Environmental Science Nuclear Power Technical Term Paper

By regulation, the design of the nuclear reactor must include stipulations for human operator error and equipment failure. Nuclear Plants in the western world use a Defense in Depth idea which is a system with numerous safety components, each with back-up and design to accommodate human error. The components include:

"Control of Radioactivity - This requires being able to control the neutron flux. If the neutron flux is decreased the radioactivity is decreased. The most common way to reduce the neutron flux is include neutron-absorbing control rods. These control rods can be partially inserted into the reactor core to reduce the reactions. The control rods are very important because the reaction could run out of control if fission events are extremely frequent. In modern nuclear power plants, the insertion of all the control rods into the reactor core occurs in a few seconds, thus halting the nuclear reaction as rapidly as possible. In addition, most reactors are designed so that beyond optimal level, as the temperature increases the efficiency of reactions decreases, hence fewer neutrons are able to cause fission and the reactor slows down automatically.

Maintenance of Core Cooling - In any nuclear reactor some sort of cooling is necessary. Generally nuclear reactors use water as a coolant. However some reactors which cannot use water use sodium or sodium salts.

Maintenance of barriers that prevent the release of radiation - There is a series of physical barriers between the radioactive core and the environment. This means that if any radiation were to leak from the reactor it would be sucked into the vacuum building and therefore prevented from being released into the environment" (Safety of nuclear power reactors, 2011).

The design of the reactor also includes numerous back-up components, independent systems meaning two or more systems performing the same task in parallel, watching of instrumentation and the deterrence of a failure of one kind of equipment affecting any other.

Further, regulation necessitates that a core-meltdown occurrence must be restricted only to the plant itself without the need to empty nearby residence. Safety is also significant for the workers of nuclear power plants. Radiation doses are controlled via the following procedures:

The treatment of equipment via secluded in the core of the reactor

Physical shielding

Limit on the time a worker spends in areas with important radiation levels

Monitoring of individual doses and of the work environment (Safety of nuclear power reactors, 2011).

Inside a nuclear power plant, emergency diesel backup generators (EDBG's) are a very important part of plant safety systems. In standard operation, a nuclear plant produces the power needed to operate its coolant circulation system and other safety critical systems. In the occasion that power from the plant itself, or from the electricity grid, should not be accessible. EDBG's spring into action to make sure that coolant circulation is maintained and the reactor can be safely shut down. So vital are EDBG's that every nuclear reactor has at least two of them, ready to start at a moment's notice. As well as being present in replacement to make certain redundancy at all times, nuclear power plant EDBG's are subject to meticulous regulatory control to guarantee their availability and reliability. They must meet strict technical requirements, characteristically being able to reach their rated voltage and occurrence within ten seconds of startup (Maden, 2011).

After setting up, EDBG's must pass recurrent and rigorous tests as prescribed by the relevant national regulator to ensure their availability and reliability. The U.S. Nuclear Regulatory Commission, for instance, requires each EBDG to be started up and loaded at least once every thirty one days, with additional tests necessary at six-monthly intervals, plus further widespread tests at every refueling outage or at least once every two years. Every ten years, when the plant is in outage, the NRC requires all redundant EBDG units to be started at the same time in order to recognize any frequent failure modes that have gone undetected in tests of the single units (Maden, 2011).

Overall the safety of nuclear power is relatively good. Throughout its history there have been three main accidents that have involved unclear power. When comparing this to other energy producing industries this is low. Every year several thousand people die in coal mines to supply this widely used fuel for electricity. There are also important health and environmental effects arising from fossil fuel use. To date, even the Fukushima accident has caused no deaths, and the IAEA reports that to date no health effects have been reported in any person as a result of radiation exposure (Safety of nuclear power reactors, 2011).The three significant accidents in the fifty year history of civil nuclear power generation are:

Three Mile Island (USA 1979) where the reactor was harshly damaged but radiation was controlled and there were no unfavorable health or environmental penalties

Chernobyl (Ukraine 1986) where the demolition of the reactor by steam explosion and fire killed thirty one people and had important health and environmental consequences. The death toll has since increased to about five

Fukushima (Japan 2011) where three old reactors, together with a fourth, were written off and the effects of loss of cooling due to a huge tsunami were insufficiently contained.

These three significant accidents took place during more than fourteen thousand reactor-years of operation. Of all the accidents and incidents, only the Chernobyl and Fukushima accidents resulted in radiation doses to the public greater than those resulting from the contact with natural sources. The Fukushima accident resulted in some radiation exposure of workers at the plant, but not such as to threaten their health. Other incidents and one accident have been totally confined to the plant. Apart from Chernobyl, no nuclear workers or members of the public have ever died as a result of exposure to radiation due to a commercial nuclear reactor incident. The majority of the serious radiological injuries and deaths that take place each year, two to four deaths and many more exposures above regulatory limits are the result of large unrestrained radiation sources, such as abandoned medical or industrial equipment. There have also been a number of accidents in experimental reactors and in one military plutonium-producing pile, but none of these resulted in loss of life outside the actual plant, or long-term environmental contamination (Safety of nuclear power reactors, 2011).

The primary safety concern has always been the possibility of an unrestrained release of radioactive material, leading to contamination and consequent radiation exposure off-site. Earlier assumptions were that this would be likely in the event of a major loss of cooling accident (LOCA) which resulted in a core melt. The TMI experience suggested otherwise, but at Fukushima this is exactly what happened. In the light of better understanding of the physics and chemistry of material in a reactor core under intense conditions it became evident that even a severe core melt coupled with breach of containment would be improbable to create a major radiological disaster from many Western reactor designs, but the Fukushima accident showed that this did not apply to all. Studies of the post-accident situation at Three Mile Island where there was no breach of containment supported the suggestion, and analysis of Fukushima is pending (Safety of nuclear power reactors, 2011).

Over the years, the price of electricity, gasoline, and heating fuel have been growing at unaffordable rates due to a fear that we will run out of petroleum, coal, and natural gas. Also, atmospheric exhaustion is on the rise due to pollution from the burning of fossil fuels.

A lot of countries throughout the world are now using nuclear energy as a major source of energy, and the United States should as well. By using nuclear power, the United States can help decrease the ozone depletion, lower the cost of energy for the citizens, and have a limitless supply of energy for billions of years to come (Dettmering, n.d.).

In order to understand nuclear energy, a person must first understand what a nuclear reaction is. There are two types; a fusion reaction and a fission reaction. A fusion reaction is when an atom of tritium smashes into a deuterium atom, and combines to form a helium atom and a neutron. This is the most powerful nuclear reaction. The other kind of reaction is a fission reaction. In a fission reaction, a neutron collides into an enriched uranium atom, splitting it, and releasing another uranium atom and two neutrons. When this process continues with the collisions it is called a nuclear chain reaction. This is the present nuclear reaction that takes place within the nuclear power plants around the world. This reaction is only one of the factors that are accountable for the creation of electricity within a nuclear power plant. Once the reaction takes place, a large quantity of heat is given off. This all happens within the reactor core.….....