Description of electron beam
Writer: Sterilization Time: 2020-09-16 Browse: 891 ℃
The mode of action of E-beam irradiation, the penetrating ability of E-beam irradiation, the technological parameters of E-beam irradiation, the advantages and disadvantages of E-beam irradiation and its cost are discussed.
Mode of action
Ionizing radiation in the form of a beam of electrons
Medical device product requirements
Materials are compatible with radiation, penetrate boxes with bulk densities up to 0.25 g/cm3
Material
compatibility Wide range of polymer
compatibility compared to gamma; some limitations due to oxidation effects
Largest processing unit:Boxes
E-beam Processing
Product exposed to an e-beam for a validated period of time to achieve a desired minimum dose
Control system can quickly stop and start the source manually or automatically
Tolerance for density variation:Low
Processing time for a typical 45-ft tractor trailer (~3,000 ft3):<8 hours typical for smaller
batches
Processing parameters
There is a need to simultaneously monitor a number of parameters to ensure that the prescribed dose is delivered (e.g. beam current, conveyor speed, product box size and weight)
Product release parameters
In order to release product to market, the following are required:
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Control of the product manufacturing processes to ensure supply of material and product packaging is consistent with the validated radiation process
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A validated processing configuration in which an array of dosimeters have been measured to demonstrate the relationship between processing parameters and minimum and maximum dose to product and a routine dosimeter measurement (validation requirements and methods are well described in ISO 11137-1)
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A measurement of routine dose for a given processing run, which indicates that a dose within specification has been delivered. This measurement can be made as soon as the irradiation process is complete, so there is no required waiting time before release.
Pros (specific to medical devices suitability) E-beam
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60-year proven track record
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Equivalent to or less expensive than gamma for certain products
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Product holdup (amount of product within the irradiator) may be smaller than in a comparable gamma plant
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Quickest processing times
Cons (specific to medical devices suitability)
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Not suitable for products that have challenging product geometries and localized regions of high-density materials
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Inability to process in palletized format
E-beam equipment
Penetrating capability
Electrons, due to their charge and mass, have a much lower product-penetrating capability than either gamma or x-ray photons and can penetrate up to approximately 15 cm single- sided or 40 cm two-sided irradiation at densities up to 0.2 g/cc for electron energies up to 10 MeV
System repair downtime (e.g.source/system for machine sources; system for Cobalt-60)
E-beam
Can vary from hours to days
Conveyor repair related items are generally quick
Accelerator-related issues can sometimes take days to repair
Reliability and maintenance
Stable and reliable in a daily production environment. Actual operational experience has demonstrated ~90% uptime
Pros (equipment-related)
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For low-density homogenous materials, e-beam is more efficient than gamma and x-ray for this subset of processing
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The source of radiation can be turned off, which allows for easy access and repair
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The source energy is electricity and does not require the material to be transported
Cons (equipment-related) E-beam
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Additional complexity of equipment and process and validation when compared to gamma processing
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Maintenance outsourcing or development of technical staff to manage and maintain equipment required
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Need for ongoing replenishment of critical components over life of equipment
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Costly parts due to complexity
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Reliable and high electrical power consumption required
Sterilization source
Cost of generator Includes accelerator, beamline, scan horn, installation, IQ and OQ. The cost of the accelerator strongly depends on beam power. Production throughput is proportional to beam power. It is possible to increase the e-beam source capacity at a later stage by adding power modules to the accelerator or by adding a second accelerator (if planned in the initial facility design).
Process management
Conveyor
Typically box conveyor sometimes with automated box flipping for dual side irradiation
Safety Systems
The Safety Access System prevents unauthorized access into the accelerator room and irradiation chamber. Should there be an authorized intrusion in the irradiation area, the safety system instantaneously stops the accelerator irradiation.
SpecificInfrastructure
Shielding
Shielding is usually made of concrete. A typical foot print for an e-beam system including shielding and conveyor is about 20m x 15m.
Common infrastructure
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Land
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Building Warehouse
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Miscellaneous
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fences, racks, furniture, forklifts
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Local authorizations
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Building permits, fire department, environmental regulations such as noise
Variable costs
Costs that are proportional to production
Operators
Operators typically work in shifts. Processing boxes requires more labor compared with pallet processing.
Power Consumption Typical accelerators have power efficiencies from 20 to 50%. Accelerator power consumption stops when products are not processed. Other power consumption is for office and other non-accelerator related components. E- beam has considerably greater demand for electricity than gamma.
Spare Parts
Spare parts stock may vary and can be expensive. The minimum spare parts to store are specialized consumables which require periodic replacements (e.g. cathode, tetrodes, klystrons, seals, filters, pipes). Other spare parts may be stored in order to reduce downtime in case of failure.
Spare parts required for the conveyor are similar compared with gamma.
Repairs / maintenance and ongoing Investment
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Maintenance Engineer
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Someone with specialized electronics and mechanics background needed for maintaining an accelerator.
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Specialized expertise available from the manufacturer may be required due to equipment complexity.
This article describes the mode of action, penetration ability, process parameters, advantages and disadvantages and cost of E-beam.
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