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The Purdue NMR (Novel Modular Reactor) represents a BWR-type small modular reactor with a significantly reduced reactor pressure vessel (RPV). Specifically, the NMR is one third the height and area of a conventional BWR RPV with an electrical output of 50 MWe. Experiments are performed in a well-scaled test facility to investigate the thermal hydraulic flow instabilities during the startup transients for the NMR. The scaling analysis for the design of natural circulation test facility uses a three-level scaling methodology. Scaling criteria are derived from

For a CO 2 ingress accident into liquid sodium in a supercritical CO 2 power conversion system coupled with a sodium-cooled fast reactor, we investigated two major design issues: i) a wastage phenomenon in regard to structural damage adjacent to the leaking position, and ii) potential channel plugging due to the formation of a particulate reaction product. In order to understand the factors affecting the occurrence of these issues, two kinds of experiments were carried out: a wastage effect test and a self-plugging test. All experimental conditions were chosen to reasonably represent the normal operating conditions and realistic design parameters of the reference plant. The test results indicate the absence of wastage, which will not lead to additional tube ruptures and damage propagation. In the current experiment, the self-plugging of PCHE channels only took place under two limited conditions: i) the sodium temperature is over 500 C and ii) the equivalent diameter of the crack opening is less than 1.5 mm with a small leakage rate of far less than 1 g/s of CO 2 ingress.

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One of the benefits of the supercritical CO 2 Brayton cycle in Sodium-cooled Fast Reactors is an enhanced plant safety, since potential reactions of CO 2 with liquid sodium have been reported to be less stringent than a sodium-water reaction found in the Rankine cycle. However, moderate chemical interactions between CO 2 and liquid sodium make detecting CO 2 ingress accidents harder. Thus, this paper proposes a new physics-based detection algorithm by comparing the real-time pressure measurements of two identical heat exchangers for the early detection. The CO 2 ingress occurs owing to a crack at the pressure boundary wall, a certain self-recovery of structural damage does not happen over time, and an accident probabilistically starts at only one component of two. The proposed physics-based method with the probabilistic analysis was compared to the pure data-based method. Finally, the damage degradation was developed with a simplified mass and energy transfer model, and the proposed algorithm was verified with experimental data. The results show that a 99.99% detection probability can be achieved for the air ingress of 30 cc/s, which is equivalent to the 0.12 g/s CO 2 ingress, in a 70 s detection time, limiting down to 0.1% false alarms due to sensor noise.

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