Nuclear safety in the United States
Encyclopedia
Nuclear safety
in the U.S. is governed by federal regulations and continues to be studied by the Nuclear Regulatory Commission
(NRC). The safety of nuclear plants and materials controlled by the U.S. government for research and weapons production, as well those powering naval vessels, is not governed by the NRC.
Following the Fukushima Daiichi nuclear disaster
, according to Black & Veatch’s annual utility survey that took place after the disaster, of the 700 executives from the US electric utility industry that were surveyed, nuclear safety was the top concern. There are likely to be increased requirements for on-site spent fuel management and elevated design basis threats at nuclear power plants. License extensions for existing reactors will face additional scrutiny, with outcomes depending on the degree to which plants can meet new requirements, and some of the extensions already granted for more than 60 of the 104 operating U.S. reactors could be revisited. On-site storage, consolidated long-term storage, and geological disposal of spent fuel is "likely to be reevaluated in a new light because of the Fukushima storage pool experience".
In October 2011, the Nuclear Regulatory Commission instructed agency staff to move forward with seven of the 12 safety recommendations put forward by the federal task force in July. The recommendations include "new standards aimed at strengthening operators’ ability to deal with a complete loss of power, ensuring plants can withstand floods and earthquakes and improving emergency response capabilities". The new safety standards will take up to five years to fully implement.
In the following, the names of federal regulations will be abbreviated in the standard way. For example, "Code of Federal Regulations, Title 10, Part 100, Section 23" will be given as "10CFR100.23".
report.
In February 2011, a major manufacturer in the nuclear industry reported a potential "substantial safety hazard" with control rods at more than two dozen reactors around the USA. GE Hitachi Nuclear Energy said it had discovered extensive cracking and "material distortion," and recommended that the boiling water reactors using its Marathon control rod blades replace them more frequently than previously told. If the design life if not revised, it "could result in significant control blade cracking and could, if not corrected, create a substantial safety hazard and is considered a reportable condition," the company said in its report to the NRC.
With the cancellation of the Yucca Mountain nuclear waste repository in Nevada, more nuclear waste is being loaded into sealed metal casks filled with inert gas. Many of these casks will be stored in coastal or lakeside regions where a salt air environment exists, and the Massachusetts Institute of Technology is studying how such dry casks
perform in salt environments. Some hope that the casks can be used for 100 years but cracking related to corrosion could occur in 30 years or less. Robert Alvarez, a former Department of Energy official who oversaw nuclear issues, said dry casks would provide safer storage until a permanent nuclear repository was built and loaded, a process that would take decades.
s, the same technology which was involved in the Fukushima Daiichi nuclear disaster
in Japan. There are also eight nuclear power plants located along the seismically active West coast. Twelve of the American reactors that are of the same vintage as the Fukushima Daiichi plant are in seismically active areas.
Earthquake risk is often measured by "Peak Ground Acceleration", or PGA. The following nuclear power plants have a two percent or greater chance of having PGA over 0.15g in the next 50 years: Diablo Canyon, Calif.; San Onofre, Calif.; Sequoyah, Tenn.; H.B. Robinson, SC.; Watts Bar, Tenn.; Virgil C. Summer, SC.; Vogtle, GA.; Indian Point, NY.; Oconee, SC.; and Seabrook, NH.
's Mark I reactor design, because it offered a relatively weak containment vessel. Three GE scientists resigned 35 years ago in protest of the design of the Mark I containment system. David Lochbaum, chief nuclear safety
officer with the Union of Concerned Scientists
, has repeatedly questioned the safety of the Fukushima I Plant's GE Mark 1 reactor design, which is used in almost a quarter of the United States' nuclear fleet.
Minimum distances must be set for an exclusion area (which is typically inside the Protected Area's fence), a low population zone and a population center distance. To calculate the minimum assured distances for each of these, a maximum possible amount of radioactivity release (called a "source term") must be assumed and worst-case wind conditions must be assumed.
Nuclear power plants in their licensing submittals so far have used extremely conservative fallout inputs from the somewhat antiquated WASH-1400
study. The NRC has disavowed the assumptions and thus the results of WASH-1400 as being far too pessimistic (see NUREG-1150
), and is in the process of generating a new state-of-the-art study (see SOARCA).
A bounding calculation using a source term from WASH-1400 typically calculates a minimum Emergency Planning Zone (EPZ) of about 5 miles (8 km) from the plant, which in practice is rounded up to 10 miles (16.1 km) for actual implementation.
The Protected Area is surrounded by a double fence, and the gap in between the fences is electronically monitored. There are very few gates, and those are well guarded. Numerous other security measures are in effect.
's Turkey Point NGS
, survived a direct hit by Category 5 Hurricane Andrew
in 1992, with no damage to the containment.
No actual missile shield has been subjected to an aircraft impact test. However, a highly similar test was done at Sandia National Laboratories
and filmed (see Containment building
), and the target was essentially undamaged (reinforced concrete is strongly resistant both to impact and to fire). 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."
[DBE] are defined as conditions of normal operation, including anticipated operational occurrences, design basis accidents, external events, and natural phenomena for which the plant must be designed to ensure functions (b)(1)(i) (A) through (C)" of 10CFR50-49. These include (A) maintaining the integrity of the reactor coolant pressure boundary; (B) maintaining the capability to shut down the reactor and maintain it in a safe shutdown condition; OR (C) maintaining the capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposures. The normal DBEs evaluated are Station Blackout (where all offsite and onsite AC power is lost for a specified duration) and loss-of-coolant accident (LOCA).
As the Fukushima I nuclear accidents showed, external threats — such as earthquakes, tsunamis, fires, flooding, tornadoes and terrorist attacks — are some of the greatest risk factors for a serious nuclear accident. Yet, nuclear plant operators have normally considered these 'beyond design basis events' so unlikely that they have not built in complete safeguards.
, or SOARCA, study) is in generation now. The new study will be based on actual test results, on probabilistic risk assessment
(PRA) methodology, and on the evaluated actions of government agencies.
The existing studies (all now disavowed by the NRC and to be replaced by SOARCA) are:
General Electric has recalculated maximum core damage frequencies per year per plant for its nuclear power plant designs:
The AP1000 has a maximum core damage frequency of per plant per year. The European Pressurized Reactor
(EPR) has a maximum core damage frequency
of per plant per year.
Unusual Event – This is the lowest of the four emergency classifications. This classification indicates that a small problem has occurred. No radiation leak is expected and federal, state and county officials are notified.
Alert –Events are in process or have occurred which involve an actual or potential substantial degradation in the level of safety of the plant. Any releases of radioactive material from the plant are expected to be limited to a small fraction of the Environmental Protection Agency (EPA) Protective Action Guide for Nuclear Incidents
(PAGs)
Site Area Emergency – Involves events in process or which have occurred that result in actual or likely major failures of plant functions needed for protection of the public. Any releases of radioactive material are not expected to exceed the EPA PAGs except near the site boundary.
General Emergency – The most serious emergency classification and indicates a serious problem. A general emergency involves actual or imminent substantial core damage or melting of reactor fuel with the potential for loss of containment integrity. Emergency sirens will be sounded and federal, state and county officials will act to ensure public safety. Radioactive releases during a general emergency can reasonably be expected to exceed the EPA PAGs for more than the immediate site area.
in Pennsylvania. The mechanical failures were compounded by the initial failure of plant operators to recognize the situation as a loss-of-coolant accident due to inadequate training and human factors
, such as human-computer interaction design oversights relating to ambiguous control room indicators in the power plant's user interface
. In particular, a hidden indicator light led to an operator manually overriding the automatic emergency cooling system of the reactor because the operator mistakenly believed that there was too much coolant water present in the reactor and causing the steam pressure release. The scope and complexity of the accident became clear over the course of five days, as employees of Met Ed, Pennsylvania state officials, and members of the U.S. Nuclear Regulatory Commission
(NRC) tried to understand the problem, communicate the situation to the press and local community, decide whether the accident required an emergency evacuation, and ultimately end the crisis. The NRC's authorization of the release of 40,000 gallons of radioactive waste water directly in the Susquehanna River led to a loss of credibility with the press and community.
The World Nuclear Association has stated that cleanup of the damaged nuclear reactor system at TMI-2 took nearly 12 years and cost approximately US $973 million. Benjamin K. Sovacool
, in his 2007 preliminary assessment of major energy accidents, estimated that the TMI accident caused a total of $2.4 billion in property damages. The health effects of the Three Mile Island accident
are widely, but not universally, agreed to be very low level. The accident triggered protests around the world.
could occur in the USA. In 1986, Commissioner Asselstine testified before Congress that:
, Richard Hubbard, and Dale Bridenbaugh "blew the whistle" on safety problems at nuclear power plant
s in the United States. The three nuclear engineers gained the attention of journalists and their disclosures about the threats of nuclear power
had a significant impact.
, 20 states in the USA have requested stocks of potassium iodide
which the NRC suggests should be available for those living within 10 miles (16.1 km) of a nuclear power plant in the unlikely event of a severe accident. Iodine is a fission product in a nuclear reactor, and in the event of a severe accident a fraction of that iodine is expected to leak from the fuel and out of the containment building. If ingested, this iodine would tend to be accumulated by a person's thyroid. Potassium Iodide (KI) is an over-the-counter drug that may reduce the amount of radioactive iodine absorbed by the body’s thyroid gland. KI offers a degree of protection only to the thyroid gland and only in cases when the release contains radioactive iodine. KI would be supplemental to evacuation and sheltering. In cases where the public may be exposed to certain types of radioactivity, state and local health officials may advise the public to take Potassium Iodide (KI) tablets.
Radioactive Iodine (radioiodine) is one of the products that can be released in a serious nuclear power plant accident. Potassium Iodide (KI) is a non radioactive form of iodine that may be taken to reduce the amount of radioactive iodine absorbed by the body’s thyroid gland. When taken before or shortly after a radiological exposure, potassium iodide blocks the thyroid glands ability to absorb radioactive iodine. KI is a secondary protection for evacuation and sheltering are the primary means of protection.
Potassium Iodide should be taken by the public during an emergency only when directed by public health officials. A TV and radio Emergency Alert System (EAS) message will be broadcast and public health officials will inform the public when to take KI. Potassium iodide is available to persons within 10 miles of the plant though the county health department. During an emergency, KI is available to the general public at evacuation Reception Centers.
Nuclear safety
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,...
in the U.S. is governed by federal regulations and continues to be studied by the Nuclear Regulatory Commission
Nuclear Regulatory Commission
The Nuclear Regulatory Commission is an independent agency of the United States government that was established by the Energy Reorganization Act of 1974 from the United States Atomic Energy Commission, and was first opened January 19, 1975...
(NRC). The safety of nuclear plants and materials controlled by the U.S. government for research and weapons production, as well those powering naval vessels, is not governed by the NRC.
Following the Fukushima Daiichi nuclear disaster
Fukushima Daiichi nuclear disaster
The is a series of equipment failures, nuclear meltdowns, and releases of radioactive materials at the Fukushima I Nuclear Power Plant, following the Tōhoku earthquake and tsunami on 11 March 2011. The plant comprises six separate boiling water reactors originally designed by General Electric ,...
, according to Black & Veatch’s annual utility survey that took place after the disaster, of the 700 executives from the US electric utility industry that were surveyed, nuclear safety was the top concern. There are likely to be increased requirements for on-site spent fuel management and elevated design basis threats at nuclear power plants. License extensions for existing reactors will face additional scrutiny, with outcomes depending on the degree to which plants can meet new requirements, and some of the extensions already granted for more than 60 of the 104 operating U.S. reactors could be revisited. On-site storage, consolidated long-term storage, and geological disposal of spent fuel is "likely to be reevaluated in a new light because of the Fukushima storage pool experience".
In October 2011, the Nuclear Regulatory Commission instructed agency staff to move forward with seven of the 12 safety recommendations put forward by the federal task force in July. The recommendations include "new standards aimed at strengthening operators’ ability to deal with a complete loss of power, ensuring plants can withstand floods and earthquakes and improving emergency response capabilities". The new safety standards will take up to five years to fully implement.
Scope
The topic of nuclear safety covers:- The research and testing of the possible incidents/events at nuclear facilities,
- What equipment and actions are designed to prevent those incidents/events from having serious consequences,
- The calculation of the probabilities of multiple systems and/or actions failing thus allowing serious consequences,
- The evaluation of the possible timing and scope of those serious consequences (the worst-possible result in extreme cases being a release of radiation),
- The actions taken to protect the public during a release of radiation,
- The training and rehearsals performed to ensure readiness in case an incident/event occurs.
- Accidents that have occurred.
In the following, the names of federal regulations will be abbreviated in the standard way. For example, "Code of Federal Regulations, Title 10, Part 100, Section 23" will be given as "10CFR100.23".
Issues
More than a quarter of U.S. nuclear plant operators "have failed to properly tell regulators about equipment defects that could imperil reactor safety", according to a Nuclear Regulatory CommissionNuclear Regulatory Commission
The Nuclear Regulatory Commission is an independent agency of the United States government that was established by the Energy Reorganization Act of 1974 from the United States Atomic Energy Commission, and was first opened January 19, 1975...
report.
In February 2011, a major manufacturer in the nuclear industry reported a potential "substantial safety hazard" with control rods at more than two dozen reactors around the USA. GE Hitachi Nuclear Energy said it had discovered extensive cracking and "material distortion," and recommended that the boiling water reactors using its Marathon control rod blades replace them more frequently than previously told. If the design life if not revised, it "could result in significant control blade cracking and could, if not corrected, create a substantial safety hazard and is considered a reportable condition," the company said in its report to the NRC.
Radioactive waste storage
The Fukushima nuclear disaster has reopened questions about the risks of U.S. nuclear reactors, and especially the pools that store spent fuel. In March 2011, nuclear experts told Congress that spent-fuel pools at US nuclear power plants are too full. A fire at a spent-fuel pool could release cesium-137. Experts say the entire US spent-fuel policy should be overhauled in light of Fukushima I.With the cancellation of the Yucca Mountain nuclear waste repository in Nevada, more nuclear waste is being loaded into sealed metal casks filled with inert gas. Many of these casks will be stored in coastal or lakeside regions where a salt air environment exists, and the Massachusetts Institute of Technology is studying how such dry casks
Dry cask storage
Dry cask storage is a method of storing high-level radioactive waste, such as spent nuclear fuel that has already been cooled in the spent fuel pool for at least one year.. These casks are typically steel cylinders that are either welded or bolted closed. When inside, the fuel rods are surrounded...
perform in salt environments. Some hope that the casks can be used for 100 years but cracking related to corrosion could occur in 30 years or less. Robert Alvarez, a former Department of Energy official who oversaw nuclear issues, said dry casks would provide safer storage until a permanent nuclear repository was built and loaded, a process that would take decades.
Earthquake risk
About one third of reactors in the US are boiling water reactorBoiling water reactor
The boiling water reactor is a type of light water nuclear reactor used for the generation of electrical power. It is the second most common type of electricity-generating nuclear reactor after the pressurized water reactor , also a type of light water nuclear reactor...
s, the same technology which was involved in the Fukushima Daiichi nuclear disaster
Fukushima Daiichi nuclear disaster
The is a series of equipment failures, nuclear meltdowns, and releases of radioactive materials at the Fukushima I Nuclear Power Plant, following the Tōhoku earthquake and tsunami on 11 March 2011. The plant comprises six separate boiling water reactors originally designed by General Electric ,...
in Japan. There are also eight nuclear power plants located along the seismically active West coast. Twelve of the American reactors that are of the same vintage as the Fukushima Daiichi plant are in seismically active areas.
Earthquake risk is often measured by "Peak Ground Acceleration", or PGA. The following nuclear power plants have a two percent or greater chance of having PGA over 0.15g in the next 50 years: Diablo Canyon, Calif.; San Onofre, Calif.; Sequoyah, Tenn.; H.B. Robinson, SC.; Watts Bar, Tenn.; Virgil C. Summer, SC.; Vogtle, GA.; Indian Point, NY.; Oconee, SC.; and Seabrook, NH.
GE Mark 1 reactor design
Experts have long criticized General ElectricGeneral Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
's Mark I reactor design, because it offered a relatively weak containment vessel. Three GE scientists resigned 35 years ago in protest of the design of the Mark I containment system. David Lochbaum, chief nuclear safety
Nuclear safety
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,...
officer with the Union of Concerned Scientists
Union of Concerned Scientists
The Union of Concerned Scientists is a nonprofit science advocacy group based in the United States. The UCS membership includes many private citizens in addition to professional scientists. James J...
, has repeatedly questioned the safety of the Fukushima I Plant's GE Mark 1 reactor design, which is used in almost a quarter of the United States' nuclear fleet.
Aging of nuclear reactors
An important concern in the nuclear safety field is the aging of nuclear reactors. Researchers at Pennsylvania State University will use ultrasonic waves to look for cracks and other defects in hot metal parts, in order to identify “microscale” defects that lead to big cracks.Population considerations
Population-criteria for siting U.S. nuclear power plants is covered under federal regulation 10CFR100.11.Minimum distances must be set for an exclusion area (which is typically inside the Protected Area's fence), a low population zone and a population center distance. To calculate the minimum assured distances for each of these, a maximum possible amount of radioactivity release (called a "source term") must be assumed and worst-case wind conditions must be assumed.
Nuclear power plants in their licensing submittals so far have used extremely conservative fallout inputs from the somewhat antiquated WASH-1400
WASH-1400
WASH-1400, 'The Reactor Safety Study, was a report produced in 1975 for the Nuclear Regulatory Commission by a committee of specialists under Professor Norman Rasmussen. It "generated a storm of criticism in the years following its release"...
study. The NRC has disavowed the assumptions and thus the results of WASH-1400 as being far too pessimistic (see NUREG-1150
NUREG-1150
NUREG-1150 is an improvement on WASH-1400 and CRAC-II using the results of plant-specific Probabilistic Risk Assessments...
), and is in the process of generating a new state-of-the-art study (see SOARCA).
A bounding calculation using a source term from WASH-1400 typically calculates a minimum Emergency Planning Zone (EPZ) of about 5 miles (8 km) from the plant, which in practice is rounded up to 10 miles (16.1 km) for actual implementation.
Terrorist attack
After 9/11, it would seem prudent for nuclear plants to be prepared for an attack by a large, well-armed terrorist group. But the Nuclear Regulatory Commission, in revising its security rules, decided not to require that plants be able to defend themselves against groups carrying sophisticated weapons. According to a study by the Government Accountability Office, the N.R.C. appeared to have based its revised rules "on what the industry considered reasonable and feasible to defend against rather than on an assessment of the terrorist threat itself".The Protected Area
The Protected Area encloses the Exclusion Zone (as defined in 10CFR100.3 ). It also serves as a security zone, within which only trusted individuals are allowed to walk unescorted.The Protected Area is surrounded by a double fence, and the gap in between the fences is electronically monitored. There are very few gates, and those are well guarded. Numerous other security measures are in effect.
The missile shield
The missile shield protecting the containment structure was originally intended to protect only from natural forces, such as tornadoes. For example, it usually is designed to withstand the impact of a telephone pole flying at 60 mile per hour and hitting end-on. One plant, FloridaFlorida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
's Turkey Point NGS
Turkey Point Nuclear Generating Station
Turkey Point Nuclear Generating Station is a twin reactor nuclear power station located on a 3,300-acre site 2 miles east of Homestead, Florida, United States, next to Biscayne National Park located about 25 miles south of Miami, Florida near the southernmost edge of Miami-Dade...
, survived a direct hit by Category 5 Hurricane Andrew
Hurricane Andrew
Hurricane Andrew was the third Category 5 hurricane to make landfall in the United States, after the Labor Day Hurricane of 1935 and Hurricane Camille in 1969. Andrew was the first named storm and only major hurricane of the otherwise inactive 1992 Atlantic hurricane season...
in 1992, with no damage to the containment.
No actual missile shield has been subjected to an aircraft impact test. However, a highly similar test was done at Sandia National Laboratories
Sandia National Laboratories
The Sandia National Laboratories, managed and operated by the Sandia Corporation , are two major United States Department of Energy research and development national laboratories....
and filmed (see Containment building
Containment building
A containment building, in its most common usage, is a steel or reinforced concrete structure enclosing a nuclear reactor. It is designed, in any emergency, to contain the escape of radiation to a maximum pressure in the range of 60 to 200 psi...
), and the target was essentially undamaged (reinforced concrete is strongly resistant both to impact and to fire). 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."
Procedures
In the U.S., the Operating License is granted by the government and carries the force of law. The Final Safety Analysis Report (FSAR) is part of the Operating License, and the plant's Technical Specifications (which contain the restrictions the operators consult during operation) are a chapter of the FSAR. All procedures are checked against the Technical Specifications and also by a Transient Analysis engineer, and each copy of an approved procedure is numbered and the copies controlled (so that updating all copies at once can be assured). In a U.S. nuclear power plant, unlike in most other industries, approved procedures carry the force of law and to deliberately violate one is a criminal act.Design Basis Events
"Design Basis EventsAs the Fukushima I nuclear accidents showed, external threats — such as earthquakes, tsunamis, fires, flooding, tornadoes and terrorist attacks — are some of the greatest risk factors for a serious nuclear accident. Yet, nuclear plant operators have normally considered these 'beyond design basis events' so unlikely that they have not built in complete safeguards.
Assessments of risks
The NRC (and its predecessors) have over the decades produced three major analyses of the risks of nuclear power: a fourth, all-encompassing one (the State-of-the-Art Reactor Consequence AnalysesState-of-the-Art Reactor Consequence Analyses
The State-of-the-Art Reactor Consequence Analyses is a study of nuclear power plant safety conducted by the Nuclear Regulatory Commission...
, or SOARCA, study) is in generation now. The new study will be based on actual test results, on probabilistic risk assessment
Probabilistic risk assessment
Probabilistic risk assessment is a systematic and comprehensive methodology to evaluate risks associated with a complex engineered technological entity ....
(PRA) methodology, and on the evaluated actions of government agencies.
The existing studies (all now disavowed by the NRC and to be replaced by SOARCA) are:
- NUREG-1150NUREG-1150NUREG-1150 is an improvement on WASH-1400 and CRAC-II using the results of plant-specific Probabilistic Risk Assessments...
(1991) - CRAC-IICRAC-IICRAC-II is both a computer code and the 1982 report of the simulation results performed by Sandia National Laboratories for the Nuclear Regulatory Commission...
(1982) (based on WASH-1400 results) - WASH-1400WASH-1400WASH-1400, 'The Reactor Safety Study, was a report produced in 1975 for the Nuclear Regulatory Commission by a committee of specialists under Professor Norman Rasmussen. It "generated a storm of criticism in the years following its release"...
(1975) - WASH-740WASH-740WASH-740, "Theoretical Possibilities and Consequences of Major Accidents in Large Nuclear Power Plants" estimated maximum possible damage from a meltdown with no containment building at a large nuclear reactor. The report was published by the U.S...
(1957) (not PRA-based)
Comparisons of risks of nuclear power plants
Reactor vendors now routinely calculate probabilistic risk assessments of their nuclear power plant designs.General Electric has recalculated maximum core damage frequencies per year per plant for its nuclear power plant designs:
- BWR/4 — 1 × 10–5 (a typical plant)
- BWR/6 — 1 × 10–6 (a typical plant)
- ABWR — 2 × 10–7 (now operating in Japan)
- ESBWR — 3 × 10–8 (submitted for Final Design Approval by NRC)
The AP1000 has a maximum core damage frequency of per plant per year. The European Pressurized Reactor
European Pressurized Reactor
The EPR is a third generation pressurized water reactor design. It has been designed and developed mainly by Framatome , Electricité de France in France, and Siemens AG in Germany...
(EPR) has a maximum core damage frequency
Core damage frequency
Core damage frequency is a term used in probabilistic risk assessment that indicates the likelihood of an accident that would cause damage to a nuclear reactor core. Core damage accidents are considered serious because damage to the core may prevent control of the nuclear reaction, which can lead...
of per plant per year.
Emergency Classifications
The NRC established a classification scale for nuclear power plant events to ensure consistency in the communications and response.Unusual Event – This is the lowest of the four emergency classifications. This classification indicates that a small problem has occurred. No radiation leak is expected and federal, state and county officials are notified.
Alert –Events are in process or have occurred which involve an actual or potential substantial degradation in the level of safety of the plant. Any releases of radioactive material from the plant are expected to be limited to a small fraction of the Environmental Protection Agency (EPA) Protective Action Guide for Nuclear Incidents
Protective Action Guide for Nuclear Incidents
Protective Action Guide for Nuclear IncidentsSevere Nuclear and radiation accidents will cause massive radioactive contamination and may cause health risks to large populations. Unlike other natural disasters, radioactive contamination is not tangible and hard to measure. Its effect will remain...
(PAGs)
Site Area Emergency – Involves events in process or which have occurred that result in actual or likely major failures of plant functions needed for protection of the public. Any releases of radioactive material are not expected to exceed the EPA PAGs except near the site boundary.
General Emergency – The most serious emergency classification and indicates a serious problem. A general emergency involves actual or imminent substantial core damage or melting of reactor fuel with the potential for loss of containment integrity. Emergency sirens will be sounded and federal, state and county officials will act to ensure public safety. Radioactive releases during a general emergency can reasonably be expected to exceed the EPA PAGs for more than the immediate site area.
Three Mile Island
On March 28, 1979, equipment failures and operator error contributed to loss of coolant and a partial core meltdown at the Three Mile Island Nuclear Power PlantThree Mile Island accident
The Three Mile Island accident was a core meltdown in Unit 2 of the Three Mile Island Nuclear Generating Station in Dauphin County, Pennsylvania near Harrisburg, United States in 1979....
in Pennsylvania. The mechanical failures were compounded by the initial failure of plant operators to recognize the situation as a loss-of-coolant accident due to inadequate training and human factors
Human factors
Human factors science or human factors technologies is a multidisciplinary field incorporating contributions from psychology, engineering, industrial design, statistics, operations research and anthropometry...
, such as human-computer interaction design oversights relating to ambiguous control room indicators in the power plant's user interface
User interface
The user interface, in the industrial design field of human–machine interaction, is the space where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the...
. In particular, a hidden indicator light led to an operator manually overriding the automatic emergency cooling system of the reactor because the operator mistakenly believed that there was too much coolant water present in the reactor and causing the steam pressure release. The scope and complexity of the accident became clear over the course of five days, as employees of Met Ed, Pennsylvania state officials, and members of the U.S. Nuclear Regulatory Commission
Nuclear Regulatory Commission
The Nuclear Regulatory Commission is an independent agency of the United States government that was established by the Energy Reorganization Act of 1974 from the United States Atomic Energy Commission, and was first opened January 19, 1975...
(NRC) tried to understand the problem, communicate the situation to the press and local community, decide whether the accident required an emergency evacuation, and ultimately end the crisis. The NRC's authorization of the release of 40,000 gallons of radioactive waste water directly in the Susquehanna River led to a loss of credibility with the press and community.
The World Nuclear Association has stated that cleanup of the damaged nuclear reactor system at TMI-2 took nearly 12 years and cost approximately US $973 million. Benjamin K. Sovacool
Benjamin K. Sovacool
Benjamin K. Sovacool is a Visiting Associate Professor at Vermont Law School and founding Director of the Energy Justice Program at their Institute for Energy and Environment. He was formerly an Assistant Professor and Research Fellow at the National University of Singapore.Sovacool's research...
, in his 2007 preliminary assessment of major energy accidents, estimated that the TMI accident caused a total of $2.4 billion in property damages. The health effects of the Three Mile Island accident
Three Mile Island accident health effects
The health effects of the 1979 Three Mile Island nuclear accident are widely, but not universally, agreed to be very low level. According to the official radiation release figures, average local radiation exposure was equivalent to a chest X-ray, and maximum local exposure equivalent to less than a...
are widely, but not universally, agreed to be very low level. The accident triggered protests around the world.
List of accidents
| Date | Location | Description | Fatalities | Cost (in millions 2006 $) |
|---|---|---|---|---|
| January 3, 1961 | Idaho Falls, Idaho, US | Criticality Steam Explosion at SL-1 National Reactor Testing Station SL-1 The SL-1, or Stationary Low-Power Reactor Number One, was a United States Army experimental nuclear power reactor which underwent a steam explosion and meltdown on January 3, 1961, killing its three operators. The direct cause was the improper withdrawal of the central control rod, responsible for... |
3 | $US22 |
| March 28, 1979 | Middletown, Pennsylvania, US | Loss-of-coolant and partial core meltdown, see Three Mile Island accident Three Mile Island accident The Three Mile Island accident was a core meltdown in Unit 2 of the Three Mile Island Nuclear Generating Station in Dauphin County, Pennsylvania near Harrisburg, United States in 1979.... and Three Mile Island accident health effects Three Mile Island accident health effects The health effects of the 1979 Three Mile Island nuclear accident are widely, but not universally, agreed to be very low level. According to the official radiation release figures, average local radiation exposure was equivalent to a chest X-ray, and maximum local exposure equivalent to less than a... |
0 | US$2,400 |
| September 15, 1984 | Athens, Alabama, US | Safety violations, operator error, and design problems force six year outage at Browns Ferry Unit 2 | 0 | US$110 |
| March 9, 1985 | Athens, Alabama, US | Instrumentation systems malfunction during startup, which led to suspension of operations at all three Browns Ferry Units | 0 | US$1,830 |
| April 11, 1986 | Plymouth, Massachusetts, US | Recurring equipment problems force emergency shutdown of Boston Edison’s Pilgrim Nuclear Power Plant | 0 | US$1,001 |
| March 31, 1987 | Delta, Pennsylvania, US | Peach Bottom units 2 and 3 Peach Bottom Nuclear Generating Station Peach Bottom Atomic Power Station, a nuclear power plant, is located southeast of Harrisburg in Peach Bottom Township, York County, Pennsylvania, on the Susquehanna River on the Maryland border.... shutdown due to cooling malfunctions and unexplained equipment problems |
0 | US$400 |
| December 19, 1987 | Lycoming, New York, US | Malfunctions force Niagara Mohawk Power Corporation to shut down Nine Mile Point Unit 1 | 0 | US$150 |
| March 17, 1989 | Lusby, Maryland, US | Inspections at Calvert Cliff Units 1 and 2 Calvert Cliffs Nuclear Power Plant The Calvert Cliffs Nuclear Power Plant is a nuclear power plant located on the western shore of the Chesapeake Bay near Lusby, Calvert County, Maryland.-Overview:... reveal cracks at pressurized heater sleeves, forcing extended shutdowns |
0 | US$120 |
| February 20, 1996 | Waterford, Connecticut, US | Leaking valve forces shutdown Millstone Nuclear Power Plant Millstone Nuclear Power Plant The Millstone Nuclear Power Station is the only nuclear power generation site in Connecticut. It is located at a former quarry in Waterford... Units 1 and 2, multiple equipment failures found |
0 | US$254 |
| September 2, 1996 | Crystal River, Florida, US | Balance-of-plant equipment malfunction forces shutdown and extensive repairs at Crystal River Unit 3 | 0 | US$384 |
| February 16, 2002 | Oak Harbor, Ohio, US | Severe corrosion of control rod forces 24-month outage of Davis-Besse reactor | 0 | US$143 |
| February 1, 2010 | Montpelier, Vermont, US | Deteriorating underground pipes from the Vermont Yankee Nuclear Power Plant Vermont Yankee Nuclear Power Plant Vermont Yankee is a General Electric boiling water reactor type nuclear power plant currently owned by Entergy. It is located in the town of Vernon, Vermont, and generates 620 megawatts of electricity at full power. The plant began commercial operations in 1972... leak radioactive tritium into groundwater supplies |
0 | US$700 |
Chernobyl
Experts have disagreed about whether an accident as serious as the Chernobyl disasterChernobyl disaster
The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in Ukraine , which was under the direct jurisdiction of the central authorities in Moscow...
could occur in the USA. In 1986, Commissioner Asselstine testified before Congress that:
While we hope that their occurrence is unlikely, there are accident sequences for U.S. plants that can lead to rupture or by-passing of the containment in U.S. reactors which would result in the off-site release of fission products comparable or worse than the releases estimated by the NRC to have taken place during the Chernobyl accident.
Whistleblowers
In 1976 Gregory MinorGregory Minor
Gregory Charles Minor was one of three middle-management engineers who resigned from the General Electric nuclear reactor division in 1976 to protest against the use of nuclear power in the United States. A native of Fresno, California, Minor received an electrical engineering degree from the...
, Richard Hubbard, and Dale Bridenbaugh "blew the whistle" on safety problems at nuclear power plant
Nuclear power plant
A nuclear power plant is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity.Nuclear power plants are usually...
s in the United States. The three nuclear engineers gained the attention of journalists and their disclosures about the threats of nuclear power
Nuclear power
Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...
had a significant impact.
Potassium iodide
According to the Nuclear Regulatory CommissionNuclear Regulatory Commission
The Nuclear Regulatory Commission is an independent agency of the United States government that was established by the Energy Reorganization Act of 1974 from the United States Atomic Energy Commission, and was first opened January 19, 1975...
, 20 states in the USA have requested stocks of potassium iodide
Potassium iodide
Potassium iodide is an inorganic compound with the chemical formula KI. This white salt is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It is less hygroscopic than sodium iodide, making it easier to work with...
which the NRC suggests should be available for those living within 10 miles (16.1 km) of a nuclear power plant in the unlikely event of a severe accident. Iodine is a fission product in a nuclear reactor, and in the event of a severe accident a fraction of that iodine is expected to leak from the fuel and out of the containment building. If ingested, this iodine would tend to be accumulated by a person's thyroid. Potassium Iodide (KI) is an over-the-counter drug that may reduce the amount of radioactive iodine absorbed by the body’s thyroid gland. KI offers a degree of protection only to the thyroid gland and only in cases when the release contains radioactive iodine. KI would be supplemental to evacuation and sheltering. In cases where the public may be exposed to certain types of radioactivity, state and local health officials may advise the public to take Potassium Iodide (KI) tablets.
Radioactive Iodine (radioiodine) is one of the products that can be released in a serious nuclear power plant accident. Potassium Iodide (KI) is a non radioactive form of iodine that may be taken to reduce the amount of radioactive iodine absorbed by the body’s thyroid gland. When taken before or shortly after a radiological exposure, potassium iodide blocks the thyroid glands ability to absorb radioactive iodine. KI is a secondary protection for evacuation and sheltering are the primary means of protection.
Potassium Iodide should be taken by the public during an emergency only when directed by public health officials. A TV and radio Emergency Alert System (EAS) message will be broadcast and public health officials will inform the public when to take KI. Potassium iodide is available to persons within 10 miles of the plant though the county health department. During an emergency, KI is available to the general public at evacuation Reception Centers.
See also
- Nuclear safetyNuclear safetyNuclear 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,...
- Protective Action Guide for Nuclear IncidentsProtective Action Guide for Nuclear IncidentsProtective Action Guide for Nuclear IncidentsSevere Nuclear and radiation accidents will cause massive radioactive contamination and may cause health risks to large populations. Unlike other natural disasters, radioactive contamination is not tangible and hard to measure. Its effect will remain...
- Nuclear powerNuclear powerNuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...
- Nuclear power in the United States
- List of nuclear reactors
- Institute of Nuclear Power OperationsInstitute of Nuclear Power OperationsThe Institute of Nuclear Power Operations , headquartered in the Atlanta suburb of Marietta, GA, is an organization established in 1979 by the U.S. nuclear power industry in response to recommendations by the Kemeny Commission Report, following the investigation of the Three Mile Island Unit 2 event...
- Nuclear Power 2010 ProgramNuclear Power 2010 ProgramThe "Nuclear Power 2010 Program" was unveiled by the U.S. Secretary of Energy Spencer Abraham on February 14, 2002 as one means towards addressing the expected need for new power plants...
- List of civilian nuclear accidents
- List of civilian radiation accidents
- List of military nuclear accidents