Nuclear waste in the ocean: What it is and why it's there

Figure 1. Effects of radiation on humans have been extensively studied, but not as much is known about the effects of radiation on marine life. Since marine life also uses DNA molecules, we can expect it may have a similar effect. The challenge is determining how exposed the marine life will be, because some radioactive molecules are soluble, and will travel farther and become very dilute, while others are insoluble. Additionally, some radioactive isotopes have a very long half life, and so will persist in radioactive form for much longer than others.
Starting in 1946, the ocean has been used to dispose of radioactive waste.[1] On February 20, 1994, the dumping of all radioactive waste was internationally banned,[2] but ongoing effects of previous dumping and the continuation of unregulated nuclear waste dumping continue to impact marine life.

The effects of nuclear waste on marine life

The effects of radioactive isotopes on humans are well studied, but their impacts on marine life are difficult to predict, since they are dependent on the exact isotopes leaked and the degree of exposure–the concentration and the length of exposure. In many cases, radioactive isotopes are absorbed in much the same way in fish as they are in humans. Kelp, plankton, and invertebrates directly absorb radioactive isotopes, while fish intake radioactive matter through their gills as well as by ingesting other organisms that are contaminated.[3] In this way, radioactive matter is concentrated in organisms higher on the food chain. Due to this, it is difficult to say just how dilute the nuclear waste must be to be considered “safe”.  Since many of these isotopes have long half lives, they will persist in the ocean for a long time.

Nuclear waste

Where does it come from?

Nuclear waste comes from a variety of sources, such as nuclear power plants, nuclear waste recycling plants, nuclear-powered vessels and weapons testing, hospitals, scientific research centers, and nuclear weapons facilities, as well as from events such as nuclear spills, the sinking of a nuclear-powered submarine, or leakage from sealed waste.[4]

Classification of nuclear waste

High-Level Waste
Used nuclear fuel
  • Very compact, highly radioactive
  • Marine dumping internationally banned by the London Convention in 1972
Low-Level Waste
Tools, clothing, and equipment from power plants
  • lightly used
  • not exposed for long
  • very prevalent, but not very radioactive
  • Internationally banned by the London Convention's Consultative Meeting in November 1993, effective as of April 1994[2]
An image of the Taishan Nuclear Power Plant
Figure 2. The Taishan Nuclear Power Plant. Of the radioactive waste dumped in the ocean, most is low-level waste consisting cemented work clothes and tools used in power plants.
Nuclear waste can be classified as high-level waste (such as used nuclear fuel), or low-level waste (such as work clothes or tools used in nuclear power plants). High level waste makes up only 3% of the total waste produced by a nuclear power plant, though it contains 95% of the radioactivity of the collective waste.[5] High level waste has been banned from sea disposal since 1975, and since then low-level waste has made up the majority of the waste produced and dumped in the ocean.[4]

Dumping of nuclear waste

Nuclear waste has been dumped in the ocean as a  liquid, solid, or in the form of nuclear pressure vessels, which may or may not contain fuel. Liquid waste is either dispersed at the surface, or contained and dropped to the sea floor. Solid waste is usually low-level reactive waste, which is then solidified in cement, placed in a metal container, and dumped in the ocean. Other, unpackaged forms of solid low level waste have been dumped, including larger components of nuclear facilities, such as steam generators and reactor vessel lids.[4]

In the past, sea disposal was used by many countries, including by Belgium, France, Germany, Italy, Japan, Netherlands, Russia, South Korea, Switzerland, UK, and USA. The process involves using either concrete containers that stay intact and store the waste until the containers fail, or metal containers that implode once they reach a certain depth, releasing the waste directly into the ocean where it is dispersed and diluted to very low concentrations.[5]

Figure 3 [4] (Figure 1 of Inventory of radioactive waste disposals at sea, on page 21 of pdf)

Figure 3 shows a global distribution of dumping sites, and the associated PBq for each area. PBq is a measurement of radioactivity, with one Bq defined as the activity of the radioactive material one nucleus gives off every second. Notice that the Arctic Sea and Northeast Atlantic have the highest PBq due to the frequency of dumping and the dumping of high-level waste, such as submarine reactors. Additionally, a huge majority of the dumping occurred in the Northern Hemisphere.[4]

Copyright belongs to IEAE. Permission was granted to reproduce image.

How does this problem impact marine ecosystems?

Dangers of nuclear waste

Current marine nuclear waste is mainly low level and mostly consists of discharge from nuclear power plants.[6] Coastal marine ecosystems are more directly affected by this low level radiation as they tend to be shallower than their deep sea counterparts, thus allowing radionuclides to accumulate in greater concentration.[7] The perceived danger of radioactive waste depends on pre-assigned concentration levels set by government bodies. Each type of radionuclide has different ranges, and if the concentration is within the range or lower, it is labelled as non-radioactive.[8]
Image of Arctica islandica, a bivalve mollusk with a sandy background
Figure 4. Arctica islandica, a bivalve mollusk, can be used to detect the fluctuations of Carbon-14. C-14 is a radionuclide that can accumulate in mollusks. Therefore, measuring its concentration can give insight the radiation exposure in marine ecosystems located in the North Atlantic.[9]

Nuclear waste containing radionuclides, an unstable atom with excess energy, can be harmful to organisms. The half life of radionuclides are important to determine how long an environment will be affected. Generally, after 10 half lives the ecosystem will no longer be affected.[10] Cesium-137, a main radioactive pollutant in marine ecosystems,[6] has a half life of 30 years, which means its effects could last as long as 300 years.[10] The ionizing radiation from radioactive waste can cause tissue damage; the extent depends on the type of radionuclide, duration of exposure, and the concentration. For the most part, an organism is able to keep up with tissue repairs.[7]

Marine organisms

A serious concern is that some radionuclides have the ability to bioaccumulate in benthic invertebrates.[10] Organisms that have a low volume-to-surface area, like plankton, tend to take in radionuclides at a high rate.[7] With plankton being at the bottom of the food chain, higher trophic levels could become contaminated. This includes commercially sourced animals, see Figure 7.[10]

The effects of nuclear waste are variable and can include: genetic mutations, development or reproductive changes, cancer, decreased life-span, and death. Generally, radiation concentrations in marine ecosystems are sublethal due to its low level, but not all organisms are affected equally. Gametes and larvae are more susceptible to radiation damage then an adult. Complex species like fish are less tolerant of radiation than organisms like bacteria and algae. Furthermore, benthic organisms are also more at risk than pelagic organisms. This is due to radioactive waste being absorbed and accumulated in the sediment more than it is in the open seawater above.[7]
Figure 5. 66 nuclear weapons were tested by the U.S. in the Marshall Island area between 1946 and 1958. These testing's represented nearly 20% of all atmospheric radiation derived from nuclear testing. Most notable locations include the Bikini (shown above) and Enewetak atolls.[11] Image sourced from the U.S. National Archives.

Meiobenthic organisms, such as harpacticoid and ostracod crustaceans, have a high sensitivity to pollutants, including radionuclides. Without a planktonic phase, meiobenthic organisms are more likely to be exposed to the accumulation of radioactive pollutants in their habitat. On the other hand, macrobenthic organisms do not immediately respond to radioactive pollutants. The long-term effects, however, can present itself in changing genetic variation, species diversity, or as a high concentration of radionuclides in their tissues.[12]

Vulnerable habitats

Nuclear waste can impact many different habitats within the ocean. Open waters are mostly impacted by medium to high level radioactive waste, due to waste-dumping practices, accidents at sea, and nuclear weapon testing.[6] Due to the location of previous dump sites and the current locations of nuclear power plants; the Northern hemisphere contains a higher concentration of radionuclides than the Southern.[10] Nuclear test sites located in the Russian Arctic sea were contaminated with radionuclides, mainly in the Kara Sea and Barents Sea, around the Novaya Zemlya island.[12][13] Some more well known dump sites were also located along the temperate coastlines of the US, Japan, and North Sea.[10]

What is the extent of the problem?

Measurable Ecosystem Changes

Although oceanic radioactive waste dumping data is limited, it is undeniable that there is an anthropogenic link to increased radioactivity within the oceans. From both indirect and direct analysis of human-ocean interactions, the extent of anthropogenic radioactivity spread in the oceans can be estimated.

Direct Measurements
As shown in Figure 6 and directly contributing to nuclear waste disposal, fourteen countries admitted an accumulated radioactive waste disposal of 85.1x1015 Bq across more than 100 oceanic sites.[4] There is limited accountability for marine nuclear waste dumping, so many more countries likely contribute to nuclear waste disposal in the oceans, and the actual anthropogenic input is more extensive than 85.1x1015 Bq.[14][4]
Figure 6. This table displays the radioactive waste disposal of 13 countries into the Atlantic, Pacific, and Artic Oceans from 1946 to 1993, totalling to 85.1x1015 Bq. Note, The Republic of Korea (now known as South Korea) admitted to radioactive dumping during 1945-1993, but the volume of disposal was never recorded.[4]
Indirect Measurements

Ecological impacts of nuclear waste within the oceans can also be indirectly studied when radionuclides are integrated into the tissues of marine organisms, as shown below in Figure 7. The Barents Sea was once a region of Russian nuclear waste disposal, yet several decades later, elevated levels of cesium isotopes exist in inhabitants of the region such as bearded seals (See Figure 7a).[15] In the Baltic Sea, radioactivity in the oceans is associated with the Chernobyl Incident and nuclear weapons testing. Settling of radionuclides into the ocean sediments is reflected in the benthic plants (see Figure 7b) of the Baltic Sea, where concentrations of 137Cs in organisms like the red algae Polysiphonia fucoides were notably higher than other biota.[16]

Figure 7. Radionuclides can get incorporated into the tissues of marine organisms.
Figure 7a. Ringed seals (like the one shown in this image) and bearded seals from the Barents Sea display increased levels of radioactivity within their tissues, suggesting these higher-trophic level organisms have a bioaccumulation of 137Cs from their marine environment.[15]
Figure 7c. Organisms such as the Pacific Bluefin Tuna presented elevated levels of radionuclides from the Fukushima contamination. As a highly active migratory animal, it poses the risk of acting as transport vectors to North and South Pacific Ocean regions .[17]
Figure 7b. This image features benthic plants like brown and red algae that live amongst ocean sediments, where surface radionuclides can rain down, accumulate, and eventually incorporate into their tissues.[16]
Figure 8. The Fukushima nuclear reactor waste spillage into the Pacific Ocean has reached countries all across the globe. Cesium radionuclides from the Fukushima Incident were detected in trace amounts in game fish in Hawaii, more than 6000 km away from the disaster site.[18] The distribution of cesium from this event demonstrates how widespread nuclear waste spillage in the ocean can be.
Measuring the Spread
Additionally, global seawater samples have revealed how far anthropogenic radionuclides can circulate around the oceans, punctuating that nuclear waste disposal is truly a global issue. In 2011, the Fukushima nuclear reactor meltdown in Japan released nuclear waste directly into the EEZ coastal waters; as shown in Figure 8, 137Cs radionuclides associated with the event were found in coastal waters in countries worldwide such as Canada, Russia, Sweden, and South Korea.[18] As demonstrated in Figure 9, this sudden influx of radioactivity undeniably impacted marine ecosystems; elevated levels of Cesium radionuclides were found in zooplankton and mesopelagic fish 30 - 600km away from the incident site.[19]
Figure 9. At the base of marine food webs are phytoplankton and zooplankton. Elevated levels of radioactivity in these organisms would indirectly result in the bioaccumulation of radioactivity in higher-trophic organisms, meaning that the whole marine food web is impacted.

Present Status

In the past nuclear waste disposal into the oceans has been unregulated and understudied, but now there has been greater attention to policy and waste management as countries debate if oceanic nuclear waste dumping is advisable. In recent years, dispersion and dilution of radionuclides into the oceans have been discussed as a disposal method, as explored by Malaysia and Japan.[20] In October 2020, the Government of Japan proposed dumping additional radioactive water from the Fukushima Reactor meltdown into the Pacific Ocean.[21]

Research in the dispersal of radionuclides is conflicting. Some scientists believe that despite existing at relatively higher levels than the open ocean, anthropogenic radionuclides do eventually disperse into safe radioactivity levels.[22] Others suggest that the dispersal of radionuclides may not be supported by current models, such as the case with Cesium radionuclides in Japan's EEZ coastal waters, where radioactivity levels have remained steadily elevated since 2011.[23]

Future Trajectory

Given the available data, it is evident that any nuclear waste spillage and policy for its disposal into the oceans must be assessed with radiation exposure to aquatic organisms and humans in mind.[9] All radioactive waste dumping is expected to have consequences; the magnitude of these consequences is still unknown though.

Given the impact, what are the solutions?

Figure 8. Participation in the Partial Test Ban Treaty as of July 2008. Light green - Signed and ratified; Green - Acceded or succeeded; Yellow - Only signed; Red - Non-signatory


Particle Nuclear Test Ban Treaty

Over the last 70 years there have been several attempts to regulate the disposal and dumping of radioactive waste into the ocean. During 1945-1980, most of the anthropogenic nuclear waste was brought about by bomb testing. The Particle Nuclear Test Ban Treaty of 1963 was signed to ban the testing of nuclear weapons within the ocean, atmosphere, and space. This drove most countries to continue testing underground.[7]

London convention

The explicit dumping of high level radioactive waste in ocean environments was banned in the 1972 London Convention.[7] In 1983, a 10 year voluntary moratorium was put into effect for low level nuclear waste dumping by sea.[6] In November 1992, the London convention commenced again, where an amendment was proposed to permanently ban the disposal of all radioactive waste into the ocean. It was opposed by the U.S., and the moratorium was extended until July of 1993.[10] By 1993, there was a complete ban on radioactive waste being disposed of in the ocean. Unfortunately, not all countries abided by the regulations and bans set in place, namely the former USSR, and still continue to dump nuclear waste.[6]

Local Solutions

Local solutions to the dumping of radioactive waste vary regionally. Some nations are moving towards using the oceans as a method of removal for nuclear waste disposal.[24] As oceanic pollution is a global issue, it requires international collaboration and agreement and local solutions remain inefficient long-term due to oceanic mixing.[19]

Global Solutions

Nuclear waste is an unavoidable hazard caused by nuclear energy, which overall is a relatively clean and sustainable energy source that does not release greenhouse gases. The waste is tricky to deal with since it continues to be radioactive for hundreds of years, so disposal generally consists of finding ways to store it where it will not affect humans or the environment for that time. Globally, the solution is to continue to support agreements that ban dumping of radioactive waste in the ocean, and to make sure there are consequences in place for any who break the laws. Additionally, further research on the specific effects of radioactive waste on marine life will inform decisions on what levels of radioactivity are “safe” and what are not, as well as exploration of other options for storing nuclear waste.

Long-term solutions in Finland

Olkiluoto, Finland is home to the first sanctioned deep underground repository for high-level nuclear waste. The country currently uses nuclear energy to power one third of their electricity with hopes to increase it to 40% by 2022. The goal of this repository is to safely contain all the used fuel generated by their power plants.[25]


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