With all the media hoopla last week about the Perseverance rover, frequently unreported was that its energy source is plutonium—considered the most lethal of all radioactive substances—and nowhere in media was the NASA projection that there were 1-in-960 odds of an accidental release of the plutonium on the mission.
“A ‘1-in-960 chance’ of a deadly plutonium release is a real concern,” says Bruce Gagnon, coordinator of the Global Network Against Weapons and Nuclear Power in Space.
Further, NASA’s Supplementary Environmental Impact Statement (SEIS) for the $3.7 billion mission acknowledges that solar energy could have been an “alternative” power source for Perseverance. Photovoltaic panels have been the power source for a succession of Mars rovers.
One in 100 rockets undergo major malfunctions on launch, mostly by blowing up. NASA in its SEIS (viewable online) described the potential impact of an accidental release of plutonium during Perseverance’s July 30, 2020, launch on the area around Cape Canaveral under the heading “Impacts of Radiological Releases on the Environment:
In addition to the potential human health consequences of launch accidents that could result in a release of plutonium dioxide, environmental impacts could also include contamination of natural vegetation, wetlands, agricultural land, cultural, archaeological and historic sites, urban areas, inland water and the ocean, as well as impacts on wildlife.
In addition to the potential direct costs of radiological surveys, monitoring and potential cleanup following an accident, there are potential secondary societal costs associated with the decontamination and mitigation activities due to launch area accidents. Those costs may include: temporary or longer term relocation of residents; temporary or longer term loss of employment; destruction or quarantine of agricultural products, including citrus crops; land use restrictions; restrictions or bans on commercial fishing; and public health effects and medical care.
Meanwhile, the US is now producing large amounts of plutonium-238, the plutonium isotope used for space missions. The US stopped producing plutonium-238 in 1988 and began obtaining it from Russia, a trade that was halted in recent years. A series of NASA space shots using plutonium-238 are planned for coming years.
Plutonium-238 is 280 times more radioactive than plutonium-239, the isotope used in atomic bombs and as a “trigger” in hydrogen bombs. There are 10.6 pounds of plutonium-238 on Perseverance.
We dodged a plutonium bullet on the Perseverance mission. The Atlas V rocket carrying it was launched without blowing up. And the rocket didn’t fall back from orbit, with Perseverance disintegrating on re-entry into the Earth’s atmosphere and dispersing its plutonium.
But with NASA planning more space missions involving nuclear power, including developing nuclear-powered rockets for trips to Mars and launching rockets carrying nuclear reactors for placement on the Moon and Mars, space-based nuclear Russian roulette is at hand.
The acknowledgement that “an accident resulting in the release of plutonium dioxide from the MMRTG [Multi-Mission Radioisotope Thermoelectric Generator] occurs with a probability of 1 in 960” is made repeatedly in the SEIS.
The amount of electricity produced by Perseverance’s plutonium generator is minuscule—some 100 watts, similar to a light bulb.
The worst US accident involving the use of nuclear power in space came in 1964, when the US satellite Transit 5BN-3, powered by a SNAP-9A plutonium-fueled radioisotope thermoelectric generator, failed to achieve orbit and fell from the sky. It broke apart as it burned up in the atmosphere. “A worldwide soil sampling program carried out in 1970 showed SNAP 9-A debris to be present at all continents and all latitudes,” according to a 1990 report by the Organization for Economic Cooperation and Development and the Swedish National Institute for Radiation Protection; the level of plutonium-238 in the Earth’s environment tripled (LA Times, 7/25/88).
After the SNAP-9A (SNAP for Systems Nuclear Auxiliary Power) accident, NASA became a pioneer in developing solar photovoltaic power. All US satellites now are energized by solar power, as is the International Space Station.
The worst accident involving nuclear power in space in the Soviet/Russian space program occurred in 1978, when the Cosmos 954 satellite with a nuclear reactor aboard fell from orbit and spread radioactive debris over a 373-mile swath from Great Slave Lake to Baker Lake in Canada. There were 110 pounds of highly enriched uranium fuel aboard.