The JHPS Working Group for Discussion on X-ray Exposure Accidents summarized the background of the X-ray exposure accident happened in Himeji, Hyogo in May 2021. The working group paid attention to the viewpoint of fostering a further awareness of the need to the radiation safety culture and discussed issues identified to contribute to the prevention of possible future X-ray accidents as one of the goals. The article introduces an example to apply the dose estimation method using a Monte Carlo simulation discussed in the working group. The authors summarized other methods of dose estimation, the technical limitations and the challenges of each method. The authors believe that these summary for dose estimation method will be informative and helpful to overcome the future issues in this area. The authors also considered that information on the energy distribution of low-energy X-rays in the body of an exposed patient is important for radiation emergency medicine and radiation protection purposes and that individual and environmental monitoring of low-energy X-rays is still challenging.