Among how much is being written these days about nuclear accidents I find much misinformed tabloid material and some articles with more technical detail than is useful for many people. After the previous article, I decided to write some notes on an intermediate level, avoiding details and numerical values. To see how I get.
From a normal operational nuclear power plant considered an initiating event: a breakdown, breakdown, etc. Start an accident. The aim of the operation in the management of the accident is to maintain the integrity of the barriers that close the nuclear fuel is more radioactive material is in the plant. Key to this is there to keep the core cooled. The core produces heat, and if it is not disposed of at the same rate as the temperature rises. This phase of the operation is very Procedures, the operations to be performed are determined by the readings of different instruments to collect data on the plant.
There are a series of postulated accidents, scenarios that are considered the worst thing that can happen in a plausible (albeit very unlikely), and emergency operating procedures are central to a secure long-term situation in all cases. In these scenarios it is assumed that the operator has a certain amount of support systems available to the plant, pumps, valves, pipes, motors, etc. That amount could be estimated at the half of which is the normal operating plant.
In Fukushima earthquake and tsunami have had to disable too many support systems, and has not provided the technical capacity to mitigate the initiating events.
If the management of accident is not successful in this first phase the nucleus is damaged. From that time called "severe accident." By producing more heat than it is evacuated its temperature rises steadily reaching its melting point. Both the nuclear fuel rods in which content will start to deform and finally merge. This situation has been analyzed theoretically and by simulation computer many times, but in reality has happened three times: at Three Mile Island (1975), where the core damage was quite limited, Chernobyl (1986), where the core is completely melted and Fukushima, where it is safe damage to the core but do not yet know the extent of it (not over and will not be the same in each reactor of the 4 that there are problems).
severe accident management I know much less than the previous phase, but to pursue the same goal: to keep the radioactive material contained everything possible. At this stage the available systems will be less than before and there will be areas of central operations contaminated difficult manuals. The decisions you make are no longer Procedures and the imagination of engineers comes into play more directly.
fuel rods must always be submerged in water, this is the minimum requirement for cooling. If you are in the air for some time, even partially, there are two sources of explosion. On one hand the material surrounding the fuel is decomposed to produce hydrogen, which will accumulate in the highlands and, mixed with oxygen in the air, can explode. On the other hand, fuel-air temperatures reach very high, and if you add water on them suddenly, the sudden evaporation produces a vapor explosion can be as destructive as those of hydrogen. Needless to say that these explosions will jeopardize, if not destroy, the structures that contain nuclear fuel, radioactive products released into the environment which we should avoid to the maximum.
At about this point is where Fukushima at this time. To further evaluate what is happening is very detailed, not enough data are available. It is not the same as the "injury" in a structure are a few cracks that its virtual disappearance. It is not the same as the kernel is based entirely or is deformed but almost solid.
news
If we see there is talk of more. There are additional problems, no doubt. Next to the reactor building is situated a swimming pool where spent fuel is stored in previous years for the plant. This pool also has to be kept filled and chilled (although the heat is greatly less than evacuate in the case of the kernel). If not cooled too overheated, boiled water and can damage the spent fuel, releasing radioactive material abroad. In comparison with the case of the nucleus, the amount of radiation is much smaller (and different type, make other isotopes).
From a normal operational nuclear power plant considered an initiating event: a breakdown, breakdown, etc. Start an accident. The aim of the operation in the management of the accident is to maintain the integrity of the barriers that close the nuclear fuel is more radioactive material is in the plant. Key to this is there to keep the core cooled. The core produces heat, and if it is not disposed of at the same rate as the temperature rises. This phase of the operation is very Procedures, the operations to be performed are determined by the readings of different instruments to collect data on the plant.
There are a series of postulated accidents, scenarios that are considered the worst thing that can happen in a plausible (albeit very unlikely), and emergency operating procedures are central to a secure long-term situation in all cases. In these scenarios it is assumed that the operator has a certain amount of support systems available to the plant, pumps, valves, pipes, motors, etc. That amount could be estimated at the half of which is the normal operating plant.
In Fukushima earthquake and tsunami have had to disable too many support systems, and has not provided the technical capacity to mitigate the initiating events.
If the management of accident is not successful in this first phase the nucleus is damaged. From that time called "severe accident." By producing more heat than it is evacuated its temperature rises steadily reaching its melting point. Both the nuclear fuel rods in which content will start to deform and finally merge. This situation has been analyzed theoretically and by simulation computer many times, but in reality has happened three times: at Three Mile Island (1975), where the core damage was quite limited, Chernobyl (1986), where the core is completely melted and Fukushima, where it is safe damage to the core but do not yet know the extent of it (not over and will not be the same in each reactor of the 4 that there are problems).
severe accident management I know much less than the previous phase, but to pursue the same goal: to keep the radioactive material contained everything possible. At this stage the available systems will be less than before and there will be areas of central operations contaminated difficult manuals. The decisions you make are no longer Procedures and the imagination of engineers comes into play more directly.
fuel rods must always be submerged in water, this is the minimum requirement for cooling. If you are in the air for some time, even partially, there are two sources of explosion. On one hand the material surrounding the fuel is decomposed to produce hydrogen, which will accumulate in the highlands and, mixed with oxygen in the air, can explode. On the other hand, fuel-air temperatures reach very high, and if you add water on them suddenly, the sudden evaporation produces a vapor explosion can be as destructive as those of hydrogen. Needless to say that these explosions will jeopardize, if not destroy, the structures that contain nuclear fuel, radioactive products released into the environment which we should avoid to the maximum.
At about this point is where Fukushima at this time. To further evaluate what is happening is very detailed, not enough data are available. It is not the same as the "injury" in a structure are a few cracks that its virtual disappearance. It is not the same as the kernel is based entirely or is deformed but almost solid.
news
If we see there is talk of more. There are additional problems, no doubt. Next to the reactor building is situated a swimming pool where spent fuel is stored in previous years for the plant. This pool also has to be kept filled and chilled (although the heat is greatly less than evacuate in the case of the kernel). If not cooled too overheated, boiled water and can damage the spent fuel, releasing radioactive material abroad. In comparison with the case of the nucleus, the amount of radiation is much smaller (and different type, make other isotopes).
From this point we should shift the focus to the environment of the plant. The plant is a source of variable intensity radioactive material (and currently quite low, thankfully), and it will be for a long period of time. (Continued)
modifcado The image I found from here
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