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Analysis of Prototype Inspection Equipment Using CFX®

Cost-effective alternative to experimentation for the detailed analysis of a prototype nuclear inspection tool.

Project Objective

Detailed analysis of a prototype inspection and maintenance tool was required to determine its effect on maintenance coolant flow when submerged in a CANDU heat-transfer system.  It would have been very costly to implement a suitable experimental apparatus to satisfy the required range of tests .

Computational Fluid Dynamics (CFD) was selected to perform the analysis because it offered a cost-effective, rapid alternative to experimental testing and was able to provide tool designers with the required information early in the design process. ANSYS® CFX® was the package used to create the model.

Scope of Work

It was essential that the analysis of the prototype nuclear inspection tool determine the effect that the equipment would have on flow through in a CANDU heat-transfer system. When the prototype nuclear tool is located in the system, it acts as a flow restrictor, and could reduce flow rates to unacceptable levels.

It was a must for the created models to account for the geometry of the nuclear inspection equipment, the geometry of bulk and feeder sub-channel flows using heavy water coolant, and to provide results over a range of flow rates. 

Work Performed

CFX® was ideal for use in this type of analysis due to the fact that the project required a broad range of situations to be tested — applications which would normally involve a large and expensive mock-up facility.

Several computer models were created and updated, as new designs or details became available.

Flow through a header was modeled without the tool, bounded by known flow properties. The prototype nuclear inspection tool was then added to the header and the changes in flow properties were observed.

Regions of high pressure, low flow, and recirculation were noted. A supporting leg of the nuclear inspection tool covered an inlet to the header, with results showing that the flow rate actually increased through the inlet.

This result was unexpected, but later supported analytically. It was caused by the tool creating a region of low pressure above the inlet, forcing more fluid through the smaller nozzle.  CFD software made the results undoubtedly clear and presentable to observers.

The bulk flow losses were quantified as a function of header flow rate. The overall flow results also provided the location of high pressure regions, to be examined in future work. 


The CFX model results clearly demonstrated that blockage caused by the device was minimal and would not have a significant impact on operations.

The ‘worst-case’ position for the device was not where it was originally thought to be, and a more accurate ‘worst-case’ position was identified. Valuable information was provided regarding how to better construct future models and experiments.

CFX® enabled the generation of clear and descriptive diagrams, which allowed for easy understanding by both analysts and management. 

Direct Client Benefits

The client was able to see the results of the prototype nuclear inspection tool analysis much quicker and in more detail than if done by experiment. The designers were also able to see which features of their design were high contributors to flow losses.  This, in turn, presented an opportunity for design improvements.

The use of CFX® allowed for easy modifications to model geometry. In addition, the external geometry could easily be changed to account for differences between generation plants.