The International Atomic Energy Agency (IAEA) has developed arrangements to help countries respond quickly to protect the public and the environment in the event of an accident involving radioactive materials launched into orbit or travelling in spacecraft.An artist's reniditon of the Cassini mission, launched to explore Saturn and its moons (Image: NASA)
Nuclear power sources have been used in recent years on missions that have left Earth's atmosphere and, in the past, as power sources in satellites in Earth orbits. The Vienna-based agency last week held a webinar for emergency response experts to address the response to accidents that could occur during the launch, operation and end-of-service mission phases of space nuclear power source applications, which could lead to a radioactive release into the Earth's atmosphere.
Unlike most terrestrial nuclear and radiological emergencies, with space activities the exact location of impact cannot always be predicted. "The IAEA has developed arrangements to share information about any pending nuclear-powered satellite re-entry. Using the data, countries can quickly respond to protect the public and the environment from the radioactivity that might spread as a result of an accident," Frederic Stephani, Incident and Emergency Assessment Officer in the IAEA, said.
In 1978, COSMOS 954 - a reconnaissance satellite powered by a small reactor fuelled with 45 kg of highly-enriched uranium, launched the previous year from the Baikonur cosmodrome in the then-Soviet Union - re-entered the Earth's atmosphere over Canada, scattering radioactive debris over a 600 km footprint in the Northwest Territories. A clean-up operation called Operation Morning Light was jointly led by Canada and the USA, and recovered 80 radioactive items. This incident became a prototype for global emergency preparedness and response arrangements for satellites carrying nuclear power sources, the IAEA said.
Global emergency preparedness and response arrangements are in place for satellites carrying nuclear power sources. The Convention on Early Notification of a Nuclear Accident requires that in case of an accident with a satellite or other space object carrying a nuclear power source or radioactive source, the countries that launched the object must notify affected states and the IAEA. The agency's Unified System for Information Exchange in Incidents and Emergencies is a secure 24/7 monitored website which provides a platform for countries to exchange urgent notifications and follow-up information during a nuclear or radiological emergency, while the Joint Radiation Emergency Management Plan of the International Organisations (JPLAN) sets out a framework for the coordinated actions of international organisations during an emergency.
The United Nations Office for Outer Space Affairs (UNOOSA) is the lead UN entity for outer space affairs and also maintains the UN Register of Objects Launched into Outer Space. "In the event of an accident, we would liaise with the launching state to gather information on the object and, if necessary, with other countries who can track space objects to determine re-entry timeframe and probable impact coordinates. We would then ensure that the most up-to-date trajectory and impact predictions are provided to the IAEA for further dissemination to aid emergency response efforts," UNOOSA Programme Officer Natercia Rodrigues said during the webinar.
Nuclear power sources are no longer used in Earth orbits because of the rapid improvements in solar panel technology and in order to avoid unnecessary potential releases of radioactive material, Sam Harbison, Chair of the United Nations Working Group on nuclear power sources in outer space, said. All the nuclear power source satellites presently in Earth orbit were launched from the 1960s to the 1980s, and it is estimated it will be more than a hundred years before the earliest of them will re-enter Earth's atmosphere, he added.
Nuclear power sources have more recently been used on probes, landers and rovers on missions that have left Earth orbit, such as the Cassini mission to explore Saturn and its moons, and robotic rovers such as the Mars 2020 Perseverance mission which was launched in July. There are aspirations to use nuclear power sources to support human colonies on the moon or Mars. "Solar panels are not sufficient for such prolonged missions, at great distances from the Sun," Harbison said. "They would have to be complemented by rocket propulsion, which is bulky, heavy and expensive. Nuclear power sources will be needed both for the return journey and to sustain human activities on the surface of the Moon or Mars."
Researched and written by World Nuclear News