HAD 102/12-2019 Radiation Protection Design for Nuclear Power Plants English
1 Introduction
1.1 Purpose
1.1.1 This guide provides an explanation and refinement of the relevant provisions of the HAF 102 Safety specifications for design of nuclear power plant. It is prepared to establish and maintain effective defense measures against radiation hazards in the design of new nuclear power plants and provide guidance for achieving radiation protection goals. The main contents of this guide may serve as a reference for design modifications and safety reviews of in-service nuclear power plants.
1.1.2 Annexes I, II and III of this guide have the equal force as the text.
1.1.3 The appendixes of this guide are informative.
1.2 Scope
1.2.1 The scope of application of this guideline includes:
(1) Radiation protection measures adopted in the design of nuclear power plants to achieve the optimal system of dose limitation and radiation protection;
(2) Radiation protection measures adopted in the design of nuclear power plants to protect the personnel and the public;
(3) Methods for calculating the radiation levels inside and outside the plant and meeting the requirements of radiation protection design;
(4) Determination of the important radiation sources and contamination sources under operation, decommissioning and accident conditions that are targeted in the design to provide protection for personnel, the public and the environment in the plant area;
(5) Radiation protection measures under accident conditions (including severe accidents);
(6) Radiation protection during the operation, treatment and storage of radioactive waste.
1.2.2 This guide does not involve safety issues related to the form and mass of radioactive waste during long-term storage or disposal, nor does it involve design measures that need to be taken to reduce the accident frequency and prevent accident development, nor does it involve radiation protection during actual operation and decommissioning processes.
2 Safety objective, dose limitation and protection optimization
2.1 Safety objective
The radiation protection design for nuclear power plant must ensure that the radiation exposure in the nuclear power plant or the radiation exposure caused by any planned emission of radioactive materials from the nuclear power plant is lower than the specified limit value under all operating states, and may be as low as reasonably achievable. At the same time, measures shall be taken to mitigate the radioactive consequences of any accident.
2.2 Dose limits and dose constraints under operating states
2.2.1 The design of nuclear power plants shall ensure that the radiation exposure generated during operation does not exceed the dose limits specified for staff and the public. The dose limit shall meet the requirements of GB 18871 Basic standards for protection against ionizing radiation and for the safety of radiation sources.
2.2.2 For occupational exposure, dose constraints shall be determined during the design stage of nuclear power plants and serve as boundary conditions for determining the scope of the optimal radiation protection scheme. The dose constraint value of occupational exposure is not a dose limit. Exceeding the dose constraint does not mean non-compliance with regulatory requirements, but it may lead to subsequent actions.
2.2.3 For public exposure, individual dose constraint shall meet the requirements of GB 6249 Regulations for environmental radiation protection of nuclear power plant.
2.3 Application of the principle of optimization
2.3.1 After taking into account the following economic and social factors, all radiation exposure shall be maintained within the specified limits and at the level that is as low as reasonably achievable:
(1) Radiation protection measures shall be taken to reduce the radiation exposure caused by the operating state and accident conditions of nuclear power plants to a certain level, so that the further increase in design, construction and operation costs is no longer worthwhile compared with the reduction in radiation exposure obtained (economic factors).
(2) In the design, consideration shall be given to reducing the differences in occupational exposure doses received by different types of staffs in radiation protection control areas, and avoiding harsh working conditions in radioactive work areas (social factors). The staff who may be exposed to the maximum radiation include refueling personnel, maintenance personnel, inspectors, and radiation protection personnel.
2.3.2 Generally, radiation protection optimization involves the selection of a series of protection measures (such as shielding, ventilation, distance control, and means to minimize radiation exposure time). To this end, feasible alternative schemes, comparison criteria and values shall be determined, and these schemes shall be evaluated and compared. Annex I describes the relevant decision analysis methods.
2.3.3 The concept of optimization shall also be applied to the design features aimed at avoiding or mitigating the consequences of nuclear power plant accidents that could result in exposure to staff or the public.
2.4 Design objective during operation
2.4.1 To ensure that the radiation dose to personnel is reduced to the level that is as low as reasonably achievable in the design while reflecting best practices, individual dose/collective dose design objectives shall be set for occupational exposure, and individual dose design objectives shall be set for public exposure. The individual dose design objective is an appropriate share of the dose limit and shall reflect the concept of dose constraint.
2.4.2 To focus the design on the relevant aspects that contribute more to the individual dose and collective dose of the staff, it is necessary to set collective dose design objectives for the staff groups that may receive the maximum doses, for example, maintenance personnel and health physicists, etc. Similarly, design objectives need to be set for the collective dose of each job type, such as the maintenance of major components, in-service inspection, refueling and waste management. The combination of the above design objectives with the dose assessment in the key design stages may serve as the basis for dose monitoring and dose management during operation.
2.4.3 The design objective of the collective dose for nuclear power plant staff may be expressed in the unit of man·Sv/GWe·a. The collective dose design objective shall be determined based on the optimal design of radiation protection or good practices.
2.5 Design objectives for accident conditions
2.5.1 The design objective of the accident condition is to limit the risks to the public caused by the radioactive materials released from the nuclear power plant, and limit the risks to the staff in the plant area due to radioactive release and direct exposure to an acceptable level. The calculated value of the accident dose shall be compared with the dose criteria stipulated in the design objectives of the accident condition to determine whether the design measures for protecting the personnel and the public in the plant area under the hypothetical accident condition are adequate. Different design objectives shall be set for accidents with different occurrence frequencies. For design basis accidents, it is required that only minor radiation impacts occur outside the plant boundary and non-residential areas, that is, there is no need to take evacuation measures from the perspective of radiation protection.
3 Radiation protection design
3.1 Radiation source
3.1.1 The size and location of the radiation source in operating state shall be determined during the design stage. Annex II briefly describes the primary radiation sources that cause radiation exposure during normal operation and decommissioning, including reactor core and pressure vessels, reactor coolant and liquid moderator systems, steam and turbine systems, waste processing systems, irradiated fuels, new fuel storage facilities, decontamination facilities, and various other radiation sources (such as sealed sources used for non-destructive testing). The largest radiation sources are the reactor core, irradiated fuel and waste resin. The design shall ensure that personnel are not directly exposed to these radiation sources.
3.1.2 During the design stage of a nuclear power plant, the size, location, possible transport mechanism and transport route of potential radiation sources under accident conditions shall be determined.
3.1.3 For accident conditions with preventive design measures, the primary radiation sources are radioactive fission products released from fuel elements or from various systems and equipment that retain the radioactive fission products. Annex III describes an example of the method for evaluating the radiation sources of the selected accident.
3.2 Radiation protection design during operation
3.2.1 Human resources
3.2.1.1 The design department shall fully understand the radiation protection measures in the design. To this end, the design team shall appoint or hire radiation protection professionals to put forward comprehensive radiation protection requirements and provide necessary training. Good operating experience shall be fed back to the design department to ensure mutual coordination between the design work and the operational procedures.
3.2.1.2 The optimization of protection and safety shall run through all stages of the life cycle of a nuclear power plant, from design, construction, operation to decommissioning. A systematic approach shall be adopted to formulate radiation protection programs and radioactive waste management programs to ensure that the principle of optimization is effectively implemented during the operation stage of nuclear power plants.
3.2.1.3 At every design stage, the design department shall recognize the importance of radiation protection.
Contents
1 Introduction
2 Safety objective, dose limitation and protection optimization
3 Radiation protection design
4 Radiation protection for plant staff during operation
6 Estimation of radiation levels during operation and decommissioning
7 Radiation monitoring during operation and decommissioning
8 Auxiliary facilities for radiation protection
9 Radiation protection under accident conditions
Terms and definitions
Annex I Application of the principle of optimization
Annex II Radiation sources during normal operation and decommissioning
Annex III Radiation sources under accident conditions
Appendix Determination of operational and decommissioning source terms
