SUMMARY

The Integral Inherently Safe Light Water Reactor (I2S-LWR) is a large pressurized water reactor that includes primary-to-secondary coolant heat exchangers located in the downcomer of the reactor pressure vessel. This integral configuration, which is often proposed in small modular reactor concepts, eliminates the possibility of large line-break accidents, reduces primary coolant inventory, and does not require large external steam generators. A microchannel heat exchanger (MCHX) configuration is selected to meet the limited volume and high heat duty requirements of this design. The thermal-hydraulic performance of a liquid-liquid and liquid-boiling (steam generating) MCHX is modeled using empirical correlations from the literature and the design is optimized to meet the I2S-LWR requirements. A test facility and a representative MCHX test section were constructed to validate the assumptions and modeling techniques used in the I2S-LWR design. Experimental heat duty and pressure drop are compared to model predictions. In addition, heat transfer coefficients, friction factors, and other important parameters are extracted from the data and compared with correlations from the literature when possible.