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Opal reactor

ANSTO's OPAL reactor is one of the world's most advanced and reliable research reactors today. To ensure we can continue operating OPAL safely and reliably and maximise utilisation, ANSTO must regularly carry out maintenance and upgrades.

On Monday 18 March, ANSTO transitioned OPAL to a shutdown state to undergo necessary upgrades and maintenance. We are currently planning to conclude the shutdown activities in late July and return OPAL to power in early August.

A key driver of this planned shutdown is replacing the reactor's unique cold neutron source (CNS), which has an operational life of 15 years. The replacement cold neutron source offers increased scientific performance.

Throughout its life, teams will work to upgrade OPAL’s functionality to improve its performance and ensure that ANSTO can continue delivering scientific, health, and industry benefits to Australia. ANSTO will keep stakeholders informed of the OPAL shutdown before, during, and after maintenance and upgrades are completed.

Project updates

17 May 2024

ANSTO’s multi-purpose reactor OPAL was shut down in March as part of an essential maintenance and upgrade program. Below, please find the latest update.

Shutdown schedule
This planned shutdown is the most significant maintenance and upgrade program in OPAL’s history. These activities include replacement of the First Reactor Protection System (FRPS) and replacement of the Cold Neutron Source (CNS).

To prepare for this first-of-a-kind program, ANSTO built a full-size reactor mock-up that allowed our teams to practice and refine the required procedures over a two-year period. However, in the real-time delivery and unique live reactor environment, we have found several processes in the program have taken longer than anticipated.

With safety driving every decision we make, based on the data we have now, the shutdown timeline has been adjusted. We are currently planning to conclude the shutdown activities in late July and return OPAL to power in early August.

Nuclear medicine supply
ANSTO has experienced minor supply disruptions to date and is pleased to report that 90.2% of nuclear medicine products are being supplied to ANSTO in full and on time.

We are in continual contact with our international suppliers and logistics providers to ensure we maintain a reliable supply of Mo-99/Tc-99m, Lu-177 and I-131 during this planned long shutdown, subject to these supplier's product availability and logistics.

Project milestones and achievements
Several project milestones have now been achieved including the successful CNS removal from the reactor pool, one of the most important milestones of the program, and the commissioning of OPAL’s FRPS.

The planned simultaneous maintenance at our Nuclear Medicine Processing and Distribution Facility remains on schedule with the facility due to be back in operation early June 2024.

24 April 2024

As part of an essential maintenance and upgrade program, the OPAL multi-purpose reactor was shut down last month. Here’s an update on this important project. 

Nuclear medicine supply 

ANSTO has experienced minimal disruptions and is pleased to report that 99.5% of nuclear medicine products are being supplied in full and on time. We continue to work closely with a number of international suppliers and logistics providers around the world. The ANSTO health team is working diligently to ensure continuity of critical nuclear medicine supply for our customers during the shutdown. 

Project update  

This OPAL upgrade program has been years in the planning and is complex and highly technical. At this stage we are working to our plan to be back to full operations early in July. As always, safety is paramount and guides everything we do. 

Project milestones 

During this shutdown period, we are replacing OPAL’s First Reactor Protection System (FRPS). FRPS monitors critical reactor parameters and is a primary system required for reactor safety. This upgrade to the latest available technology will provide improved safety, reliability and maintainability for the future.  

Four years of detailed planning were undertaken to ensure the FRPS upgrade could be completed in the same window of opportunity as the Cold Neutron Source (CNS) replacement. We are pleased to report that new FRPS has been installed and is currently undergoing commissioning.  

How do you shut down a nuclear reactor? 

Like to learn more about the processes to shut down a reactor? Read this article 


18 March 2024

In line with our plans and preparations, ANSTO commenced the planned OPAL shutdown on 18 March 2024, to allow for necessary upgrades and scheduled maintenance. 

All key stakeholders and customers will continue to receive regular communications over the course of the shutdown.


12 February 2024

It takes years of meticulous planning to implement a successful nuclear reactor maintenance and upgrade schedule.  Our specialist Engineering, Maintenance and Operations teams began work on this project in 2015. This is a highly complex operation with the team building a full-scale CNS mock-up to assist in the planning and training of supervisors and technicians. Training commenced in July 2022 with each training session taking around 3 months to complete.  

ANSTO’s preparation ahead of this shutdown is well underway and running to plan.

In the below video interview, Dr Anna Sokolova, Instrument Scientist, Small Angle Neutron Scattering, explains the important of the CNS upgrade, what happens at the Australian Centre for Neutron Scattering and how these instruments are used in wide-ranging research, from COVID-19 to energy, food science, quantum computing and more.


Cold Neutron Source Replacement

When OPAL undergoes essential maintenance and upgrades, this will increase the performance of scientific instruments and ensure the reliability of nuclear medicine supply, silicon irradiations, and more.

A critical component of the planned maintenance is replacing the cold neutron source. ANSTO Instrument Scientist – Small Angle Neutron Scattering, Dr Anna Sokolova, explains why the cold neutron source is important.

Watch now

Go behind the scenes

It takes years to plan and implement a successful nuclear reactor maintenance and upgrade schedule, and we’re pleased to share this journey with you.

Senior Project Manager of Maintenance & Engineering, Andrew Eltobaji, speaks from our nuclear reactor mock-up facility. He outlines what the cold neutron source does and how ANSTO plans on replacing it.

Watch now

Frequently Asked Questions

What is happening?

On Monday 18 March 2024, ANSTO's OPAL reactor transitioned to a shutdown state to undergo necessary upgrades and scheduled maintenance. It is planned that OPAL will return to full operations on Friday 5 July, 2024. These are the current proposed dates of shutdown. Dates may shift slightly, however, key stakeholders will be notified in advance of any possible date change.

Why does maintenance need to take place?

The OPAL reactor is a complex facility with a unique design. Maintenance and upgrades are business as usual for infrastructure of its kind.

Even when OPAL is most successful, our teams work to upgrade its functionality behind the scenes; this will most likely be the case throughout the entire life of the reactor.

Most maintenance and upgrade activities are performed during regular reactor operation to ensure safe and reliable operation. However, from time to time, there is a need to perform maintenance and upgrade activities whilst the reactor is in a shutdown state.

Will customers be impacted?

Nuclear medicine, irradiations, and research customers will be impacted; however, we are working to minimise disruption wherever possible.

Customers will be contacted by their ANSTO Account Manager with specific information regarding supply and services throughout the shutdown.

What work has ANSTO carried out to date in preparation for the shutdown?

ANSTO has assembled a dedicated project team who have developed a life-size OPAL pool mock-up in Building 2.

The mock-up is designed to be used for training for key project activities. 

The project team has utilised the pool mock-up facility to develop, trial and provide training in the cold neutron source removal and replacement activities.

Is ANSTO working with the regulator on this matter?

Yes, ANSTO is working with the regulator because regulatory approval is required to perform the cold neutron source replacement aspect of the OPAL shutdown.

Will the shutdown improve OPAL’s performance?

Teams continuously work to upgrade OPAL’s functionality to improve its performance and ensure that ANSTO can continue delivering scientific, health, and industry benefits to Australia.

The replacement cold neutron source offers increased scientific performance.

In future communications, we will outline the science behind our new cold neutron source and it’s potential.

Who is undertaking the work?

A team of almost 20 engineers and nuclear reactor technicians will work to replace the cold neutron source in OPAL as part of the shutdown.