Влияние общества на человека
Приготовление дезинфицирующих растворов различной концентрации
Практические работы по географии для 6 класса
Организация работы процедурного кабинета
Обработка изделий медицинского назначения многократного применения
Изменения в неживой природе осенью
Уборка процедурного кабинета
Сольфеджио. Все правила по сольфеджио
Балочные системы. Определение реакций опор и моментов защемления
Innocent human suffering/casualties
The 2005 report prepared by the Chernobyl Forum, led by the International Atomic Energy Agency (IAEA) and World Health Organization (WHO), attributed 56 direct deaths (47 accident workers and nine children with thyroid cancer) and estimated that there may be 4000 extra cancer deaths among the approximately 600 000 most highly exposed people. Although the Chernobyl Exclusion Zone and certain limited areas remain off limits, the majority of affected areas are now considered safe for settlement and economic activity due to radioactive decay.
Many will claim that polluting our own lands is an unacceptable cost. However, 200 years of infertile ground in the exclusion zone is absolutely nothing compared to the fact that our ancestors have ruled this land for the last 10 000 – 12 000 years and will continue to rule it for the next 10 000 years.
Inaccuracies in the estimated casualty report
A majority of individuals were exposed to radiation as a direct result of the Soviet Union’s unwillingness to evacuate (one week delay) and their unwillingness to prevent contaminated agricultural products from being distributed. Furthermore, the dictatorship in Belarus deliberately continued to distribute agricultural products from badly contaminated areas to their people (this is the case even today). I have been in Belarus myself and can personally attest to this as I have spoken to tens of people who has no choice but to consume contaminated food. 60% of the fallout landed in Belarus and the dictatorship is still deliberately feeding their own population with contaminated agricultural products.
The real future casualty numbers (attributed to a future attack cell) must therefore be considerably reduced:
Estimated casualty report for “Operation Regime Ender”
· Less than 50 direct deaths
· Less than 1000 future deaths cause by cancer
· Less than 10 000 exposed people.
Understanding Nuclear reactor technology
A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate.
The most significant use of nuclear reactors is as an energy source for the generation of electrical power (see Nuclear power) and for the power in some ships (see Nuclear marine propulsion). This is usually accomplished by methods that involve using heat from the nuclear reaction to power steam turbines.
The key components common to most types of nuclear power plants are:
· Nuclear fuel
· Nuclear reactor core
· Neutron moderator
· Neutron poison
· Coolant (often the Neutron Moderator and the Coolant are the same, usually both purified water)
· Control rods
· Reactor vessel
· Boiler feedwater pump
· Steam generators (not in BWRs)
· Steam turbine
· Electrical generator
· Cooling tower (not always required)
· Radwaste System (a section of the plant handling radioactive waste)
· Refuelling Floor
· Spent fuel pool
· Reactor Protective System (RPS)
· Emergency Core Cooling Systems (ECCS)
· Standby Liquid Control System (emergency boron injection, in BWRs only)
· Containment building
· Control room
· Emergency Operations Facility
The people in a nuclear power plant
Nuclear power plants typically employ just under a thousand people per reactor (including security guards and engineers associated with the plant but possibly working elsewhere).
· Nuclear engineers
· Reactor operators
· Health physicists
· Nuclear Regulatory Commission Resident Inspectors
Nuclear Reactors are classified by several methods; a brief outline of these classification schemes is provided.
Classification by type of nuclear reaction
- Nuclear fission. Most reactors, and all commercial ones, are based on nuclear fission. They generally use uranium and its product plutonium as nuclear fuel, though a thorium fuel cycle is also possible. This article takes "nuclear reactor" to mean fission reactor unless otherwise stated. Fission reactors can be divided roughly into two classes, depending on the energy of the neutrons that sustain the fission chain reaction:
· Thermal reactors use slowed or thermal neutrons. Almost all current reactors are of this type. These contain neutron moderator materials that slow neutrons until their neutron temperature is thermalised, that is, until their kinetic energy approaches the average kinetic energy of the surrounding particles. Thermal neutrons have a far higher cross section (probability) of fissioning the fissile nuclei uranium-235, plutonium-239, and plutonium-241, and a relatively lower probability of neutron capture by uranium-238 compared to the faster neutrons that originally result from fission, allowing use of low-enriched uranium or even natural uranium fuel. The moderator is often also the coolant, usually water under high pressure to increase the boiling point. These are surrounded by reactor vessel, instrumentation to monitor and control the reactor, radiation shielding, and a containment building.
· Fast neutron reactors use fast neutrons to cause fission in their fuel. They do not have a neutron moderator, and use less-moderating coolants. Maintaining a chain reaction requires the fuel to be more highly enriched in fissile material (about 20% or more) due to the relatively lower probability of fission versus capture by U-238. Fast reactors have the potential to produce less transuranic waste because all actinides are fissionable with fast neutrons, but they are more difficult to build and more expensive to operate. Overall, fast reactors are less common than thermal reactors in most applications. Some early power stations were fast reactors, as are some Russian naval propulsion units. Construction of prototypes is continuing (see fast breeder or generation IV reactors).
- Nuclear fusion. Fusion power is an experimental technology, generally with hydrogen as fuel. While not currently suitable for power production, Farnsworth-Hirsch fusors are used to produce neutron radiation.
- Radioactive decay. Examples include radioisotope thermoelectric generators as well as other types of atomic batteries, which generate heat and power by exploiting passive radioactive decay.
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 ( 410 to 1400 kPa). The containment is the final barrier to radioactive release (part of a nuclear reactor's defence in depth strategy), the first being the fuel ceramic itself, the second being the metal fuel cladding tubes, the third being the reactor vessel and coolant system.
The containment building itself is typically an airtight steel structure enclosing the reactor normally sealed off from the outside atmosphere. The steel is either free-standing or attached to the concrete missile shield. In the United States, the design and thickness of the containment and the missile shield are governed by federal regulations (10 CFR 50.55a).
While the containment plays a critical role in the most severe nuclear reactor accidents, it is only designed to contain or condense steam in the short term (for large break accidents) and long term heat removal still must be provided by other systems. In the Three Mile Island accident the containment pressure boundary was maintained, but due to insufficient cooling, some time after the accident, radioactive gas was intentionally let from containment by operators to prevent over pressurization. This, combined with further failures caused the release of radioactive gas to atmosphere during the accident.
Containment systems for nuclear power reactors are distinguished by size, shape, materials used, and suppression systems. The kind of containment used is determined by the type of reactor, generation of the reactor, and the specific plant needs.
Suppression systems are critical to safety analysis and greatly affect the size of containment. Suppression refers to condensing the steam after a major break has released it from the cooling system. Because decay heat doesn't go away quickly, there must be some long term method of suppression, but this may simply be heat exchange with the ambient air on the surface of containment. There are several common designs, but for safety-analysis purposes containments are categorized as either "large-dry," "sub-atmospheric," or "ice-condenser."
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