In the field of radiation protection, thermoluminescent personal dosimeters are core tools for monitoring the radiation dose received by workers, and their accuracy directly affects occupational health management and safety assessment. However, due to environmental interference, equipment aging, and other factors, thermoluminescent personal dosimeter readings may deviate or become abnormal. This article will elaborate on the regular calibration process and strategies for identifying and handling abnormal data, providing actionable solutions for relevant organizations.
1. Regular Calibration: Ensuring the Reliability of Measurement Reference Standards
Calibration is a crucial step in maintaining the accuracy of thermoluminescent personal dosimeters. It is recommended to conduct a standard source comparison experiment quarterly—using a metrologically certified cesium-137 or cobalt-60 radioactive source as a reference standard, covering the energy range that may be encountered in daily work. During operation, care should be taken to place the dosimeter chip in the center of the source to ensure geometric consistency; at the same time, ambient temperature and humidity parameters should be recorded, as these factors can affect the crystal luminescence efficiency.
Standardized annealing procedures are equally important. According to national standards, lithium sodium fluoride (LiF) detectors should be burned at a constant temperature of 240℃±2℃ for 30 minutes to eliminate residual signals. Using a precision temperature-controlled muffle furnace with a programmed temperature rise curve can prevent overheating and sensitivity degradation. Regularly creating calibration curves using components irradiated with standard doses is also an effective means of compensating for individual component differences.
2. Outlier Screening: Multi-dimensional Analysis and Source Tracing Technology
When outlier data appears, it is essential to first distinguish between systematic errors and random fluctuations. Statistical tests of the dataset are performed using the Grubbs criterion to eliminate suspicious values with a probability below 5%. Then, a comparative analysis of parallel samples worn by multiple personnel in the same position is conducted to determine if it is an individual's specific exposure.
Environmental electromagnetic interference is a significant factor. A spectrum analyzer is used to scan the electromagnetic noise distribution in the workplace, focusing on investigating harmonic components generated by high-frequency medical equipment. For areas with strong magnetic fields, fiber optic transmission is recommended instead of traditional cable connections.
Component performance degradation can also lead to chronic drift. By observing the historical data trajectory of a single dosimeter through trend charts, a gradual upward or downward trend may indicate that aging components may need to be replaced.
3. Preventive Maintenance: Building a Closed-Loop Management System
Establishing a complete traceability chain is crucial. Original calibration certificates should be retained starting from the procurement stage, and electronic files should be updated and identification codes generated after each calibration.
Personnel training should include both practical exercises and theoretical assessments. Emphasis should be placed on training the correct wearing position (e.g., at the chest and collar) and avoiding the mixing of different types of components; the working principle of the dosimeter and common fault manifestations should also be explained.
Management of thermoluminescent personal dosimeters requires a systematic engineering approach. Through standardized calibration procedures, scientific data analysis methods, and a rigorous quality control system, not only can the reliability of radiation protection data be guaranteed, but it can also provide strong support for occupational health management. With the development of IoT technology, real-time remote monitoring and intelligent early warning of dosimeter status can be realized in the future, promoting the transformation of radiation protection towards proactivity and intelligence.
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