Evolution of temperature and humidity in an underground repository over the operation period

Abstract

The aim of the study is to describe the ambient conditions in an underground repository of nuclear waste over a 100-year-long operation period. The evolution over time of the moisture and the temperature in the ventilation network was assessed by means of numerical simulations. Condensation events are described in terms of location, frequency and flow rate. The physical conceptual model takes into account the heat and vapour advection and exchanges with walls, and heat conduction through the host rock. The results of simulations were analysed to highlight how the architectural design, the gradual extension of storage zones, the ventilation rate and the weather conditions are likely to influence the ambient conditions all along the shafts, the galleries and the storage modules. They illustrate the significant effects on ambient conditions of the wall thermal inertia, the variation in atmospheric pressure over the shaft height, and the ventilation partition in some galleries between incoming and outgoing air from storage modules.

A Review of Ventilation and Environmental Control of Underground Spaces

“…Ventilation can transport weather fluctuations in moisture, and moisture exchange within walls can help to partly buffer weather temperature fluctuations. They will be progressively smoothed out as the distance from the inlet increases [10]. In the winter, outdoor air with low humidity can be supplied to remove moisture from underground spaces.…”

“…They noted that a direct air shaft outperformed an inclined air shaft. Architectural design, gradual extension of storage zones, ventilation rates, and weather conditions, which are likely to influence ambient conditions along shafts, galleries, and storage modules, should all be considered when designing ventilation for an underground repository [10]. The piston effect allows tunnels and platforms to be ventilated, which saves energy.…”

RTM for Waste Repositories

“…The hydraulic transient is also impacted upon by the ventilation systems used during the operation period to ensure adequate gallery aeration for the workers and for the infrastructure. It will create heat and vapor exchanges with walls and storage packages, pressure variations and evaporation, and sometimes vapor condensation (Benet et al 2014b). Mechanical effects can be induced during construction and excavation of underground drifts that will cause both tunnel convergence (Lisjak et al 2015) and damage to the rock in the vicinity of the opening, with the formation of an associated excavated disturbed zone (EDZ) (Armand et al 2014).…”

Ventilation and environmental control of underground spaces: a short review

“…The train piston effect is also important, which may help to reduce energy consumption. Ventilation design for underground repository should consider architectural design, gradual extension of storage zones, ventilation rates and weather conditions, which are likely to influence ambient conditions along shafts, galleries and storage modules [33].…”