Effects of ventilation and backfill on a mined waste disposal facility Original Research Article

The effects of ventilation and backfill on the temperature and relative humidity of waste packages in a mined underground nuclear waste disposal facility are evaluated. The evaluations account for ventilation of the underground drifts for the first 100 years and emplacement of crushed unconsolidated backfill in the drifts after 100 years. Three areal mass loading (AML) strategies are evaluated: 20, 40, and 80 tU acre−1 (MTU acre−1). It is found that ventilation decreases the peak waste package temperature by 10°C for the 20 MTU acre−1 case, by 15°C for 40 MTU acre−1, and by 42°C for 80 MTU acre−1. The flow of moisture is minimal for below boiling conditions and increases greatly for above boiling conditions. Even for the lowest AML of 20 MTU acre−1, a dry-out zone of 3.3 m radius surrounding the drifts develops and for the highest thermal loading of 80 MTU acre−1 as much as 8.6 m is dried. The emplacement of low conductivity backfill significantly increases waste packages temperature by over 100°C and leads to low relative humidity to 10 000 years.