CAJ | 학술논문

乏燃料干法后处理中高温熔盐化学工艺过程中存在设备腐蚀问题，以凝固盐层作为容器保护内衬的熔盐冷冻壁技术被认为是一种可行的解决方式。为开展该技术研究，自行研制并搭建了一套硝酸盐(40.0-7.0-53.0wt%NaNO2-NaNO3-KNO3)冷冻壁技术研究实验装置。该装置上熔盐运行温度150?250oC，熔盐最大流量500 L·h?1，循环导热油运行温度5?120oC，导热油流量1.5?15 m3·h?1。目前在该装置上开展了冷冻壁静态形成及平衡维持等工艺研究，实验中采用容器外壁循环导热油冷却换热实现冷冻壁的形成及维持，并试验了冷冻壁技术在熔盐静态工况下应用的工艺条件。冷冻壁形成平均速率可控制在0.2?0.5 mm·min?1。在冷冻壁静态形成过程中，随厚度增大，热交换量逐渐减小，同时冷冻壁层温差逐渐增大，并均呈衰减趋势变化；处于平衡维持状态时，径向温度分布、热流量及冷冻壁厚度均保持稳定，熔盐发热功率即为平衡状态时的热流量，其大小同时与外壁导热油的冷却热流量相等；实验还获得了较理想的静态应用工艺操作条件，为氟化物熔盐冷冻壁的研究及应用积累了经验。
핍연료간법후처리중고온용염화학공예과정중존재설비부식문제，이응고염층작위용기보호내츤적용염냉동벽기술피인위시일충가행적해결방식。위개전해기술연구，자행연제병탑건료일투초산염(40.0-7.0-53.0wt%NaNO2-NaNO3-KNO3)냉동벽기술연구실험장치。해장치상용염운행온도150?250oC，용염최대류량500 L·h?1，순배도열유운행온도5?120oC，도열유류량1.5?15 m3·h?1。목전재해장치상개전료냉동벽정태형성급평형유지등공예연구，실험중채용용기외벽순배도열유냉각환열실현냉동벽적형성급유지，병시험료냉동벽기술재용염정태공황하응용적공예조건。냉동벽형성평균속솔가공제재0.2?0.5 mm·min?1。재냉동벽정태형성과정중，수후도증대，열교환량축점감소，동시냉동벽층온차축점증대，병균정쇠감추세변화；처우평형유지상태시，경향온도분포、열류량급냉동벽후도균보지은정，용염발열공솔즉위평형상태시적열류량，기대소동시여외벽도열유적냉각열류량상등；실험환획득료교이상적정태응용공예조작조건，위불화물용염냉동벽적연구급응용적루료경험。
Background:As corrosion of processing equipment from the high aggressive reagent is a serious problem during the pyroprocessing, the molten salt frozen-wall is proposed as an option for protecting the metallic walls from corrosion by a layer of frozen salt.Purpose:In order to study this means of corrosion protection, the research on the formation and controlling of molten salt frozen-wall was carried out.Methods: Nitrate molten salt (melt point: 142 oC) was used as the research medium and heat transfer oil was adopted as coolant. An experimental platform for the research of molten salt frozen-wall was built, which contains an up-flow tapered test tank covered with heat exchange jacket. The frozen-wall was formed and maintained by controlling the internally heating and the cooling of outer part of the test tank. The thickness of frozen wall was directly measured by caliper and also figured out by the measured temperatures.Results:The operation temperature of molten salt ranges from 150 oC to 250 oC; the maximum flowrate of molten salt is 500 L·h?1; the operation temperature of heat transfer oil ranges from 5 oC to 120 oC; and the flowrate of oil ranges from 1.5 m3·h?1 to 15 m3·h?1. Under the expected operating conditions, a layer of frozen can be easily and predictably deposited and maintained on surfaces contacted by the salt. The molten salt frozen-wall was adherent and stable. The average formation rate ranges from 0.2 mm·min?1 to 0.5 mm·min?1. The heat flow decreases with the thickness increasing during the process of formation, at the same time temperature difference through frozen-wall layer gradually increased, and the change trends are all damped. The frozen-wall could reach static equilibrium by controlling the heat transfer rate. When frozen-wall is in a state of balance, the temperature gradient and the thickness of frozen-wall are constant; the decay heat of fission produces simulated by heating rod is equal to the heat flow through frozen-wall layer, and is also equal to the cooling power of heat transfer oil. We also simulated the real application scenarios to test the operation parameters and get some good results.Conclusion:All the research results would be helpful for the developing of fluoride molten salt frozen-wall technology.