Nuclear safety

From Wikipedia, the free encyclopedia

This diagram demonstrates the defense in depth strategy of design of modern nuclear power plants. Current plants may have some or all of these defenses, the defenses vary depending on the type of plant, the nation constructing them, the use (civilian, military, naval vessels) and the age. 1st layer of defense is the inert, ceramic quality of the uranium oxide itself. 2nd layer is the airtight zirconium alloy of the fuel rod. 3rd layer is the reactor pressure vessel made of steel more than a dozen centimeters thick. 4th layer is the pressure resistant, airtight containment building. 5th layer is the reactor building or in newer powerplants a second outer containment building.
This diagram demonstrates the defense in depth strategy of design of modern nuclear power plants. Current plants may have some or all of these defenses, the defenses vary depending on the type of plant, the nation constructing them, the use (civilian, military, naval vessels) and the age.
1st layer of defense is the inert, ceramic quality of the uranium oxide itself.
2nd layer is the airtight zirconium alloy of the fuel rod.
3rd layer is the reactor pressure vessel made of steel more than a dozen centimeters thick.
4th layer is the pressure resistant, airtight containment building.
5th layer is the reactor building or in newer powerplants a second outer containment building.

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, the use and storage of nuclear materials for medical, power, industry, and military uses. In addition, there are safety issues involved in products created with radioactive materials. Some of the products are legacy ones (such as watch faces), others, like smoke detectors, are still being produced.

Nuclear weapon safety, as well as the safety of military research involving nuclear materials, is generally handled by separate agencies than civilian safety, for various reasons, including secrecy.

Contents

[edit] Agencies

Many nations utilizing nuclear power have special institutions overseeing and regulating nuclear safety.

Internationally the International Atomic Energy Agency "works for the safe, secure and peaceful uses of nuclear science and technology."

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.[1][2]

In the UK nuclear safety is regulated by the Nuclear Installations Inspectorate (NII) and the Defence Nuclear Safety Regulator (DNSR).

[edit] Key concepts

[edit] Concerns

There are concerns that a combination of human and mechanical error at a nuclear facility could result significant harm to people and the environment:[3]

Operating nuclear reactors contain large amounts of radioactive fission products which, if dispersed, could 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 deaths by cancer and other diseases.[4]

Some specific concerns relate to:

[edit] Vulnerability of plants to attack

Nuclear power plants are generally (although not always) considered "hard" targets. In the US, 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.[5] The NRC's "Design Basis Threat" criteria for plants is a secret, and so what size attacking force the plants are able to protect against is unknown. However, to scram 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 a more problematic concern. The most important barrier against the release of radioactivity in the event of an aircraft strike is the containment building and its missile shield. The NRC's Chairman 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."[6]

In addition, supporters point to large studies carried out by the US 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 USA. Spent fuel is usually housed inside the plant's "protected zone"[7] 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.[8]

[edit] 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. [9] General Electric has recalculated maximum core damage frequencies per year per plant for its nuclear power plant designs: [10]

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

[edit] Complexity

Nuclear power plants are one of the most complex energy systems ever designed,[11] and opponents of nuclear power have cricitized the sophistication and complexity of the technology. In their assessment, "nuclear power is a very dangerous, expensive way to boil water to generate energy..."[12] Similarly, Dr Helen Caldicott has said: "... in essence, a nuclear reactor is just a very sophisicated and dangerous way to boil water -- analagous to cutting a pound of butter with a chain saw."[13] These critics of nuclear power advocate the use of energy conservation and appropriate renewable energy technologies to create our energy future.[14]

Amory Lovins, from the Rocky Mountain Institute, has argued that centralized electricity systems with giant power plants are becoming obsolete. In their place are emerging "distributed resources"—smaller, decentralized electricity supply sources (including efficiency) that are cheaper, cleaner, less risky, more flexible, and quicker to deploy.[15]Such technologies are often called "soft energy technologies" and their impacts are seen to be more gentle, pleasant, and manageable than hard energy technologies such as nuclear power.[16]

An issue related to complexity is that the nuclear energy systems have an exceedingly long stay time. The completion of the sequence of activities related to one commercial nuclear power station, from the start of construction through the safe disposal of its last radioactive waste, may take 100-150 years.[11]

[edit] Enforcement organisations

[edit] Nuclear accidents

[edit] See also

[edit] References

  1. ^ About NRC, U.S. Nuclear Regulatory Commission, Retrieved 2007-6-1
  2. ^ Our Governing Legislation, U.S. Nuclear Regulatory Commission, Retrieved 2007-6-1
  3. ^ Union of Concerned Scientists: Nuclear safety
  4. ^ Nuclear Power Plants: Vulnerability to Terrorist Attack p. 3.
  5. ^ Nuclear Security – Five Years After 9/11 accessed 23 July 2007
  6. ^ STATEMENT FROM CHAIRMAN DALE KLEIN ON COMMISSION'S AFFIRMATION OF THE FINAL DBT RULE. Nuclear Regulatory Commission. Retrieved on 2007-04-07.
  7. ^ The Nuclear Fuel Cycle. Information and Issue Briefs. World Nuclear Association (2005). Retrieved on 2006-11-10.
  8. ^ Lewis Z Kock (2004). Dirty Bomber? Dirty Justice. Bulletin of the Atomic Scientists. Retrieved on 2006-11-10.
  9. ^ [1]
  10. ^ Next-generation nuclear energy: The ESBWR
  11. ^ a b Nuclear power – the energy balance
  12. ^ Southern Alliance for Clean Energy
  13. ^ Helen Caldicott (2006). Nuclear power is not the answer to global warming or anything else, Melbourne University Press, ISBN 0 522 85251 3, p.xvii
  14. ^ Southern Alliance for Clean Energy
  15. ^ [2]
  16. ^ Amory B. Lovins (1977). Soft Energy Paths: Toward a Durable Peace, Penguin Books.
v • d • e
Nuclear technology
Engineering
Material
Power
Core topics
Medicine
Therapies
Weapons
Languages