OECD/NEA CTH (Blind Benchmark on CANDU Thermal-hydraulics)


The BFBT (NUPEC BWR Full-size Fine-mesh Bundle Tests) and PSBT (NUPEC PWR Sub-channel Bundle Tests) benchmarks provided direct benefits to the industry for testing the capabilities for simulating void fraction, pressure drop and CHF and for the development and validation of new methods. It has been almost a decade since the initial benchmarks were performed and a considerable amount of development has been done since that time. . Building on the success of the OECD-NEA/US-NRC sponsored BFBT and PSBT benchmarks McMaster University, in collaboration with North Carolina State University and NINE company, will host a new thermal-hydraulic benchmark. The CANDU Owners Group (COG) has provided full-scale experimental data for a 28-element CANDU fuel assembly, including pressure drop and detailed pin temperatures for single-phase and boiling conditions. While the number of nuclear power plants using 28-element fuel arrays is limited, the phenomena measured during these experiments are relevant to that of other heavy-water fuel designs and to phenomena present in Light Water Reactors.

The high-quality heat transfer and dryout data encourages advancement in understanding and modelling of complex flow behaviour. A unique aspect of these data are the traversing thermocouples which provide axial and azimuthal sheath temperatures along every fuel pin for both pre- and post-CHF conditions. A wide range of test conditions (inlet pressure, mass flows and inlet temperatures) will be provided to the participants along with the temperature scans, CHF location and power, and post-dryout sheath temperatures. Similar to the BFBT and PSBT benchmarks, the complete set of data will be made available to participants after completion of the benchmark.

The benchmark consists of two phases. Each phase consists of different exercises:
• Phase I – Pre-CHF Benchmark
  - Ex. 1 – Single and two-phase pressure drop benchmark.
  - Ex. 2 – Single-phase heat transfer benchmark.
  - Ex. 3 – Two-phase heat transfer benchmark.
• Phase II – CHF Benchmark
  - Ex. 1 – Steady-state CHF benchmark under nominal geometrical conditions.
  - Ex. 2 – Steady-state CHF benchmark under aged channel conditions.
  - Ex. 3 – Transient heat transfer and CHF benchmark.
  - Ex. 4 – Post-dryout sheath temperature benchmark.

CANDU geometry and conditions while different than BWR/PWR, cover a some conditions of interest (e.g. some CHF occurs in annular film dryout conditions while other data covers nucleate boiling heat transfer). There is international interest in a new benchmark for full scale data in bundle geometries. The operators in Canada have agreed in principle to release some full-scale data from their experimental data base for CHF and Post Dry Out phenomena.

The workshop at BEPU2020 Conference will be the 2nd workshop of CTH activities – CTH-2.

 

 

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