<p>The research presented in this dissertation investigates the influence of soil-structure<br>
interaction on seismic isolation of nuclear reactor vessels using numerical simulations. This<br>
research is motivated by the nuclear industry searching for viable solutions to standardize<br>
the design of reactor vessels. Seismic isolation of reactor vessels is a potential solution as it<br>
enables deployment of standardized reactor vessels irrespective of site seismic hazard<br>
thereby saving time and cost by allowing large-scale factory fabrication of standard<br>
modules and by eliminating the need for repeated approval of reactor vessel design. Seismic<br>
isolation is also a technology that has matured from successful implementation in buildings<br>
and bridges allowing easier transition to nuclear applications. Currently, the<br>
implementation of component-level seismic isolation in nuclear industry is challenging due<br>
to gaps in research and lack of specific guidelines.</p>
<p><br></p>
<p><br>
In this research, the effectiveness and potential limitations of using conventional friction<br>
pendulum bearings for component-level isolation are investigated based on conceptual<br>
numerical models of seismically isolated reactor vessels at different nuclear power plant<br>
sites subject to a variety of ground motions. The numerical modeling and analysis<br>
approach presented in this research are checked using experimental data and results from<br>
multiple numerical codes to ensure reliability of the obtained analysis results.</p>
<p><br></p>
<p><br>
Within the scope of this study, it is found that slender vessels are particularly vulnerable<br>
to rotational acceleration at the isolation interface. Rotational acceleration at the isolation<br>
interface is caused by rotation at the foundation level of the containment building housing<br>
the isolated reactor vessel and by excitation of higher horizontal translational modes of the<br>
seismically isolated system. Rotation of the building foundation increases with decrease in<br>
shear wave velocity of the soil surrounding the building foundation. When the containment<br>
building is embedded below the soil surface, the effect of embedment on peak horizontal<br>
acceleration of the isolated vessel depends on the amount of increase in shear wave velocity<br>
at the foundation level of the building. When embedment does not result in any change in<br>
shear wave velocity, it is found to have negligible impact on the acceleration response of the<br>
isolated vessel.</p>
<p><br></p>
<p> The optimum location to support a vessel for seismic isolation is found to be on a plane<br>
passing through its center of mass. It minimizes horizontal acceleration in the isolated<br>
vessel as well as the tendency of isolator to uplift. Isolator uplift and exceedence of<br>
displacement capacity of the isolator during extreme events are possible drawbacks in using<br>
seismic isolation technology since they produce impact forces due to uplift and<br>
re-engagement of the isolator or due to collision between the isolated system and the moat<br>
wall. If such cases are avoided, seismic isolation of reactor vessel could provide more than<br>
50% reduction in peak acceleration of vessel except for low-intensity motions that do not<br>
engage the isolator.<br>
<br>
</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/20369094 |
| Date | 26 July 2022 |
| Creators | Samyog Shrestha (13149003) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/Seismic_isolation_of_nuclear_reactor_vessels_considering_soil-structure_interaction/20369094 |
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