Optimization of Borated CR-39 Detector for Conformance to Fast and Thermal Neutron Dosimetry Applications

The response of the borated CR-39 detector (a registered trademark of TASTRACK Industries) has been investigated with the aim of studying its application in both fast and thermal neutron dosimetry. Optimization tests on the neutron sensitivity and background tracks were performed to ensure the detector’s acceptable sensitivity to the personal dose equivalent of fast and thermal neutrons. The detectors were irradiated to dose equivalents of reference neutron sources, with a ²⁴¹Am-Be source for fast neutrons and a miniature neutron source reactor for thermal neutrons.

The irradiated detectors were processed with various chemical etching parameters to optimize their performance to an acceptable level. The chemical etching procedures were carried out for 4 h and 6 h with a KOH water solution and for 6 h and 9 h with a NaOH water solution at 70°C for all detector samples.

The results showed good repeatability and remarkable signal-to-noise ratio values were achieved in etching for 6 h and 9 h with the NaOH water solution of 7 M at 70°C. By selecting these parameters for chemical etching, the detector’s efficiency increased by approximately a factor of 2. Thus, the borated CR-39 material maintained reliable performance for both fast/thermal neutrons through the same optimized chemical etching parameters, 6 h with 7-M NaOH water solutions at 70°C.

Through this study, we achieved an excellent response from the borated CR-39 to thermal neutrons. We improved the detector’s efficiency by shortening the etching time without enhancing the etching temperature or etchant concentration. These optimized parameters demonstrated consistent results, ensuring the detector’s ability to measure equivalent neutron doses across different environments without needing specific adjustments to the etching conditions.