Did you enjoy your trip? If you were alive during the Fukushima meltdown in 2011, you received an extra dose of radiation equal to that received on a roundtrip flight from Vancouver to Tokyo. This is the result according to research presented by Nikolaos Evangeliou of the Norwegian Institute for Air Research at the annual meeting of the European Geophysical Union earlier this year.
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
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.
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.
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.
Citizen science usually isn’t this personal. In 2011, roughly 65,000 Japanese citizens living near the crippled Fukushima Daiichi Nuclear Power Plant started measuring their own radiation exposure in the wake of the Tōhoku earthquake and tsunami. That’s because no one, not even experts, knew how accurate the traditional method of estimating dosage—taking readings from aircraft hundreds of meters above the ground—really was. Now, in a first-of-its-kind study, scientists analyzing the thousands of citizen readings have come to a surprising conclusion: The airborne observations in this region of Japan overestimated the true radiation level by a factor of four.
No Fukushima contamination was found in any of the 14 fish Alaskan fish samples that were collected between February and September 2016, according to the Alaska Department of Environmental Conservation. The results, released on the Alaksa DEC website, show that the sampled herring, cod, and pollock, halibut, and salmon did not have any detectable levels of 131I, 134Cs (the Fukushima fingerprint radionuclide with a half-life of ~2 years) or 137Cs in the tissues. These samples were from across Alaskan waters from Southeast to Bristol Bay and the Aleutian archipelago and the Bering Sea. Results from 2016 are similar to their results from 2015 and are part of the network of institutions monitoring for Fukushima radiation in marine waters and seafoods.
The average minimum detectable concentrations for these Alaskan samples on this gamma spectrometer were 63.7 Bq kg-1, 2.1 Bq kg-1, and 1.9 Bq kg-1 respectively for 131I 137Cs, and 134Cs. While InFORM does not analyze for 131I, those detection thresholds for cesium are 2-3 times higher than are typical for our biotic monitoring program. This may be due to either a smaller sample size or a shorter time in the gamma spectrometer for the Alaskan samples, but the result remains that levels are well below those where intervention is needed (intervention levels for 131I = 170 Bq kg-1 and 134Cs + 137Cs = 1200 Bq kg-1 according to the US Food and Drug Administration). InFORM monitoring in 2016 found 9 salmon (out of 123) from BC and Yukon rivers with detectable levels (where the minimum detectable concentrations were less than 1 Bq kg-1) of 137Cs after a six hour detector run. These nine samples are currently being freeze-dried for an extended, 2 week long, detection run. Results from this additional analysis are expected probably mid-late spring 2017.
An interesting aspect of these 2016 Alaskan samples is that this was the first time a field-deployable gamma spectrometer has been sent by the US Food and Drug Administration to a site for local analyses of samples. Data from the spectrometer were then electronically sent to FDA scientists for analysis. The thought is that this model could be used in the event of nuclear emergency to allow for more rapid analyses of environmental samples.
Alaska DEC will continue monitoring fish samples for Fukushima radiation for at least 2017 and possibly beyond.