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level: Nuclear Radiation

Questions and Answers List

level questions: Nuclear Radiation

QuestionAnswer
how can radiation be detected using film badges?when exposed to ionising radiation, photographic film will turn from being transparent to dark and non transparent on each the open window allows all types of radiation through, therefore showing exposure to beta and gamma radiation one set of windows are plastic of different thicknesses allowing the person examining the film to tell what kinds of beta radiation they have been exposed to another set of windows are different types of metals (including lead and tin) allowing the detection of gamma rays and other ionising radiation the final exposure of the film will show how much and what kind of radiation someone has been exposed to
what three subatomic particles make up an atomprotons neutrons electrons
what is meant by ionisationthe addition or removal of electrons from an atom to form an ion, this can be carried out by nuclear radiation
why can ionisation take place?because ionising radiation may come close to or collide with the atom and forces the electron away from the atom
what is alpha radiationhelium nucleus with 2 protons and 2 neutrons. It has a large mass compared to other ionising radiation and a strong positive charge
what is beta radiationa beta particle is a fast moving electron it has a very small mass and a negative charge
what is a gamma raya high energy electromagnetic wave caused by changes within the nucleus they are part of the electromagnetic spectrum and so travel at the speed of light they have no mass or charge
what is meant by penetrating powerability to penetrate materials the material is said to have absorbed the radiation
describe the penetrating power of alpha radiationalpha radiation has a low penetrating power and the range of the alpha radiation in an absorbing material is less than that of beta or gamma. alpha radiation transfers more energy to an absorber than beta or gamma radiation. alpha radiation is absorbed by the thickness of the skin or by a few centimetres of air
describe the penetrating power of beta radiationbeta radiation is more penetrating than alpha radiation. it can pass through the skin but is absorbed a few centimetres of body tissue or a few millimetres of aluminium
describe the penetrating power of gamma radiationthe most penetrating of the three radiations. it can easily penetrate body tissue. it requires several centimetres of lead or about 1m of concrete to absorb it
describe the range, ionising power and detection in an electric field of alpha radiation3-5cm range highly ionising deflected towards the negative plate in an electric field
describe the range, ionising power and detection in an electric field of beta radiationaround 15cm range regular ionising power deflected towards the positive plate in an electric field
describe the range, ionising power and detection in an electric field of gamma raysvery long range (much longer than beta and alpha) weak ionising power no detection in an electrical field
what is meant by a radioactive atomthe nuclei of the atom is unstable and will naturally undergo radioactive decay, causing the release of ionising radiation which allows the nucleus to become more stable
what is each type of radiation caused bya decay, either spontaneous (natural) or induced (a reaction has caused the decay)
name some sources of natural background radiationcosmic rays - radiation that reaches the earth from outer space animals rocks - some rocks contain radioactive substances that produce a radioactive gas called radon soil and plants
name some sources of artifical background radiationx-rays - a form of radiation we use when going through air security or have an x ray in hospital nuclear missiles - bombs have been exploded by man, releasing radiation into the environment nuclear power - nuclear power stations have released radiation into the atmosphere
what percentage of background radiation does artificial radiation account for?around 15 percent nearly all of it comes from medical procedures
describe how radiation can be detectedusing a Geiger muller tube the gm tube is a hollow cylinder filled with gas at low pressure. the tube has a thin window made of Mica at one end. There is a central electrode inside the GM tube. A high-voltage supply is connected across the casing of the tube and the central electrode. When the alpha, beta or gamma radiation enters the tube it produces ions in the gas, the ions created enable the tube to conduct. A current is produced in the tube for a short time, producing a voltage pulse. Each voltage pulse corresponds to one ionising radiation entering the GM Tube. The voltage pulse is amplified and counted
how can radiation be detected using film badges?when exposed to ionising radiation, photographic film will turn from being transparent to dark and non transparent on each side of the film badge are various 'windows' the open window allows all types of radiation through, therefore showing exposure to beta and gamma radiation one set of windows are plastic of different thicknesses allowing the person examining the film to tell what kinds of beta radiation they have been exposed to another set of windows are different types of metals (including lead and tin) allowing the detection of gamma rays and other ionising radiation the final exposure of the film will show how much and what kind of radiation someone has been exposed to
what is the formula for (radio)activityA=N/t where time is in seconds Activity in Becquerels (Bq) Number of disintegrations has no unit
what is meant by activitythe number of radioactive atoms which disintegrate and emit radioactivity per second number of disintegration per unit time
what is background radiationRadiation that is present in the atmosphere; can be caused by natural materials (granite rocks) or man-made materials (hospital waste)
what must be done to ensure activity of a radioactive source is calculated correctlybackground activity must first be measured and taken into account
how can background radiation level be foundwith no radioactive sources in the room, start a stopwatch and GM Tube with a counter at the same time After 60 seconds, stop the GM tube and counter and record the number of counts in 60 seconds Calculate the background activity in the room repeat this process a number of times and find the average background activity
what is meant by half lifethe time taken for the activity of a radioactive source to reduce by half
describe how half life of a source can be measuredbefore the source is used, the background count rate is measured using a GM tue connected to a counter, the count rate from the source is measured at fixed intervals over a period of time the background count is then subtracted from each measurement of the count rate and the actual count rate from the source is calculated (this is known as corrected count rate) a table and a graph can then be plotted of corrected count rate against time and this can be used to calculate the half life of the source
what is dosimetrythe way in which we can quantify the biological effect of radiation on humans
what is meant by absorbed dosethe energy absorbed per unit mass of the absorbing material it is given the symbol 'D' ionising radiation carries energy, and this energy can be absorbed by tissue and possibly cause damage to the tissue
what is the formula for absorbed dose?D=E/m Where D is absorbed dose in Grays (Gy) E is energy in Joules m is mass in kg
what is meant by equivalent dose?a measure of the biological effect of radiation due to several factors It is given the symbol 'H'
what factors do equivalent dose depend on?type of radiation the absorbed dose the body organs/tissues that have been exposed to said radiation
what is meant by radiation weighting factor?a measure of the harmful effect of nuclear radiation on human tissue It is given the symbol Wr
What is the formula for equivalent dose?H=DWr Where H is measured in Sieverts (Sv) Absorbed dose in Grays (Gy) Radiation Weighting factor has no unit
what is meant by equivalent dose ratethe equivalent dose absorbed per second
what is the formula for equivalent dose rateḢ=H/t Where Ḣ is equivalent dose rate in sieverts per second (Sv s-1) H is equivalent dose in sieverts t is time in seconds
what is meant by effective dose?measure of the risk of long-term effects of ionising radiation on the human body, organs and tissues
what is the average annual background radiation in the UK/ average equivalent dose for a member of the public due to background radiation2.2mSv
what is the annual effective dose limit for a member of the public?1mSv
what is the annual effective dose limit for a radiation worker?20mSv
describe ways in which we can minimise the dangers of ionising radiation?keeping radioactive sources away from the body and never bringing them close to the eyes limiting time of exposure to ionising radiation shielding radioactive sources fro the body and handling them using tongs storing radioactive sources in lead lined containers to ensure they have no exposure to the environment while in storage wearing goggles and washing hands after using radioactive sources monitoring radiation a person receives using film badges all areas containing ionising radiation will show the hazard symbol
what are the biological effects of radiation?cells can be altered and their functions changed because of ionising radiation cells can be destroyed exposure to ionising radiation can lead to the creation of cancer cells
name practical uses of ionising radiationdestroying cancer cells radioactive tracers sterilising medical instruments irradiating foods
describe how ionising radiation can be used to kill cancer cellsgamma rays can be directed through the body to target tumours that cannot be treated with conventional surgery the positioning and the intensity of the gamma ray sources are carefully calculated to ensure that the cancer cells receive enough radiation to kill them while the surrounding tissue remains in healthy condition
describe how radiation is used in radioactive tracersionising radiation can also be used to trace blood flow around the body. If a liquid containing a gamma source with a short half life is injected into your blood, it will be traced around your body where there is a blockage the activity of the radiation will be highest due to collection of blood. Using a gamma camera , a special gamma ray detector - these areas can be located
how can ionising radiation be used to sterilise medical equipmentmedical instruments are too expensive to be thrown away so are washed several times in hot water and then resealed in plastic wrapping. Then the whole package is irradiated with a dose of gamma rays. Any bacteria in the container are now destroyed and the instrument remain sterile until the package is opened.
how can ionising radiation be used to irradiate foodfoods with a high sugar and water content are often irradiated with gamma radiation to destroy any bacteria which may cause them to spoil quickly the food does not remain radioactive after exposure to gamma rays so is safe to eat
what is a nuclear reactionwhen the nucleus of an atom changes, new nuclei are formed and energy is released
describe nuclear fissionthe process by which energy is released when a large atom is hit by a neutron, becomes unstable and splits into two or more smaller pieces plus two or three neutrons when this happens some of the mass of the atom is lost and is converted directly to heat energy. This heat energy can be used to generate electricity in a nuclear power station
what is a chain reactionProcess that normally happens in a nuclear reactor; the splitting of an uranium nucleus by a neutron which releases neutrons and causes further nuclei to split; release large values of energy
what is nuclear fusionthe process by which energy can be released when two smaller nuclei fuse together to form a larger nucleus this is the same process that occurs within stars such as our sun that produces heat energy and light
describe how nuclear reactions are used in nuclear power stations to generate electrical energyin nuclear power stations, nuclear fuels like uranium and plutonium undergo controlled chain reactions in the reactor to produce heat energy. The chain reaction is controlled by Boron control rods. As boron is a non-fissile material it will not undergo a fission reaction when bombarded with neutrons. When the boron absorbs the neutrons, the chain reaction will slow down due to the lack of neutrons producing reactions. In times of high energy demand, control rods are raised, allowing more reactions to take place, and control rods are lowered in times of low demand to absorb neutrons and lower the number of reactions and the heat energy produced. The heat from the nuclear reaction is used to change water into steam in the boiler, this steam drives the turbine as heat energy is converted to kinetic energy. This then causes the production of electrical energy from kinetic energy.
describe the advantages of nuclear fuelsunlike fossil fuels, nuclear fuels do not produce carbon dioxide or sulphur dioxide 1kg of nuclear fuel is the same as 2.9 million kg of coal nuclear fuels can easily be transported by road or rail since smaller volumes of nuclear fuels are used compared to the likes of coal Waste products are produced in small volumes
describe the disadvantages of nuclear fuelsnuclear fuels are non-renewable sources of energy if there is an accident, large amounts of radioactive material could be released into the environment (although, modern reactor designs are extremely safe so this rarely happens) nuclear waste remains radioactive and hazardous to health for thousands of years, so it must be stored safely
what is a fusion reactora proposed form of power generation which would be an ideal way of generating electrical energy from nuclear fusion reactions it would work by combining isotopes of hydrogen
what would be the difficulties of using a fusion reactor to generate electrical energythere would have to be huge amounts of energy in order for the fusion reaction to take place once the reaction has begun, it can be sustained but the atoms that fuse form a plasma, which would be at a temperature of millions of degrees, so would have to be contained using a very strong magnetic field