Разделение изотопов и применение их в ядерном реакторе

In the United States, a 2007 University of Maryland survey showed that 73 percent of the public surveyed favours the elimination of all nuclear weapons, 64 percent support removing all nuclear weapons from high alert, and 59 percent support reducing U.S. and Russian nuclear stockpiles to 400 weapons each. Given the unpopularity of nuclear weapons, U.S. politicians have been wary of supporting new nuclear programs. Republican-dominated congresses "have defeated the Bush administration's plan to build so-called 'bunker-busters' and 'mini-nukes'."

 

As of 2010, Australia has no nuclear power stations and the current Rudd Labor government is opposed to nuclear power for Australia.Australia also has no nuclear weapons.

 

Thirty-one countries operate nuclear power plants. Nine nations possess nuclear weapons:

Today, some 26,000 nuclear weapons remain in the arsenals of the nine nuclear powers, with thousands on hair-trigger alert. Although U.S., Russian, and British nuclear arsenals are shrinking in size, those in the four Asian nuclear nations—China, India, Pakistan, and North Korea—are growing, in large part because of tensions among them. This Asian arms race also has possibilities of bringing Japan into the nuclear club.

During Barack Obama's successful U.S. presidential election campaign, he advocated the abolition of nuclear weapons. Since his election he has reiterated this goal in several major policy addresses.[62] In 2010, the Obama administration negotiated a new weapons accord with Russia for a reduction of the maximum number of deployed nuclear weapons on each side from 2,200 to between 1,500 and 1,675—a reduction of some 30 percent. In addition, President Obama has committed $15 billion over the next five years to improving the safety of the nuclear weapons stockpile.

Public opinion surveys on nuclear issues

In 2005, the International Atomic Energy Agency presented the results of a series of public opinion surveys in the Global Public Opinion on Nuclear Issues report.[145] Majorities of respondents in 14 of the 18 countries surveyed believe that the risk of terrorist acts involving radioactive materials at nuclear facilities is high, because of insufficient protection. While majorities of citizens generally support the continued use of existing nuclear power reactors, most people do not favour the building of new nuclear plants, and 25% of respondents feel that all nuclear power plants should be closed down. Stressing the climate change benefits of nuclear energy positively influences 10% of people to be more supportive of expanding the role of nuclear power in the world, but there is still a general reluctance to support the building of more nuclear power plants.

In the United States, the Nuclear Energy Institute has run polls since the 1980s. A poll in conducted March 30 to April 1, 2007 chose solar as the most likely largest source for electricity in the US in 15 years (27% of those polled) followed by nuclear, 24% and coal, 14%. Those who were favourable of nuclear being used dropped to 63% from a historic high of 70% in 2005 and 68% in September, 2006.

A CBS News/New York Times poll in 2007 showed that a majority of Americans would not like to have a nuclear plant built in their community, although an increasing percentage would like to see more nuclear power.

The two fuel sources that attracted the highest levels of support in the 2007 MIT Energy Survey are solar power and wind power. Outright majorities would choose to “increase a lot” use of these two fuels, and better than three out of four Americans would like to increase these fuels in the U. S. energy portfolio. Fourteen per cent of respondents would like to see nuclear power "increase a lot".

A poll in the European Union for Feb-Mar 2005 showed 37% in favour of nuclear energy and 55% opposed, leaving 8% undecided.[149] The same agency ran another poll in Oct-Nov 2006 that showed 14% favoured building new nuclear plants, 34% favoured maintaining the same number, and 39% favoured reducing the number of operating plants, leaving 13% undecided. This poll showed that the approval of nuclear power rose with the education level of respondents.

A September 2007 survey conducted by the Center for International and Security Studies at the University of Maryland showed that:

63 percent of Russians favor eliminating all nuclear weapons, 59 percent support removing all nuclear weapons from high alert, and 53 percent support cutting the Russian and U.S. nuclear arsenals to 400 nuclear weapons each. In the United States, 73 percent of the public favors eliminating all nuclear weapons, 64 percent support removing all nuclear weapons from high alert, and 59 percent support reducing Russian and U.S. nuclear arsenals to 400 weapons each. Eighty percent of Russians and Americans want their countries to participate in the Comprehensive Test Ban Treaty.

According to a 2010 Soka Gakkai International survey of youth attitudes in Japan, Korea, the Philippines, New Zealand and the USA, 67.3% reject the use of nuclear weapons under any circumstances. Of the respondents 59.1% said that they would feel safer if nuclear weapons no longer existed in the world. Identified as most needed measures toward nuclear abolition were political and diplomatic negotiations (59.9%), peace education (56.3%) and strengthened measures within the UN framework (53.7%). While 37.4% said that nuclear abolition is possible, 40.7% said that nuclear arms reduction not abolition is possible.

What had been growing acceptance of nuclear power in the United States was eroded sharply following the 2011 Japanese nuclear accidents, with support for building nuclear power plants in the U.S. dropping slightly lower than it was immediately after the Three Mile Island accident in 1979, according to a CBS News poll. Only 43 percent of those polled after the Fukushima nuclear emergency said they would approve building new power plants in the United States.

A 2011 poll suggests that skepticism over nuclear power is growing in Sweden following Japan's nuclear crisis. 36 percent of respondents want to phase-out nuclear power, up from 15 percent in a similar survey two years ago.

Criticism

Some environmentalists criticise the anti-nuclear movement for under-stating the environmental costs of fossil fuels and non-nuclear alternatives, and overstating the environmental costs of nuclear energy. Of the numerous nuclear experts who have offered their expertise in addressing controversies, Bernard Cohen, Professor Emeritus of Physics at the University of Pittsburgh, is likely the most frequently cited. In his extensive writings he examines the safety issues in detail. He is best known for comparing nuclear safety to the relative safety of a wide range of other phenomena.

 

Anti-nuclear activists are accused of representing the risks of nuclear power in an unfair way. The War Against the Atom (Basic Books, 1982) Samuel MacCracken of Boston University argued that in 1982, 50,000 deaths per year could be attributed directly to non-nuclear power plants, if fuel production and transportation, as well as pollution, were taken into account. He argued that if non-nuclear plants were judged by the same standards as nuclear ones, each US non-nuclear power plant could be held responsible for about 100 deaths per year.

The Nuclear Energy Institute(NEI) is the main lobby group for companies doing nuclear work in the USA, while most countries that employ nuclear energy have a national industry group. The World Nuclear Association is the only global trade body. In seeking to counteract the arguments of nuclear opponents, it points to independent studies that quantify the costs and benefits of nuclear energy and compares them to the costs and benefits of alternatives. NEI sponsors studies of its own, but it also references studies performed for the World Health Organisation, for the International Energy Agency, and by university researchers.

Critics of the anti-nuclear movement point to independent studies that show that the capital resources required for renewable energy sources are higher than those required for nuclear power.

Some people, including former opponents of nuclear energy, criticise the movement on the basis of the claim that nuclear energy is necessary for reducing carbon dioxide emissions. These individuals include James Lovelock, originator of the Gaia hypothesis, Patrick Moore, and Stewart Brand, creator of the Whole Earth Catalog. Lovelock goes further to refute claims about the danger of nuclear energy and its waste products.In a January 2008 interview, Moore said that "It wasn't until after I'd left Greenpeace and the climate change issue started coming to the forefront that I started rethinking energy policy in general and realised that I had been incorrect in my analysis of nuclear as being some kind of evil plot."

Some anti-nuclear organisations have acknowledged that their positions are subject to review. Nuclear-energy opponents take the position that militant environmentalist organisations have not changed their views:

While some environmentalists, in the interests of reducing the CO2 emissions associated with burning carbon-based fuels, have switched from anti- to pro-nuclear power in recent years, it is clear that many — if not most — of the militant environmentalist organizations remain adamantly opposed to the expansion of nuclear power. Many even propose decommissioning and dismantling the existing nuclear power electrical plants.

In April 2007, Dan Becker, Director of Global Warming for the Sierra Club, declared, "Switching from dirty coal plants to dangerous nuclear power is like giving up smoking cigarettes and taking up crack."

James Lovelock, who originally proposed the Gaia hypothesis, criticizes holders of such a view: "Opposition to nuclear energy is based on irrational fear fed by Hollywood-style fiction, the Green lobbies and the media." ". . .I am a Green and I entreat my friends in the movement to drop their wrongheaded objection to nuclear energy."

 

Nuclear safety covers the actions taken to prevent nuclear and radiation accidents or to limit their consequences. This covers nuclear power plants as well as all other nuclear facilities, the transportation of nuclear materials, and the use and storage of nuclear materials for medical, power, industry, and military uses.

 

The nuclear power industry has improved the safety and performance of reactors, and has proposed new (but generally untested) “inherently” safe reactor designs but there is no guarantee that the reactors will be designed, built and operated correctly. Mistakes do occur and the designers of reactors at Fukushima in Japan did not anticipate that a tsunami generated by an earthquake would disable the backup systems that were supposed to stabilize the reactor after the earthquake. Catastrophic scenarios involving terrorist attacks are also conceivable.

 

Nuclear weapon safety, as well as the safety of military research involving nuclear materials, is generally handled by agencies different from those that oversee civilian safety, for various reasons, including secrecy.

 

In spite of accidents like Chernobyl, studies have shown that nuclear deaths are mostly in uranium mining and that nuclear energy has generated far less deaths than the high pollution levels that result from the use of conventional fossil fuels.

Contents

1 Agencies

2 Nuclear power plant

2.1 Complexity

2.2 Failure modes of nuclear power plants

2.3 Vulnerability of nuclear plants to attack

2.4 Plant location

2.5 Nuclear safety systems

3 Hazards of nuclear material

4 New nuclear technologies

5 Safety culture and human errors

6 Risk assessment

7 Morality

8 Nuclear and radiation accidents

8.1 2011 Fukushima I accidents

8.2 Other accidents

9 Developing countries

 

Agencies

 

IAEA headquarters in Vienna, Austria

Internationally the International Atomic Energy Agency "works with its Member States and multiple partners worldwide to promote safe, secure and peaceful nuclear technologies."[4] Some scientists say that the 2011 Japanese nuclear accidents have revealed that the nuclear industry lacks sufficient oversight, leading to renewed calls to redefine the mandate of the IAEA so that it can better police nuclear power plants worldwide. There are several problems with the IAEA says Najmedin Meshkati of University of Southern California:

It recommends safety standards, but member states are not required to comply; it promotes nuclear energy, but it also monitors nuclear use; it is the sole global organization overseeing the nuclear energy industry, yet it is also weighed down by checking compliance with the Nuclear Non-Proliferation Treaty (NPT).

Many nations utilizing nuclear power have special institutions overseeing and regulating nuclear safety. Civilian nuclear safety in the U.S. is regulated by the Nuclear Regulatory Commission (NRC). The safety of nuclear plants and materials controlled by the U.S. government for research, weapons production, and those powering naval vessels is not governed by the NRC. In the UK nuclear safety is regulated by the Nuclear Installations Inspectorate (NII) and the Defence Nuclear Safety Regulator (DNSR). The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) is the Federal Government body that monitors and identifies solar radiation and nuclear radiation risks in Australia. It is the main body dealing with ionizing and non-ionizing radiation and publishes material regarding radiation protection.

 

Other agencies include:

Canadian Nuclear Safety Commission

Radiological Protection Institute of Ireland

Federal Atomic Energy Agency in Russia

Kernfysische dienst, (NL)

Pakistan Nuclear Regulatory Authority

Bundesamt für Strahlenschutz, (DE)

Atomic Energy Regulatory Board (India)

Nuclear power plant

 

Complexity

Nuclear power plants are some of the most sophisticated and complex energy systems ever designed. Any complex system, no matter how well it is designed and engineered, cannot be deemed failure-proof. Stephanie Cooke has reported that:

The reactors themselves were enormously complex machines with an incalculable number of things that could go wrong. When that happened at Three Mile Island in 1979, another fault line in the nuclear world was exposed. One malfunction led to another, and then to a series of others, until the core of the reactor itself began to melt, and even the world's most highly trained nuclear engineers did not know how to respond. The accident revealed serious deficiencies in a system that was meant to protect public health and safety.

 

A fundamental issue related to complexity is that nuclear power systems have exceedingly long lifetimes. The timeframe involved from the start of construction of a commercial nuclear power station, through to the safe disposal of its last radioactive waste, may be 100 to 150 years.[10]

See also: Design basis accident

 

Failure modes of nuclear power plants

There are concerns that a combination of human and mechanical error at a nuclear facility could result in significant harm to people and the environment:

Operating nuclear reactors contain large amounts of radioactive fission products which, if dispersed, can pose a direct radiation hazard, contaminate soil and vegetation, and be ingested by humans and animals. Human exposure at high enough levels can cause both short-term illness and death and longer-term death by cancer and other diseases.

Nuclear reactors can fail in a variety of ways. Should the instability of the nuclear material generate unexpected behavior, it may result in an uncontrolled power excursion. Normally, the cooling system in a reactor is designed to be able to handle the excess heat this causes; however, should the reactor also experience a loss-of-coolant accident, then the fuel may melt or cause the vessel it is contained in to overheat and melt. This event is called a nuclear meltdown.

Because the heat generated can be tremendous, immense pressure can build up in the reactor vessel, resulting in a steam explosion, which happened at Chernobyl. However, the reactor design used at Chernobyl was unique in many ways. For example, it had a large positive void coefficient, meaning a cooling failure caused reactor power to rapidly escalate. Typical reactor designs have negative void coefficients, a passively safe design. More importantly though, the Chernobyl plant lacked a containment structure. Western reactors have this structure, which acts to contain radiation in the event of a failure. Containment structures are, by design, some of the strongest structures built by mankind.

Intentional cause of such failures may be the result of nuclear terrorism.

Vulnerability of nuclear plants to attack

Nuclear power plants are generally (although not always) considered "hard" targets. In the U.S., plants are surrounded by a double row of tall fences which are electronically monitored. The plant grounds are patrolled by a sizeable force of armed guards. The NRC's "Design Basis Threat" criteria for plants is a secret, and so what size of attacking force the plants are able to protect against is unknown. However, to scram (make an emergency shutdown) a plant takes less than 5 seconds while unimpeded restart takes hours, severely hampering a terrorist force in a goal to release radioactivity.

Attack from the air is an issue that has been highlighted since the September 11 attacks in the U.S. However, it was in 1972 when three hijackers took control of a domestic passenger flight along the east coast of the U.S. and threatened to crash the plane into a U.S. nuclear weapons plant in Oak Ridge, Tennessee. The plane got as close as 8,000 feet above the site before the hijackers’ demands were met.

The most important barrier against the release of radioactivity in the event of an aircraft strike on a nuclear power plant is the containment building and its missile shield. Current NRC Chairman Dale Klein has said "Nuclear power plants are inherently robust structures that our studies show provide adequate protection in a hypothetical attack by an airplane. The NRC has also taken actions that require nuclear power plant operators to be able to manage large fires or explosions—no matter what has caused them."

 

In addition, supporters point to large studies carried out by the U.S. Electric Power Research Institute 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 in the U.S. Spent fuel is usually housed inside the plant's "protected zone" or a spent nuclear fuel shipping cask; stealing it for use in a "dirty bomb" is extremely difficult. Exposure to the intense radiation would almost certainly quickly incapacitate or kill anyone who attempts to do so.

In September 2010, analysis of the Stuxnet computer worm suggested that it was designed to sabotage a nuclear power plant. Such a cyber attack would bypass the physical safeguards in

Plant location

In many countries, plants are often located on the coast, in order to provide a ready source of cooling water for the essential service water system. As a consequence the design needs to take the risk of flooding and tsunamis into account. Failure to calculate the risk of flooding correctly lead to a Level 2 event on the International Nuclear Event Scale during the 1999 Blayais Nuclear Power Plant flood,[21] while flooding caused by the 2011 Tōhoku earthquake and tsunami lead to the Fukushima I nuclear accidents.

The design of plants located in seismically active zones also requires the risk of earthquakes and tsunamis to be taken into account. Japan, India, China and the USA are among the countries to have plants in earthquake-prone regions. Damage caused to Japan's Kashiwazaki-Kariwa Nuclear Power Plant during the 2007 Chūetsu offshore earthquake underlined concerns expressed by experts in Japan prior to the Fukushima accidents, who have warned of a genpatsu-shinsai (domino-effect nuclear power plant earthquake disaster).

Nuclear safety systems

Main article: Nuclear safety systems

The three primary objectives of nuclear safety systems as defined by the Nuclear Regulatory Commission are to shut down the reactor, maintain it in a shutdown condition, and prevent the release of radioactive material during events and accidents.[26] These objectives are accomplished using a variety of equipment, which is part of different systems, of which each performs specific functions.

 

Hazards of nuclear material

Nuclear material may be hazardous if not properly handled or disposed of. Experiments of near critical mass-sized pieces of nuclear material can pose a risk of a criticality accident. David Hahn, "The Radioactive Boy Scout" who tried to build a nuclear reactor at home, serves as an excellent example of a nuclear experimenter who failed to develop or follow proper safety protocols. Such failures raise the specter of radioactive contamination.

Even when properly contained, fission byproducts which are no longer useful generate radioactive waste, which must be properly disposed of. Spent nuclear fuel that is recently removed from a nuclear reactor will generate large amounts of decay heat which will require pumped water cooling for a year or more to prevent overheating. In addition, material exposed to neutron radiation—present in nuclear reactors—may become radioactive in its own right, or become contaminated with nuclear waste. Additionally, toxic or dangerous chemicals may be used as part of the plant's operation, which must be properly handled and disposed of.

 

New nuclear technologies

The next nuclear plants to be built will likely be Generation III or III+ designs, and a few such are already in operation in Japan. Generation IV reactors would have even greater improvements in safety. These new designs are expected to be passively safe or nearly so, and perhaps even inherently safe (as in the PBMR designs).

Some improvements made (not all in all designs) are having three sets of emergency diesel generators and associated emergency core cooling systems rather than just one pair, having quench tanks (large coolant-filled tanks) above the core that open into it automatically, having a double containment (one containment building inside another), etc.

However, safety risks may be the greatest when nuclear systems are the newest, and operators have less experience with them. Nuclear engineer David Lochbaum explained that almost all serious nuclear accidents occurred with what was at the time the most recent technology. He argues that "the problem with new reactors and accidents is twofold: scenarios arise that are impossible to plan for in simulations; and humans make mistakes". As one director of a U.S. research laboratory put it, "fabrication, construction, operation, and maintenance of new reactors will face a steep learning curve: advanced technologies will have a heightened risk of accidents and mistakes. The technology may be proven, but people are not".

Safety culture and human errors

One relatively prevalent notion in discussions of nuclear safety is that of safety culture. The International Nuclear Safety Advisory Group, defines the term as “the personal dedication and accountability of all individuals engaged in any activity which has a bearing on the safety of nuclear power plants”.The goal is “to design systems that use human capabilities in appropriate ways, that protect systems from human frailties, and that protect humans from hazards associated with the system”.

At the same time, there is some evidence that operational practices are not easy to change. Operators almost never follow instructions and written procedures exactly, and “the violation of rules appears to be quite rational, given the actual workload and timing constraints under which the operators must do their job”. Many attempts to improve nuclear safety culture “were compensated by people adapting to the change in an unpredicted way”. For this reason, training simulators are used.

An assessment conducted by the Commissariat à l’Énergie Atomique (CEA) in France concluded that no amount of technical innovation can eliminate the risk of human-induced errors associated with the operation of nuclear power plants. Two types of mistakes were deemed most serious: errors committed during field operations, such as maintenance and testing, that can cause an accident; and human errors made during small accidents that cascade to complete failure.