<p>The detection of nuclear materials is crucial in cases of potential leaks or accidents; however, transporting samples out of such locations may be challenging, necessitating on-site analysis. While total reflection X-ray fluorescence (TXRF) analysis is a highly useful method for determining nuclides with long half-lives, such as uranium isotopes, no commercially available portable TXRF spectrometers can currently operate without an external power source, which may not always be accessible on-site. In this study, we modified the design of a commercially available portable TXRF spectrometer to develop a battery-powered device, enabling TXRF analysis outdoors and in locations without an external power supply. To test the applicability of the device, we analyzed the uranium content in a sample solution, using yttrium as an internal standard. The relative sensitivity coefficient was the same as that of the commercial spectrometer but the limit of detection was deteriorated. Addressing the equipment issues identified in this study is expected to enable efficient and rapid on-site TXRF analysis.</p> Graphical Abstract <p></p>