Last updated date: Reason for update:
01 November 2022 Added a worked example to show how to use ‘activity value division steps’ to determine a notifiable incident.

This Regulatory Guide informs licence holders on the actions to be taken if a radiation incident occurs, when ARPANSA must be notified, and how to make such a notification. 

Associated forms


Sections 57A & 58 of the Australian Radiation Protection and Nuclear Safety Regulations 2018 (Regulations) places obligations on licence holders to prevent, control and minimise incidents; in doing so they must take into account human and organisational factors. 

Incidents that must be reported to ARPANSA are defined as are the actions that must be taken by the licence holder if an incident occurs. 

An incident is: 

  • any unintended event, including an operating error, equipment failure, initiating event, accident precursor, near miss or other mishap; or 
  • any unauthorised act, whether or not malicious, the consequences or potential consequences of which are not negligible.

Notifiable incidents

A notifiable incident requires immediate action and must be reported to ARPANSA within 24 hours.

A notifiable incident means any of the following:

  • an incident that exposes a person to a dose of ionising radiation that exceeds an effective dose limit mentioned in section 77 of the Regulations or an equivalent dose limit mentioned in section 79
  • an incident involving a diagnostic or interventional medical procedure resulting in an observable acute radiation effect
  • an incident involving exposure to non-ionising radiation from controlled apparatus that exceeds the non-ionising radiation exposure limits or results in noticeable eye or skin damage
  • theft or loss of controlled material or controlled apparatus, other than controlled material or controlled apparatus in Group 1
  • an incident involving the release of controlled material if the result of the activity value division steps* for the controlled material is greater than 104
  • an incident involving transport of a package of controlled material if the result of the activity value division steps for the controlled material is greater than 104 and the package is damaged in such a way that safety provisions are degraded

* activity value division steps for sources or controlled materials are the following:

  1. Divide the activity of each nuclide in the sources or controlled materials by the activity value set out in Part 1 of Schedule 1 for the nuclide;
  2. If there is more than one nuclide in the sources or controlled materials, total the result of paragraph (a) for each nuclide.

Note: Section 5 of the Regulations affects how the activity of a parent nuclide mentioned in Part 2 of Schedule 1 (or marked a in Part 1 of Schedule 1) is worked out, by providing for inclusion of the activity of certain progeny nuclides that are included in secular equilibrium with the parent nuclide.

Worked example

Suppose there are two vials in a laboratory cupboard, one containing 10 MBq of Co-60 and the other containing 100 MBq of Cs-137.  Assume a fire destroys the cupboard and the vials and all activity is released. Is this a notifiable incident?

Schedule 1 Part 1 of the ARPANS Regulations gives activity values of 105 Bq and 104 Bq for Co-60 and Cs-137 respectively.  If all activity is released, the result would be:

(107/105) + (108/104) =102 + 104 > 104  

Hence this is a notifiable incident

What to do if a notifiable incident occurs

Preserve the site

It is essential that the integrity of the incident site is preserved to allow an analysis of the conditions at the site and a thorough investigation as to the cause(s) of the incident.

Special attention should be paid to the importance of securing the site or the facility to prevent any destruction or cross-contamination of the physical information as well as to protect responding personnel and others.  

See Regulatory Guide: Radiation incident site preservation for further information.

Priority should be given to controlling and mitigating the consequences of the serious incident.


Within 24 hours of a notifiable incident occurring the licence holder must tell ARPANSA.

  • Call the ARPANSA 24/7 Duty Officer on (03) 9432 5384
  • As soon as possible complete an 'Incident Notification Form' and send it to

Investigate and provide a written report within 14 days

When investigating a radiation incident the following questions should be considered:

  • What happened?
  • How did it happen? 
  • Why did it happen?  Consider such things as environmental factors (e.g. distractions, shielding); human factors (e.g. experience, shielding, fatigue); controls (e.g. training, normal procedures, supervision); human and organisational factors (e.g. hazard identification, auditing, safety culture)
  • Was the severity of the incident and its likelihood of occurrence accurately reflected in the risk assessment? 

These questions will help identify the root cause and contributing factors with the ultimate aim to improve controls and conditions to support individuals’ actions and reduce the risk of recurrence.

A written report must be provided to ARPANSA that contains an account of the incident and its consequences including where possible:

  • A root cause analysis
  • An estimate of the dose received by any person 
  • An assessment of any impact on the environment
  • An assessment of human and organisational factors
  • Any corrective action taken as a result of the accident 
  • Actions taken to prevent the recurrence of similar events
  • The impact on safety
  • Identified security implications 

NOTE: If the report is not final it should still be submitted within 14 days and clearly marked as preliminary. The final version must be provided as soon as practicable and within a reasonable timeframe.

Review of plans and arrangements

Following a notifiable incident the licence holder must review and update plans and arrangements for managing safety. This review should include the design process for equipment or processes relevant to the incident and the performance of the risk assessment, review and safety approval system that authorised an activity that led to the incident.

The licence holder must complete the review within 6 months of the incident happening and must provide the CEO with a written summary of the outcome of actions resulting from the review within 7 months of the incident happening. The CEO may extend these periods on request.

Reporting other incidents

Any other incidents - such as operating errors, equipment failures, initiating events, accident precursors, near misses or other mishaps - that are not notifiable within 24 hours should be reported to ARPANSA as part of routine compliance reporting.  

This allows ARPANSA to follow-up as necessary especially where there may be learnings for other licence holders or the industry more broadly. 

Incidents of the type mentioned in the NDRP will be included in the Australian Radiation Incident Register (ARIR), Australia's national database of incidents and events resulting from activities involving radiation. 

ARPANSA may also submit relevant information to international registers such as that maintained by the IAEA for events on the International Nuclear and Radiological Event Scale (INES).  

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