Covering 71% of the Earth surface, the ocean has been used as a place to dispose of wastes from human activities for hundreds of years. After nuclear industry entered into the era, ocean, for its tremendous capability of dilution, had been considered again as a potential site to dispose of the inconvenient radioactive wastes. In 1946, the first ocean dumping took place at a site in the North East Pacific Ocean. Since then, 47 sites (Fig. 1) in the ocean were chosen for dumping operations, with 1960s-1970s being the most active period.
Fig 1 World-wide distribution of sea dumping sites used for disposal of low-level radioactive wastes
Scientifically, the objective of ocean disposal was to “isolate radioactive wastes from man’s surrounding environment for a period of time long enough so that any subsequent release of radioactive materials from the dumping site will not result in unacceptable radiological risks”. Therefore, it was required that the design of containers must ensure the containment of wastes long enough to minimize subsequent releases of radioactive wastes. For decades, scientists had been researching on geological conditions above and beneath the sea floor, as well as disposal technologies. Some concluded that the sub-seabed was an ideal location for disposal of high-level radioactive wastes because of its stability and non-vulnerability to terrorist attacks.
On the other side, the anti- ocean dumping campaigns were just as passionate as the scientists. Greenpeace has been campaigning against the ocean disposal of radioactive wastes since 1978 and significant progress has been made. They generally represented the public ideas that dumping radioactive wastes into the sea was dangerous to marine biosphere and would eventually harm humans. The campaigners considered it irresponsible for countries that produce the nuclear wastes to transfer the wastes out of their own territory through disposal or diffusivity of wastes into the ocean. In addition, the campaigners argued that it was much more difficult to remedy under the sea than on the land if any leakage happened. Eventually, the NGOs won the battle. The dumping of all radioactive wastes at sea from ships was banned in 1993 by London Convention. Later, this decision entered into United Nations Law of the Sea Convention and became globally effective.
This project aims to review the revolution of international regulation on ocean dumping of radioactive wastes from 1972 to 1996. It is also aimed to find out how influential public ideas during this period is, which eventually brought this revolution. The technical political review on Sub-Seabed Disposal (SSD) of high-level radioactive wastes serve to picture the feasibility of such an option, while the debates over SSD were also discussed to figure out why such an alternative did not get through. The advantages and disadvantages of SSD and other alternatives will be discussed in the last part of the paper.
II. Radioactive Wastes Classification
Before we dived into the history of ocean disposal of radioactive wastes, it would be beneficial for us to look at the classification of radioactive wastes first. There have been various schemes applied by different countries to classify radioactive wastes. The International Atomic Energy Agency (IAEA) defines six classes of radioactive wastes. U.S. Nuclear Regulatory Commission (NRC) categorized regulated radioactive wastes into four categories: Low-level wastes (LLW), Wastes Incidental to Reprocessing (WIR), High-level wastes (HLW) and Uranium mill tailings. WIR has been distinguished from high level wastes, because of its proliferation potential.
For the purpose of disposal, radioactive wastes can be generally divided into two major categories: LLW and HLW. LLW includes items that have been contaminated by radioactive material or have become radioactive through exposure to neutron radiation. HLW is either spent fuel or wastes materials remaining after spent fuel is reprocessed. They are highly radioactive and need to be isolated for millenniums.
III. Ocean Dumping of Radioactive Wastes
3.1 International Practice of Ocean Dumping
The U.S., the Former Soviet Union and Russia, France, the U.K., Germany, Sweden, Japan, South Korea, Belgium, Switzerland and Netherlands have dumped radioactive wastes into the ocean. The dumping operations were performed either unilaterally or under the voluntary supervision of Nuclear Energy Agency of the Organization for Economic Co-operation and Development (NEA/OECD). The inventory of those dumping activities is displayed in Table 1 and Table 2.
Table 1 Countries engaged in ocean dumping of radioactive wastes unilaterally
Table 2 Radioactive wastes dumped into the north Atlantic Ocean under the supervision of NEA/OECD, 1967-1982 (Participating countries include: Belgium, the Netherlands, Switzerland and the U.K.)
In the U.S., between 1946 and 1970, ocean dumping of radioactive wastes was conducted under the licensing authority and direction of the Atomic Energy Commission (AEC). The U.S. suspended ocean dumping in 1970, not for environmental reasons, but because this practice was not economic competitive. In 1973, the U.S. ratified the 1972 London Dumping Convention, which prohibited the ocean disposal of high level nuclear wastes and required a special permit for dumping of low-level radioactive wastes (LLW).
The Former Soviet Union built up magnificent repository of nuclear weapon without giving equivalent attention to the accumulation of radioactive wastes. It started its dumping operation since 1959 and continuously dumped liquid and solid radioactive wastes into the ocean. The major source of radioactive wastes came from its navy, who experienced hard time decommissioning its submarines. In 1993, Russia dumped 31,500 cubic feet of LLW into the Sea of Japan, which aroused vigorous international criticism and protests. What made it more controversial is that the Russian government leaders used its continued dumping as a stake to get foreign funds. They claimed that they were willing to solve the problem within their territory, but they lacked the funds to build up storage facilities on land. Northern European Countries, the U.S., and Japan have sponsored Russia in building up long-term storage facility. Right recently, Russian military also alleged that they have dumped radioactive wastes into Baltic Sea in 1990s.
Interestingly, Russia’s dumping in the Sea of Japan in 1993 promoted Japanese government to change its stance on ocean dumping. As a densely populated land scarce island nation, Japan used to consider Ocean Dumping as one of the solutions to its accumulated radioactive wastes from nuclear power plants. Therefore, in the 1980s, Japan did not support an international moratorium on ocean dumping of radioactive wastes. In 1993, Japan’s processing and underground storage facilities were completed at Rokkasho Village, Aomori Prefecture, which prepared it to ban the ocean dumping. Therefore, Japan supported the amendment to London convention to ban the dumping of LLW.
The U.K. was annually dumping radioactive wastes in various parts of the Atlantic Ocean from 1949 through 1966, and in 1968 and 1970. From 1965 to 1972, the Netherlands conducted radioactive wastes dumping in the Atlantic Ocean. From 1968 to 1972, the South Korea dumped radioactive wastes in the Sea of Japan.
3.2 International Regulations on Ocean Dumping
The “Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter 1972”, the “London Convention” for short, is one of the earliest global regulations to protect marine environment from human activities. Its objective is to control all sources of marine pollutants from human activities. In 1975, London Convention came into force. High-level wastes was put in Annex I list (so-called black list) from the beginning, so any dumping of HLW was prohibited. However, the low-level wastes was originally in Annex II list (so-called grey list), meaning that the signatories could continue dumping LLW, with the special permits from the IAEA. The dumping would then be recorded under the convention.
In 1993, the prohibition extended to cover all radioactive wastes through the adoption of Resolution LC.51(16). The LLW was then moved from the grey list to the black list. The updated Convention entered into force on 20 February 1994 for all Contracting Parties to the Convention, except the Russian Federation which, on 18 February 1994, issued a declaration of non-acceptance of this resolution. On 17 May 2005, the Government of the Russian Federation informed the International Maritime Organization (IMO) that it had accepted the ban under Resolution LC.51(16). As a result, the prohibition of disposal of radioactive wastes in the ocean is finally in force for all Contracting Parties to the London Convention, after 12 years of its adoption. There are currently 86 States are Parties to the Convention.
In 1996, the "London Protocol" was agreed to further modernize the Convention and, eventually, replace it. Under the Protocol all wastes dumping is prohibited, except for possibly acceptable wastes on "reverse list". This is in contrast with the 1972 Convention, under which dumping is allowed, except for materials on a banned list. The purpose of the Protocol is similar to that of Convention, but the Protocol is more restrictive because it adopts a precautionary and prevention approach. The Protocol entered into force on 24 March 2006 to supersede the London Convention. There are currently 38 Parties to the Protocol.
Fig 2 Parties to the London Convention and Protocol
3.3 The impact of ocean dumping on marine environment
It is difficult for scientists to conclude what kind of impact the ocean dumping has caused to the marine environment. At the first place, the location of drums on the sea floor is difficult to identify. Although there were designated dumping sites, most of drums did not fall on the exact locations because of unpredictable ocean turbulence. In addition, other anthropologic wastes that are identical to nuclear wastes made it harder to recognize the dumped radioactive drums.
Even though, there are some limited research data available on the radioactivity of the dumping sites. The U.S. Department of Interior and the U.S. Geological Survey (USGS) collaboratively conducted a search for the 47,800 radioactive drums dumped between 1946 and 1970 in the Pacific Ocean west of San Francisco. They used sidescan sonar to create images of large areas of the ocean floor and found what they believed to be radioactive wastes containers. The condition of the drums ranged from completely intact to seriously deteriorated. In a follow-up survey conducted by USGS and the British Geological Survey (BGS), the radioactivity of the area was tested, using the BGS’s proven towed seabed gamma-ray spectrometer system (the so called BGS EEL system). Samples of sea-floor sediment were also collected to the lab. Both measurements by EEL and laboratory samples indicate only very low levels of artificial radionuclides. The study suggested some leakage from the drums, but the contamination caused only a slight localized increase of radionuclides.
A collaborative study conducted by the U.S. and Russia in 1998 concluded no indication was found that the Former Soviet Union’s dumping in Russian Arctic caused elevated concentrations of radionuclides in waters of the Arctic Ocean. Another study conducted in the Sea of Japan in 1999 indicates that there was no significant increase of anthropogenic radioactive contamination in the region other than global fallout deposition after the Russian dumping incident in 1993.
IAEA’s Marine Environmental Laboratory in Monaco has been engaged in marine radioactivity assessment programs related to radioactive wastes dumping in the ocean since 1992. Their result found that global fallout is still the main source of anthropogenic radionuclides in the ocean, although in some regions like the Irish and North Seas, authorized releases from nuclear reprocessing facilities dominate. In the Baltic and Black Seas, the dominant source of radioactivity is the Chernobyl accident. Ocean dumping sites only represent sources of local importance with negligible radiological impact.
3.4 Environmental NGOs’ Impact on Regulation Revolution
The amendment to London Convention in 1993 and the London Convention’s evolvement into 1996 Protocol demonstrated that the anti-ocean dumping environmental regime has changed from regulation to precaution and prevention. Environmental NGOs (ENGOs) played a decisive role in this revolution of global environmental regime.
The initiatives to establish global dumping regulation were not supported by scientific evidence showing that ocean dumping was causing significant harm to the marine environment. In fact, most of the scientific studies were used by proponents of ocean dumping, such as Russia, U.K., Japan, and France, as negotiation stakes in international conference. However, L. Lingius analyzed that ENGOs have successfully influenced the regime change by “mobilizing public opinion”, “transnational coalition-building”, “monitoring environmental commitments of states”, and “advocating precaution and protection of the environment”.
Starting in 1978, Greenpeace, a widely staffed, well organized ENGO launched a campaign against ocean dumping. Beginning that year, Greenpeace intended to hinder the annual European dumping operation at a site approximately 700 km off Spain’s northwest coast. The campaigners put their dinghies under the platforms of the dumping ships to protest against dumping. In 1980, Greenpeace blockaded a canal to prevent shipment of radioactive wastes to Atlantic Ocean in Netherlands. Greenpeace’s campaign effectively attracted public’s attention towards ocean dumping and pressurized authorities to take measures. Dutch government officially suspended all dumping of radioactive wastes after the protest.
In 1981, Greenpeace applied for “observer status” at the meetings of the London Dumping Convention, held annually in UN’s International Maritime Organization (IMO). This progress helped Greenpeace to voice out as one of the influential force during international negotiations on the dumping issue. Greenpeace reckoned the Convention was “doing little more than keeping a record of whatever information its signatory countries saw fit to give it about the quantities and sorts of wastes that were being dumped at sea”. They urged for a stronger enforcement role to be played by the Convention.
Spain’s domestic public opinion on ocean dumping was awakened by Greenpeace’s protests, because a big amount of wastes were dumped near its coast. Spanish government therefore proposed a moratorium in 1983, which suspending all dumping at sea pending study of the impact of LLW on the marine environment and human health. The proposal was passed with majority of the member’s votes, although two major countries the U.S. and the U.K. were against it. The U.K. immediately indicated it would not be bound by the decision. At this point, Greenpeace strengthen its transnational force by collaborate with British National Union of Seamen (NUS), which is the British seamen’s organization. NUS had concerned on safety of seamen in handling with radioactive wastes. The seamen refused to operate “Greenpeace-proof” ships. The coalition was further strengthened by General Works’ Union, the Train Driver’s Union and the National Union of Railwaymen. The union workers refused to handle radioactive wastes for transportation or disposal. The domestic pressure like transport boycotts forced the U.K. government to change its policy and gave up its dumping plans. The 1983 moratorium was revisited again in 1985 and was extended until LLW was banned in 1993 Convention amendment.
Greenpeace was able to propose to the signatory countries that the London Dumping Convention should be changed into London Convention in recognition of the shift away from ocean dumping. The proposal was agreed. Later, Greenpeace, Scandinavian and certain Northern European countries successfully advocated the precautionary principle, which promoted the revolution of London Convention into London Protocol in 1996.
Without the support of scientific evidence, the ENGOs, who get both public and political support, won the battle.
IV. Sub-Seabed Disposal Option
4.1 The technical aspects
Professor Charles Hollister at Woods Hole Oceanographic Institution was the first person raised the concept of SSD in 1973. He saw the potential underneath the tranquil layer of sea sediments as a geological stable repository for nuclear wastes. A sub-seabed research program at Sandia National Laboratories was then initiated in 1974, which grew into the Sub-Seabed Working Group (SWG) involving 10 countries and 200 scientists and supported by Nuclear Energy Agency of the Organization for Economic Cooperation and Development (NEA/OECD). The SWG ran from 1974 to 1986, until research fund was cut by the major participating country, the U.S.
Experiments conducted by Sub Seabed Working Group supported Hollister's opinion. These experiments suggested that if wastes canisters were deposited just tens of meters below the ocean floor, any radioactive substances that leaked out would be bound up by the sticky clays for millions of years, by which the radioactivity of the nuclides would have reduced to an accepted background level. The SWG concluded that sub-seabed burial of HLW was technically feasible, but its long-term safety assessment required further research before the option is used.
Two methods of emplacing HLW beneath the deep ocean floor were proposed and designed at that time:
(i) Free-fall Penetrator emplacement. Developed by Ove Arup & Partners, penetrator option involved dropping of torpedo-like penetrators containing HLW along free fall projectiles at sites where they will completely embed themselves in the seabed sediments. The penetrator option was very encouraging at that time and several possible alternative designs were made, as shown in Fig.3a. Only the free-fall penetrators were actually used in in situ emplacement experiments, although the more sophisticated techniques shown in Fig.3a might be more preferable due to their high precision in positioning.
Freeman et al designed a free-fall penetrator (Fig.3b) and successfully dropped 4 such model penetrators in Great Meteor East (GME) Area in 1983. The 2 tonne penetrators were designed to pass through 5 km of water to achieve maximum possible penetration on impact with the sediment. The minimum terminal velocity of about 50 m s-1 was reached and embedment depths of more than 30m were recorded. The maximum penetration depth obtainable could be of the order of 50m. The success of this experiment increased scientists’ confidence in the feasibility of SSD through penetrator method.
Fig. 3 Different options for penetrator emplacement in deep ocean sediments & penetrator design
(ii) Drilled emplacement. No experiment has ever been taken with this option. First designed by Taylor Woodrow Construction Ltd in 1985, drilled emplacement deploys deep water drilling technology to create holes in the seabed. Hollister & Nadis illustrated the images of the most updated drilling operation design (Fig.4), which was published on Scientific American in 1998. According to the article, drilling emplacement requires a series of operations (Fig.5): after lowering a long, segmented drill pipe several kilometers down to the ocean floor (a), a “reentry cone” is put around the pipe and dropped to the bottom (b). (The cone could guide another drill pipe to the hole later, should there be any needs.) Drill the pipe into the ocean floor for several kilometers (c). Lower the wastes canisters along the pipe using an internal cable (d). After that part of the hole is packed with mud (e), other canisters will be emplaced above it (f). The topmost canister would reside at least tens of meters below the seafloor (g). In about 1000 years, the metal sheathing would corrode, leaving the nuclear wastes exposed to the sediments (h). In 24,000 years, the radionuclides would migrate outward less than one meter (i).
4.2 Cost of Disposal
SSD seems to be an economic alternative. The disposal costs of the two options were studied by Taylor Woodrow and Arup & Partners, and their respective costs are 0.1 x 10-3 ECU/kWh and 0.13 x 10-3 ECU/kWh, based on 1986 data. In order to make reasonable comparison, the 1985 data shows that the mined geological repository would cost about 0.33 x 10-3 ECU/kWh, which is higher than the SSD options. More data needed to substantiate this statement in today’s context because SSD has not been studied for long. The cost of deep water drilling may have decreased over the years due to its mature application in Deep Water Oil Drilling.
4.3 Risk Assessment
The latest risk assessment of the SSD penetrator option done by Sandia National Laboratory in 1997 indicated “that SSD would be a safe and economic method of HLW disposal and that predictions could be made with a high degree of confidence” . The risk assessment result is shown in Table 3. The average individual dose is about 5.2 x 10-10 Sv/yr for SSD option. Abnormal scenarios, such as damaged emplaced canister, enhanced leach rate, and changes in ocean currents, were investigated and found to be almost no effect. The Individual Dose v.s. Time is shown in Fig. 6. It shows the individual doses from a sub seabed HLW repository would be low compared to average individual dose levels from natural background, food, water, inhalation, and medical. In addition to that, the huge volume of sea water could dilute any leakage that might happen. All the release from a 105 MTHM (Metric Ton of Heavy Metal) repository would increase the background radioactivity level of the ocean by only a factor of 4 x 10-8. Risk assessment done during the same period for 105 MTHM mined geological repositories in salt, shale, clay, and granite estimated a risk range from 1.2 x 10-10 to 1.1 x 10-3 Sv/yr, which in average is higher than the 5.2 x 10-10 Sv/yr for sub seabed. The study also predicted 105 year collective population dose from a mined geologic repository in tuff ranged from factors of 102 to 103 higher than those from SSD.
Table 3 Peak Individual Dose – Post-Emplacement Release
4.4 Debates over SSD
From Sandia National Lab’s risk assessment, SSD option is extremely safe, not only because it will be located at the most stable geological location, but also because the large water column on top is a perfect separation from human’s immediate environment and the terrorists. Moreover, the sediments at the seabed perform as a natural barrier for radionuclides from escaping into the seawater. Their strong adsorption capacity can capture any accidental or pre-designed leakage from the canisters for millions of years. So, the impact of SSD to the marine ecological environment will be negligible. In addition, the cost of the SSD option seems to be very competitive. Since it is assessed to be safe, economic, and feasible, why was this option banned in 1996?
Ever since the scientific research on SSD attracted ENGO’s attention, there were hot debates over SSD, as to whether it should be covered within the jurisdiction of the London Convention. Opponents to the SSD sought to have the sub seabed option defined as constituting dumping and thereby prohibit it under the London Convention. Scientists who support SSD argued that their concept of Disposal was completely different from Dumping. They considered dumping the same as littering, which should be banned for all kinds of radioactive wastes and had actually been banned in 1993 London Convention. SSD involves careful emplacement of wastes canisters into the sediment of ocean floor, with at least tens of meters on top to trap any potential leakage, which happens millions of years later when the radioactivity of the nuclides have declined to natural background level.
Let’s take a closer look at how London Convention defined “dumping”. According to Article III of the London Convention, “dumping” is:
(1)(a)(i): Any deliberate disposal at sea of wastes or other matter from vessels, aircraft, platforms or other man-made structures at sea.
(1)(a)(ii): Any deliberate disposal at sea of vessels, aircraft, platforms or other man-made structures at sea.
(1)(b)(i): “Dumping” does not include: The disposal at sea of wastes or other matter incidental to, or derived from the normal operations of vessels, aircraft, platforms or other man-made structures at sea and their equipment, other than wastes or other matter transported by or to vessels, aircraft, platforms or other man-made structures at sea, operating for the purpose of disposal of such matter or derived from the treatment of such wastes or other matter on such vessels, aircraft, platforms or structures; II. Placement of matter for a purpose other than the mere disposal thereof, provided that such placement is not contrary to the aims of this Convention.
(1)(c): The disposal of wastes or other matter directly arising from, or related to the exploration, exploitation, and associated off-shore processing of sea- bed mineral resources will not be covered by the provisions of this Convention. 
Because the SSD option did not emplaced wastes in the water column, the Sub-Seabed Working Group (SWG) considered the wording “at sea” in London Convention did not cover SSD. During a discussion at London Convention in 1984, the opposition led by Greenpeace argued that this is a narrow basis for evaluation and a better basis would be provided by considering the object and purpose of London Convention to protect marine environment as a whole. Besides Greenpeace, the Nordic countries, Spain, Kiribati, and Nauru, are also major opponents. Within SWG, there were conflicts among member States. “Some wished the group to take a low profile while others seemed to indicate a preference for termination”.
In the London Convention Meeting of 1985 and 1986, a neutral decision was negotiated which embodied the following principal: “no such disposal should take place unless and until it is proven to be technically feasible and environmentally acceptable, including a determination that such wastes can be effectively isolated from the marine environment and a regulatory mechanism is elaborated under the London Dumping Convention.” The decision alone was acceptable for the proponents, because it did not bring an end to the Sub-Seabed Working Group.
But then in 1986, the major sponsor of the SWG -the U.S. Department of Energy cut off funding for research on sub seabed options in favor of pursuing the Yucca mountain project. Without funding, there is minimal research progress during 1987 to 1996. And the decision to prohibit SSD was finally made in 1996, when London Protocol came to replace London Convention.
The scientists from the Working Group argue that since London Convention allowed SSD to be reviewed in 25 years, the funding for research itself shall not be banned, because 25 years allows sufficient time for more research on scientific and engineering feasibility of SSD alternative. This is absolutely rational, because all reasonable disposal options should be actively explored. Even if one was to be chosen, there should be other feasible alternatives to perform as a back-up option.
Although the withdraw of funding from the U.S. is the most direct and fatal political causation of the failure of SSD, the international conflict over the issue of ocean dumping of LLW (discussed in the previous chapter) also “poisoned” the political atmosphere for considering SSD. The campaign against radioactive wastes disposal was caused by the significant loss of public confidence in nuclear industry due to Three Mile Island and Chernobyl. Some environmentalists of the campaign opposed the SSD option as a way to put an end on nuclear industry. However, with the unsolved problem of HLW and some nations’ and sub-national organizations’ determination on acquisition of Nuclear power, this kind of hope is not only meaningless, but also harmful to the environment itself, because it might delay the progress of finding the best solution.
V. Other Alternatives for HLW
According to the MIT 2003 report31, there are generally three methods by which countries are tackling or proposing to tackle with HLW. The U.S., Canada, Sweden and Finland are among a few countries who decided to dispose HLW directly, France and the U.K. are reprocessing wastes, while some other countries are using temporary storage repository and will decide later on reprocessing to disposal.
Mined geologic disposal of HLW has been the most studied option among the leading nuclear countries. Although details vary among nations, the basic approach is based on a multibarrier containment strategy, combined with a suitable geologic, hydrologic, and geochemical environment. The proposed U.S. repository at Yucca Mountain in Nevada is located above the water table in saturated zone. The cylindrical stainless canisters are designed to be surrounded by a 2cm thick shell of corrosion-resistant Alloy 22, which further be shielded by a 1.5cm thick Titanium from dripping water. DOE has submitted a license application for the Yucca Mountain project in 2008, but Obama Administration abandoned the Yucca Mountain in 2009. Hollister criticized the Yucca Mountain Project was a shortsighted decision, and he predicted in 1998 that the project might be abandoned because of its limited capacity, which almost has become a reality today.
The Finnish repository is located in the granitic rock at Olkiluoto. Its design is based on KBS-3 concept developed by Swedish company KBS for its own nuclear wastes disposal. The mechanism is to emplace copper-iron canisters in vertical emplacement holes in crystalline bedrock at a depth of about 500 meter. In Sweden, SKB will submit an application for a permit to build a final repository in Forsmark, Osthammar.
Deep boreholes drilled into stable crystalline rock several kilometers below the earth’s surface is considered as an alternative to the mined geologic repositories. Deep boreholes experienced a similar cold reception as SSD in 1980s, because of the popularity of mined repository option. With the development of drilling technology that makes it cheaper, this alternative starts to attract attention again. In a Swedish design, the borehole is proposed to be 80 centimeters in diameter to emplace cylindrical canisters, with compressed bentonite clay vertically separating canisters from each other.
There are several advantages of deep boreholes. Firstly, large areas of the world have suitable geology condition for deep borehole as shown in Fig.7 (one point to note is that this figure does not cover vast area of the ocean seabed). Secondly, it occupies relatively smaller area of land than mined geological repositories and might cause less political controversial. However, because of the depth, the canisters emplaced in the deep boreholes are not so easy to retreat as those in mined geological repository.
If we compared the deep borehole alternative with the drilling option in SSD, we can find that they have similar design principals, except that SSD drilling is operated underneath a water column of several kilometers. Would this water column provide another layer of barrier to biosphere and terrorist acquisition? Would it increase the risk of wastes disposal? Or would it cause even more difficulties to retreat and recover the spent fuel, which might be useful in the future? These are questions that need to be answered before preference is given to either of the alternatives.
Fig 7 Distribution of Crystalline Basement Rock Exposed to the Surface
Spent fuel reprocessing is another alternative pursued by countries such as France, Russia, U.K. and Japan. It uses chemical procedures to separate useful components, such as remaining uranium and fresh plutonium, from spent nuclear fuel obtained from nuclear reactors. The reprocessing technology, firstly developed to create the world’s first atomic bomb, is now commercialized for civic use to extend fuel cycle supply. The separated plutonium and uranium can be recycled in reactors and converted to radionuclides with much shorter half-lives. However, although the half-lives of spent fuels are reduced, the amount of wastes produced is not, the necessity to find disposal sites for HLW still exists (the engineering requirement of the sites may be different because of the different characteristics of spent fuels).
Moreover, the proliferation risk of the concentrated plutonium after reprocessing has become one of the key reasons that diverts States’ stance on reprocessing. In general, U.S. policies have been discouraging nuclear reprocessing, except for Bush Administration’s encouragement on research in this field. In 2001, President Bush’s National Energy Policy recommended that “the United States should also consider technologies to develop reprocessing and fuel treatment technologies that are cleaner, more efficient, less wastes intensive, and more proliferation-resistant”. Although Bush Administration sought for $ 405 million for Global Nuclear Energy Partnership (GNEP), the Congress only provided $179 and focused the program on basic research, specifically denying funding for construction of commercial-scale reprocessing plant and fast neutron reactor.
In addition to the proliferation risk, cost of reprocessing is the other reason that hinders its expansion. MIT 2003 reported has done an economic analysis and concluded that the current reprocessing technology (MOX) is roughly 4 times more expensive than the once-through fuel cycle. The economics of reprocessing largely depends on the price of natural uranium and the cost to dispose of HLW. If price of natural uranium stays low, while the cost of disposal remains high, the reprocessing would not be an economic competitive option.
Other alternatives have also been studied. Disposal in glaciated areas, in Antarctica for example, would require substantial changes to international legal and political agreements, which faces the same challenge as SSD did. Disposal into space would provide the greatest degree of isolation from biosphere, but its practicality, cost, technological complexity, and potential risks all argue against it at the moment. Finally, nuclear transmutation, the conversion of long-lived radionuclides into shorter-lived or even stable nuclides, is not considered feasible in the near future.
The issues related to ocean disposal of radioactive wastes are naturally complex and the Sub-Seabed Disposal (SSD) option has been facing all kinds of challenges. Firstly, ocean disposal usually happens at sites out of a nation’s own territory and therefore requires international legal and political consensus, which is more complicated than mined geological repositories. Secondly, it is counterintuitive to ban ocean dumping while allow sub-seabed disposal for the public. The conflicts over ocean dumping poisoned the political environment to consider SSD. The political obstacle is much larger than the technical obstacle for SSD. Thirdly, various alternatives are competing with SSD in resources and political attention.
In my opinion, funding for research in SSD should be resumed to examine this option thoroughly before the next review in 2021. After obtaining stronger scientific support and sounder engineering techniques, the pathway for SSD to get through all kind of international legal and political conflicts would require building up of international institutional framework, which is strong enough to discuss this issue in a coherent way. It should be able to coordinate the work done by research group like Sub-seabed Working Group and regional nuclear agency like NEA. It should have strong political influence in member States to set up agenda that would be internationally recognized. Moreover, it should have sufficient public relations capacity to work with ENGOs and the public of all nations. The nations who are interested in such an alternative should start soon to prepare for research and conversation.
Another interesting point to note is that IMO amended the London Protocol to allow carbon sequestration under seabed from 10 Feb 2007. Sub-seabed carbon sequestration faced the same controversy as SSD as to whether it was under the jurisdiction of London Protocol, but it eventually got through all the technical, social, and political agendas much faster than SSD. Lessons learned from carbon sequestration in terms of site selection, decision rules, a common framework at the global level which reviews technological feasibility, sets standards, monitors operations, and settles issues of liability, would be beneficial for SSD to learn and to follow. Most importantly, SSD needs to get equivalent amount of support from the public and majority of the Governments as carbon sequestration does.
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