Application of the dose rate spectroscopy to the dose-to-curie conversion method using a NaI(Tl) detector

• A modified DTC conversion method using the dose rate spectroscopy was established.
• In-situ calibration factors were calculated from the MCNP simulation.
• Radioactivities of the disk sources were accurately calculated using a modified DTC conversion method.
• A modified DTC conversion method was applied to the assay of the radioactive material.

Dose rate spectroscopy is a very useful method to directly calculate the individual dose rate from the converted energy spectrum for the dose rate using the G-factor which is related to the used detector response function. A DTC conversion method for the estimation of the radioactivity based on the measured dose rate from the radioactive materials can then be modified into a simple equation using the dose rate spectroscopy. In order to make the method validation of the modified DTC conversion method, experimental verifications using a 3″φx3″ NaI(Tl) detector were conducted at the simple geometry of the point source located onto a detector and more complex geometries which mean the assay of the simulated radioactive material. In addition, the linearity about the results from the modified DTC conversion method was also estimated by increasing the distance between source positions and a detector to confirm the method validation in the energy, dose rate, and distance range of the gamma nuclides.