Tag Archives: Plutonium

The Apollo 13 Mission and Rescue: How much plutonium was added to the Earth’s environment?

By Jay T. Cullen

The purpose of this short post is to compare the relative amounts of radioactive plutonium released to our environment from the Apollo 13 mission in April 1970 and the

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Apollo 13 mission patch/emblem with a depiction of the Greek god of the Sun and latin phrase “Ex Luna, Scientia” which means “From the Moon, Knowledge.”

Fukushima Daiichi nuclear power plant disaster that began in March 2011.  Apollo 13 was the third mission planned to bring American astronauts to land on the moon and conduct scientific studies there.  On April 11 1970 the Saturn V rocket carrying astronauts James Lovell (Commander), Fred Haise (Lunar Module Pilot) and Jack Swigert (Command Module Pilot) was launched from the Kennedy Space Center in Florida.

The mission plan was to land Lovell and Haise in the Fra Mauro highland area of the moon but, due to unforeseen circumstances, that never came to pass.  As many of you know as was popularized in the 1995 film directed by Ron Howard and starring Tom Hanks (Lovell), the late Bill Paxton (Haise) and Kevin Bacon (Swigert) the lunar landing was aborted after a malfunction in one of the service module oxygen tanks caused an explosion that crippled the spacecraft.

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Photo of the damaged Service Module taken shortly after it was jettisoned by the Apollo 13 crew.

What followed was a technical problem solving masterpiece to bring the astronauts safely back to Earth with limited power and life support systems. The rescue of Lovell, Haise and Swigert has been characterized as a “successful failure” and NASA’s finest hour.

Plutonium in the Environment from Apollo 13

A consequence of not having landed on the moon was that the descent stage of the Lunar Module (LM; which would normally have brought Lovell and Haise down to the surface and been left behind when they returned) was now being brought back to Earth.  The power and life support afforded by the LM was central to the successful rescue of the crew.  What is significant about this is that the power supply attached to the descent stage of the LM to be left on the lunar surface to provide electric power for the Apollo Lunar Surface Experiment Packages (ALSEP) was a SNAP-27 Radioisotope Thermal Generator (RTG) containing 1,650 TBq (TBq = 1012 Becquerel) or roughly 3.9 kilograms of plutonium oxide fuel.  While the RTG was essential to bring astronauts home safely the high velocity reentry of the LM raised the possibility of contaminating the atmosphere and surface Earth with worrying amounts of Pu.  To avoid the possibility of the RTG coming down in a populated area the flight engineers had the LM enter the Earth’s atmosphere such that the RTG would be deposited in the remote Pacific Ocean near the Tonga Trench where water depth is about 6-9 kilometers.  Measurements in the atmosphere and ocean following the reentry of the LM suggested that the RTG had survived intact and little of the Pu was broadcast in the environment.  Tests of the RTG casing suggest that this 3.9 kg of Pu, somewhere on the seafloor of the Pacific, will not be mobilized for another ~800 years.
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Plutonium Released From Fukushima

The triple meltdown and hydrogen explosions at the Fukushima Daiichi Nuclear Power Plant (FDNPP) are known to have released some of FDNPP Pu isotope inventory to the environment.  Direct measurements of air, water and soil and modeling of the temperature and pressure in the reactors during the meltdowns by the international scientific community have allowed the total amount of Pu broadcast to the environment during the period of peak releases in the weeks to month following the disaster. These direct measurements made globally, the models and comparisons with isotopes that were released in much greater quantities (e.g. 137-Cesium and 131-Iodine) indicate that about 2.3 x 109 Bq or about 580 milligrams of Pu left the FDNPP in the wake of the disaster.  This is about 700,000 fold less Pu than Apollo 13’s RTG.  While the Apollo 13 Pu is likely to have little environmental impact given that it will be released slowly to the deep ocean over time I think it is interesting to compare the total amounts given the perceived impact of the FDNPP releases.  Both the FDNPP and Apollo 13 Pu are dwarfed by the ~11 PBq (PBq = 1015 Bq) of Pu-239,240 released to the atmosphere as a result of nuclear weapons testing in the 20th century.

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Most Recent Measurements of Plutonium in Pacific: Fukushima Fallout Undetectable

By Jay T. Cullen

@JayTCullen and @FukushimaInFORM

The purpose of this post is to report results from two recently published studies on plutonium releases from Fukushima to the Pacific Ocean. The post contributes to an ongoing series where results from peer-reviewed studies on the impact of the triple meltdowns at the Fukushima Dai-ichii nuclear power plant on the health of the Pacific ecosystem and residents of the west coast of North America are reported. A frequently asked question of those involved in monitoring the health of the North Pacific is why more measurements of the long lived, alpha-emitting isotopes of plutonium (239Pu half-life 24,100 years; 240Pu 6,570 years) are not being made given the potential for these isotopes to pose radiological health risks. Previous work indicates that 239+240Pu releases from Fukushima were about 100,000 and 5,000,000 times lower than releases from the Chernobyl disaster in 1986 and 20th century weapons testing respectively. Initial measurements of Pu isotopes in seawater and marine sediments off the coast from Fukushima indicated no detectable change occurred in Pu inventories in the western Pacific after the disaster. These two most recent studies monitored the activity and isotopic composition of Pu in seawater and marine sediments off of Japan from 2008-2013. Similar to earlier work these studies find that the release of Pu isotopes by the Fukushima accident to the Pacific Ocean has been negligible. The Fukushima signal is not detectable in the ocean off Japan relative to legacy sources from atmospheric weapons testing in the 20th century. Given these accumulating results 239+240Pu from Fukushima is unlikely to negatively impact the health of the Pacific Ocean ecosystem and levels in the environment from Fukushima will not pose a danger to the population of North America.
Continue reading Most Recent Measurements of Plutonium in Pacific: Fukushima Fallout Undetectable

Update on Fukushima Plutonium Releases to the Pacific Ocean

By Jay T. Cullen

This post reports on the most recent study of plutonium releases from Fukushima to the Pacific Ocean. The post contributes to an ongoing effort to report peer-reviewed studies on the impact of the triple meltdowns at the Fukushima Dai-ichii nuclear power plant on the health of the Pacific ecosystem and residents of the west coast of North America. Plutonium is an alpha-emitting isotope that carries significant radiological health risks if internalized with risk of exposure increasing with the activity of Pu isotopes in the environment. Previous work indicates that 239,240-Pu releases from Fukushima were about 100,000 and 5,000,000 times lower than releases from the Chernobyl disaster in 1986 and 20th century weapons testing respectively. Initial measurements of Pu isotopes in seawater and marine sediments off the coast from Fukushima indicated no detectable change occurred in Pu inventories in the western Pacific after the disaster. More recent and more expansive work supports earlier studies drawing the conclusion that up to two years after the accident the release of Pu isotopes by the Fukushima accident to the Pacific Ocean has been negligible.


A paper by Bu and colleagues was recently published in the peer-reviewed journal Environmental Science and Technology which investigated the activity of Pu isotopes marine sediments collected within 30 km of the Fukushima reactor sites. 239,240,241-Pu and radiocesium isotopes (134-Cs and 137-Cs) were measured. Given that Pu is a particle reactive element that would tend to be concentrated in sediments such measurements should help to determine the extent and degree of Fukushima derived Pu in the marine environment. Sample collection sites are indicated in the map below.

Map showing the locations for (a) sediment samples collected within the 30 km zone around the FDNPP site and (b) sediment samples collected outside the 30 km zone around the FDNPP site in previously published studies by Bu and colleagues.
Relatively high activities of 134-Cs and 137-Cs and a decay corrected ratio near 1 indicated that the sediments were indeed contaminated with Fukushima derived radionuclides.
137-Cs activities and 134-Cs/137-Cs activity ratios in the marine sediments (decay corrected to 15 March 2011) determined by Bu et al. 2014. The blue dashed line represents the 134Cs/137Cs activity ratio fingerprint of the radiocesium released by the Fukushima disaster.
In contrast to the clear imprint of Fukushima derived Cs on the marine sediments the activities of 239,240-Pu and 241-Pu were low compared with the background level before the accident. The Pu activity ratios (240-Pu/239-Pu and 241-Pu/239-Pu) suggested that the Pu detected was the result of global fallout and the pacific proving ground (PPG) close-in fallout resulting from atmospheric weapons testing in the 20th century. The following figure is a mixing diagram that helps to determine the relative contributions to the observed Pu contamination of marine sediments off the Japanese coast.
Mixing plot of 241-Pu/239-Pu atom ratio vs 240-Pu/239-Pu activity ratio in Fukushima sediments compared with Pu compositions of global weapons fallout, Fukushima release, and the Pacific Proving Ground weapons fallout. The closed orange circles (soil and litter samples) and closed black circles (aerosol samples) represent the Fukushima source; the closed pink circle represents the global weapons test fallout; the closed blue circles represent the surface sediment samples collected outside the 30 km zone; the open black circles represent sediment samples within 30 km of the Fukushima site; the closed violet circle represents Sagami Bay sediment samples; the closed wine colored circles represent Pacific Proving Ground source.
The mixing diagram indicates that the isotopic ratio of Pu in marine sediments is inconsistent with a significant release of Fukushima Pu to the marine environment. The isotopic composition of Pu in marine sediments is consistent with Pu deposited during atmospheric weapons testing in the last century.

While initial releases from the plant and ongoing releases due to groundwater infiltration and terrestrial runoff have been negligible thus far according the authors they rightly point out that significant inventories of Pu are insecurely stored at the Fukushima site. So far estimates suggest that about 2.3×10^9 Bq of 239,240-Pu or 580 milligrams of the isotopes have been broadcast to the environment from Fukushima. Bu et al. (2014) estimate that contained within the roughly 270,000 tons of radioactive liquid waste stored in large tanks at Fukushima there exists approximately a further 1×10^8 Bq of 239,240-Pu. Given that future earthquakes or other events could mobilize this Pu, continued monitoring of Pu isotopes in the marine environment is necessary and prudent.