Output 1.6: CTBT Implementation

Development of verification systems and arrangements in support of Australia's commitments related to the Comprehensive Nuclear-Test-Ban Treaty.

Performance Measures

  • Australia's obligations under the Comprehensive Nuclear-Test-Ban Treaty (CTBT) are met.
  • Legal and administrative mechanisms which support Australia's commitments related to the CTBT are effective.
  • Contribute to the development of CTBT verification, including through the work of the CTBT Organization (CTBTO) Preparatory Commission.
  • Contribute to Australia's CTBT outreach efforts.

Performance Assessment

International Obligations

Australia hosts 23 facilities for the CTBT International Monitoring System (IMS). All are certified as operating to CTBTO technical specifications. The effective operation of Australia's IMS stations is a routine focus for ASNO.

Performance of Australian seismo-acoustic stations, operated by Geoscience Australia and the Australian National University, has been very good throughout the year with the exception of the auxiliary seismic station at Charters Towers. The station was damaged by a landslip in February 2019 and took some time to return to operation.

Some IMS data is also used for civil and scientific purposes. Data from seismic stations is used in the Australian National Earthquake Alert Centre for the detection and location of numerous Australian and overseas earthquakes and for tsunami warning. IMS infrasound data has even been used to confirm meteor sightings.

Performance of Australian radionuclide stations was excellent, with very high station data availability throughout the year. One major station upgrade was completed in Darwin (AUP09/AUX09) followed by a CTBTO revalidation visit in December 2019. ARPANSA, which operates the Australian RN stations, also supported the operation of stations in Fiji and Kiribati.

During the year, ASNO has continued to work with the CTBTO and Western Australian Government agencies to reduce the risk of accidental damage to the seabed cable that brings to shore data from the Cape Leeuwin hydrophone array and to facilitate routine maintenance of the cable. ASNO is working also with ARPANSA and the Australian Antarctic Division to ensure that the redevelopment of facilities on Macquarie Island has minimal impact on the operation of the IMS radionuclide monitoring facility on the island.

Nuclear-Test-Ban Verification

ASNO administers funding for Geoscience Australia to carry out nuclear test monitoring through its network of seismic stations as well as those of the CTBT's International Monitoring System. This arrangement, set out in a Letter of Understanding between Geoscience Australia and ASNO, is reviewed each year. ASNO is satisfied that Geoscience Australia has met its requirements under the Letter of Understanding during the reporting period.

Although the CTBT is not yet in force, its International Monitoring System is now substantially in place, with around 90 per cent of Treaty-designated stations in operation. The system detects and reports on many thousands of events each year. Almost all of these can be clearly identified as natural in origin and in the twenty-first century only the DPRK appears to have conducted nuclear test explosions. The table below details nuclear tests conducted by the DPRK.

Table 19: DPRK Nuclear Test Explosions
Date Approximate seismic magnitude Estimated explosive yield (kT) Comment
9 Oct 2006 mb 3.9 < 1 Likely partial failure
25 May 2009 mb 4.56 1 – 5 Seismic detection consistent with a simple fission device
12 Feb 2013 mb 4.93 3 – 13 Seismic detection consistent with a simple fission device
6 Jan 2016 mb 4.83 2.5 – 10 Claimed by DPRK to be test of a ‘hydrogen bomb'. Seismic detection consistent with a simple fission device.
9 Sep 2016 mb 5.06 4.4 – 19 Seismic detection consistent with a simple fission device
3 Sep 2017 mb 6.05 150–240 Seismic detection consistent with a more advanced weapon design – potentially thermonuclear as claimed by DPRK

Since the 2017 declared nuclear explosion, Geoscience Australia has reported to ASNO on the detection of 47 tectonic events located in the vicinity of the DPRK test site at P'unggye-ri. The sizes of the events ranged from mb 2.5 to 4. Based on the signal characteristics, these appear to be a continuing series of aftershocks following the large September 2017 test explosion. Based on technical analysis of the detections, it seems unlikely that they indicate new human activity at the test site.

Australian Participation in CTBTO verification development activities

The CTBTO Preparatory Commission, including its member states, continues to carry out work to ensure the Treaty's verification regime will be ready to meet requirements in the CTBT when the Treaty enters into force. ASNO coordinates and contributes to Australia's specialist support for this work, which is focused mainly on meetings of the CTBTO's Working Group B. Experts from Geoscience Australia and ARPANSA contribute mainly in relation to ongoing development of the CTBT's IMS and International Data Centre (IDC).

When the CTBT enters into force, it will provide for on-site inspections (OSI) to determine whether a nuclear explosion has taken place in a particular area. ASNO's Malcolm Coxhead, as Task Leader for the elaboration of an Operational Manual on the conduct of OSI, continued to chair discussions on this subject at the CTBTO Preparatory Commission's technical working group.

Each few years the CTBTO conducts field exercises to help to test equipment and procedures for conducting an on-site inspection, in order to refine preparedness for entry into force of the CTBT. Malcolm Coxhead has contributed, as part of a group of experts, to developing viable and technically sound scenarios for a further series of ‘build-up exercises' (BUEs). These were scheduled to take place in 2020, but have been deferred due to COVID–19. They should proceed in 2021, if the more than 100 participants are able to travel to the exercise site in Slovakia.

ASNO coordinates the involvement of Australians in training aimed at supporting the operation of the IMS and IDC. While around 90 per cent of CTBT IMS stations are now in place worldwide, detailed preparatory work is continuing to bring the IMS and IDC to a satisfactory level of readiness. ASNO coordinates Australia's contribution to the CTBTO's work in this area, working with technical specialists from Geoscience Australia and ARPANSA.

During the reporting period, three Australian experts participated in international workshops in support of CTBT verification and three Australians participated in CTBTO training activities in relation to their function as operators of IMS stations.

ANSTO's Alison Flynn, a specialist in the development of novel radiation detection systems, has participated in regular events as part of a three-year program to train future specialists to conduct OSI under the CTBT. Alison Flynn has completed training, subject to participation in the BUEs.


In September 2019, ASNO worked with the CTBTO to promote signatures and ratifications of the CTBT by states in Australia's region at a meeting of the International Parliamentary Union in Wellington. In 2019, Australia has also engaged with Timor-Leste on the CTBT as part of capacity-building assistance on nuclear non-proliferation.

A fundamental requirement for an effective CTBT will be the ability of States Parties to form sound technical judgements about the nature of events detected by the IMS. Australia continues to work with and alongside the CTBTO to promote relevant technical capacity in the National Data Centres of signatory states.

Dr Robert Floyd at the International Youth Nuclear Congress.

Dr Robert Floyd at the International Youth Nuclear Congress.