IVR策略下反应堆压力容器变形数值模拟

堆内熔融物滞留技术(In-Vessel Retention, IVR)是我国三代核电厂设计中广泛采用的严重事故的缓解策略，其成功的关键在于反应堆压力容器(Reactor Pressure Vessel, RPV)外壁面导出热量高于堆内衰变热。在堆内高温熔融池的作用下，RPV会发生明显的热膨胀并导致外壁面冷却流道形状改变，从而对局部换热情况产生影响。为了提供RPV外壁面换热研究的输入条件，通过COMSOL多物理场耦合计算软件搭建了一个热工水力和固体力学耦合计算模型，研究了严重事故下RPV的热膨胀形变情况。结果表明：对于双层熔融池结构，在RPV外部实现冷却条件下，下封头区域的热膨胀形变将导致外冷却流道宽度将减小13 mm~17 mm，在工程设计中应予以考虑；内压对RPV膨胀形变影响明显，严重事故后对一回路泄压是IVR策略成功的重要因素之一。

Simulation of Reactor Pressure vessel deformation under IVR strategy

In-Vessel Retention (IVR) is widely used as the mitigation strategy for severe accident in the design of China third-generation nuclear power plants. The key to the success lies of this strategy is the heat dissipation from the outer wall of the reactor pressure vessel (RPV) higher than the decay heat. Under the action of the high temperature corium pool in the reactor, Significant thermal expansion of the RPV will occurs and the shape of the cooling channel outside the RPV will be extruded, which may affect the local heat transfer. In order to provide the input conditions for the heat transfer study of cooling channel, a thermal-hydraulic and solid mechanics coupling calculation model was built through the COMSOL multiphysics coupling calculation software to study the thermal expansion and deformation of the RPV under severe accidents. The results show that: for the double-layer corium pool under the cooling condition of the RPV, the outer cooling channel will be extruded 13 mm~17 mm, which should be considered in the engineering design;the internal pressure have a obvious influence on the expansion and deformation of the RPV, depressurizing of the primary circuit after a serious accident is one of the keys for the success of the IVR strategy.