GB/T 17568-2019Specifications for design construction and use of gamma irradiation facilities (English PDF)

3.1 Radiation processing

A process in which ionizing radiation (ray) acts on the irradiated substance to improve its quality or performance.

3.2 Gamma irradiation device

A device that uses gamma radiation (rays) to process articles and materials through safe and reliable radiation processing technology.

3.3 Processing capacity

Under the conditions of a certain loading density of the product and the required minimum absorbed dose, the amount of material processed by the irradiation device per unit time.

Note: The unit of processing capacity is m3/h. In practical applications, the standard processing capacity is generally used to measure the productivity of the irradiation device.

3.4 Standard processing capacity

Using activity of 3.7 x 10^16Bq (1 million Ci) 60Co as the radioactive source, the product density is 0.2g/cm³, and the minimum absorbed dose is Under the condition of 25kGy, the volume utilization rate of the irradiation box is 100%, the volume of the product processed by the irradiation device per hour.

Note: The standard processing capacity unit is m3/h.

3.5 Dose unevenness

The ratio of the maximum to minimum absorbed dose in the product of each irradiation unit.

3.6 Control area

An area divided into a radiation workplace, in which special protective measures and safety measures are required or may be required, so that:

a) Control normal exposure or prevent the spread of pollution under normal working conditions;

b) Prevent potential exposure or limit its extent.

Note: The irradiation room and labyrinth of the gamma irradiation device are control areas.

3.7 Supervision area

Anything that has not been identified as a controlled area, usually does not need to take special protective measures and safety measures, but needs to constantly check its occupational exposure conditions What area.

Note: The operation area, control room, ventilation room, equipment room, water treatment room and other areas are all supervision areas.

3.8 Run appraisal

Obtain evidence to prove that when the equipment is used in accordance with the equipment operation procedures, the installed equipment is operating within the predetermined range, and documented the process of.

4.1 Composition and classification of devices

See Appendix A for the composition of gamma irradiation equipment, and Appendix B for classification.

4.2 Device safety requirements

4.2.1 Safety principles

4.2.1.1 Defense in Depth

The source should adopt multi-layer protection and safety measures (i.e. defense in depth) commensurate with its potential exposure When a certain level of defensive measures fails, the next level of defensive measures can be used to make up for or correct them to achieve:

a) Prevent accidents that may cause exposure;

b) Mitigating the consequences of any such accidents that may occur;

c) After any such accident, restore the source to a safe state.

4.2.1.2 Redundancy

The number of items used should be more than the minimum number of items necessary to complete a certain safety function to ensure that in case an item is lost during operation In the case of effective or ineffective, it can make the whole not lose function. For example, there are more than 3 anti-personnel interlocks at the personnel entrance.

4.2.1.3 Diversity

Diversity can improve the safety and reliability of the device, and can reduce common cause failures, including system diversity and multiple dose monitoring.

Use different operating principles, different physical variables, different operating conditions, different components, etc.

4.2.1.4 Independence

Independence means that when a safety component fails, it will not cause the function of other safety components to fail or lose their function. by The method of functional separation and physical isolation enables the security organization to gain independence. To improve the independence of the system, the following measures can be taken:

a) Ensure redundancy (multi-channel interlocking) independence between components;

b) Ensure the independence between the various components of the defense in depth;

c) Ensure the independence between the various components of the diversity;

d) Ensure the independence between items important to safety and items not important to safety.

4.2.2 Safety signs

Ionizing radiation warning signs should be installed at the entrance of the gamma irradiation facility workshop and other necessary places. Ionizing radiation warning signs should be Figure F2 in Appendix F of GB 18871-2002.

4.3 Radiation protection criteria

4.3.1 The legitimacy of practice

For the establishment of a project for the construction of gamma-irradiation equipment, a legitimacy analysis should be carried out to determine the legitimacy of the project.

4.3.2 Optimization of protection and safety

The design and construction of gamma irradiation equipment should take into account social and economic factors, the size of the individual exposure dose, the number of people exposed, and the The possibility of exposure is kept as low as reasonably achievable, that is, the ALARA principle.

4.3.3 Personal dose control

4.3.3.1 Personal dose limitation

Personal dose limitation is a part of the radiation protection system and a constraint condition in the optimization process. The following dose limits do not include natural Background exposure and medical exposure.

a) Occupational exposure ---The annual average effective dose for 5 consecutive years determined by the regulatory authority (but no retrospective average), 20mSv;

---The effective dose in any year, 50mSv;

b) Public exposure ---Annual effective dose, 1mSv;

---Annual effective dose Under special circumstances, if the annual average dose for 5 consecutive years does not exceed 1mSv, then a single year The effective dose can be increased to 5mSv.

4.3.3.2 Dose constraint value

During the engineering design, operation and decommissioning of gamma irradiation equipment, the dose constraint value is specified as:

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

b) The annual effective dose value for members of the public is 0.1mSv.

4.3.4 Limits of contamination by radioactive materials

4.3.4.1 For wet storage source gamma irradiation equipment, the concentration of 60Co radioactive pollutants in the source well water should be controlled below 10Bq/L.

4.3.4.2 According to GB 18871-2002 Table B11, the clothing, body surface of the staff and the equipment, tools, ground and other surfaces of the workplace beta The level of radioactive pollution control is shown in Table 1.

6.2 Design principles

6.2.1 The design unit shall reasonably determine the project scale, installed source quantity and other ancillary facilities of the gamma irradiation device based on the owner's letter of attorney.

6.2.2 The design unit shall, in accordance with the provisions of this standard and relevant national standards, and on the basis of ensuring radiation safety, improve the processing of the device as much as possible. Ability to reduce dose unevenness.

6.3 Design calculation

The shielding protection, ventilation system and important equipment of the gamma-irradiation device shall be appropriately and effectively verified in accordance with existing standards and publications The calculation method is calculated. The calculation result should be stated in the design document. The calculation book should be properly kept in the design unit for reference during re-calibration.

6.4 Design requirements

6.4.1 Safety interlock requirements

Gamma-irradiation device should be equipped with a safety interlock system with complete functions and reliable performance to control the area, especially the entrance and exit, source operating system, radiation Carrying out effective monitoring and safety interlocking for the object transportation system.

6.4.2 Safety facilities

6.4.2.1 The source lifting device, the personnel access door and the cargo access door of the irradiation room shall be accessed by the same independent key or multiple keys together.

Control, this key or a bunch of keys should also be connected to an effective portable radiation detection alarm, such as taking out the key from the console and putting it The radiation source is automatically lowered to a safe position. Only qualified and authorized operators by the operating unit can use the key.

6.4.2.2 Visibly set up light and sound signal devices at all entrances of the irradiation room to warn people outside the irradiation room.

6.4.2.3 An unmanned inspection button should be installed in the irradiation room and interlocked with the console. The operator should enter the irradiation room for inspection before the source is upgraded.

Check, the unmanned check button setting position should avoid the blind spot of patrol inspection.

6.4.2.4 The emergency lowering source (generally a pull switch) and a door open button are set in the irradiation room. The emergency lowering source (generally a pull switch) button should cover the entire irradiation room and the labyrinth area.

6.4.2.5 An emergency stop button should be installed on the console, which can terminate the operation of the irradiation device and lower the radioactive source to a safe position at any time.

6.4.2.6 Interlock the personnel access door and the source lifting system. If the door is not closed, the source cannot be raised; when the source is in a non-safe position, it cannot be opened The personnel access door, if the personnel access door is forcibly opened, the source will be automatically lowered; when the power fails, the personnel access door cannot be opened according to the normal operating procedures.

6.4.2.7 Set up a fixed radiation level monitor, set up probes in the labyrinth, cargo outlet and water treatment device of the irradiation room, and Control system interlocking. Set the dose alarm threshold respectively. When the radiation level detected by the probe in the labyrinth of the irradiation room exceeds the threshold, the personnel passage The door cannot be opened; when the radiation level detected by the probe at the cargo exit exceeds the threshold, the cargo conveying system is automatically stopped, and the source is lowered and sent Sound and light alarm. When the radiation level detected by the water treatment probe exceeds the threshold, the water treatment system will be automatically stopped, and the source will be lowered at the same time, and an audible and visual alarm will be issued.

6.4.2.8 Set up a safety door (or set the door blocking function of the irradiation container) at the entrance and exit of the goods, and cooperate with the transportation of the irradiation container to prevent people from opening and closing.

The operator enters and interlocks with the control system. When the source rack is in a non-safe position and the power is cut off, the door cannot be opened or the irradiation container cannot be moved according to normal operating procedures.

6.4.2.9 Install anti-personnel photoelectric in the entrance of the personnel passage and the entrance of the goods, and interlock with the control system. When the source is in a non-safe position, If the photoelectric alarm is triggered, the source is automatically lowered; when the source is in a safe position, if the photoelectric switch is not turned on, the source cannot be raised.

6.4.2.10 A calibration source should be set up at the entrance of the irradiation room, such as a 0.37MBq cesium-137 source, and the operator should Use the calibration source to check whether the dose meter is normal.

6.4.2.11 Set up an automatic source reduction system for power failure to avoid accidents of personnel exposure due to failure of monitoring instruments due to power failure.

6.4.2.12 Set up the source frame forced landing system so that the source frame can be released when some kind of failure occurs in the lifting source.

6.4.2.13 Set up the water level monitoring and alarm and water replenishment system of the source well to avoid the radiation dose level in the irradiation room caused by the drop of the water level of the source well Rise. When an ultra-low water level alarm occurs, the personnel access door cannot be opened according to normal operating procedures.

6.4.2.14 The irradiation room should be equipped with a ventilation system and interlocked with the control system. When the ventilation system fails, the source is automatically lowered or the source cannot be raised.

6.4.2.15 The irradiation room should be equipped with a smoke alarm device and interlocked with the control system. When there is a smoke alarm, the ventilation system will be automatically stopped and automatically lowered. Source, the cargo transfer system ceased operation.

6.4.2.16 Each detachable shielding plug in the irradiation room, including the shielding plug for loading the source, shall be interlocked with the control system to facilitate the shielding plug during loading and unloading of the source.

If it is unloaded, the source will be lowered automatically or the source cannot be raised.

6.4.2.17 The source frame should be equipped with a protective cover or anti-collision bar, and be firmly connected with the structure of the irradiation room, and its strength and structure should be able to effectively prevent the cargo from falling.

Accidents such as collapse, cargo emergence, tilting of the cargo box, unhooking of the spreader, etc. cause the shield or the anti-collision bar to deform or tilt and block the source frame. For dynamic spoke According to the device, the source section of the cargo conveying system should be equipped with a guiding and positioning mechanism, and an anti-collision alarm device should be installed at the entrance.

The feeding system and the lifting system of the source rack are interlocked. The structure of the door lock of the irradiation box should have the function of preventing accidental opening, and an opening detection device should be provided.

The source lifting pulley system shall be provided with facilities to prevent the wire rope from falling out of the groove.

6.4.2.18 A mobile TV monitoring system should be installed with its own lighting function to ensure that the irradiation room and source rack can be clearly monitored under the radiation state. And has image storage function.

6.4.2.19 Spraying devices shall be provided in the irradiation room. The pipes inside the shielding body of the sprinkler should be made of stainless steel;

Manual valve control mode; interface with fire truck should be reserved.

6.4.2.20 The safety requirements listed above are all applicable to the fixed source chamber wet storage source irradiation device. For fixed source chamber dry storage source gamma radiation 6.4.2.7 Water treatment system is equipped with fixed radiation level monitor requirements and 6.4.2.13 requirements; for self-shielding gamma radiation Device, without 6.4.2.3~6.4.2.10, 6.4.2.12, 6.4.2.13, 6.4.2.15~6.4.2.19 requirements; for underwater gamma irradiation device, only 6.4. 2.2, 6.4.2.7, 6.4.2.13 apply.

6.4.3 Fire protection requirements

The fire resistance level of the irradiation room and the workshop in the operation area shall not be lower than Class II, and shall be equipped with fire alarm devices, which can be timely issued in case of fire danger. Now, alarm, shut down, the radioactive source will automatically drop to a safe position, and effective fire extinguishing measures can be taken in time.

6.4.4 Power supply requirements

The gamma-irradiation device should ensure normal power supply. During the operation of the device, when the power failure time exceeds 10s (regardless of normal or accident), the source frame should be able to Enough to automatically drop to a safe position, and the device automatically shuts down. The irradiation device should be equipped with the necessary backup power supply. When the accident is out of power, the monitoring instrument and The power supply time of the safety interlock device should be guaranteed not less than 30min to ensure safety.

6.4.5 Seismic requirements

In areas where severe earthquakes may occur, the design and construction of gamma irradiation devices should be equipped with seismic detectors. Once the detector reacts The radioactive source can be automatically lowered to a safe position. "Severely damaged earthquake" refers to an earthquake whose design basic seismic acceleration is greater than or equal to 0.3g.

Note: g is the acceleration due to gravity.

6.4.6 Ventilation system

According to the design of the installed source and the size of the irradiation room, determine the intake and exhaust air volume. Two exhaust fans should be installed to ensure that when the radioactive source drops into the well After 5 minutes of storage, the limit of ozone concentration in the irradiation room, NO2 concentration (including NO, N2O, NO2 and other nitrogen oxides are changed Calculated as the concentration of NO2) meet the limit specified in Table 1 of GBZ 2.1-2017, that is: the maximum allowable concentration of ozone should not exceed 0.30mg/m³. The time-weighted average allowable concentration of NO2 (including the NO2 concentration converted from various nitrogen oxides such as NO, N2O, NO2, etc.) should not exceed 5mg/m³. A wet storage source gamma irradiation device with a source volume greater than 37 x 10^16Bq (1 million Ci), when the radioactive source is continuously stored When the source well is not working, the ventilation system should be activated regularly to prevent the accumulation of hydrogen generated by ionization and radiolysis in the source well water in the irradiation room To the explosion limit. The design unit should calculate the time interval and time for starting the ventilation system based on specific parameters such as the source activity and the size of the irradiation room.

The minimum time for each ventilation is clearly stated in the design document.

The height of the exhaust outlet should be calculated and determined in accordance with the provisions of GB 3095, the amount of harmful gas emissions and the environmental and meteorological data near the irradiation device.

6.4.7 Water treatment system

All gamma irradiation devices for wet storage sources should be equipped with a water treatment system to ensure the water quality of the source well, and the conductivity of the source well water is required to be low.

More than 10µS/cm, total chloride ion (Cl-) content is not more than 1mg/L; pH value is 5.5~8.5.

6.4.8 Water cooling system

Irradiation devices above 37 x 10^16Bq (1 million Ci) should be equipped with a water cooling system.

6.4.9 Shielding structure

The design of the shielding structure of the gamma-irradiation device should follow the relevant national regulations, regulations and standards.

The strength grade of the shielding structure concrete should not be lower than C20, and meet the requirements of the durability of concrete, and the concrete density should not be lower than 2.3g/cm³; The impermeability grade of concrete with impermeability requirements should not be lower than P6, and the minimum thickness should not be less than 250mm.

The shielding design should ensure the integrity and safety of the radiation shielding. For parts with weak radiation shielding (such as exhaust air and wall passages, etc.), There should be compensation measures to prevent leaking beams; the thickness of the roof of the irradiation room should consider both penetration radiation and sky scattering; the design of the labyrinth should make the labyrinth entrance The exposure dose of external radiation workers meets the requirements of 4.3.3; when designing the source activity, the external surface dose level of the shield should also meet the requirements of A.1.1.

6.4.10 Source storage well

Ensure that the dose level above the well should meet the requirements of A.1.4 when designing source activity and flipping the radioactive source.

There should be no penetrating parts (such as pipes, pipe plugs) at the bottom of the source water well. When designing pipelines such as the well water treatment system, appropriate anti-siphoning should be adopted Measures to prevent the water level from falling below 30cm from the design normal water level due to siphoning.

The reinforced concrete outer wall and bottom plate of the source well should meet the requirements of impermeability and bearing capacity with the compactness of the concrete itself; underground storage source The concrete of the well shall not use chloride admixture. Stainless steel wells should be covered in the source well.

6.5 Design documents

6.5.1 Design document content

The design unit of the gamma irradiation device shall submit the following technical documents to the owner:

a) Design instructions and drawings for process and radiation safety;

b) Automatic control system software and hardware instructions and drawings;

c) Equipment use and maintenance instructions;

d) Architectural and structural drawings and instructions;

e) Electrical drawings and instructions;

f) Drawing and description of ventilation system;

g) Drawings and descriptions of water supply and drainage and water treatment systems.

6.5.2 Modification of design documents

After the design documents are submitted to the owner, the owner generally shall not modify it by himself. When it is necessary to modify, the design unit shall submit a modification notice.

When the proprietor and the unit entrusted by the proprietor propose amendments, it shall be approved by the design unit. Modifications that have a significant impact on safety shall be Approval by regulatory authorities.

The modification notice should be filed together with the original drawings and documents.

7.1 Construction unit

7.1.1 The construction unit shall have a construction qualification certificate of level two or above issued by the state.

7.1.2 The construction unit shall strictly follow the construction drawings provided by the design unit and shall not modify it without authorization. If there is any change, the design unit should provide The revised notice issued and the designer's signature.

7.2 Construction requirements

7.2.1 A complete construction plan should be formulated before construction, and a large-volume concrete construction method should also be formulated for the shielding structure of mass concrete.

The construction plan shall be implemented after approval by the supervision unit.

7.2.2 Before pouring the concrete of the shield structure, it should be inspected by relevant professional on-site and approved by the supervisor in writing before pouring.

7.2.3 The concrete wall of the shield structure shall not leave construction joints from FL-0.30m to FL 2.00m. FL is the wall height range The elevation of the ground where the insider can reach. […]