North Korea’s apparent nuclear detonation on Sept. 3 has drawn our attention to a remarkable international organization that helps detect and identify nuclear tests.
For the Vienna-based Comprehensive Test Ban Treaty Organization (CTBTO), the latest North Korean explosion was easy to detect and locate. With a seismic magnitude of 6.1 and a blast yield of 160 kilotons (Hiroshima was around 15), the purported hydrogen bomb test mimicked a major earthquake. It was quickly sourced to North Korea’s nuclear test site.
Confirming that the event was definitely a nuclear test, as opposed to another type of explosion or an earthquake, is trickier.
For that we rely on detection of short-lived radioactive isotopes that may leak from the test site, notably the noble gas xenon. The CTBTO has not yet announced such a finding, although South Korean monitors have reportedly detected xenon-133.
Other potential sources of the gas must be eliminated before a definitive conclusion can be reached.
In the past, such fallout has usually been discerned after a North Korean test, but not always. Much depends on whether the cavity created by the test leaks or collapses.
Nuclear test ban treaty
The CTBTO’s International Monitoring System, which detected the North Korean test, is designed to verify compliance with the 1996 Comprehensive Nuclear Test Ban treaty, which bans all nuclear tests in all environments for all time.
The International Monitoring System comprises 321 monitoring systems worldwide, using four technologies:
- seismic, to detect tests under ground
- radionuclide detection, to detect breakdown products
- hydroacoustic, to detect tests under water
- infrasound, for atmospheric tests
The CTBTO’s international monitoring system is sensitive enough to detect underground nuclear tests below 1 kiloton.
Construction of the system began in 1996 and is now 90% complete.
Australia hosts six seismic, two infrasound, and one hydroacoustic station, including a large seismic array and infrasound station at Warramunga in the Northern Territory.
Data from the International Monitoring System is transmitted to Vienna via a global communications satellite network, mostly in real time, where it is compiled, analyzed, and distributed to member states. Sixteen laboratories are available for analyzing radioactive fallout.
The treaty also provides for on-site inspections to confirm that a nuclear test has been conducted. The system is funded by member states according to the usual United Nations formula based on national GDP.
A difficult, important achievement
As a member of the Australian delegation, I observed the complex preparatory scientific talks on the system at the Committee on Disarmament in Geneva in the early 1980s. It is a miracle of statecraft and science that this collaborative international infrastructure has actually come into being.
The scientists did not get everything they wanted due to political and financial constraints. Some errors were made in the rush to complete the technical specifications. Installation of some of the stations in remote and inaccessible areas has proved daunting.
The hydroacoustic system, for instance, passed a significant milestone in June when the final station was completed, on France’s Crozet Islands in the southern Indian Ocean.
After 20 years of planning and construction and the investment of millions of dollars, not only is the International Monitoring System almost complete, but it is functioning far better than its designers anticipated.
It also has unexpected side benefits, such as providing early warning of tsunamis and detecting nuclear disasters. The network successfully detected the 2004 Indian Ocean tsunami and tracked radioactive plumes from the 2011 Fukushima nuclear disaster.
Nuclear test ban treaty
The test ban treaty itself is not in such good shape. More than two decades after it was opened for signature it is still not in force, rendering the CTBTO only “provisional.” This is due to the requirement that all 44 states with a significant nuclear capacity must ratify it.
Currently 183 states have signed, and 162 have ratified. But eight of the 44 with a nuclear capacity have still not ratified: China, Egypt, India, Iran, Israel, Pakistan, North Korea, and the United States. China, Egypt, Iran, Israel, and the US have at least signed. China says it is awaiting US ratification before it moves.
After a flawed lobbying effort, US president Bill Clinton’s administration failed to secure senate approval for US ratification in 1999. The treaty has not been resubmitted since, despite president Barack Obama’s undertaking that he would try.
Given president Donald Trump’s apparent focus on emphasizing American military prowess, it seems unlikely that he will favor ratification of the treaty.
More immediately threatening is the return of periodic Republican attempts to defund the CTBTO. These are usually beaten back on the grounds that the US benefits greatly from the worldwide monitoring that only a global system can provide, notwithstanding impressive US national capabilities.
As it has in the past, the Australian government should make representations in Washington in support of CTBT ratification and preservation of funding for the system.
Paradoxically though, even if the other seven holdouts ratify, the one country that continues to conduct nuclear tests into the 21st century, North Korea, can stymie entry into force forever. Its accession to the CTBT should be part of any negotiation with North Korea on its nuclear program.
The good news is that the global monitoring system continues to go from strength to strength, providing reassurance that all nuclear tests, including those less brazen than North Korea’s, will be caught.
The CTBTO’s verification system provides hope that science can quietly triumph while political solutions elude us.