The 20 MW Special Purpose Reactor (SPR) is a heat pipe cooled microreactor that was designed for electricity production in remote locations where reliable power grids are not always available. The key to the SPR is the alkali metal heat pipes, which offer entirely passive operation capacity with high mobility. Prior to deployment, safety analyses for postulated accident scenarios are required for the licensing of the SPR. For instance, the failure of a heat pipe during system operation has the potential to put neighboring heat pipes in jeopardy. The prediction of a potential "cascade failure" of multiple heat pipes is essential to assess the safety of the system. However, understanding and predicting the performance of heat pipes is challenging due to the complex nature of two-phase flows within the heat pipe core and wick structure. Therefore, in order to develop and validate heat pipes models, high-fidelity experimental data is needed to gain insight into the behaviour of individual heat pipes and in the integral effects of heat pipes arrays. High-resolution experimental data on the behavior of single heat pipes were measured at the MIchigan single SOdium Heat pipe separate-effect (MISOH1) test facility [8]. To investigate the effects of multiple heat pipes, the MIchigan SOdium Heat pipe bundle (MISOH2) test facility was built at the University of Michigan. The facility consists of ten sodium heat pipes, with heat pipes and heating elements arranged at the center and vertices of a hexagonal lattice, respectively. The cooling intensity in the condenser section of each heat pipe can be individually controlled with variable double channel heat exchangers using both air and water as cooling fluids. The experimental results can provide valuable insights for the design and operation guidance of the SPR, as well as for heat pipe codes validation.