Department of Defence and Australian Defence Force (Defence), Defence Base in South Australia, 9 November 2020
|Inspection report details|
|Licence holder:||Department of Defence and Australian Defence Force (Defence)|
|Location inspected:||Defence base in South Australia|
|Date/s of inspection:||9 November 2020|
An inspection was conducted as part of ARPANSA’s baseline inspection program to assess compliance with the Australian Radiation Protection and Nuclear Safety Act 1998 (the Act), the Australian Radiation Protection and Nuclear Safety Regulations 2018 (the Regulations), and conditions of facility licence F0252.
The scope of the inspection included an assessment of Defence’s performance at Port Wakefield against the Performance Objectives and Criteria (POCs) and applicable codes and standards. The inspection consisted of a review of records, interviews, and physical inspection of the facility.
Defence, being the organisation responsible for defending and protecting Australia and advancing its strategic interests, has the need to test explosive ordinance. As such, Defence holds a 1.2-3 MeV linear accelerator (linac) which is used to perform non-destructive testing (NDT).
The main codes and standards applicable to this facility are:
- Australian Standard Safety In Laboratories - Ionizing Radiations (AS 2243.4)
- Health Physics Society (HPS) Installations using non-medical x-ray and sealed gamma-ray sources, energies up to 10 MeV (ANSI/HPS N43.3-2008)
- Codes that appear in section 59 of the Regulations.
Performance reporting and verification
If a person were to be exposed or is considered to have potentially been exposed, Defence staff will report this through their event notification system, Sentinel. Also reporting of such an incident would be performed up the chain-of-command (i.e. the Defence Ionising Radiation Protection Officer (DIRPO) is informed, then layers of management through to the nominee and also to the Defence Radiation Safety and Assurance (DRSA) section which is Defence’s primary internal authority for the domain of radiation safety. Any event where ARPANSA is required to be informed will be through DRSA).
If Sentinel were to be unavailable, there are other avenues through which an event can be communicated until such time as the system is once again operable and a report can be generated. Regardless, the chain-of-command is always kept informed.
There is also a large number of fora where radiation safety is specifically included for information sharing purposes, be they operational or managerial.
Since the last inspection in 2018, there has not been a radiation related event.
The linac itself is a commercially available off-the-shelf product. As such, there is little required in terms of configuration management for the accelerator itself. However, the setup of the area in which it resides must be managed to ensure it remains compliant with applicable codes and standards and therefore continues to remain safe.
Since the last inspection the duration of the audible/visual warning system associated with the linac has been increased in accordance with the ANSI/HPS standard. The audible/visual warning system allows personnel to distinguish the difference between the ‘warning’ before radiography commences and when radiography is undertaken through the use of different coloured lights and sounds. While the standard discourages the constant use of an audible signal due to the potential for desensitisation, the warning sounds in comparison with those made during radiography are readily distinguishable. In addition, as the linac is situated at a Defence site, staff are trained to recognise a variety of different alarms and understand what they mean. Non-illuminated warning signage has also been updated to reflect the requirements of the ANSI/HPS standard.
Inspectors also clarified the situation around fail-safe circuitry implemented at the facility. AS 2243.4 requires that where visible and audible signals or both are provided they shall be designed to be failsafe. Currently this is not the case, however, Defence personnel advised that if a situation arose where warning signs were found to not be working then facility operations would cease until the issue is resolved as an administrative measure to meet the intent of the requirement. Staff/management responsible for the facility are currently investigating how they may introduce a fail-safe engineering control.
Inspection Testing and Maintenance
The linac is maintained by Varian as the original equipment manufacturer (OEM). This is a contracted service which sees the accelerator serviced twice per year (approximately once every 6 months) and includes a 24-hour call service back-up in the event that an issue arises that could potentially be fixed by operators on-site (trouble-shooting). When maintenance is required on the linac, all operations cease and the apparatus is handed over to the OEM. Upon completion, both the OEM and Defence personnel perform a test of the equipment’s serviceability before it is handed back for operational use. Defence does not undertake any technical maintenance of the linac.
The linac itself has three emergency stop (e-stop) devices incorporated into its design. One of these is selected during each use of the accelerator as a test to ensure its functionality. Subsequent taskings will then ensure the other e-stops are chosen to confirm that each device continues to shut down the facility when required.
In addition, there are other emergency stop devices and interlocks incorporated into the site that houses the accelerator which if pressed or broken will de-energise the linac. These currently have no set maintenance/servicing performed on them. As required by the ANSI standard they shall be inspected and periodically, appropriately serviced, and operationally tested at an interval that must not exceed 6 months (subject to the nature of operations) with records kept. This requirement has not been addressed in its entirety for all safety devices at this facility and is considered to be an area for improvement.
All operations must be conducted by at least two trained radiography technicians. There are two separate NDT qualifications required by staff taking part in the operations of the linac. Operators are required to complete the level 2 radiographic testing technician course and assistants are required to complete level 1.
A Defence Ionising Radiation Protection Officer (DIRPO) who has completed the DIRPO or ANSTO advanced radiation safety officer course must also be available. Staff certificates of completion for the aforementioned courses were provided during the desktop inspection.
Given the nature of the site and the facility, the likelihood of any credible accident scenario with radiological consequences as a result of an external event is deemed unlikely.
The site within which the facility exists is strictly controlled. Access is only given to individuals with a specific need to enter the facility and they must also be registered as an occupationally exposed radiation worker. When industrial radiography work is to be performed, on-site security are informed and proceed to check if anyone is in the vicinity. Those found to be within the area who should not be are advised to leave immediately.
Multiple keys are required to access and use the facility. Many of these are stored in Security Construction and Equipment Committee (SCEC) approved electronic key cabinets to which only authorised personnel have access. When work is completed, keys are secured back in their original locations. Systems in place to manage these arrangements are also audited periodically.
As the site is a restricted area, staff are escorted or unescorted in accordance with Defence procedures and are required to wear ID/security passes at all times.
The facility sits within a secured and restricted Defence establishment. The perimeter is fenced with only one possible route for entry which is gated and patrolled. As such the security implemented at the site is deemed to be appropriate.
Only persons who are considered to be occupationally exposed radiation workers are allowed to enter the controlled area that encompasses the radiography facility. As such, passive personal dosimetry is required at all times. Dose records were provided to inspectors that show doses remain low (within the margin of error for the minimum detectable dose over the reporting period, 100µSv ± 30%). Personnel are also required to wear electronic personal dosimeters (EPDs) and the accumulated doses as a result of operations are recorded. Accumulated doses have never reached a level that required reporting to the DIRPO in accordance with procedure (≥20 µSv).
A radiation survey is required to be performed to demonstrate safety for continued operation of the linac. This is performed annually, following maintenance activities, if the equipment were to be relocated/reoriented within the enclosure, or on replacement. The current survey continues to demonstrate expected dose rates around the radiography building.
Emergency preparedness and response
In terms of the linac, the operating procedures have an additional annex that describes what to do in the event of an emergency (i.e. the linac fails to shut down). While such an incident has not occurred, any incident that requires the use of an emergency stop requires reporting to the DIRPO.
As for the base, emergency exercises resulting in evacuation of the site occurs annually. This is just one of the emergency plans attached to the Port Wakefield emergency management plan and is focussed on the base as a whole as opposed to the controlled area where the linac is operated. However, one of the identified emergencies within that plan specifically relates to a radiation/x-ray incident and has to-date not been tested. During the course of the desktop inspection Defence informed inspectors that they are currently in the process of planning an emergency exercise centred on the occurrence of such an incident. This will occur in a number of phases essentially performing multiple exercises to test their response based on varying amounts of information (from fully informed practice exercise to a realised
event). ARPANSA inspectors encouraged Defence personnel at the base to keep them informed of this process.
The licence holder was found to be in compliance with the requirements of the Act, the Regulations, and licence conditions.
The inspection revealed the following area for improvement:
- The inspection, servicing and testing of the interlocks and other safety devices in accordance with the requirements of ANSI/HPS 43.3-2008.
It is expected that improvement actions will be taken in a timely manner.