Development of system design and seismic performance evaluation for reactor pool working platform of a research reactor

The reactor pool working platform (RPWP) has been newly designed for an open-tank-in-pool type research reactor, and its seismic response, structural integrity, serviceability, and seismic margin have been evaluated during and after seismic events in this paper. The main important concept of the RPWP is to minimize the pool top radiation level by physically covering the reactor pool of the open-tank-in-pool type research reactor and suppressing the rise of flow induced by the primary cooling system. It is also to provide easy handling of the irradiated objects under the pool water by providing guide tubes and refueling cover to make the radioisotopes irradiated and protect the reactor structure assembly. For this concept, the new three dimensional design model of the RPWP is established for manufacturing, installation and operation, and the analytical model is developed to analyze the seismic performance. Since it is submerged under and influenced by water, the hydrodynamic effect is taken into account by using the hydrodynamic added mass method. estigate the dynamic characteristics of the RPWP, a modal analysis of the developed analytical model is performed. To evaluate the structural integrity and serviceability of the RPWP, the response spectrum analysis and response time history analysis have been performed under the static load and the seismic load of a safe shutdown earthquake (SSE). Their stresses are analyzed for the structural integrity. The possibility of an impact between the RPWP and the most adjacent structure is investigated for the serviceability. The analysis results show that the maximum stress values of the base frame, guide tubes and refueling cover of the RPWP under the seismic event are within the specified code limits. It is confirmed that an impact does not take place under a seismic event. Also, the seismic margin of the RPWP is studied, and the seismic limit to sustain the structural integrity and serviceability is attained based on the deterministic and probability methods. Lastly, the hydrodynamic effect on the seismic performance of the RPWP is quantitatively investigated and from the result, an objective basis of the consideration of the hydrodynamic influence is acquired. Therefore, it is concluded that the newly devised RPWP is safely designed in that no damage to the structural integrity and serviceability, and a sufficient seismic margin is expected.