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Tuesday, 23 September 1997
Page: 6797

(Question No. 746)


Senator Brown asked the Minister for the Environment, upon notice, on 20 August 1997:

(1) Is the Minister aware that a spacecraft named Cassini is due to be launched on 6 October 1997 by the National Aeronautics Space Agency (NASA) from Cape Kennedy, Florida, for a Saturn-bound mission, and that the instruments on this spacecraft are powered by radioisotope thermoelectric generators (RTG) fuelled by 72.3 pounds of plutonium, an amount in excess of the total plutonium released into the atmosphere by all of the open nuclear tests combined.

(2) Is the Minister aware that: (a) out of 24 previous NASA missions, three satellites have crashed either on lift-off or during re-entry into the atmosphere, namely a 1 in 8 failure; (b) this resulted in the release of radioactivity in to the atmosphere; and (c) that out of 39 missions by the former USSR, 6 spacecraft have crashed with similar results.

(3) Is the Minister aware of the acute toxicity of plutonium, and that medical authorities indicate that the inhalation of one-millionth of a gram is enough to result in lung cancer.

(4) Has the Minister seen NASA's up-to-date environmental impact statement regarding Cassini, and (b) can a report be given to parliament on the odds calculated by NASA for failure on lift-off, for accidental re-entry into the atmosphere during the spacecraft's gravity swing manoeuvre around the Earth and for release of plutonium into the atmosphere.

(5) Is the Minister aware that the development of new sensitive solar cells by the European Space Agency obviates the need for the use of plutonium-fuelled RTG's in space missions.

(6) In view of the high probability of fatal contamination of the atmosphere and biosphere by accidental release of plutonium from spacecraft, which poses a fatal risk to Australians as well as other people, will the Government consider requesting the United States of American and NASA to postpone despatching plutonium-bearing spacecraft pending the application of safe solar cells.

(7) In the event of a decline of such a request by the US and NASA, will the Minister consider an injunction to the World Court of Justice in the Hague, by the Australian Government, in order to delay the launch of Cassini, as has been done by the United Nations in the context of atmospheric nuclear tests, and in view of the similar nature of the health effects of these tests and the accidental release of plutonium for plutonium-fuelled spacecraft.


Senator Hill —The answer to the honourable senator's question is as follows:

Senator Brown's question raises issues which fall within the portfolio responsibilities of both the Minister for Industry, Science and Tourism and myself. As such, I have consulted with my colleague, The Hon John Moore MP, about this matter and the following reply represents the Government's response.

(1) I am aware that a spacecraft named Cassini is due to be launched no earlier than 6 October 1997 by the National Aeronautics Space Agency (NASA) from Cape Canaveral, Florida, for a Saturn-bound mission. Because the Cassini spacecraft will be operating at a distance from the sun that makes the use of solar power systems not feasible, Cassini's electrical power source will be provided by Radioisotope Thermoelectric Generators (RTGs). RTGs provide power through the natural radioactive decay of plutonium (mostly Pu-238, a non-weapons grade isotope). RTGs are not nuclear reactors, have no moving parts, and use neither fission nor fusion processes to produce energy. Cassini will employ three RTGs, each of which will carry 10.8 kg (23.8 lb) of plutonium dioxide fuel.

(2) Launch reliability should be considered with respect to the launch vehicle being used for Cassini, in this case the Titan IV launch vehicle. As of February 1997, there have been 20 Titan IV launches, of which 19 have been successful. The single failure, in August 1993, was due to a flaw in one of the solid rocket motors which was caused by an inadequate repair procedure following manufacture. This problem has been fixed. I am advised that since RTG's were redesigned in 1965, to prevent the release of radioactive material, there have been two accidents during NASA missions where RTG's were on board. These were the 1968 NIMBUS-B satellite launch and the 1970 Apollo 13 lunar module re-entry. In both cases the plutonium fuel was fully contained.

(3) Plutonium is a hazardous material and if a small particle is inhaled, there is a chance that a cancer may result from long term radiation exposure. However, the risk to human health as a result of the Cassini launch is extremely low because of the design of the fuel and the RTG's.

The following should be noted with respect to the plutonium fuel aboard Cassini: The fuel is divided among 18 small independent modular units, each with its own heat shield and impact shell to reduce the chances of fuel release in an accident. In addition, multiple layers of protective materials are used to protect the fuel and prevent its accidental dispersion. The fuel itself is in a heat-resistant, ceramic form, which reduces its chance of vaporising in an accidental fire or in re-entry environments. The fuel is also highly insoluble, has a low chemical reactivity, and primarily fractures into large, non-respirable particles and chunks. This would mitigate the potential health effects in the unlikely event of an accident involving the release of this fuel.

An extensive independent safety evaluation of the Cassini mission was performed as part of the nuclear launch safety approval process by an Inter-agency Nuclear Safety Review Panel, which is supported by experts from the US Government, industry and academia.

(4) (a) I am advised that the following environmental impact assessments have been produced in the USA: Final Environmental Impact Statement for the Cassini Mission (June 1995), Nuclear Safety Analyses for Cassini Mission Environmental Impact Statement Process (April 1997), and Final Supplemental Environmental Impact Statement for the Cassini Mission (June 1997). The Department of Industry, Science and Tourism holds a copy of the Cassini environmental impact statement (EIS). Neither I nor my Department have had reason to examine the EIS.

(b) Odds calculated by NASA are contained in the aforementioned reports. NASA's analysis estimates that the probability of an early launch accident is 1 in 160, the probability of a late launch accident is 1 in 48, the probability of an inadvertent earth re-entry is less than one in 1 million, and the probability for an accident releasing plutonium dioxide into the atmosphere is 1 in 19,200 for pre-launch phase, 1 in 1,490 for early launch, 1 in 476 for late launch, 1 in 1,250,000 for short term inadvertent re-entry, and 1 in 5,000,000 for long-term inadvertent re-entry.

(5) A Cassini spacecraft equipped with the highest efficiency solar cells available, or even the new high-efficiency cells under development by ESA, would make Cassini too massive for launching to Saturn. I am advised that the ESA scientists who developed the high-efficiency cells have stated that their cells would not enable a solar powered Cassini mission.

(6) In view of the circumstances outlined above the Government does not consider it appropriate to request the United States of America and NASA to postpone despatching plutonium-bearing spacecraft pending the application of safe solar cells.

(7) I do not consider an injunction to the World Court of Justice in the Hague on behalf of the Australian Government in order to delay the launch of Cassini is necessary or appropriate.