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The small PWR has been paid more and more attention due to its diversity of application and flexibility in the site selection. However, the large core power density, the small containment space and the rapid accident progress characteristics make it difficult to control the containment pressure like the traditional PWR during the LOCA. The pressure suppression system has been used by the BWR since the early design, which is a suitable technique that can be applied to the small PWR. Since the configuration and operating conditions are different from the BWR, the pressure suppression system should be redesigned for the small PWR. Conducting the experiments on the scale down test facility is a good choice to reproduce the prototypical phenomena in the test facility, which is both economical and reasonable. A systematic scaling method referring to the H2TS method was proposed to determine the geometrical and thermohydraulic parameters of the pressure suppression containment response test facility for the small PWR conceptual design. The containment and the pressure suppression system related thermohydraulic phenomena were analyzed with top-down and bottom-up scaling methods. A set of the scaling criteria were obtained, through which the main parameters of the test facility can be determined.

• Based on the H2TS scaling method, three groups of experimental facilities, namely prototype, 1/2 model and 1/4 model, were designed and built, and the proportional reduced-height scaling experiment was carried out. • The scaling distortion of natural circulation steady-state characteristics was described. • The relation curves between the dimensionless parameters such as Reynolds number, equivalent resistance coefficient, Grashof number and modified Grashof number were described in detail. Based on the H2TS scale-down method, three groups of experimental facilities, namely prototype, 1/2 model and 1/4 model, were designed and built. Natural circulation experiments on different pressure and heating power were carried out. The distortion of natural circulation steady-state characteristics in the reduced-height scale-down method is analyzed. The experimental results show that: The relation curves between the dimensionless parameters such as Reynolds number, equivalent resistance coefficient, Grashof number and modified Grashof number, which represent the main characteristics of natural circulation, are not seriously distorted in reduced-height scaling simulation. The fitting curves of these dimensionless numbers between prototype and model can be mapped. The steady state characteristics of natural circulation can accurately reproduce the prototype in the process of scale-down proportional modeling. [ABSTRACT FROM AUTHOR]

Based on the H2TS (Hierarchical, two-tiered Scaling) scaling method, three groups of experimental facilities, namely prototype, 1/2 model and 1/4 model, were designed and built, and the reduced-height proportional scaling experiment was carried out. The scaling distortion of natural circulation flow and its influencing factors were analyzed. The experimental results show that the natural circulation flow rate and heating power generally show an exponential relationship. The m values of the prototype, 1/2 model and 1/4 model facilities are basically consistent. The reduced-height scaling 1/2 model and 1/4 model can reproduce the natural circulation flow of the prototype, but there is a maximum distortion of about 20%. The scaling distortion of natural circulation flow rate is less affected by loop resistance coefficient, system pressure and heating power. [ABSTRACT FROM AUTHOR]

• Aerosol Spent Fuel Pool scrubbing phenomena was analyzed. • PIRT of containment depressurization venting process was developed. • H2TS was used to complete the scaling analysis of SFP scrubbing phenomena. For the Chinese Advanced Passive Pressurized Water Reactor, one of the possible containment depressurization measures is to discharge to the Spent Fuel Pool (SFP) during severe accidents. During containment depressurization venting process, carrier gas with aerosol is injected into the SFP from the containment through a discharge sparger. To obtain the aerosol retention effect during this process, a scaled-down test facility have been designed and built. In this paper, the Phenomena Identification and Ranking Tables (PIRT) in the discharge pipe and the SFP is developed. Then, based on the Hierarchical Two-tiered Scaling analysis (H2TS) method, the scaling analysis of SFP scrubbing phenomena is completed. A jet flow model and a particle retention model are developed to analyze these important phenomenon, and a series of similarity criteria are obtained. Based on these similarity criteria, the CASSI test facility is designed, and the scaling rationality is evaluated. [ABSTRACT FROM AUTHOR]