Emplacement drift temperature reduction by cooling enhancement and ventilation

The application of cooling enhancement in a short vertical container emplacement layout is analyzed. Two 25 m-long heat pipes upward oriented at 45 degrees are installed at each emplacement borehole to promote heat transport into the pillar area. In addition, ventilation of the emplacement drifts is assumed for a period for two to twenty years. It is concluded that the maximum borehole temperature can be reduced from 230 degrees C to 136 degrees C using only the heat pipes, and to 110 degrees C applying the heat pipes together with moderate air cooling. The ventilation alone without heat pipes can only reduce the temperature to around 200 degrees C. It is also demonstrated that the heat transferred from the container area to farther distances into the pillar raises rock temperatures significantly, by 10-20 degrees C, and the increase in temperature remains noticeable for at least a 1000 years. In addition, due to the more efficient heat distribution caused by the heat pipes, it shown that it is possible to store more waste in the same repository area, together with decreased hot-spot temperatures. Based on these results, it is expected, that as a result of using heat pipes, there will be decreased thermal cycling in the container area together with improved drying, and permanent as well as temporary water removal in the pillar area