Will NASA Recover Apollo 13's Plutonium 238?

Apollo 13 Astronaut Fred Haise extracts the fuel element for the SNAP-26 RTG during training

Credits: NASA

Somewhere among the jagged trenches of the South Pacific sits a graphite fuel cask containing 3.9 kg of plutonium from Apollo 13.

The fate of the radioactive plutonium-238 has long been overshadowed by the successful return of the three NASA astronauts on board the ill-fated mission.

The plutonium was supposed to fuel the System for Nuclear Auxiliary Power, or SNAP-27 Radioisotope Thermoelectric Generator (RTG), designed to power a set of experiments on the lunar surface but after an explosion crippled the craft and forced the crew to abandon plans of a lunar landing, the plutonium became yet another problem for mission control.

Officials from NASA confidently told The New York Times that the biggest risk was that the 40-pound generator might hit someone when it fell to Earth.

“It will keep a few fish warm,” a NASA official said. The Atomic Energy Commission, on the other hand, conceded the slight possibility that it could become ground into dust and dispersed.

NASA learned its lessons about engineering the fuel casks the hard way: in 1964, the Transit-5-BN mission aborted and the RTG burned up upon reentry above Madagascar, in keeping with its design.

Traces of plutonium were found in the area months later. In 1968, the Nimbus B-1 weather satellite was aborted soon after takeoff from Vandenberg Air Force Base and the plutonium from the SNAP-19B2 RTG plunged into 300 feet of water off the California coast, with no release of radiation.

Apollo 13’s SNAP-27 fuel, as far as we know, slipped beneath the waves and came to rest 6 to 9 kilometers deep in the Tonga Trench, one of the deepest areas in the ocean.

Subsequent testing by the U.S. Department of Energy has shown no spike in background radiation.

Not surprisingly, NASA has no desire to go looking for the small cask, even with advances in submersible technology that would make such a mission at least technically feasible.

“I don’t think that anyone has seriously considered that because of the cost of recovery,” said Leonard Dudzinski, a NASA program executive who deals with radioisotope power systems.

President Nixon (right) presenting the nation’s highest civilian award to the Apollo 13 crew (left to right, J. L. Swigert, F. W. Haise, J. A. Lovell) 

Credits: NASA

Indeed, NASA is trying to source additional plutonium 238 for its future deep space missions, the U.S. no longer produces the isotope and Russia has proved to be an unreliable source, but the useful life of the Apollo 13’s plutonium has expired.

The plutonium poses little danger to the environment: the corrosion resistant cladding should withstand seawater for approximately 870 years, ten times the plutonium’s half life.

According to NASA, the plutonium itself was in oxide form and was both chemically and biologically inert when it plunged into the ocean.

Over the years, the plutonium cask, far out of sight, has fueled two contradictory positions on the safety of RTGs for deep space missions.

For NASA, its safe return to Earth proved the effectiveness of their safety engineering. “We recognize that the Apollo 13 [RTG system] worked,” Dudzinski said. “Follow on RTGs were based on that design and improved on that design.”

Critics have taken different lessons from the untimely plunges of the RTGs. In 1997, a group of safety experts, including physicist Dr. Michio Kaku, warned that 32 kg of plutonium contained in the Saturn-bound Cassini satellite posed a greater danger than NASA would acknowledge, but ultimately, their warnings did not prevented the mission from happening.

NASA Pays for Plutonium Production to Fuel Deep-Space Probes

Voyager-1

NASA will now foot the entire bill for the United States' production of plutonium-238 spacecraft fuel, which recently started up again for the first time in a quarter-century.

The space agency had been splitting costs for the reboot with the U.S. Department of Energy, which actually produces plutonium-238.

But NASA is the only projected user of the stuff, so the arrangement changed in the White House's federal budget request for 2014, which was unveiled earlier this month.

"Since the [Obama] Administration has a 'user pays' philosophy, we are now in a position to pay for basically the entire enterprise, including the base infrastructure at DOE," NASA chief financial officer Beth Robinson said in an April 10 press conference.

"We'll be partnering with DOE in the next couple of months to figure out how to best do this, and how to streamline the program to produce plutonium-238."

Plutonium-238 is not a bomb making material, but it is radioactive, emitting heat that can be converted to electricity using a device called a radioisotope thermo-electric generator.

For decades, RTGs have powered NASA probes to destinations in deep space, where sunlight is too weak and dispersed to be of much use to a robot.



The DOE stopped producing Pu-238 in 1988, after which NASA began sourcing the fuel from Russia. But the agency received its last Russian shipment in 2010, and supplies have been dwindling ever since, worrying many scientists and space-exploration advocates.

So NASA and the DOE have been working together on a Pu-238 restart, which officials from both agencies have estimated will cost between $75 million and $90 million over five years.

This effort has made significant progress. NASA officials announced last month that researchers at the DOE's Oak Ridge National Laboratory in Tennessee had irradiated targets of neptunium-237 with neutrons, successfully generating small amounts of plutonium-238 — the nation's first in 25 years.

Scaling up from these early test activities shouldn't be too much of a chore, officials said.

"By optimizing the production process, it is estimated that 1.5 to 2 kilograms [3.3 to 4.4 pounds] per year will be produced by 2018. This amount will be enough to meet NASA's projected needs for future planetary missions. The Science budget request fully funds this requirement," NASA officials wrote in the agency's 650-page explanation of its 2014 budget request.

"For the first time, NASA’s request also includes $50 million to support the radioisotope power system development infrastructure through full-cost recovery mechanisms at the Department of Energy," they added.

U.S. restarts Plutonium 238 production for space probes

A glowing red hot pellet of plutonium-238 dioxide to be used in a radioisotope thermoelectric generator for space missions.

The Department of Energy has produced its first batch of non-weapons grade plutonium, used to power space probes, since a nuclear reactor shutdown 25 years ago, NASA officials said on Monday.

The U.S. space agency turned to buying radioactive plutonium-238 from Russia after safety issues prompted the Department of Energy to close its Savannah River Site in South Carolina in the late 1980s.

The Russian supply line ended in 2010, leaving NASA with a small and aged supply of plutonium for space probes flying missions that are ill-suited for solar power.

Plutonium naturally radiates heat, which can be converted into electricity by a device called a radioisotope thermo-electric generator.

NASA has been flying nuclear-powered probes since the 1970s. Ongoing missions using such probes include the Mars rover Curiosity, the Saturn-orbiting Cassini spacecraft, Pluto-bound New Horizons and the twin Voyager probes, which are leaving the solar system.

"The new plutonium is very important to us," Jim Green, the head of NASA's planetary science division, said during a briefing at a Lunar and Planetary Science Conference in Houston.

In partnership with NASA, the Department of Energy irradiated the radioactive metal neptunium-237 with neutrons at the Oak Ridge National Laboratory in Tennessee for about a month and successfully produced a small amount plutonium.

"This is just a test," Green said, adding that a report from the Energy Department on production plans and costs should be finished before the end of the year.

NASA is looking for the department to produce about 3.3 to 4.4 pounds (1.5 to 2 kg) of plutonium-238 per year.

Newly made plutonium has the added benefit of reviving older plutonium that has decayed past the point of being viable for deep space probes.

"The new material when we add with our old plutonium, which is more than 20 years old in some cases, really allows us to get the appropriate energy density out," Green said.

NASA also has been working on a more energy efficient generator, called the Advanced Stirling Radioisotope Generator, which can produce four times more electrical power per kilogram of plutonium-238.

Green said two such flight-ready generators are on schedule for completion in 2016. Neither has yet been assigned for a specific mission.