Merits of ventilation for the proposed repository at Yucca Mountain

摘要

The current conceptual design of the proposed repository assumes that the emplacement drifts are continuously ventilated with a low air flow of 0.1m~3/s for up to 100 years.Although this design provides low relative humidity during pre-closure,the moisture transport by ventilation is not capable of maintaining a deficit in the overall water inventory beyond the first 30 years,if a water percolation rate of 10 mm/year is assumed.Water will accumulate over the repository horizon,since the rock temperature in the pillar area will most likely be above the boiling point for several hundred years,making the pillar area inaccessible for water seepage.This water accumulation during pre-closure generates a disadvantageous initial condition for post-closure,during which,for a period of several thousand years,the return of water increases relative humidity up to saturation.Another disadvantage of the ventilation with a low air flow is that no benefit is achieved in reducing the maximum drift wall or air temperatures averaged spatially over an emplacement period whden compared to a completely sealed repository.Therefore,ventilation with a low airflow does not contribute significantly to the solution to the heat and mositure removal,thus the psychrometric,corrosion,and waste containment problems of the proposed repository.