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15 Cards in this Set
- Front
- Back
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What is nuclear waste? |
Radioactive wastes are generated by different kinds of facilities. The major contributor is the nuclear power industry but other users such as the defence industry, hospitals, manufacturing industries and educational facilities produce radioactive wastes in a variety of physical and chemical forms. |
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Radioactive waste has been categorised by a classification system.
What are the three categories? |
High Level Waste (HLW)This is radioactive waste produced by the chemical reprocessing of nuclear fuel. It contains mainly fission products and other heavy nuclei that are generated in the reactor core. Intermediate Level Waste (ILW)This is radioactive waste with a radioactive content that requires shielding but requires no cooling as it is not thermally hot. Intermediate level waste includes the old components from a nuclear reactor, chemical residues and other support structures form a nuclear reactor core. Low Level Waste (LLW)This is radioactive waste with a low level of radioactivity requiring no shielding. Examples of low level waste include discarded protective clothing, packaging material and medical equipment such as syringes and needles. Other than nuclear power stations this waste is generated from hospitals and other industries. |
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What are the disposal methods of the three categories of waste? |
High Level Waste (HLW) Disposal methods for high level waste include solidifying the waste in a glass matrix and sealing it in a corrosion resistant steel lined drum. The drums are stored in specially engineered cooling pools or storage vaults.
Intermediate Level Waste (ILW) Intermediate level wastes are mixed with cement and solidified in stainless steel drums which are stored in special facilities above ground or in shaft or trenches underground. Low Level Waste (LLW) This type of waste is short lived and is stored on sites with special licences until it has decayed and is then disposed off as ordinary waste. |
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Some areas of Europe are still affected by radioactive materials from the Chernobyl disaster. In parts of Wales, for example, caesium produces high levels of radioactivity in the grass. One effect seen in the area is the increased risk of thyroid cancer in children. The figure shows the rate of radioactive decay for caesium.
(a) From the Figure , work out the half-life of caesium. (b) If caesium activity at time zero is 16 times higher than is safe for human health, how long will it take for caesium activity to reach a safe level? |
(a) 30 years. (b) 120 years. |
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What precautions should be taken when handling radioactive materials? |
Precautions include: wearing protective clothing wear radiation film badges keeping as far away as is practicable - for example, by using tongs keeping your exposure time as short as possible, keeping radioactive materials in lead-lined containers, labelled with the appropriate hazard symbol. |
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People who work with radiation wear film badges, which are checked regularly to monitor the levels of radiation absorbed.
How do these work? |
There is a light-proof packet of photographic film inside the badge. The more radiation this absorbs, the darker it becomes when it is developed. To get an accurate measure of the dose received, the badge contains different materials that the radiation must penetrate to reach the film. |
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Explain why distance is the best protection against ionising radiation. |
Alpha and beta radiation are stopped by a few centimetres of air. Gamma radiation is difficult to shield against but the further away you are the less hits you. |
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X-rays are damaging to human tissues. Why can a patient be exposed to X-rays but a dentist leaves the room when they give you a dental X-ray? |
Although the dosage is low for any one patient, the dentist would be exposed to the radiation every day and the damage would add up. |
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Why would workers in a nuclear power plant wear radiation-sensing badges while at work even though they never directly enter the reactor? |
Nobody knows when radioactive contamination could leak out, so dosage badges tell people how much radiation they have been exposed to. |
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Why is it impossible to be totally safe from ionising radiation? |
Background radiation present all of the time is unavoidable. |
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Why do radiation dosage badges have a series of different screens covering the sensitive photographic plate? |
The different screens allow different types of ionising radiation to pass through and when the different areas of the photographic plate are examined, the type of ionising radiation that the wearer has been exposed to can be worked out. |
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Some radioactive waste will need to be stored for thousands of years. Explain why it has to be stored for so long. |
The isotopes that the radioactive waste contains have very long half-lives and so they will remain radioactive for a long time. |
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A student made the comment: ‘All radiation badges do is to tell you if you have had too much radiation. Surely by then it is too late, you have been exposed to the radiation and the damage is done.’ Answer this comment, explaining why radiation badges are used. |
The possible damaging effects of ionising radiation increase with the amount of radiation you are exposed to. If a radiation dosage badge shows that you have been exposed to radiation, then precautions can be taken to reduce your future exposure. Also, the cause can be investigated to ensure that others are not exposed. |
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Explain why it is difficult to be certain that a cancer diagnosed in someone from the Chernobyl area is a result of their exposure to ionising radiation from the accident. |
People get cancer that is not as a result of ionising radiation and it is almost impossible to say whether a particular patient would have a cancer anyway even without exposure to radiation. However, studies show that there are more cancers in the contaminated areas than would normally be expected. |
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What are the key points to remember? |
Background radiation is all around us. The majority of background radiation is from radon gas given off by rocks. The proportion of ionising radiation in background radiation that is due to human activity is very small. Using nuclear power carries risks and creates very long-lived radioactive waste. The effects of nuclear incidents like Chernobyl will last a very long time. Ionising radiation can cause health problems, which are more likely if the dose is larger. Precautions are taken where people work with ionising radiation. |
