中、低放核废料贮存容器失效的概率评判

Probabilistic assessment of failure for low-medium level nuclear waste storage container

为了评判混杂纤维混凝土核废料贮存容器的耐久性,依据试验优选掺加聚丙烯纤维(用量为0.9kg/m3)、长度为20mm的玄武岩纤维(用量为2.5 kg/m3)的混杂纤维混凝土(抗压强度为67.8MPa,抗拉强度为6.32MPa)作为贮存容器材料。采用ANSYS分析贮存容器在300年服役期内时变衰变热-力耦合作用下,沿容器壁厚方向的应力分布规律,模拟结果表明:径向应力较小,轴向应力均为压应力,环向最大拉应力为抗拉强度的57%。运用蒙特卡洛分析法求得核废料衰变热引起的温差在容器内产生的拉应力频率均值和标准差,考虑贮存容器抗力随时间的折减,得到容器300年服役期内的失效概率曲线,结果表明:曲线呈上升趋势,150年内增加幅度平缓,150年至300年内增长速度加快,300年时失效概率达到0.176。本文研究为评判中、低放核废料贮存容器的耐久性提供了定量依据。

This paper reports a study based upon experimental investigation and analytical simulation which assesses the durability of hybrid fiber reinforced concrete for nuclear waste storage container.According to the test results,mixed with polypropylene fibers(0.9kg/m 3) and 20mm basalt fiber(2.5kg/m 3) as the storage container material,its compressive strength is 67.8MPa,the tensile strength is 6.32MPa.The software Ansys is used to analyze the temperature stress distribution of the container wall thickness direction under the decay heat-force coupling in 300 years: radial stress is small,axial stress is the compressive stress and the ratio of maximum hoop tensile stress to tensile strength is 0.57.At last mean and variance of tensile stress arise from decay are solved by Monte Carlo method,strength reduction of stress are considered in 300 years,the increasing curve of probability of failure are given.The curve shows ascendant trend,the growth rate of failure probability is relatively slow in 150 years,and speed up in150~300 years and finally reaches 0.176 which provides a quantitative basis for the evaluation of low-level nuclear waste storage container durability.