Keywords radioactive contamination; pollution control
1 Overview
Radioactive contamination, is due to human activities caused by the material, human body, places, environmental media surface or internal appearance of more than the national standard of radioactive substances or rays, harmful to the human environment and health. Radioactive pollution control is the possible generation or has occurred radioactive pollution control, prevention, mitigation, avoidance of radioactive contamination of all technology and management activities. We in the nuclear power production practice, we must strictly control radioactive contamination, which nuclear power overhaul activities of radioactive contamination control is one of the key tasks we are concerned about, this paper will be devoted to overhaul work concerned about the control of radioactive contamination of the region and channel to discuss in detail.
2 Sanitary entrance and exit areas
2.1 Contents and methods of contamination control
During the overhaul, the surface contamination of sanitary entrances and exits in the control area is surveyed, which usually includes hot and cold changing rooms, door A1, door A2 corridor access, radiation monitoring room and other areas of frequent activities of the staff. In carrying out the census of contamination, the main lockers, floors, tables and chairs, window sills and instrumentation equipment in these places, etc., to detect contamination in a timely manner and take measures to prevent the spread of radioactive contamination.
2.2 Schedule
Daily census in the morning and afternoon, you must fill in the daily pollution inspection and measurement sheet, so that the staff can understand the radiation information in a timely manner.
3 Nuclear auxiliary plants
3.1 Contents and methods of pollution control
Using the method of indirect measurement to measure the surface contamination of the corridors, staircases, and floors of the nuclear service plants, nuclear auxiliary plants, nuclear safety plants, fresh fuel and solid waste storage plants, and when affected by environmental influences, the surface of the corridors, stairs, and floors can be wiped to take samples for measurement. Once the contamination is found, the contamination isolation warning tape should be set up, and the service personnel should be notified immediately to decontaminate, and the decontamination should be confirmed.
Use the surface contamination meter to directly measure the surface contamination of the elevator floor and buttons.
3.2 Schedule
For the nuclear service plant, the frequency of measurement can be determined according to the site work, but not less than once a week, when the main pump can be pumped out of the components transported into the main pump decontamination maintenance room, the frequency of the inspection is changed to 1 time a day in the morning and 1 time in the afternoon.
For the nuclear auxiliary plant, nuclear safety plant, new fuel and solid waste storage plant, according to the site equipment overhaul situation and the number of work sites, to determine the frequency of pollution census, in principle, not less than 1 time per day.
4 Reactor plant
4.1 Pollution control content and methods
Reactor plant in the work site more, frequent maintenance activities, resulting in a high potential for the spread of radioactive contamination, its supervision and census is the focus of the contamination control should be strictly controlled, timely detection of radioactive contamination, rapid decontamination, to prevent the spread of contamination. In the on-site supervision and inspection, it is necessary to pay attention to the following: whether the state of radiation instrumentation at the site is normal; whether the staff and goods are in and out of the contaminated area according to the regulations; whether there are staff staying near the radiation hotspot without any reason; whether the staff measure the on-site dose rate and whether they know the radiation state at the site; whether the on-site organization and dose sharing are reasonable, and so on.
For the measurement in the reactor plant, it should be "representative and universal" to maximize the control of radioactive contamination, and the measurement methods are as follows:
4.1.1 Wiping paper is used to wipe the corridors, stairs and floors of the reactor plant for sampling measurements (i.e., indirect measurement), and the sampling points are selected according to the work site or contaminated isolation area. The sampling point is selected according to the work site or contamination isolation area, and the sampling measurement is usually selected from the range of site operations and staff frequent access and the measurement points specified in the measurement roadmap of the reactor plant;
4.1.2 Portable instrumentation is used to directly measure the surface contamination of the floor of the elevator and buttons in the reactor plant, and sampling measurements are usually used if the nearby ambient dose rate has an impact;
4.1 .3 Sampling measurements are used for entrances and exits, exteriors, and peripheral areas of work site contamination isolation areas within the reactor plant.
4.2 Timing
The reactor plant is the main pollution control inspection point and should be censored once a day in the morning and once in the afternoon, and not less than three times a day during steam generator and main pump maintenance and after the start of low water.
5 Work site pollution isolation zone pollution control (excluding reactor plant)
Wipe sampling and measurement on the outside of the threshold of the entrance and exit of the contaminated isolation zone and the perimeter, should be censored once a day in the morning and afternoon, to effectively prevent the spread of radioactive contamination.
6 other temporary control area pollution control
The control area outside the boundary door, gantry crane below the ground and the equipment in the area, the use of portable meters for direct measurement combined with indirect measurement. In principle, not less than 2 times per week. One measurement after the operation with the risk of contamination spreading, in order to detect the contamination in time and deal with it.
7 Peripheral supervision area pollution control
Peripheral supervision area regular inspection, including monthly inspection and semi-monthly inspection. Pollution census is mainly carried out on the main corridors, resting places, VIP corridors, etc. in the radiation protection supervision area. Measure the surface pollution diffusion in the monitoring area, and fill out the inspection sheet, make a good record and save.
8 Radioactive surface contamination control values
Nuclear power plants should be in accordance with national standards and procedural provisions, the strict implementation of surface contamination control, contamination control work based on the surface contamination control values see GB18871 or related standards.
In practice, the ground wiping sample measurement, usually deducted from the background 0.15-0.35 Bq/cm2. The actual measured value should be the surface contamination of the loose contamination value, some nuclear power plants are usually calculated according to the 40 Bq/cm2 of the 1/50 ground loose contamination control limits, more than or detection value is slightly higher than the background, that is, the need to be decontaminated.
9 Radioactive Pollution Control Management Daily
All of the above work should be carried out during the overhaul of radioactive contamination control, management of the daily newspaper for detailed records, to facilitate timely reporting, communication and feedback of radiation contamination information, overhaul during the period, but also the radiation information and changes in the reactor plant with the patrol table publicized in the entrance to the containment, so as to facilitate timely understanding of the staff of the work site Radiation situation. In addition, in the management daily report should describe the completion of site operations, the status of the work site, the recent overhaul of the site need to pay attention to matters, the peripheral work situation, as well as other situations, etc. For violations and radiation protection events, a 24-hour event list should be issued to the staff to propose corrective action.
10 Deficiencies in radioactive contamination control
10.1 Radioactive contamination control management procedures and work regulations in overhaul work need to be further improved and refined;
10.2 Radioactive contamination control of nuclear power production in the technical means, economic means, and staff participation in the need for further optimization of the management;
10.3 Nuclear power plants or nuclear facilities Radioactive pollution control related enterprises, industry standards need to be strengthened.
11 Summary
The realization of the goal of radioactive pollution control needs to be fully guaranteed through administrative and technical means, in the overhaul of pollution control work, there should be applicable work procedures and management procedures, there should be training, assessment of qualified full-time technicians and managers and other multifaceted measures, therefore, in the overhaul of the nuclear power plant and the management of radioactive wastes should pay attention to the quality of work Therefore, in the nuclear power overhaul work and radioactive waste management work should pay attention to the quality of work and the cultivation of nuclear safety culture awareness, pay attention to every detail of the work, work with a rigorous scientific attitude, but also need the participation of all the maintenance staff and attention to the effective implementation of the whole process of radioactive contamination management in nuclear power production practice, to protect the environment of the workplace, the protection of the public and the health of the staff.
References
[1] Luo Shanggeng. Introduction to Radioactive Waste. Beijing Atomic Energy Press, 2003.
[2]State Council. Regulations on the Management of Radioactive Waste.
[3] Presidential Decree. Law on Prevention and Control of Radioactive Waste Pollution .