Nuclear power: Encyclopedia II - Nuclear power - Risks

Nuclear power - Risks

Opponents of nuclear power, such as Greenpeace, argue against its use due to issues like the long term problems of storing radioactive waste, the potential for severe radioactive contamination by an accident, and the possibility that its use will lead to the proliferation of nuclear weapons. They point to the nuclear accidents.

According to a 1978 finding by the Supreme Court of the United States, comprehensive testing and study had not yet removed the risk of a major nuclear accident [47]. In the 1980s and 1990s each US nuclear plant underwent an Individual Plant Examination process using Probabilistic Risk Assessment to quantify the risks and identify and address high-risk areas.

In a peer reviewed article, Oldberg and Christensen (1995) demonstrate the existence of a statistical fallacy in the technology that is used in the safety-related inspections of components of the reactor pressure boundary. When a counterargument was submitted to the peer review process by the U.S. Nuclear Regulatory Commission, it was rejected (Oldberg, 2005).

It follows from the existence of this fallacy that such attributes of nuclear power as its risks, expected costs, expected benefits and expected utility are not determinable but seem determinable. One's ability to make decisions, such as whether to shut down existing plants or whether to build new ones, is crippled but seems not to be crippled.

Organs of the nuclear power industry that include the U.S. Nuclear Regulatory Commission and the ASME Section XI Committee have ignored this state of affairs for more than a decade (Oldberg, 2005). Thus, the fallacy remains active.

According to the USNRC Inspection Handbook, plant inspectors are required to provide a variety of subjective assessments without empirical bases or confidence intervals, which are used in the derivation of hazard risk probabilities. The Oldberg and Christensen articles referenced earlier point out that these "probabilities" are sometimes not probabilities, with attendant damage to one's ability to perform risk assessments and confusion about this ability.

To highlight what they believe are the risks, opponents quote the situation in the United States, where under the Price-Anderson Nuclear Industries Indemnity Act corporations requested and were granted immunity beyond (in 2005) $10 billion (all the available insurance plus pool monies combined) from civil liability (including from possible criminal behavior, although that would be subject to criminal prosecution) from a nuclear incident which causes harm to the public. (Beyond the $10 billion, Congress is required by law to act.)

Proponents argue that the risks are small and that fear has been the single largest obstacle to the widespread use of nuclear power. Assessment of nuclear risk was last done in the 1991 NUREG-1150 report. Additionally, competing technologies may have equivalant risks. Coal currently contributes significantly to problems like global warming, acid rain, various diseases due to airborne pollution, and the storage of large amounts of ash. Contrary to popular belief, coal power actually results in more radioactive waste being released into the environment than nuclear power [48].

Nuclear power - Accident or attack

Opponents argue that a major disadvantage of the use of nuclear reactors is the threat of a nuclear accident or terrorist attack and the possible resulting exposure to radiation. Proponents argue that the potential for a meltdown, as in the Chernobyl accident is very small due to the care taken in designing adequate safety systems, and that the nuclear industry has much better statistics regarding humans deaths from occupational accidents than coal or hydropower [49]. However, the Chernobyl accident caused great negative health, economic, environmental and psychological effects in a widespread area. The accident at Chernobyl was caused by a combination of the faulty RBMK reactor design, the lack of a containment building, poorly trained operators, and a non-existent safety culture. The RBMK design, unlike nearly all designs used in the Western world, featured a positive void coefficient, meaning that a malfunction could result in ever-increasing generation of heat and radiation until the reactor was breached. [50] Even in Three Mile Island, the most severe civilian nuclear accident in the Western world, the reactor vessel and containment building were never breached so that very little radiation was released into the environment.

Design changes are being pursued in the hope of lessening some of the risks of fission reactors; in particular, automated and passively safe designs are being pursued. Fusion reactors which may come to exist in the future theoretically have little risk since the fuel contained in the reaction chamber is only enough to sustain the reaction for about a minute, whereas a fission reactor contains about a year's supply of fuel. Subcritical reactors never have a self sustained nuclear chain reaction.

Opponents of nuclear power express concerns that nuclear waste is not well protected, and that it can be released in the event of terrorist attack, quoting a 1999 Russian incident where workers were caught trying to sell 5 grams of radioactive material on the open market [51], or the incident in 1993 where Russian workers were caught selling 4.5 kilograms of enriched uranium [52][53][54] . The UN has since called upon world leaders to improve security in order to prevent radioactive material falling into the hands of terrorists [55], leading to the guarding of nuclear shipments by thousands of police [56]. (Other energy sources, such as hydropower plants and liquefied natural gas tankers, are more vulnerable to accidents and attacks) Proponents of nuclear power contend, however, that nuclear waste is already well protected, and state their argument that there has been no accident involving any form of nuclear waste from a civilian program worldwide. In addition, they point to large studies carried out by NRC and other agencies that tested the robustness of both reactor and waste fuel storage, and found that they should be able to sustain a terrorist attack comparable to the September 11 terrorist attacks [57]. Spent fuel is usually housed inside the reactor containment building [58].

According to the Nuclear Regulatory Commission, 20 American States have requested stocks of potassium iodide which the NRC suggests should be available for those living within 10 miles of a nuclear power plant in the unlikely event of a severe accident.[59].

Nuclear power - Air pollution

Like renewables (except biomass), nuclear generation does not directly produce carbon dioxide, sulfur dioxide, nitrogen oxides, mercury, and other pollutants associated with the combustion of fossil fuels (pollution from fossil fuels causes many times more deaths each year in the US alone [60]).

This has led some environmentalists to advocate increased reliance on nuclear energy as a means to reduce greenhouse gas emissions (which contribute to global warming)[61].

However, just like any power source (including renewables like wind and solar energy), the facilities to produce and distribute the electricity require energy to build and subsequently decomission. Nuclear fuel must also be collected and processed to extract it from ore. The collection, construction, and transportation equipment used in these processes are either directly powered by diesel and gasoline engines, or draw electricity from the power grid, which in most countries is fed mostly by fossil fuel-powered generators.

Various parties have tried to estimate the amount of energy consumed by these processes (given today's mix of energy resources) and calculate, over the lifetime of a nuclear power plant, the amount of carbon dioxide saved (related to the amount of electricity produced by the plant) vs. the amount of carbon dioxide used (related to construction and fuel acquisition).

Some life cycle studies of nuclear power show emissions per kilowatt-hour to be around one third of those of a mid-size gas-fired power station [62], [63]. However, according to one life cycle study (van Leeuwen and Smith 2001-2005 [64]), carbon dioxide emissions from nuclear power per kilowatt hour are from 20-120% of those for natural gas-fired power stations depending on the availablity of high grade ores. The study goes on to say that these high grade ores are becoming more scarce and indeed there are not enough to supply the world's current power plants for the next decade let alone any future plants. The study was criticized in 2001 by the World Nuclear Association [65], with a detailed rebuttal [66] by van Leeuwen and Smith. Other life cycle analyses show similar emissions from nuclear power and renewables like wind power [67], but because of the relative cost of nuclear energy, the abatement costs of renewables are 3-4 times more favourable [68], and that is without taking into account having to deal with radioactive waste.

It is difficult to know what will happen to the carbon dioxide balance of nuclear power in the future. For instance, if energy production systems changed over entirely to renewable or nuclear sources, and transportation systems used this "clean" electricity (or stored electricity in the form of hydrogen) instead of burning fossil fuels directly, there would be no carbon dixoide emissions from construction, fueling, and distribution operations. The energy efficiency of these tasks is also a major consideration. More efficient methods may be found in the future, but this is difficult to predict, and may require funding for research.

Fission reactors do produce gases such as iodine-131 or krypton-85 which have to be stored on-site for several half-lives until they have decayed to levels officially regarded as safe. However, according to several independent organizations, a person receives more radioactivity from household appliances than from nuclear power [69].

Nuclear power - Waste heat in water systems

Nuclear reactors require water to keep the reactor cool. The process of extracting energy from a heat source, called the Rankine cycle, requires the steam to be cooled down. Rivers are the most common source of cooling water, as well as the destination for waste heat. The temperature of exhaust water must be regulated to avoid killing fish; long-term impact of hotter-than-natural water on ecosystems is an environmental concern.

The need to regulate exhaust temperature also limits generation capacity. On extremely hot days, which is when demand can be at its highest, the capacity of a nuclear plant may go down because the incoming water is warmer to begin with (and is thus less effective as a coolant, per unit volume). This was a significant factor in the European heat wave of 2003. Engineers consider this in making better power plant designs because increased cooling capacity will increase costs.

This is also a problem for coal power plants[70].

Nuclear power - Health effect on population near nuclear plants

Most of the human exposure to radiation comes from natural background radiation. Most of the remaining exposure comes from medical procedures. Several large studies in the US, Canada, and Europe have found no evidence of any increase in cancer mortality among people living near nuclear facilities. For example, in 1990, the National Cancer Institute (NCI) of the National Institutes of Health announced that a large-scale study, which evaluated mortality from 16 types of cancer, found no increased incidence of cancer mortality for people living near 62 nuclear installations in the United States. The study showed no increase in the incidence of childhood leukemia mortality in the study of surrounding counties after start-up of the nuclear facilities. The NCI study, the broadest of its kind ever conducted, surveyed 900,000 cancer deaths in counties near nuclear facilities.

However, in Britain there are elevated childhood leukemia levels near some industrial facilities, particularly near Sellafield, where children living locally are ten times more likely to contract the cancer. The reasons for these increases, or clusters, are unclear, but one study of those near Sellafield has ruled out any contribution from nuclear sources. Apart from anything else, the levels of radiation at these sites are orders of magnitude too low to account for the excess incidences reported. One explanation is viruses or other infectious agents being introduced into a local community by the mass movement of migrant workers. Likewise, small studies have found an increased incidence of childhood leukemia near some nuclear power plants has also been found in Germany [71] and France [72]. Nonetheless, the results of larger multi-site studies in these countries invalidate the hypothesis of an increased risk of leukaemia related to nuclear discharge. The methodology and very small samples in the studies finding an increased incidence has been criticized. [73] [74] [75] [76]. Also, one study focussing on Leukaemia clusters in industrial towns in England indicated a link to high-capacity electricity lines suggesting that the production or distribution of the electricity, rather than the nuclear reaction, may be a factor.

Aside from the immediate effects of the Chernobyl accident (see above), there is continuing impact from soils containing radioactivity in Ukraine and Belarus. For this reason a Zone of alienation was established around the Chernobyl plant.

Nuclear power - Nuclear proliferation

Opponents of nuclear power point out that nuclear technology is often dual-use, and much of the same materials and knowledge used in a civilian nuclear program can be used to develop nuclear weapons. This concern is known as nuclear proliferation and is a major reactor design criterion.

The military and civil purposes for nuclear energy are intertwined in most countries with nuclear capabilities. In the US for example the first goal of the Department of Energy is "To protect our national security by applying advanced science and nuclear technology to the Nation’s defense." [77]

The enriched uranium used in most nuclear reactors is not concentrated enough to build a bomb. Most nuclear reactors run on 4% enriched uranium; Little Boy used 90% enriched uranium; while lower enrichment levels could be used the minimum bomb size would rapidly become infeasibly large as the level was decreased. However, the technology used to enrich uranium for power generation could be used to make the highly enriched uranium needed to build a bomb. In addition, designs such as CANDU can be more easily misused to generate plutonium suitable for bomb making. It is believed that the nuclear programs of India and Pakistan used CANDU reactors to produce fissionable materials for their weapons, however, this is a myth. India used a research reactor named CIRUS, based on the Canadian NRX design, which was donated by Canada under the condition that it not be used for weapons production[78]. Pakistan is believed to have produced the material for its weapons from an indigenious enrichment program [79].

To prevent weapons proliferation, safeguards on nuclear technology were published in the Nuclear Non-Proliferation Treaty (NPT) and monitored since 1968 by the International Atomic Energy Agency (IAEA). Nations signing the treaty are required to report to the IAEA what nuclear materials they hold and their location. They agree to accept visits by IAEA auditors and inspectors to verify independently their material reports and physically inspect the nuclear materials concerned to confirm physical inventories of them in exchange for access to nuclear materials and equipment on the global market.

Several states did not sign the treaty and were able to use international nuclear technology (often procured for civilian purposes) to develop nuclear weapons (India, Pakistan, Israel, and South Africa). South Africa has since signed the NPT, and now holds the distinction of being the only known state to have indigenously produced nuclear weapons, and then verifiably dismantled them[80]. Of those who have signed the treaty and received shipments of nuclear paraphernalia, many states have either claimed to or been accused of attempting to use supposedly civilian nuclear power plants for developing weapons, including Iran and North Korea. Certain types of reactors are more conducive to producing nuclear weapons materials than others, and a number of international disputes over proliferation have centered on the specific model of reactor being contracted for in a country suspected of nuclear weapon ambitions.

New technology, like SSTAR, may lessen the risk of nuclear proliferation by providing sealed reactors with a limited self-contained fuel supply and with restrictions against tampering.

One possible obstacle for expanding the use of nuclear power might be a limitated supply of uranium ore, without which it would become necessary to build and operate breeder reactors. However, at current usage there is sufficient uranium for an extended period - "In summary, the actual recoverable uranium supply is likely to be enough to last several hundred (up to 1000) years, even using standard reactors." [81] (see Fuel resources above). Breeder reactors have been banned in the US since President Carter's administration prohibited reprocessing because of what it regarded as the unacceptable risk of proliferation of weapon grade materials.

Some proponents of nuclear power agree that the risk of nuclear proliferation may be a reason to prevent nondemocratic developing nations from gaining any nuclear technology but argue that this is no reason for democratic developed nations to abandon their nuclear power plants. Especially since it seems that democracies never make war against each other (See the democratic peace theory).

Proponents also note that nuclear power (like some other power sources) provides steady energy at a consistent price without competing for energy resources from other countries, something that may contribute to wars.

Adapted from the Wikipedia article "Risks", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki