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Nuclear Safety(Nuclear Accidents, Security,radiation)

Long Term Effects of Radiation

Long after the acute effects of radiation have subsided, radiation damage continues to produce a wide range of physical problems. These effects- including leukemia, cancer, and many others- appear two, three, even ten years later.

Blood Disorders

According to Japanese data, there was an increase in anemia among persons exposed to the bomb. In some cases, the decrease in white and red blood cells lasted for up to ten years after the bombing.


There was an increase in cataract rate of the survivors at Hiroshima and Nagasaki, who were partly shielded and suffered partial hair loss.

Malignant Tumors

All ionizing radiation is carcinogenic, but some tumor types are more readily generated than others. A prevalent type is leukemia. The cancer incidence among survivors of Hiroshima and Nagasaki is significantly larger than that of the general population, and a significant correlation between exposure level and degree of incidence has been reported for thyroid cancer, breast cancer, lung cancer, and cancer of the salivary gland. Often a decade or more passes before radiation-caused malignancies appear.


Beginning in early 1946, scar tissue covering apparently healed burns began to swell and grow abnormally. Mounds of raised and twisted flesh, called keloids, were found in 50 to 60 percent of those burned by direct exposure to the heat rays within 1.2 miles of the hypocenter. Keloids are believed to be related to the effects of radiation.

Radioactive Fallout

Fallout is the radioactive particles that fall to earth as a result of a nuclear explosion. It consists of weapon debris, fission products And, in the case of a ground burst, radiated soil. Fallout particles vary in size from thousandths of a millimeter to several millimeters. Much of this material falls directly back down close to ground zero within several minutes after the explosion, but some travels high into the atmosphere. This material will be dispersed over the earth during the following hours, days (and) months. Fallout is defined as one of two types: early fallout, within the first 24 hours after an explosion, or delayed fallout, which occurs days or years later.

Most of the radiation hazard from nuclear bursts comes from short-lived radio nuclides external to the body; these are generally confined to the locality downwind of the weapon burst point. This radiation hazard comes from radioactive fission fragments with half-lives of seconds to a few months, and from soil and other materials in the vicinity of the burst made radioactive by the intense neutron flux.

Most of the particles decay rapidly. Even so, beyond the blast radius of the exploding weapons there would be areas (hot spots) the survivors could not enter because of radioactive contamination from long-lived radioactive isotopes like strontium 90 or cesium 137. For the survivors of a nuclear war, this lingering radiation hazard could represent a grave threat for as long as 1 to 5 years after the attack.

Predictions of the amount and levels of the radioactive fallout are difficult because of several factors. These include; the yield and design of the weapon, the height of the explosion, the nature of the surface beneath the point of burst, and the meteorological conditions, such as wind direction and speed.

An airburst can produce minimal fallout if the fireball does not touch the ground. On the other hand, a nuclear explosion occurring at or near the earth's surface can result in severe contamination by the radioactive fallout.

Many fallout particles are especially hazardous biologically. Some of the principal radioactive elements are as follows:

Strontium 90 is very long-lived with a half-life of 28 years. It is chemically similar to calcium, causing it to accumulate in growing bones. This radiation can cause tumors, leukemia, and other blood abnormalities.

Iodine 131 has a half-life of 8.1 days. Ingestion of it concentrates in the thyroid gland. The radiation can destroy all or part of the thyroid. Taking potassium iodide can reduce the effects. The amount of tritium released varies by bomb design. It has a half-life of 12.3 years and can be easily ingested, since it can replace hydrogen in water. The beta radiation can cause lung cancer.

Cesium 137 has a half-life of 30 years. It does not present as large a biological threat as Strontium 90. It behaves similar to potassium, and will distribute fairly uniformly throughout the body. This can contribute to gonadal irradiation and genetic damage.

Plutonium 239 has a half-life of 24,400 years. Ingestion of as little as 1 microgram of plutonium, a barely visible speck, is a serious health hazard causing the formation of bone and lung tumors. When a plutonium weapon is exploded, not all of the plutonium is fissioned.

Ozone Depletion

When a nuclear weapon explodes in the air, the surrounding air is subjected to great heat, followed by relatively rapid cooling. These conditions are ideal for the production of tremendous amounts of nitric oxides. These oxides are carried into the upper atmosphere, where they reduce the concentration of protective ozone. Ozone is necessary to block harmful ultraviolet radiation from reaching the Earth's surface.

Oxides of nitrogen form a catalytic cycle to reduce the protective ozone layer.

The nitric oxides produced by the weapons could reduce the ozone levels in the Northern Hemisphere by as much as 30 to 70 percent. Such a depletion might produce changes in the Earth's climate, and would allow more ultraviolet radiation from the sun (sun should be lower-case) through the atmosphere to the surface of the Earth, where it could produce dangerous burns and a variety of potentially dangerous ecological effects.

It has been estimated that as much as 5,000 tons of nitric oxide is produced for each megaton of nuclear explosive power.

Consequences of ozone depletion

Since the ozone layer absorbs UVB ultraviolet light from the Sun, ozone layer depletion is expected to increase surface UVB levels, which could lead to damage, including increases in skin cancer. This was the reason for the Montreal Protocol. Although decreases in stratospheric ozone are well-tied to CFCs and there are good theoretical reasons to believe that decreases in ozone will lead to increases in surface UVB, there is no direct observational evidence linking ozone depletion to higher incidence of skin cancer in human beings. This is partly due to the fact that UVA, which has also been implicated in some forms of skin cancer, is not absorbed by ozone And it is nearly impossible to control statistics for lifestyle changes in the populace.

  • Increased UV

Ozone, while a minority constituent in the earth's atmosphere, is responsible for most of the absorption of UVB radiation. The amount of UVB radiation that penetrates through the ozone layer decreases exponentially with the slant-path thickness/density of the layer. Correspondingly, a decrease in atmospheric ozone is expected to give rise to significantly increased levels of UVB near the surface.

Increases in surface UVB due to the ozone hole can be partially inferred by radiative transfer model calculations, but cannot be calculated from direct measurements because of the lack of reliable historical (pre-ozone-hole) surface UV data, although more recent surface UV observation measurement programmes exist.

Because it is this same UV radiation that creates ozone in the ozone layer from O2 (regular oxygen) in the first place, a reduction in stratospheric ozone would actually tend to increase photochemical production of ozone at lower levels (in the troposphere), although the overall observed trends in total column ozone still show a decrease, largely because ozone produced lower down has a naturally shorter photochemical lifetime, so it is destroyed before the concentrations could reach a level which would compensate for the ozone reduction higher up.

  • Biological effects of increased UV

The main public concern regarding the ozone hole has been the effects of surface UV on human health. So far, ozone depletion in most locations has been typically a few percent. Were the high levels of depletion seen in the ozone hole ever to be common across the globe, the effects could be substantially more dramatic. As the ozone hole over Antarctica has in some instances grown so large as to reach southern parts of Australia and New Zealand, environmentalists have been concerned that the increase in surface UV could be significant.

  • Effects on Humans

UVB (the higher energy UV radiation absorbed by ozone) is generally accepted to be a contributory factor to skin cancer. In addition, increased surface UV leads to increased tropospheric ozone, which is a health risk to humans. The increased surface UV also represents an increase in the vitamin D synthetic capacity of the sunlight. The cancer preventive effects of vitamin D represent a possible beneficial effect of ozone depletion. In terms of health costs, the possible benefits of increased UV irradiance may outweigh the burden.

  • Effects on Crops

An increase of UV radiation would be expected to affect crops. A number of economically important species of plants, such as rice, depend on cyan bacteria residing on their roots for the retention of nitrogen. Cyan bacteria are sensitive to UV light and they would be affected by its increase.

  • Effects on Plankton

Research has shown a widespread extinction of plankton 2 million years ago that coincided with a nearby supernova. There is a difference in the orientation and motility of planktons when excess of UV rays reach earth. Researchers speculate that the extinction was caused by a significant weakening of the ozone layer at that time when the radiation from the supernova produced nitrogen oxides that catalyzed the destruction of ozone (plankton are particularly susceptible to effects of UV light, and are vitally important to marine food webs).

The Reality of Safety Risks

The United States has 104 nuclear power plants and 37 non-power reactors licensed by the Nuclear Regulatory Commission (NRC) to operate in the United States. Another 20 nuclear power plants have been permanently shut down and are in various stages of decommissioning. Federal regulations are intended to protect the public from harm caused by exposure to radioactive material released by sabotage of any US nuclear reactor. But Americans face undue risk because these security regulations are not consistently enforced and because the regulations underestimate the terrorism threat. Practical measures must be taken to reduce the sabotage risk.

Existing security regulations are intended to protect against intentional fuel damage from:

  • A small group of skilled and well-armed outsiders aided by one insider

  • A single insider acting alone

  • A 4-wheel drive land vehicle bomb

Nuclear reactor owners are required, as an explicit condition of the operating license issued by the NRC, to follow all applicable regulations including the security regulations much as licensed drivers are required to adhere to the Motor Vehicle Code. Owners use security procedures augmented by internal audits to comply with the regulations. In addition, the NRC periodically conducts independent audits.

Force-on-Force Security Tests

The NRC began conducting force-on-force tests at operating nuclear power plants in 1991 with its Operational Safeguards Response Evaluation (OSRE) program. In an OSRE test, mock intruders challenge physical protection (i.e., intrusion detection systems, locked doors, etc.) as well as the security guard force. The mock intruders attempt to simulate disabling enough equipment to cause damage to the fuel in the nuclear reactor. The NRC conducts an OSRE test at each site about once every eight years.

The NRC will begin a pilot program of force-on-force tests administered by the nuclear plant owners themselves in November 2001. This Safeguards Performance Assessment (SPA) program calls for NRC-observed force-on-force tests to be conducted at each site once every three years.

The NRC discontinued its OSRE program in 1998 after having only tested 57 of the 68 nuclear power plant sites. The OSRE tests at 27 of the 57 sites tested revealed significant weaknesses indicating "that a real attack would have put the nuclear reactor in jeopardy with the potential for core damage and a radiological release."

The NRC reinstated its OSRE program later in 1998 due to the resulting outcry from the public and Capitol Hill. The results since reinstatement are similar: 6 of the last 11 OSRE tests conducted in 2000 and 2001 have resulted in the mock intruders successfully simulating disabling enough equipment to cause reactor damage.

Nuclear Reactor Safety Problems

The existing security regulations do not provide adequate protection against known terrorist threat capabilities. For example, the regulations do not require protection against attacks by aircraft, boats, and trucks. In addition, the regulations assume that only a single insider will attempt sabotage. September 11th demonstrated that terrorists may devote the time and effort necessary to place more than one individual working at a nuclear reactor site.

The NRC does not use force-on-force tests to demonstrate security compliance at reactors that have permanently shut down and non-power reactors.

The NRC does not use force-on-force tests to demonstrate security compliance for spent fuel storage at operating reactors and reactors that have permanently shut down.

The NRC does not use force-on-force tests to demonstrate security compliance for operating reactors during outages when dozens of temporary workers, with minimal background checks, are allowed onsite. In addition, the defense-in-depth approach to safety is reduced during outages to sometimes only a single layer, making nuclear reactors more vulnerable to sabotage.

The NRC assumes that the mock intruders will be able to disconnect the nuclear power plant from its electrical grid because the transmission lines are unprotected outside the security fences. Yet the NRC does not use force-on-force tests to demonstrate security compliance for operating reactors under the lighting conditions that would be present. For example, UCS viewed the videotape of armed guards responding to four separate mock intrusions, including several conducted at night. None of the guards appeared to be equipped with a flashlight. Had the normal building lighting been extinguished, as it would without offsite power, these security guards would have literally been left "in the dark."

For the past decade, the NRC force-on-force tests have revealed serious security problems at approximately half of the operating plant sites. The majority of plant sites have only been tested once. There’s little assurance that sites failing an OSRE several years ago have adequate security today.

Existing security regulations require nuclear reactors to be protected from sabotage by an insider, either acting alone or in conjunction with a small band of outsiders. The NRC limits the role of the insider during its force-on-force tests to a passive function (i.e., providing the mock intruders with information). In reality, the insider could actively aid in the sabotage attack by mispositioning switches and disabling emergency systems.

The NRC assumes that its regulations governing access control and access authorization are fully effective in preventing sabotage by an insider. These regulations require background checks, drug and alcohol screening, and continuing behavior observation. But while background checks and the drug and alcohol screening have resulted in individuals being denied access or having their access privileges withdrawn, the continuing behavior observation has seldom, if ever, identified a potential problem. Thus, all individuals getting past the background checks and screenings have virtually unfettered ability to sabotage the nuclear reactor and spent fuel.

International measures to improve safety

On nuclear safety issues, there is a great deal of international cooperation, in particular the exchange of operating experience under the auspices of the World Association of Nuclear Operators (WANO), which was set up in 1989.

On Nuclear Safety IAEA Convention was drawn up during a series of expert level meetings from 1992 to 1994 and was the result of considerable work by Governments, national nuclear safety authorities and the IAEA Secretariat. Its aim is to legally commit participating States operating land-based nuclear power plants to maintain a high level of safety by setting international benchmarks to which States would subscribe.

Party’s obligations are based to a large extent on the principles contained in the IAEA Safety Fundamentals document The Safety of Nuclear Installations. These obligations cover for instance, siting, design, construction, operation, the availability of adequate financial and human resources, the assessment and verification of safety, emergency preparedness and quality assurance.

The Convention is an incentive instrument, not designed to ensure fulfillment of obligations by Parties through control and sanction, but is based on their common interest to achieve higher levels of safety. These levels are defined by international benchmarks developed and promoted through regular meetings of the Parties. The Convention obliges Parties to report on the implementation of their obligations for international peer review. This mechanism is the main innovative and dynamic element of the Convention.

In October 1996, Convention entered into force. As of April 2007, there were 65 signatories to the Convention and 60 contracting parties. All countries with operating nuclear power plants are now among the 41 parties to the Convention.

Since the late 1980s, particularly in relation to Eastern Europe a major international program of assistance has been carried out by the OECD, IAEA and Commission of the European Communities to bring early Soviet-designed reactors up to near western safety standards, or at least to effect significant improvements to the plants and their operation. The European Union has also brought pressure to bear, particularly in countries, which aspired, to EU membership.

Modifications have been made to overcome deficiencies in the 12 RBMK reactors still operating in Russia and Lithuania. Among other things, these have removed the danger of a positive void coefficient response. In these reactors, automated inspection equipment has also been installed.

The other class of reactors which has been the focus of international attention for safety upgrades is the first-generation of pressurized water VVER-440/230 reactors. These were designed before formal safety standards were issued in the Soviet Union and they lack many basic safety features. Some are still operating in Bulgaria, Russia and Armenia, under close inspection.

Later Soviet-designed reactors are very much safer and the most recent ones have Western control systems or the equivalent, along with containment structures.

The Nuclear Safety Convention came into force in 1996. It is the first international legal instrument on the safety of nuclear power plants worldwide. It commits participating countries to maintain a high level of safety by setting international benchmarks to which they subscribe and against which they report. It has been ratified by 41 states and has 65 signatories.

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