IAEA CRP Benchmark of ROCOM Boron Dilution and PTS test cases

The last decade has seen an increasing use of three-dimensional CFD codes to predict steady state and transient flows in nuclear reactors because a number of important phenomena such as pressurized thermal shocks, coolant mixing, and thermal striping cannot be predicted by traditional one-dimensional system codes with the required accuracy and spatial resolution.

The nuclear industry now also recognizes that CFD codes have reached the desired level of maturity (at least for single-phase applications) for them to be used as part of the NPP design process, and it is the objective of a IAEA CRP to assess the current capabilities of such codes in this regard, and contribute to the technology advance in respect to their verification and validation. CFD is already well-established in addressing certain safety issues in NPPs, as reported and discussed at various international workshops. The development, verification and validation of CFD codes in respect to NPP design necessitates further work on the complex physical modelling processes involved, and on the development of efficient numerical schemes needed to solve the basic equations. In parallel, it remains an overriding necessity to benchmark the performance of the CFD codes, and for this experimental databases need to be established, both for separate-effect tests and for full-size integral tests.

At the IAEA it was decided to set up a benchmark of ROCOM boron dilution and PTS test cases. All the test data had previously been opened, so only an ‘open’ benchmark exercise could be contemplated. Two sets of test data could be made available, relating to Pressurized Thermal Shock (PTS) and boron dilution (pump start-up). The ROCOM facility is at 1:5 scale, based on the 4-loop Konvoi reactor concept. There are 4000 measuring points by means of the Wire-Mesh Sensor (WMS) measurement technique, for which data collection is available up to a frequency of 10 kHz. It was noted that each experiment had been repeated five times to ensure authenticity of the data. In both cases, initial and boundary conditions are specified. Data have been recorded at P1 and P2 confidence levels. A CAD file of the test geometry is also available – it has recently been updated. All test data are available in tabular form, for ease of interpretation.

The Benchmark will help to analyze the CFD code capabilities for CFD in nuclear reactor design applications.