What Is Workplace Monitoring?

Monitoring of workers by providing data on the working environment and radiation levels related to the operations they perform.

Monitoring of workers by providing data on the working environment and radiation levels related to the operations they perform. ^[1]

The main purposes of workplace monitoring are: to determine the level of radiation in the workplace and confirm the degree of safety; to provide basic information for estimating the possible exposure of workers on the scene and to evaluate the safety of the workplace; Measures to prevent the spread of pollution or the expansion of accidents.

The implementation of workplace monitoring can be broadly classified into several different types, such as routine monitoring, work-related monitoring and special monitoring.

Routine monitoring A type of monitoring that is of a confirmatory nature and is associated with continuous operation. The purpose is to show that the working environment is appropriate for continuous operation and that no changes have occurred that require re-evaluation of the operating procedures. You can use a continuously working stationary site monitor to determine if an anomaly or emergency has occurred.

Work-related monitoring The monitoring of specific operations or providing the necessary basis for the decision of an operational action.

Special monitoring is mainly aimed at the following two occasions: The necessary data for proper monitoring of the working environment is not sufficient; Operations where accidents may be suspected or accidents may occur. The purpose of special monitoring is to provide more detailed information for radiation protection and to determine operating procedures. Therefore, special monitoring should have clear goals and deadlines. Once the goals have been reached, they can be replaced by routine monitoring or operational monitoring.

Workplace monitoring data can also be used to identify pros and cons of operating processes and design characteristics, and provide a basis for workplace zoning and personal monitoring plans.

According to the monitoring targets, workplace monitoring includes external exposure monitoring, surface pollution monitoring, and air pollution monitoring.

For external exposure monitoring, appropriate radiation monitoring instruments are used to conduct patrols in the workplace to determine the surrounding dose equivalent or directional dose equivalent. The purpose is to determine the level of the radiation field, check the effect of external exposure control in the workplace, identify the rationality of the operating procedures, and control the work. The time and space that personnel spend on site and provide a basis for the need for individual dose monitoring.

For routine monitoring: Any new device that can produce radiation is delivered or the existing device undergoes or is likely to undergo significant changes (such as the reactor or critical device restart or restart after restart), and the surrounding area must be surveyed; routine monitoring The frequency depends on the expected change of the radiation level in the workplace. If the radiation field is not easy to change, only general surveys are required. If it is easy to change, the monitoring point should be selected in advance for periodic monitoring. If the radiation level in the workplace is sudden and rapid Increasing tendency, and the severity of its change is unpredictable, it is necessary to set up a monitoring system with alarm function that can work continuously in the workplace. For work-related monitoring, the development of a monitoring scheme depends to a large extent on the impact of the operations performed on the radiation field. If the operation itself does not interfere with the radiation field, only the dose equivalent rate of the area where the worker is located can be patrolled, but it should be patrolled before each operation. If the operation itself has a large effect on the radiation field, a series of measurements need to be performed on the entire operation process. The beta radiation field is susceptible to operating procedures. For mixed beta and gamma radiation fields, attention should be paid to changes in the beta and gamma dose rate ratio caused by operational monitoring.

Surface contamination monitoring is performed to check the surface of workplace equipment, workbenches, floors, walls, staff surfaces and work clothes for radioactive contamination. The main purposes are: to detect pollution incidents in time so as to take corresponding measures to prevent pollution from spreading; to check whether the pollution control measures are effective and whether the operation violates the regulations; to determine the level of surface contamination and to provide a basis for taking decontamination measures; Develop personal and air monitoring plans or modify operating procedures to provide the necessary information.

The design of the surface pollution monitoring program should meet the following goals: Determine the monitoring cycle and monitoring method based on the actual conditions and experience of the workplace. Direct or indirect monitoring methods can be used to monitor representative surfaces in the premises. For slowly spreading pollution, regularly inspect the representative surfaces of cleaning tools, work shoes, gloves, etc. For workplaces that may cause large or rapid spread of pollution, monitoring points must be set up on both sides of the exit to ensure that workers leave the workplace without pollution or the level of contamination is below the control level. Work-related monitoring is complementary to routine monitoring. During and after the operation, measuring the surface of equipment or objects related to the operation can help control the spread of pollution. Work-related monitoring also includes checking items removed from the workplace. In the workplace where the sealed source is used, the sealed source may leak. The leak tightness of the source must be checked regularly. Surface contamination is generally measured by the wiping method. The period of inspection depends on the level of the source and the conditions of use.

Air pollution monitoring. Monitoring performed to determine radioactive gas and aerosol concentrations in the workplace. Inhalation of airborne radioactive materials is the main way for workers to receive internal exposure. Therefore, monitoring air pollution is an important measure to control internal exposure. The main purpose is to detect accidental airborne radioactive pollution, in order to take timely countermeasures, and to develop internal exposure monitoring programs And surveys or estimates of upper population intakes.

Regarding the formulation of the monitoring plan, the following aspects should be considered: In the places where a large amount of radioactive gases, volatiles are operated, and operating positions that often pollute the air, such as uranium mining, smelting, and treatment of plutonium and other transuranium elements, all Perform routine monitoring; set up samplers at several selected locations in the workplace that can represent the breathing zone of the worker, determine the radioactive concentration in the air based on the activity in the sample collected, and the number and period of sampling according to the change in air radioactive concentration In order to estimate the individual's intake, workers must wear personal samplers when necessary; In order to detect accidental airborne radioactive contamination, a continuous sampling monitoring system can be set up in the workplace.

Monitoring of external exposure in the workplace can only give the radiation field properties and radiation levels as a function of space and time. Due to the difficulty of controlling the movement of staff in the premises, it is difficult to monitor the data used to estimate the dose equivalent of staff organs or tissues, but some simplified assumptions can be made. For example, in places where the radiation level is sufficiently low, it is assumed that staff Always be at the highest dose-equivalent rate in the workplace during work, so you can estimate the upper limit of the dose-equivalent you might receive. At this time, there is no need to limit the time that the staff can move in the place; if the radiation level in the place is high, the time that the staff can move in the high-dose rate area must be limited. The evaluation of work-related monitoring is often performed for a specific working time, during which the dose received by the worker should not exceed the limit set by the protection management department.

The relationship between the level of surface contamination and the exposure dose to workers is difficult to quantify, but when the level of surface contamination is kept below appropriate control limits, it has been shown that the control of pollution is effective and that there is no abnormal internal contamination on the site It is generally not necessary to monitor other projects. If the level of contamination exceeds the control limit, the source of the pollution should be investigated, and whether or not personal pollution and air monitoring should be performed should be determined on a case-by-case basis. Because alpha and beta radionuclides are different, they should be monitored and evaluated separately.

Air pollution monitoring data can be used to estimate total staff intake over a period of time. The estimation results can be compared with the relevant limits of the protection standard. Since the radioactive concentration in the place air may change greatly with time and space, to estimate the representativeness of the area sampling, it should be compared with the measurement results of the personal sampler, and appropriate corrections should be made. In addition, the aerosol particle size distribution should be taken into account when assessing hazards, and correction factors should be introduced if necessary. ^[2]