Numerical computer program for calculation of the concentration pattern of hydrogen gas depending on time and height in boreholes for disposal of heat producing MAW wastes and HTR fuel elements in salt deposits

This report deals with two numerical models for computing the transport of hydrogen gas and air through granulated salt material embedding a column of waste containers in a borehole. Primarily, the differential equations for the description of the transport of hydrogen gas and air are introduced. For the solution of these computer codes are developed. The concentration of hydrogen gas depending on time and height in the column and the release of hydrogen gas from the top of the salt-column can be computed with these codes. Atmospheric pressure variations on the upper boundary of the salt column are simulated by sinus-functions. Additionally, model I - assuming the waste column being of constant height - is designed to compute the pressure distribution as a function of time in the surrounding salt-filled annulus. The high gas-permeability of the granulated salt material allows a very fast penetration of the variations of atmospheric pressure. So only very small pressure differences in the salt-column are predicted. In modell II instantaneous pressure dispersion is assumed. Additionally, modell II is designed to variate the height of the waste column during the deposition process in the borehole. (orig./HP)