Abstract

Ensuring the thermal stability of heat-generating nuclear waste glass canisters in interim storage and the thermal stability of bentonite in the deep geological repository are crucial to preserving the function of the waste form. Yet thermal stability might be challenged by further heated air conditions and excessive heat load in the waste form, such that the maximum temperature would be higher than the glass transition temperature undesirably. The finite element method was carried out for the n × n × 4 (n = 1, 3, 5) multicanister system for the sake of predicting the maximum temperatures of interim storage. The internal heat source amount and exiting air temperature of the system were varied to see different storage environments. The maximum heat load of a 15.8 kW/m³ canister was in a safe range (glass transition temperature of 500°C), whereas an 18.6 kW/m³ canister was not. There is a possibility to extend thermal stability to a system larger than n = 5 for 15.8 kW/m³ based on the converging maximum temperature trends. Besides, the maximum temperature of the canister and bentonite clay in a deep geological repository is potentially below the thermal criterion if the canister cools down for about 65 to 70 years.

摘要

确保临时储存的发热核废料玻璃罐的热稳定性和深地质处置库中膨润土的热稳定性对于保持废物形态的功能至关重要。然而，热稳定性可能会受到进一步加热的空气条件和废物形式的过度热负荷的挑战，使得最高温度会不希望地高于玻璃化转变温度。为了预测临时储存的最高温度，对 n × n × 4 (n = 1, 3, 5) 多罐系统进行了有限元方法。系统的内部热源量和出风温度因存储环境不同而不同。最大热负荷为 15.8 kW/m ³碳罐处于安全范围内（玻璃化转变温度为 500°C），而 18.6 kW/m ³碳罐则不是。基于收敛的最高温度趋势，对于 15.8 kW/m ³的系统，有可能将热稳定性扩展到大于 n = 5 的系统。此外，如果罐冷却约 65 至 70 年，深地质处置库中罐和膨润土的最高温度可能低于热标准。