computer Fluid Dynamics (CFD) codes. The author believes that presently available Code Packages in this field are sufficiently accurate. A number of case studies are presented in this paper, with the aim of encouraging the use of these rather simple methods of study. Moreover, a comparison of calculation results with a field test results confirms also the quantitative reliability of the calculation method here proposed. The main conclusions of this exercise could be the following: - The use of CFD Computer Codes seems suitable for atmospheric dispersion calculations of interest to the nuclear plant designer and safety analyst; in particular, for design studies aimed at the definition of nuclear plant and stack arrangements, the result of this exercise seem to indicate that the methods here used are completely suitable for the comparison of various solutions. - The use of CFD codes may avoid wrong decisions, like the elimination of a stack in the design of a nuclear plant; excessive and detrimental over-conservatism can also be avoided. - When adequate guidance is provided, as this paper attempts to do (Appendix), the CFD calculation methods are rather robust and simple to perform.