The phrase "a rationale behind" is correct and usable in written English.
You can use it when you are wanting to explain the reasoning or logical justification for doing something. For example, "The professor provided a rationale behind their decision to change the course curriculum."
There is a rationale behind the squeaky carrot toys.
But there is also a rationale behind the emphasis on size and volume.
In the past, he has only been willing to say that such a rationale behind his departure was possible.
It may seem crude to put a price on how much people are worth but there is a rationale behind its usefulness.
There was a rationale behind Mason's decision to pair them up — pungent, local voices with uncommon ardor and instinctive expertise — but at the time it was little more than a lark.
If there is a rationale behind Livingstone's comments it can be found, perhaps, in Immanuel Kant's claim in the Groundwork of the Metaphysics of Morals that the only thing that is uniquely good is a good will.
Notable exceptions to this are the STI (Zieffler et al. 2012) and PIPS (Walter et al. 2014), which document rationale behind selecting a scale.
England did not pick the strongest squad possible but that was a decision with a logical rationale behind it and one in line with other teams.
A standard rationale behind such changes is a desire to incorporate the large informal sector that arises when regulations and market limitations proliferate under a relatively weak state.
The binding free energy analysis provides a plausible rationale behind the experimental dissociation constants and suggests a key role of ligand protein van der Waals interactions in restoring binding affinity.
There used to be a serious rationale behind his clothes, which gave his man-tailored suits a sense of content.
