The paper describes a sensor system utilising Ultra Wide Band (UWB) ultrasonic beacons to emulate ionising radiation intensity mapping within complex environments. By strategically deploying a UWB beacon onto a robot platform and integrating this with its onboard systems, and by positioning stationary ground beacons around the environment, it is possible to emulate synthetic ionising radiation intensity. This involves setting up a system that can estimate the robot position based on distances to each beacon, and subsequently applying the inverse square law to determine radiation intensity. The system will provide continuous radiation intensity estimates as the robot navigates its environment, providing a suitable simulation alternative to an ionising radiation detector that requires the use of radioactive sources. Through experimental validation and calibration, the accuracy of radiation intensity calculations is verified, showing reliable performance in comparison to currently utilised technologies. Finally, an example deployment and the achieved performance is shown demonstrating the possible application of the technology.