Evaluation of inherent distortions in the IIST facility using the RELAP5/MOD3 code

The Institute of Nuclear Energy Research (INER) integral system test (IIST) facility is a reduced-height, reduced-pressure test facility constructed at INER that is used to simulate the thermal hydraulics of the Maanshan nuclear power plant (NPP). A small-scaled facility is not capable of simulating all the physical phenomena of an NPP because the behavior of an NPP during accidents is very complicated. Proper scaling then plays an important role in the design of a test facility to ensure the usefulness and applicability of experimental data obtained from a small-scaled facility. However, distortions caused by necessary compromises in the design and construction of a small-scaled test facility exist. The analysis here evaluates whether the inherent distortions in the IIST facility will distort the thermal-hydraulic behaviors of a natural-circulation experiment and influence the usefulness and applicability of the experimental data. Based on the current calculations, the IIST experimental results are found to be partially distorted. Appropriate consideration of and correction for these distortion effects are needed before the results of the IIST natural-circulation experiments can be used to reliably investigate the Maanshan NPP behavior expected by way of an appropriate scale-up procedure.