Nuclear reactors are built with many inherent and engineered safety features with defence in depth philosophy, to maintain integrity of core during normal as well as accidental conditions. However, a severe accident scenario such as hypothetical core meltdown has to be considered in safety analysis of the plant, towards demonstrating a safe and coolable geometry of degraded core. Progression of corium, its subsequent interaction with coolant and settlement in the reactor vessel determines the extent of core damage and needs thorough investigation for ensuring safe mitigation of the accident. A comprehensive experimental program has been taken up at IGCAR to investigate severe accident phenomena in Sodium cooled Fast Reactors (SFR). Highly exothermic thermite reaction is used to generate a high temperature melt consisting of ceramic and iron simulating the corium. A dedicated test facility ‘THEME’ has been setup and few small scale simulation experiments were conducted to study various phenomena like subassembly melting, corium interaction with coolant and settlement of debris on corecatcher.

核反应堆的建造具有许多固有的和设计的安全功能，具有纵深防御理念，以在正常和意外条件下保持堆芯的完整性。然而，在工厂安全分析中必须考虑严重事故场景，例如假设的堆芯熔化，以证明退化堆芯的安全和可冷却几何形状。真皮的进展、随后与冷却剂的相互作用以及反应堆容器中的沉降决定了堆芯损坏的程度，需要彻底调查以确保安全减轻事故。IGCAR 已开展一项综合实验计划，以研究钠冷快堆 (SFR) 中的严重事故现象。高度放热的铝热反应用于生成由陶瓷和铁组成的高温熔体，模拟了真皮。一个专门的测试设施“THEME”已经建立，并进行了少量的小规模模拟实验来研究各种现象，如组件熔化、真皮与冷却剂的相互作用以及碎屑在取芯器上的沉降。