Nuclear safety in the United States is governed by federal regulations issued by the Nuclear Regulatory Commission (NRC). The NRC regulates all nuclear plants and materials in the United States except for nuclear plants and materials controlled by the U.S. government, as well those powering naval vessels.About NRC, U.S. Nuclear Regulatory Commission. Retrieved 2007-6-1.Our Governing Legislation, U.S. Nuclear Regulatory Commission. Retrieved 2007-6-1.
The 1979 Three Mile Island accident was a pivotal event that led to questions about U.S. nuclear safety. Earlier events had a similar effect, including a 1975 fire at Browns Ferry and the 1976 testimonials of three concerned GE nuclear engineers, the GE Three. In 1981, workers inadvertently reversed pipe restraints at the Diablo Canyon Power Plant reactors, compromising seismic protection systems, which further undermined confidence in nuclear safety. All of these well-publicised events, undermined public support for the U.S. nuclear industry in the 1970s and the 1980s. In 2002, the USA had what former NRC Commissioner Victor Gilinsky termed "its closest brush with disaster" since Three Mile Island's 1979 meltdown; a workman at the Davis-Besse reactor found a large rust hole in the top of the reactor pressure vessel.
Recent concerns have been expressed about safety issues affecting a large part of the nuclear fleet of reactors. In 2012, the Union of Concerned Scientists, which tracks ongoing safety issues at operating nuclear plants, found that "leakage of radioactive materials is a pervasive problem at almost 90 percent of all reactors, as are issues that pose a risk of nuclear accidents".
Following the Japanese 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.Eric Wesoff, Greentechmedia. "Black & Veatch's 2011 Electric Utility Survey." June 16, 2011. Retrieved October 11, 2011. 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 (NRC) instructed agency staff to move forward with seven of the twelve 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 analysis of possible or potential incidents or events at nuclear facilities, The equipment and procedures designed to prevent those incidents or events from having serious consequences, The actions to reduce the consequences of those incidents or events, The calculation of the probabilities, and the seriousness, of equipment, procedures or actions failing, The evaluation of the possible timing and scope of those consequences, The actions taken to protect the public during a release of radioactivity, The training and rehearsals performed to ensure readiness in case an incident/event occurs. This article will also consider 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".
History In the 1950s and 60's, the United States Atomic Energy Commission (AEC) began developing safety regulations against nuclear fallout for civilian nuclear reactors. Because the effects of nuclear fallout are more widespread and longer lasting than other forms of energy production accidents, the AEC desired a more proactive response towards potential accidents than ever before. One step to prevent nuclear reactor accidents was the Price-Anderson Act. Passed by Congress in 1957, the Price-Anderson Act ensured government assistance above the $60 million covered by private insurance companies in the case of a nuclear reactor accident. The main goal of the Price-Anderson Act was to protect the multi-billion-dollar companies overseeing the production of nuclear reactors. Without this protection, the nuclear reactor industry could potentially come to a halt, and the protective measures against nuclear fallout would be reduced. Because of the limited experience in nuclear reactor technology, however, engineers had a difficult time calculating the potential risk of released radiation. Engineers were forced to imagine every unlikely accident, and the potential fallout associated with each accident. The AEC's regulations against potential nuclear reactor fallout were centered on the ability of the power plant to the Maximum Credible Accident (MCA). The MCA involved a "large release of radioactive isotopes after a substantial meltdown of the reactor fuel when the reactor coolant system failed through a Loss-of-Coolant Accident". The prevention of the MCA enabled a number of new nuclear fallout preventive measures. Static safety systems, or systems without power sources or user input, were enabled to prevent potential human error. Containment buildings, for example, were reliably effective at containing a release of radiation and did not need to be powered or turned on to operate. Active protective systems, although far less dependable, can do many things that static systems cannot. For example, a system to replace the escaping steam of a cooling system with cooling water could prevent reactor fuel from melting. Nonetheless, this system would need a sensor to detect the presence of releasing steam. Sensors can fail, and the results of a lack of preventive measures would result in a local nuclear fallout. The AEC had to choose, then, between active and static systems to protect the public from nuclear fallout. With a lack of set standards and probabilistic calculations, the AEC and the industry became divided on the best safety precautions to use. This division gave rise to the Nuclear Regulatory Commission (NRC). The NRC was committed to 'regulations through research', which gave the regulatory committee a knowledge bank of research on which to draw their regulations. Much of the research done by the NRC sought to move safety systems from a deterministic viewpoint into a new probabilistic approach. The deterministic approach sought to foresee all problems before they arose. The probabilistic approach uses a more mathematical approach to weigh the risks of potential radiation leaks. Much of the probabilistic safety approach can be drawn from the radiative transfer theory in Physics, which describes how radiation travels in free space and through barriers.
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 Commission 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 is 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 Daiichi nuclear disaster has reopened questions about the risks of U.S. nuclear reactors, and especially the pools that store Spent nuclear fuel. In March 2011, nuclear experts told Congress that Spent nuclear 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 cask storage 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 cask storage would provide safer storage until a permanent nuclear repository was built and loaded, a process that would take decades.
At places like Maine Yankee, Connecticut Yankee and Rancho Seco, reactors no longer operate, but the spent fuel remains in small concrete-and-steel silos that require maintenance and monitoring by a guard force. Sometimes the presence of nuclear waste prevents re-use of the sites by industry.
Without a long-term solution to store nuclear waste, a nuclear renaissance in the U.S. remains unlikely. Nine states have "explicit moratoria on new nuclear power until a storage solution emerges".
Some nuclear power advocates argue that the United States should develop factories and reactors that will recycle some of the spent nuclear fuel. (It is not now the policy of the United States to recycle its spent nuclear fuel.) But the Blue Ribbon Commission on America's Nuclear Future said in 2012 that "no existing technology was adequate for that purpose, given cost considerations and the risk of nuclear proliferation".
Earthquake risk About one third of reactors in the US are boiling water reactors, 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. (Closure date of the two units: 2024/2025); Sequoyah, Tenn.; H.B. Robinson, SC.; Watts Bar, Tenn.; Virgil C. Summer, SC.; Vogtle, GA. (new build of two units included); Indian Point, NY. (Closure date of the two units: 2021); Oconee, SC.; and Seabrook, NH.
GE Mark 1 reactor containment design General Electric's Mark I reactor containment design has been long criticized by experts over its relatively weak containment vessel.John Byrne and Steven M. Hoffman (1996). Governing the Atom: The Politics of Risk, Transaction Publishers, p. 132. Notably, Three GE scientists resigned in 1976 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 containment design. In a 2012 nuclear power safety report, David Lochbaum and Edwin Lyman said: