Fukushima-related measurements
by the CTBTO- Page 2

Enhanced cooperation with other international organizations

Following an initiative by United Nations Secretary-General Ban Ki-moon, relevant international organizations have agreed to enhance cooperation to help mitigate the consequences of the nuclear disaster in Japan. These organizations include the CTBTO, the International Atomic Energy Agency (IAEA), the World Meteorological Organization (WMO), the UN Development Programme (UNDP), the World Health Organization (WHO) and the UN Office for Disarmament Affairs (UNODA), see press release of 25 March 2011.

Click for a regional dispersion simulation (Austrian Meteorological Service ZAMG)

The CTBTO contributes to this effort by providing information on the detection of radioactive isotopes from its worldwide monitoring network. The CTBTO can also assist in predicting the global dispersion of radioactive material by using its atmospheric transport modelling (ATM) tool which has been developed in cooperation with the WMO. This method allows for the calculation of the dispersion of a given radionuclide emission, using meteorological data. This calculation can be performed as back tracking in order to identify the area where a radionuclide may have been released, calculated from the station where it was observed. In the case of Fukushima, where the point of release was known, the CTBTO applied forward ATM to predict where radionuclides would travel in the future.

Although the emissions were initially based on estimates only, they proved to be 95% correct as the radionuclides reached the stations mostly within hours of the time predicted. With information made available later by the IAEA on the release level of radioactive substances at the Fukushima power plant – the so-called source term – the CTBTO has been able to quantify and refine its global dispersion predictions.

Radioactivity outside of Japan below harmful levels

Over 2000 nuclear tests have been conducted all over the world, many of them in the 1950s and 1960s as atmospheric tests.

The present event has understandably given rise to concerns about manmade radiation. In particular, atmospheric nuclear testing in the 1950s and 1960s caused widespread fallout, resulting in radiation-related diseases and deaths and rendering vast areas inhabitable to this day (see effects of nuclear testing). These nuclear tests had the most direct effects on the immediate region. The danger from fallout decreases with distance, as radioactive particles are dispersed into the atmosphere or washed out through precipitation. A number of radioactive isotopes also have a limited half-life of a few days or weeks, which reduces the overall radioactivity with time. Other radioactive substances though, such as plutonium, linger for thousands of years. The locations where over 1,500 underground nuclear tests were carried out worldwide are highly contaminated and have had to be completely fenced off to limit the danger to humans.

Radioactive isotopes in baby teeth

Airborne radioactivity due to Cold War nuclear testing. Source: U.S. Department of Commerce, Earth System Research Laboratory.

The cumulative effects of the hundreds of atmospheric nuclear tests released such vast amounts of radioactivity that the overall level of radioactivity in the Earth's atmosphere increased to levels that even dwarfed the Chernobyl disaster (see right). Radioactive isotopes could be traced in baby teeth of children born even at great distances from the test sites in these decades.

By comparison, the levels detected at stations outside Japan up until 13 April 2011 have been far below levels that could cause harm to humans and the environment. The levels are comparable to natural background radiation such as cosmic radiation and radiation from the environment on Earth and lower than from manmade sources such as medical applications or nuclear power plants (under normal operations) or isotope production facilities. This demonstrates how extremely sensitive the CTBTO's monitoring stations are.

Monitoring continues

The Philippine Nuclear Research Institute is one of the institutions receiving CTBTO monitoring data.

The radionuclide monitoring stations of the CTBTO’s global detection system monitor the abundance of radioactive substances in the air continuously. The CTBTO shares its monitoring data and analysis results with its 183 Member States; 130 States and 1,300 scientific and academic institutions currently make use of this opportunity to receive CTBTO data and data bulletins. This means that they also continue to receive first-hand information on possible radioactive releases and dispersal from the stricken Fukushima power plant.


The CTBTO is building a global verification system to detect nuclear explosions to verify the Comprehensive Nuclear-Test-Ban Treaty. When complete, its 337-facility network of seismic, hydroacoustic and infrasound stations will watch underground, the oceans and the atmosphere, and its radionuclide stations will sniff the air for tell-tale signs of a nuclear explosion.

Nearly 270 monitoring stations, of which 63 are radionuclide sensors, are already operational and send data to the International Data Centre in Vienna, Austria, for processing and analysis. While the system is designed to detect nuclear blasts, it also picks up a vast amount of data that could be used for civil and scientific purposes.