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==See also==
==See also==
*[[Nuclear safety systems]]
*[[Lists of nuclear disasters and radioactive incidents]]
*[[Lists of nuclear disasters and radioactive incidents]]
*[[Deep geological repository]]
*[[Deep geological repository]]

Revision as of 21:11, 29 March 2011

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.[1] 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.[2] Catastrophic scenarios involving terrorist attacks are also conceivable.[1]

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. [3]

Agencies

File:Iaea-vienna.JPG
IAEA headquarters in Vienna, Austria

Internationally the International Atomic Energy Agency "works for the safe, secure and peaceful uses of nuclear science and technology."[citation needed] 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.[4] 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).[4]

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.[5][6] 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[7] and publishes material regarding radiation protection.[8]

Other agencies include:

Complexity

Nuclear power plants are some of the most sophisticated and complex energy systems ever designed.[9] 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.[10]

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.[9]

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:[11]

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.[12]

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.

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.

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.[13] 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.[14][15]

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."[16]

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"[17] 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.[18]

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 place and so the exploit demonstrates an important new vulnerability.[19]

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".[20] 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".[20]

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”.[21] 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”.[21]

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”.[21] 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.[20]

Risk assessment

The AP1000 has a maximum core damage frequency of 5.09 x 10−7 per plant per year. The Evolutionary Power Reactor (EPR) has a maximum core damage frequency of 4 x 10−7 per plant per year. General Electric has recalculated maximum core damage frequencies per year per plant for its nuclear power plant designs:[23]

BWR/4 -- 1 x 10-5
BWR/6 -- 1 x 10-6
ABWR -- 2 x 10-7
ESBWR -- 3 x 10-8

Morality

Historically many scientists and engineers have made decisions on behalf of potentially affected populations about whether a particular level of risk and uncertainty is acceptable for them. Many nuclear engineers and scientists that have made such decisions, even for good reasons relating to long term energy availability, now consider that doing so without informed consent is wrong, and that nuclear power safety and nuclear technologies should be based fundamentally on morality, rather than purely on technical, economic and business considerations.[24]

According to Stephanie Cooke, it is difficult to know what really goes on inside nuclear power plants because the industry is shrouded in secrecy. Corporations and governments control what information is made available to the public. When information is released, it is often couched in jargon and incomprehensible prose, which makes it difficult to understand.[25]

Kennette Benedict has said that nuclear technology and plant operations continue to lack transparency and to be relatively closed to public view:[26]

Despite victories like the creation of the Atomic Energy Commission, and later the Nuclear Regular Commission, the secrecy that began with the Manhattan Project has tended to permeate the civilian nuclear program, as well as the military and defense programs.[26]

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,[27] while flooding caused by the 2011 Tōhoku earthquake and tsunami lead to the Fukushima I nuclear accidents.[28]

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[29][30] 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).[31]

Nuclear and radiation accidents

2011 Fukushima I accidents

The 40-year-old Fukushima I Nuclear Power Plant, built in the 1970s, endured Japan's worst earthquake on record in March 2011 but had its power and back-up generators knocked out by a 7-meter tsunami that followed.[28] The designers of the reactors at Fukushima 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. Nuclear reactors are such "inherently complex, tightly coupled systems that, in rare, emergency situations, cascading interactions will unfold very rapidly in such a way that human operators will be unable to predict and master them".[32]

Lacking electricity to pump water needed to cool the atomic core, engineers vented radioactive steam into the atmosphere to release pressure, leading to a series of explosions that blew out concrete walls around the reactors. Radiation readings spiked around Fukushima as the disaster widened, forcing the evacuation of 200,000 people and causing radiation levels to rise on the outskirts of Tokyo, 135 miles (210 kilometers) to the south, with a population of 30 million.[28]

Back-up diesel generators that might have averted the disaster were positioned in a basement, where they were overwhelmed by waves. The cascade of events at Fukushima had been foretold in a report published in the U.S. several decades ago:[28]

The 1990 report by the U.S. Nuclear Regulatory Commission, an independent agency responsible for safety at the country’s power plants, identified earthquake-induced diesel generator failure and power outage leading to failure of cooling systems as one of the “most likely causes” of nuclear accidents from an external event.[28]

While the report was cited in a 2004 statement by Japan’s Nuclear and Industrial Safety Agency, it seems adequate measures to address the risk were not taken by Tokyo Electric. Katsuhiko Ishibashi, a seismology professor at Kobe University, has said that Japan’s history of nuclear accidents stems from an overconfidence in plant engineering. In 2006, he resigned from a government panel on nuclear reactor safety, because the review process was rigged and “unscientific”.[28]

Louise Fréchette and Trevor Findlay have said that more effort is needed to ensure nuclear safety and improve responses to accidents:

The multiple reactor crises at Japan's Fukushima nuclear power plant reinforce the need for strengthening global instruments to ensure nuclear safety worldwide. The fact that a country that has been operating nuclear power reactors for decades should prove so alarmingly improvisational in its response and so unwilling to reveal the facts even to its own people, much less the International Atomic Energy Agency, is a reminder that nuclear safety is a constant work-in-progress. [33]

Following the Fukushima emergency, the European Union decided that reactors across all 27 member nations should undergo safety tests.[34]

Other accidents

Serious nuclear and radiation accidents include the Chalk River accidents (1952, 1958 & 2008), Mayak disaster (1957), Windscale fire (1957), SL-1 accident (1961), Soviet submarine K-19 accident (1961), Three Mile Island accident (1979), Church Rock uranium mill spill (1979), Soviet submarine K-431 accident (1985), Chernobyl disaster (1986), Goiânia accident (1987), Zaragoza radiotherapy accident (1990), Costa Rica radiotherapy accident (1996), Tokaimura nuclear accident (1999), Sellafield THORP leak (2005), and the Flerus IRE Cobalt-60 spill (2006).[35][36]

Developing countries

There are concerns about developing countries "rushing to join the so-called nuclear renaissance without the necessary infrastructure, personnel, regulatory frameworks and safety culture".[37] Some countries with nuclear aspirations, like Nigeria, Kenya, Bangladesh and Venezuela, have no significant industrial experience and will require at least a decade of preparation even before breaking ground at a reactor site.[37]

The speed of the nuclear construction program in China has raised safety concerns. The challenge for the government and nuclear companies is to "keep an eye on a growing army of contractors and subcontractors who may be tempted to cut corners".[38] China is advised to maintain nuclear safeguards in a business culture where quality and safety are sometimes sacrificed in favor of cost-cutting, profits, and corruption. China has asked for international assistance in training more nuclear power plant inspectors.[38]

See also

References

  1. ^ a b Jacobson, Mark Z. and Delucchi, Mark A. (2010). "Providing all Global Energy with Wind, Water, and Solar Power, Part I: Technologies, Energy Resources, Quantities and Areas of Infrastructure, and Materials" (PDF). Energy Policy. p. 6.{{cite web}}: CS1 maint: multiple names: authors list (link)
  2. ^ Hugh Gusterson (16 March 2011). "The lessons of Fukushima". Bulletin of the Atomic Scientists.
  3. ^ [1]
  4. ^ a b By Stephen Kurczy (March 17, 2011). "Japan nuclear crisis sparks calls for IAEA reform". CSMonitor.com.
  5. ^ About NRC, U.S. Nuclear Regulatory Commission, Retrieved 2007-6-1
  6. ^ Our Governing Legislation, U.S. Nuclear Regulatory Commission, Retrieved 2007-6-1
  7. ^ Health and Safety www.australia.gov.au
  8. ^ Radiation Protection www.arpansa.gov.au
  9. ^ a b Jan Willem Storm van Leeuwen (2008). Nuclear power – the energy balance
  10. ^ Stephanie Cooke (2009). In Mortal Hands: A Cautionary History of the Nuclear Age, Black Inc., p. 280.
  11. ^ Union of Concerned Scientists: Nuclear safety
  12. ^ Globalsecurity.org: Nuclear Power Plants: Vulnerability to Terrorist Attack p. 3.
  13. ^ U.S. NRC: "Nuclear Security – Five Years After 9/11". Accessed 23 July 2007
  14. ^ Threat Assessment: U.S. Nuclear Plants Near Airports May Be at Risk of Airplane Attack, Global Security Newswire, June 11, 2003.
  15. ^ Newtan, Samuel Upton (2007). Nuclear War 1 and Other Major Nuclear Disasters of the 20th Century, AuthorHouse, p.146.
  16. ^ "STATEMENT FROM CHAIRMAN DALE KLEIN ON COMMISSION'S AFFIRMATION OF THE FINAL DBT RULE". Nuclear Regulatory Commission. Retrieved 2007-04-07.
  17. ^ "The Nuclear Fuel Cycle". Information and Issue Briefs. World Nuclear Association. 2005. Retrieved 2006-11-10.
  18. ^ Lewis Z Koch (2004). "Dirty Bomber? Dirty Justice". Bulletin of the Atomic Scientists. Retrieved 2006-11-10. {{cite web}}: External link in |publisher= (help)
  19. ^ "Was Stuxnet Built to Attack Iran's Nuclear Program".
  20. ^ a b c Benjamin K. Sovacool. A Critical Evaluation of Nuclear Power and Renewable Electricity in Asia, Journal of Contemporary Asia, Vol. 40, No. 3, August 2010, p. 381.
  21. ^ a b c M.V. Ramana. Nuclear Power: Economic, Safety, Health, and Environmental Issues of Near-Term Technologies, Annual Review of Environment and Resources, 2009. 34, pp.139-140.
  22. ^ Severe Accidents in the Energy Sector (see pages 287,310,317)
  23. ^ Next-generation nuclear energy: The ESBWR
  24. ^ Pandora's box, A is for Atom- Adam Curtis
  25. ^ Stephanie Cooke (March 19, 2011). "Nuclear power is on trial". CNN.com.
  26. ^ a b Kennette Benedict (26 March 2011). "The road not taken: Can Fukushima put us on a path toward nuclear transparency?". Bulletin of the Atomic Scientists. {{cite web}}: Cite has empty unknown parameter: |1= (help)
  27. ^ COMMUNIQUE N°7 - INCIDENT SUR LE SITE DU BLAYAIS ASN, published 1999-12-30, accessed 2011-03-22
  28. ^ a b c d e f Jason Clenfield (March 17, 2011). "Japan Nuclear Disaster Caps Decades of Faked Reports, Accidents". Bloomberg Businessweek.
  29. ^ ABC News. Strong Quake Rocks Northwestern Japan. July 16, 2007.
  30. ^ Xinhua News. Two die, over 200 injured in strong quake in Japan. July 16, 2007.
  31. ^ Genpatsu-Shinsai: Catastrophic Multiple Disaster of Earthquake and Quake-induced Nuclear Accident Anticipated in the Japanese Islands (Abstract), Katsuhiko Ishibashi, 23rd. General Assembly of IUGG, 2003, Sapporo, Japan, accessed 2011-03-28
  32. ^ Hugh Gusterson (16 March 2011). "The lessons of Fukushima". Bulletin of the Atomic Scientists.
  33. ^ Louise Fréchette and Trevor Findlay (March 28, 2011). "Nuclear safety is the world's problem". Ottawa Citizen.
  34. ^ James Kanter (March 25, 2011). "Europe to Test Safety of Nuclear Reactors". New York Times.
  35. ^ Newtan, Samuel Upton (2007). Nuclear War 1 and Other Major Nuclear Disasters of the 20th Century, AuthorHouse.
  36. ^ The Worst Nuclear Disasters
  37. ^ a b Louise Fréchette and Trevor Findlay (March 28, 2011). "Nuclear safety is the world's problem". Ottawa Citizen.
  38. ^ a b Cite error: The named reference nyt-20091215 was invoked but never defined (see the help page).