Hello Lechumi, I got my food start in a sugar plant!
As Evans mentioned, your auditor is looking for R specifically to be added to your HACCP. As sugar is a commodity, it will be difficult to track the origin of the sugar with any great accuracy.
In our HACCP for R hazards we utilized and referenced the Codex Alimentarius, which at the time had no known hazards associated radiologically for sugar. We also explained in the HACCP that sugar is not typically exposed to ionizing radiation to remove any hazards.
However, we were audited to SQF standards, not ISO, and you will want to review your auditors comments to make sure you cover any specifics.