Development of a Microfluidic Setup to Study the Corrosion Product Deposition in Accelerated Flow Regions
Journal: npj materials degradation
Publication Date: 14 December, 2017
A Novel Approach to Investigate CRUD Deposition
The formation, accumulation and release of corrosion products in water-cooling circuits of nuclear power plants causes serious issues such as a reduction of heat transfer from the primary to the secondary circuit, an increased radiation field around the primary circuit, a perturbation of the power distribution along the reactor core and change in the response of measurement components.
Corrosion studies are presently carried out using expensive, large-scale test rigs that replicate the operating conditions and water chemistry of nuclear stations. Now, researchers at the University of Manchester and Rolls-Royce have proposed a new innovative, small-scale micro-fluidic test system specifically conceived to study corrosion products deposition in nuclear reactor water circuits. This new microsystem is much cheaper to build and operate and is extremely sensitive to environmental changes, thus holding the promise of achieving a better understanding of corrosion in nuclear reactors in the future.
- CRUD (Chalk River Unidentified Deposit) forms in the water circuits of nuclear reactors due to corrosion of structural materials and the consequent release of species into the coolant.
- The deposition of CRUD is known to occur preferentially in regions of the primary circuit of Pressurised Water Reactors (PWRs) where the water flow accelerates.
- The autoclave used for this work was a recirculating 12 litre stainless steel vessel that can operate up to a temperature of 360°C and a pressure of 200 bar and prototypical nuclear power plant water chemistry. A micro-fluidic system was developed to achieve flow velocity up to 80 m/s.
- By monitoring the pressure drop across a micro-orifice it is possible to accurately monitor the build-up rate of CRUD in real time with an accuracy up to 1 micron per hour.
- This novel setup could be used to optimize the water chemistry in the primary circuit of a nuclear power plants. For example, the researchers show that 2 ppm of lithium added as lithium hydroxide in high purity water has the beneficial effect of arresting and reversing the deposition of CRUD.