Nuclear power plants/facilities accidents

Half-lives span a very wide range (Table 17.5). Consider strontium-90, for which the half-life is 28 a. This nuclide is present in nuclear fallout, the fine dust that settles from clouds of airborne particles after the explosion of a nuclear bomb, and may also be present in the accidental release of radioactive materials into the air. Because it is chemically very similar to calcium, strontium may accompany that element through the environment and become incorporated into bones once there, it continues to emit radiation for many years. About 10 half-lives (for strontium-90, 280 a) must pass before the activity of a sample has fallen to 1/1000 of its initial value. Iodine-131, which was released in the accidental fire at the Chernobyl nuclear power plant, has a half-life of only 8.05 d, but it accumulates in the thyroid gland. Several cases of thyroid cancer have been linked to iodine-131 exposure from the accident. Plutonium-239 has a half-life of 24 ka (24000 years). Consequently, very long term storage facilities are required for plutonium waste, and land contaminated with plutonium cannot be inhabited again for thousands of years without expensive remediation efforts. 

The nuclear explosions that devastated Hiroshima and Nagasaki killed 100,000 to 200,000 people instantaneously. Probably an equal number died later, victims of the radiation released in those explosions. Millions of people were exposed to the radioactivity released by the accident at the Chernobyl nuclear power plant. The full health effects of that accident may never be known, but 31 people died of radiation sickness within a few weeks of the accident, and more than 2000 people have developed thyroid cancer through exposure to radioactive iodine released in the accident. Even low levels of radiation can cause health problems. For this reason, workers in facilities that use radioisotopes monitor their exposure to radiation continually, and they must be rotated to other duties if their total exposure exceeds prescribed levels. 

Information is available on the levels of241 Am in soil and sediment in areas affected only by global fallout, at DOE installations and other nuclear facilities, as well as sites of nuclear explosions and accidents (Alberts et al. 1989 Bennett 1979 Cooper et al. 1994 DOE 1980 Pattenden and McKay 1994 Robison et al. 1997a, 1997b Sanchez et al. 1996). 241Am levels in soil around nuclear power plants in the United States were indistinguishable from fallout background (EPRI 1981). 

Highly publicized nuclear accidents such as those that occurred at Chernobyl and Three Mile Island must be considered anomalies. Nuclear power plants have multiple safety measures in place to prevent radiation leaks. The small amount of radioactive waste produced by nuclear reactors is controlled and usually contained in the plant facility. 

The existing nuclear power plants in the United States are used exclusively to generate electricity. As large and relatively complex facilities, there are a number of upsets and accidents that can challenge the operation of the plants and the barriers in place to prevent the release of radioactive materials. As shown in Figure 3, the NGNP prototype or subsequent high temperature gas-cooled reactors will be... 

Some major accidents at nuclear power plants, such as the leak of radioactivity from the Three-Mile Island facility in Pennsylvania in 1979 and the far more serious one from the Chernobyl plant in Ukraine in 1986, have resulted in high levels of mistrust and fear in many people. Yet, despite these problems, nuclear energy remains an important source of electricity. In the late 1990s, nearly every European country employed nuclear fission in power plants, and such plants provide the majority of electricity in Sweden and France. Today, the United States obtains about 20% of its electricity from nuclear power plants, and Canada slightly less. 

A great deal of controversy now exists about the efficiency of the safety systems in nuclear power plants. Accidents such as the one at the Three Mile Island facility in Pennsylvania in 1979 and the one at Chernobyl in the Soviet Union in 1986 have led many people to question the wisdom of continuing to build fission-based power plants. 

Usually one distinguishes between "near field" and "far field" effects of radioactivity releases. Near field effects are observed close to the release source, as for example the nuclear power plant or nuclear waste storage facility. The dissolution of nuclear waste by rain or ground water is a typical near field problem. As the source is known, it can be controlled and its environment monitored. If the radioactivity exceeds permitted levels, access to the contaminated area can be restricted. Far field effects involve the behavior of radionuclides which have spread out of such a restricted area, caused either by nuclear power accidents and weapons tests or by leakage from nuclear power plants. 

D. Kamei, T. Kuno, S. Sato, K. Nitta, T. Akiba, Impact of the Fukushima Daiichi nuclear power plant accident on hemodialysis facilities An evaluation of radioactive contaminants in water used for hemodialysis. Then Apher. Dial. 16, 2012, 87-90. 

Potential external events were identified by reviewing previous Safety Analysis Reports of similar DOE facilities (Restrepo 1995) and the recommended list of external events used to evaluate commercial nuclear power plant risks (NRC 1983). In addition, an attempt was made to identify any other potential external-initiating event unique to the site that had not been considered in previous studies. It is important to note that operational accidents (e.g., criticality, internal fires) occurring inside the HCF and assodated radioactive material storage facilities are not considered in this screening process. These types of "internal initiating events are identified separately using preliminary hazard checklists (see Appendix 3A). 

The ATHEANA method was developed hy the US Nuclear Regulatory Commission to increase the degree to which an HRA can represent the kinds of human behaviors seen in accidents and near-miss events at nuclear power plants and other industrial facilities (USNRC, 2000). The method provides a detaded search process to identify human actions and their contexts that can produce human fadure. Such situations are said to have an error-forcing context (EEC) in ATHEANA terminology (Forester 1. et ah, 2007). 

Kazakhstan has a nuclear scientific-industrial complex which was set up as a part of a nuclear infrastructure of the former USSR. More than 50% of the uranium resources of the former Soviet Union are in Kazakhstan, with seven uranium mines. Two UO2 plants produced up to 35% of the total uranium in the USSR in 1990. There are extensive facilities for producing UO2 pellets for VVER fuel elements from Russian enriched uranium. Kazakhstan has several research reactors and one operating nuclear power plant, the BN-350 fast reactor, which started operation in 1973 with a design life of 20 years. Work on its lifetime extension has the intention of bringing it into compliance with current safety standards. 1995 and 1996 were devoted to this work. In October 1996. experimental investigation on accident-proofdecay heat removal by natural circulation was carried out. The reactor BN-350 was restarted in February 4, 1997 at a power level of 420 MW(th). 

In all technical installations, malfunctioning or failure of systems or components may lead to an accident with more or less serious consequences for the plant, the staff and, possibly, the environment as well. This also applies to nuclear power plants. For this reason, from the beginning of nuclear power production extensive measures have been taken to preclude accidents or to reduce the probability and the consequences of an accident to a level well below that of other technical installations or of naturally occurring events. As a consequence of these efforts, nuclear power plants of an adequate design currently show the highest safety level among all types of electricity-generating facilities. 

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