National Environmental Protection Standards of the People's Republic of China

HJ979 - 2018

Electron Accelerator Irradiation Device

Radiation safety and protection

(Radiation Safety and Protection on Electron Accelerator

Irradiation Facilities)

(Release)

This electronic version is a release. Please refer to the official standard documents of China Environmental Science Publishing House.

Published on November 30, 2018 and implemented on March 01, 2019

Ministry of Ecology and Environment

contents

Foreword................................................................................................................................................................................................... I

1 Scope of application....................................................................................................................................................................................... 1

2 Normative citation documents....................................................................................................................................................................................... 1

3 Terms and definitions.....................................................................................................................................................................................1

4 General requirements.................................................................................................................................................................................... 1

4.1 Radiation safety requirements...............................................................................................................................................................................1

4.2 Radiation protection requirements........................................................................................................................................................................ 2

Radiation shielding of electron accelerator irradiation device..................................................................................................................................................................... 3

5.1 Shielding Design Principles........................................................................................................................................................................... 3

5.2 Shielding design calculation........................................................................................................................................................................ 3

6 Safety design of electron accelerator irradiation device...................................................................................................................................................... 3

6.1 Interlocking requirements............................................................................................................................................. 3

6.2 Security Facilities............................................................................................................................................. 3

6.3 Other requirements............................................................................................................................................. 4

7 days of regular maintenance (management) and records...............................................................................................................................................................................................................................5

7.1 Maintenance and maintenance of the device.......................................................................................................................................... 5

7.2 Record........................................................................................................................................................................ 5

Appendix A Calculation of Shielding Protection for Electron Accelerator Irradiation Devices.............................................................................. 7

Appendix A Example 10 MeV Electron Accelerator Radiation Shielding Calculation............................................................... 12

Appendix B Calculation of the Production and Emission of Harmful Gases................................................................................................................................. 18

Preface

In order to implement the Law of the People's Republic of China on the Prevention and Control of Radioactive Pollution and the Regulations on the Safety and Protection of Radioactive Isotopes and Radioactive Devices, protect the environment, safeguard human health and standardize the radiation safety of electron accelerator (electron beam and X-ray) irradiation devices, this standard is formulated.

This standard stipulates the radiation safety and protection principles of electron accelerator (electron beam and X-ray) irradiation devices, including dose control, division of radiation workplace, radiation shielding, safety design, daily maintenance (management) and recording requirements.

The technical content of this standard refers to the International Atomic Energy Agency (IAEA) "Radiation Safety of Gamma, Electron Beam and X-ray Irradiation Devices" (IAEA SSG-8, 2010), refers to international and domestic standards, and combines with the practice of radiation processing in China.

Appendix A and B of this standard are informative appendices.

This standard is proposed by the Department of Radiation Source Safety Supervision of the Ministry of Ecology and Environment.

This standard is formulated by the Department of Nuclear Facilities Safety Supervision of the Ministry of Ecological Environment and the Division of Scientific and Technological Standards.

The main drafting units of this standard are: Beijing Sanqiang Nuclear Radiation Engineering Technology Co., Ltd., Nuclear and Radiation Safety Center of the Ministry of Environmental Protection, Beijing Environmental Protection Bureau, Shandong Lanfu High Energy Physics Technology Co., Ltd., Zhongke Haiwei Science and Technology Development Co., Ltd., China Nuclear Energy Research Institute and China Nuclear Power Corporation. Engineering Co., Ltd.

This standard was approved by the Ministry of Ecology and Environment on November 30, 2018.

This standard has been implemented since March 1, 2019.

This standard is interpreted by the Ministry of Ecology and Environment.

I

Radiation Safety and Protection of Electron Accelerator Irradiation Device

1 Scope of application

This standard stipulates the radiation safety and protection principles of electron accelerator (electron beam and X-ray) irradiation devices, including dose control, division of radiation workplace, radiation shielding, safety design, daily maintenance (management) and recording requirements.

This standard is applicable to electron beam irradiation devices with energy not higher than 10 MeV and X-ray irradiation devices with energy not higher than 5 MeV for radiation processing. Self-shielding irradiation device is not applicable to this standard.

2 Normative Reference Documents

This standard refers to the following documents or their provisions. The valid version of any undated reference document is applicable to this standard.

GB3095 Environmental Air Quality Standard

Radiation Protection Regulations for GB5172 Particle Accelerator

Basic Standards for Ionizing Radiation Protection and Radiation Source Safety of GB18871

GBZ2.1 Occupational exposure limits for hazardous factors in the workplace Part 1: Chemical hazards

GBZ2.2 Occupational exposure limits for hazardous factors in the workplace Part 2: Physical factors

Terms and definitions

3.1 Electroaccelerator irradiation facilities

It is composed of electron accelerator, irradiation chamber, transmission equipment, safety facilities and control system, etc. It is used to realize radiation processing technology.

3.2 under beam equipment

It refers to the independent control unit which receives irradiation in the material conveying device under the beam extraction window (outside).

3.3 Host Room Main Machine Room

Places where equipment such as electron beam generator (electron gun) and beam acceleration structure (such as accelerator tube) are installed.

3.4 irradiation room

The radiation field is formed by the radiation emitted by the electron accelerator, which is used to complete the radiation processing process.

3.5 interlock

The electronic accelerator can automatically cut off the power supply or beam in a certain dangerous state, and ensure that no radiation can be produced without satisfying the set safety conditions.

3.6 tenth-value

Also known as one tenth of the value of thickness. When placed on a beam path, the radiation level can be reduced to 1/10 of the thickness of the specified material.  It can be divided into the first tenth value and the next tenth value , which is called the equilibrium tenth value .

4 General requirements

4.1 Radiation Safety Requirements

4.1.1 Security Principles

4.1.1.1 Deep Defense

One

The application of electron accelerator irradiation device and its potential irradiation size and possibility should be taken appropriate multi- protection and safety measures (i.e. in-depth defense) to ensure that when a certain level of defensive measures fail, the next level of defensive measures can be made up or corrected to achieve:

(1) Preventing accidents that may cause radiation exposure;

(2) To mitigate the consequences of any similar accident that may occur;

(3) After any such accident, restore the device to a safe state.

4.1.1.2 Redundancy

The number of items used should be more than the smallest number of items necessary to complete a safety function. In the event of failure or inactivity of an item during operation, it will not lose its function as a whole. For example, there should be three or more interlocks in the personnel entrance and exit of the irradiation room and the main engine room.

4.1.1.3 Diversity

Multivariate performance can improve the safety and reliability of the device and reduce common cause faults. System diversity and multiple dose monitoring can adopt different operating principles, different physical variables, different operating conditions, different components and so on. For example, mechanical, electrical, electronic and dose interlocking can be used for the safety interlocking of personnel entrance and exit in irradiation room and host room respectively.

4.1.1.4 Independence

Independence means that when a security component fails, it will not cause other security components to fail or lose their function. By means of function separation and entity isolation, the security agencies can be independent. In order to improve the independence of the system, the following measures can be taken:

(1) Guarantee the independence of redundancy (multi-channel interlocking) components;

(2) Guarantee the independence of defensive components in depth;

(3) Guarantee the independence of the pluralistic components;

(4) Guarantee the independence between safe and non-safe items.

4.1.2 Zoning of Radiation Workplaces

According to GB18871, the workplaces of electron accelerator irradiation devices are divided into:

Control areas, such as main engine room, irradiation room and areas within their respective entrances and exits;

Supervisory areas, such as equipment operating rooms, auxiliary facilities of electron accelerator irradiation devices not included in the control area, and other areas requiring frequent monitoring and evaluation of occupational exposure conditions.

4.1.3 A striking warning sign should be set up at the entrance and exit of the control area and other necessary places, which meets the requirements of GB18871.

4.1.4 Documents such as manual of use, operating procedures and emergency procedures, as well as identification and safety identification of key security components should be in Chinese.

4.2 Radiation Protection Requirements

4.2.1 Radiation Protection Principles

(1) The legitimacy of radiation practice

The legitimacy analysis must be carried out to determine the legitimacy of the project for the establishment of the irradiation device of the electron accelerator.

(2) Radiation protection optimization

Two

The design and construction of electron accelerator irradiation devices require that all irradiation doses be kept within the prescribed limits. After considering social and economic factors, the size of individual irradiation doses, the number of irradiated persons and the possibility of exposure should be maintained at the lowest level reasonably achievable, that is, ALARA (As Low As Reaso Reaso). The nable Achievable principle.

(3) Personal dose restriction

The dose limits of occupational exposure and public exposure of radiation workers should meet the requirements of GB18871. In the engineering design of electron accelerator irradiation device, the dose constraint value of radiation protection is stipulated as follows:

(a) The annual effective dose of radiation workers is 5 mSv;

B) The annual effective dose of individual members of the public is 0.1 mSv.

4.2.2 Radiation Shielding Design Basis

The shielding design of the electron accelerator irradiation device must be d on the maximum energy and beam intensity of the accelerator.

The dose equivalent rate outside the irradiation device of the electron accelerator should not exceed 2.5 mu Sv/h at 30 cm of the external shielding surface and around the external shielding area. If the shielding body is a public area, the shielding design must conform to the requirement of individual dose constraint value of public members.

The standard is applicable to electron beams with energy not higher than 10 MeV and X-rays with energy not higher than 5 MeV, and the neutron protection problem is not considered in the design of radiation shielding.

Radiation shielding of 5-electron accelerator irradiation device

5.1 Shielding Design Principles

In the shielding design of electron accelerator irradiation device, not only the shielding requirement of maximum beam power, but also the energy and the shielding requirement should be considered.

When the beam intensity is adjustable, the shielding difference under the combination of maximum energy and/or maximum beam intensity should also be considered.

5.2 Shielding Design and Calculation

5.2.1 Shielding design calculation should include: irradiation room and main engine room and their respective labyrinths, roofs, holes and so on.

5.2.2 Shielding design and calculation results should be explained in design documents.

5.2.3 The shielding calculation method of the electron accelerator irradiation device can be referred to Appendix A. For special X-ray irradiation devices, the calculation should be d on the target parameters or X-ray emittance provided by the accelerator manufacturer. The shielding calculation method of the electron accelerator irradiation device should be used for both electron beam irradiation and X-ray irradiation.

Six

Safety Design of Electron Accelerator Irradiation Device

6.1 Interlocking Requirements

In the design of electron accelerator irradiation device, safety interlocking protection device with complete functions and reliable performance must be set up to effectively interlock and monitor the entrance and exit doors of the control area, the startup and shutdown of the accelerator and the device under the beam. The high voltage must be cut off automatically when the safety interlock causes the accelerator to stop.

When the safety interlocking device fails, the accelerator can not run. Safety interlocking devices should not be bypassed, and they must be restored to their original state after maintenance and repair.

6.2 Safety Facilities

(1) Key control. The main control key switch of the accelerator must be interlocked with the main engine room door and the irradiation room door. If the key is removed from the console, the accelerator should stop automatically. The key must be connected to an effective portable radiation monitoring alarm. In operation, the key is unique and can only be used by the operating duty officer.

Three

(2) Door-crane interlocking. The door of irradiation room and main engine room must be interlocked with beam control and high voltage accelerator. When the door of irradiation room or main engine room is opened, the accelerator can not be turned on. When the door is opened, the accelerator should stop automatically.

(3) Underbeam device interlock. Reliable interface and protocol files must be established for the control of electron accelerator irradiation device and Under-beam device. The accelerator should stop automatically when the device under the beam deviates from normal operation or stops operation due to faults.

(4) Signal warning device. Lighting and sound warning signals should be set up at the entrance and exit of the control area to warn the personnel in the host room and irradiation room before starting the machine. The main engine room and the entrance and exit of the irradiation room are equipped with a working state indicator device, which is interlocked with the irradiation device of the electron accelerator.

(5) Patrol button. Inspection buttons should be set up in the main engine room and irradiation room and interlocked with the console. Before starting the accelerator, the operator enters the main engine room and irradiation room and press the "patrol button" sequentially. No one stays during the patrol.

(6) Anti-human mistakenly entering device. Three safety interlocking devices (usually optoelectronic devices) are installed in the entrance and exit passages of personnel in the main engine room and irradiation room, and are interlocked with the start and stop of the accelerator.

(7) emergency stop device. An emergency shutdown device (usually a pull-wire switch or a button) is installed on the console, in the main engine room and in the irradiation room to terminate the operation of the accelerator in an emergency state. The emergency stop device in the irradiation chamber and its labyrinth should adopt pull-wire switch and cover all areas. Opening mechanism should also be set up in the main engine room and irradiation room so that people can leave the control area.

(8) Dose interlocking. Fixed radiation monitors are installed in the labyrinth of the irradiation room and the host room, interlocking with the entrance and exit doors of the irradiation room and the host room. When the radiation level in the host room and irradiation room is higher than the threshold set by the instrument, the door of the host room and irradiation room cannot be opened.

(9) Ventilation interlock. The ventilation system and control system of the main engine room and irradiation room are interlocked. After the accelerator shuts down, the door can only be opened after a predetermined time is reached to ensure that the concentration of indoor ozone and other harmful gases is below the allowable value.

(10) Smoke alarm. The smoke alarm device should be installed in the irradiation room. In case of fire danger, the accelerator should stop immediately and stop ventilation.

6.3 Other requirements

6.3.1 Electrical System

(1) It is necessary to design the power supply conditions of accelerator devices, plant construction and public works to ensure the stability of voltage and current.

(2) Emergency lighting system should be set up in main engine room, irradiation room and control room.

(3) Reliable grounding systems shall be provided for all power supply systems and related equipment.

(4) High-voltage interlocking and high-voltage discharge protection devices shall be installed in all high-voltage dangerous parts.

6.3.2 Water Supply System

(1) A certain amount of water flow and pressure should be provided according to the total water requirement of the accelerator.

(2) The design is d on the water quality, water temperature and heat exchange load required by the process of the accelerator device and the sub-beam device.

6.3.3 Ventilation System

(1) Ventilation system should be set up in the main engine room and irradiation room to ensure that the concentration of ozone and other harmful gases produced by irradiation decomposition meets the requirements of GBZ2.1. Emissions of harmful gases should meet the requirements of GB3095.

(2) Ozone generation and emission. The calculation model and parameters are shown in Appendix B.

(3) The main exhaust outlet in the irradiation room should be located at a position which is easy to emit ozone, such as under the scanning window.

Four

(4) The height of the exhaust outlet shall be determined according to the regulations of GB3095, the discharge of harmful gases and the environmental and meteorological data near the irradiation device.

6.3.4 Fire Protection System

The fire resistance level of irradiation room and main engine room should not be lower than the second level, and fire alarm devices and effective fire extinguishing facilities should be set up.

Seven

Daily maintenance (management) and records

7.1 Maintenance and Maintenance of Equipment

Operating units of irradiation installations must formulate maintenance and repair systems for irradiation installations, regularly inspect (inspect) the main safety equipment of each accelerator, and maintain the effectiveness and stability of the main safety equipment of irradiation installations. The alteration of safety facilities shall be approved by the design unit and approved by the supervision department before proceeding.

7.1.1 day inspection

Common safety equipment on electron accelerator irradiation device should be checked every day, and it must be repaired in time when abnormal situation is found. The routine daily inspection items shall include at least the following contents:

(1) working status indicator lights, alarm lights and emergency lighting lights;

(2) Display status of safety interlock control of irradiation device;

(3) The working status of personal dose alarm instrument and portable radiation monitoring instrument.

7.1.2 months examination

Important safety equipment or safety procedures on electron accelerator irradiation devices should be inspected regularly every month. When abnormal conditions are found, they must be repaired or corrected in time. Monthly inspection items shall include at least:

(1) Operation status of fixed radiation monitor equipment in irradiation room;

(2) Console and all other emergency stop buttons;

(3) The effectiveness of ventilation system;

(4) Verify the effectiveness of the security interlocking function;

(5) Smoke alarm function is normal.

7.1.3 Half-year Inspection

The safety condition of electron accelerator irradiation device should be checked regularly every six months, and corrective measures must be taken in time when abnormal conditions are found. The scope of inspection shall at least include:

(1) Cooperate with the annual inspection;

(2) Operation status of all safety equipment and control system.

7.2 Records

Operating units of irradiation installations must establish a strict record system for operation and maintenance. During operation and maintenance, they should complete the record of operation logs, record important activities related to the installations and keep log files. Records are generally not less than the following:

(1) Operation conditions;

(2) The situation of irradiated products;

(3) Faults and troubleshooting methods;

(4) The entry of foreign personnel into the control area;

(5) Wearing of personal dosimeters;

Five

(6) Radiation monitoring results of personal dose, workplace and surrounding environment;

(7) Contents and results of inspection and maintenance;

(8) Others.

Six

Appendix A Shielding Protection Calculation of Electron Accelerator Irradiation Device

(Information appendix, d on NCRP-51 and NCRP-151 reports)

A.1 Radiation Source Term

Electron beam bombardment targets, structural materials and irradiated products will produce bremsstrahlung (X-ray). X-ray is the main radiation source in radiation protection design of electron accelerator irradiation device.

Table A.1 shows the X-ray emissivity Q of a single-energy electron incident on a high Z thick target (Z > 73) at a distance of 1 m from the target.

Table A.1 X-ray Emissivity (in Gy.m.mA-1.min-1)

When X-ray passes through material, it decays exponentially. In shielding calculation, the transmittance Bx of X-ray must be determined first.

After passing through the thickness of the shield, the dose rate is reduced to the allowable value according to the value of the transmittance.

Shielding of A.2 Direct X-ray

A.2.1 Determining X-ray Transmittance BX

H D2

Bx 1 1 10 6