At a nuclear power plant, workers wear protective clothing and dosimeters to measure their exposure to radiation, the nuclear fuel is held in an airtight steel vessel, and the reactor is covered with reinforced concrete. All of these efforts work to:A.cool the nuclear fuel.B.preserve the nuclear fuel to allow time for half-life decay.C.contain the radiation.D.absorb the free neutrons.

Which of these safety features aims to keep nuclear radiation contained?A.Neutron modifiersB.Cold-water tanksC.Control rodsD.Steel-reinforced concrete

Handling: radioactive sources must not be handled directly and should only be used for the shortest time possible. R gloves should be worn and hands should be washed thoroughly after use.

Types of nuclear safety precaution:

Radioactivity Radioactivity  is the phenomenon exhibited by the atomic nucleus due to its instability. The unstable nucleus will emit radiation and energy is lost due to the radiation emitted by the nucleus. The radioactive nucleus will emit energetic particles such as photons, neutrinos, electrons, neutrons, protons or alpha particles. If the nucleus of the atom has too many neutrons, it will emit beta particles and one of the neutrons changes into a proton. IrradiationA torch beam lights up a person's hand because the hand is exposed to light, which is visible electromagnetic radiation. Exposing objects to beams of radiation is called irradiation. This term applies to all types of radiation, including radiation from the nuclei of atoms.Irradiation from radioactive decay can damage living cells. However, it can be put to good use as well as being a hazard.Irradiation for sterilisationIrradiation can be used to preserve fruit sold in supermarkets. The fruit is exposed to a radioactive source, typically cobalt-60. The gamma rays emitted by the cobalt-60 nuclei destroy bacteria on the fruit without changing the fruit in any significant way. The process does not cause the irradiated object itself to become radioactive.Medical irradiationDoctors use radioactive sources for sterilisation of surgical instruments. They may also use beams of gamma rays to kill cancerous tumour cells deep inside the body. The beams are aimed at the tumour from many different directions. This:maximises the dose on the tumour cells, butminimises the dose on the surrounding soft tissue cellsThis technique can damage healthy tissue, so careful calculations are done to find the best dose. This is enough to kill tumour cells but not so high that healthy tissue is damaged.Efforts are made to ensure that irradiation does not cause any long-term effects. This is done by considering:the nature of the radioactive decay (alpha, beta or gamma)the toxicity of the radiationsterilisation can be done without high temperaturesit can be used to kill bacteria on things that would be damaged by heatingGamma radiation is used to irradiate cancers in the brain. Treatment is given for 15 minutes every four days. During treatment, the gamma source is rotated 360° around the head. The patient remains still during treatment.ContaminationContamination occurs if an object has a radioactive material introduced into it. For example, an apple is:irradiated if it is exposed to radiation from cobalt-60, butcontaminated if cobalt-60 is injected into itAs with irradiation, contamination can be very useful as well as being potentially harmful.Medical contaminationInjected radioactive sources (such as technetium-99) can be used as tracers. These substances make soft tissues, such as blood vessels or the kidneys, show up in medical imaging procedures.An isotope emits gamma rays that easily pass through the body. The rays reach a detector outside the body, for example an x-ray machine or a ‘gamma camera’. In this way, the radioactive isotope can be followed as it flows through the body. Changes in the amount of gamma emitted from different parts would indicate how well the isotopes are flowing, or if there is a blockage.In medical applications that involve injecting radioactive sources, efforts are made to ensure that contamination does not cause any long-term effects. This is done by choosing isotopes that:have very short half-livesare not poisonousIn medical applications that involve using radioactive sources, efforts are made to ensure that irradiation does not cause any long-term effects. This is done by considering:the nature of the radioactive decay (alpha, beta or gamma)the half-life of the radioactive isotopethe toxicity of the substance and its radiationThe half-life should be long enough to produce useful measurements but short enough for the radioactive sources to decay to safe levels soon after use. If an isotope is chosen with a long half-life, the damaging effects of the radiation lasts too long and the dose received continues to rise.The sources used typically have half-lives of hours. This means that after a few days there will be little radioactive material left in a person’s body.Contamination to check for leaksTracers can be used to find leaks in water pipes. A gamma-emitting radioactive isotope is added to water in the pipe. Where there is a leak, contaminated water seeps into the ground, causing a build-up of gamma emissions in that area. The build-up of gamma emissions can be detected using a Geiger-Muller tube. This makes it easier to decide where to dig to find the leak.The isotope used for this purpose must:be a gamma emitter, so it is easily detectedhave a half-life of several days, to allow the emissions to build up in the soilnot be poisonous to humans because it will form part of the water supplyThe two processes of irradiation and contamination are often confused. However they are very different and useful in their own right.   Q 2.1Describe the ways in which science is applied and used to address the issue of Radiation.

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