Radioactivity and Particles

what are the dangers of beta and gamma

Beta and gamma radiation do provide serious health risk when outside the body. both can penetrate skin and flesh and can cause cells damage by ionization. Gamma radiation is the most penetrating, the damaged caused will depend on how much their energy is absorbed by ionising atoms along their path. Beta and alpha are lower risk due to lower ionising power.

what is atomic notation

Each type of atom has its own atomic number, which identifies the element, and the mass number depends on the total number of nucleons, or particles in the nucleus. The atomic number going on the bottom and mass on top.

gamma decay equation

Gamma radiation is high-energy electromagnetic radiation. After an unstable nucleus has emitted an alpha or beta particle it sometimes has surplus energy, it emits this energy as gamma radiation. Gamma rays are pure energy so they do not have a mass or charge. When a nucleus emits a gamma ray there is not charge to either the atomic number or the mass number of the nucleus.

what are gamma rays?

Gamma rays are electromagnetic waves with very short wavelengths, released from a decaying nucleus

what is artificial radiation?

Generating electricity in nuclear power stations has been responsible for the leaking of radioactive material into the environment. Testing nuclear weapons in the atmosphere has also increased the amounts of radioactive isotopes on the earth. Radioactive tracers are used in industry and medicine. Radioactive materials are also used to treat certain forms of cancer. However, the majority of background radiation is natural.

what is activity

The rate at which a source of unstable nuclei decays Activity is measured in units called Becquerels (Bq)

what is an example of fission

The resulting nucleus uranium-235 is unstable and splits apart. The fragments of this decay are two daughter nuclei of barium-144. And krypton-89. The decay also produces gamma radiation and three more neutrons.

what is nuclear fission

The splitting of an atomic nucleus 1)A slow moving neutron is absorbed by a nucleus 2) this makes the nucleus become unstable and split 3) this produces daughter nuclei and the process repeats in a chain reaction

why does alpha particles have a short range?

They interact with atoms along their paths, causing ions to form. this means that they rapidly give up the energy that they had when they were ejected from the unstable nucleus. therefore has a high ionising power

alpha decay equations

This is a balanced equation: - The total of the atomic numbers (neutrons and protons) are the same on each side of the equation - The total number of protons in the side of the equation are the same

when the nucleus is splitting apart in fission, it loses mass where does it go?

This lost mass is converted energy. Most of the energy is carried away as the kinetic energy of the two lighter nuclei. Some is emitted as gamma radiation. The three neurons produced by the fission may hit another nuclei of uranium-235 so causing the process to repeat. This keeps on going and the reaction gets faster and faster.

nuclear decay is a

random process This means that is it not possible to predict which unstable nucleus in a piece of radioactive material can decay, or when decay will happen.

what type of isotope is used in medicine?

short half-lives are suited to medical use. This is because the activity of a source will rapidly become very small as the isotope decays rapidly.

What is the atomic number?

the chemical behaviour and properties of a particular element depend upon how the atoms combine with other atoms. This is determined by the number of electrons in the atom. Although atoms may gain or lose electrons, the protons in the atom always stay the same. This is the atomic number. Also called the proton number

The longer period of exposure to radiation

the greater the risk of serious cell damage.

what is critical mass

the minimum amount of nuclide that provides the number of neutrons needed to sustain a chain reaction

what does it mean when the atom is neutral

the number of protons are balanced by the number of negative charge of electrons.

what do the protons and electrons do? what about neutrons?

the number of protons in an atom identifies the element. The chemical behaviour of an element depends on the number of electrons it has and this always balances the number of protons in a nucleus. However, the number of neutrons in the nucleus can vary slightly.

what is nuclear fusion

the process of combining lightweight nuclei to make heavier nuclei

What is the atomic mass?

the total number of protons and neutrons in the nucleus of an atom determines the atomic mass. The mass of the electrons that make up the atom is tiny and can be ignored. Can also be called the nucleon number.

example of nuclear disaster, where does nuclear waste go

the tsumani and earthquake that caused the large damage and loss of life in 2011. Fukoshima nuclear power station resulting in the release of radioactive materials into the air and the ocean as well as making a large area of land around the damaged power station unsafe for humans to live there it may be transformed into a glass, which is then sealed inside stainless-steel containers that are entombed far below the Earth's surface at government-approved sites. Sometimes HLW is stored in underground tanks or silos, too. Finding suitable locations for radioactive waste is no easy task.

what conditions are needed for fuison

very high temperatures to overcome the repulsive forces

what must we do before taking measurements from the radioactive sample? what do we do after that (calculations)

we must measure the local background radiation. We must subtract the background radiation measurement from measurements taken from the sample so we know the radiation producted by the sample itself. We then measure the rate of decay of the sample at regular time intervals. The rate of decay is shown by the count rate on the rate metre.

radioactive decay graph

we plot a graph of number of decays per seconds against time for a radioactive isotope we would, therefore, expect the rate of decay to fall as time passes because there are fewer nuclei to decay.

for fission to take place _____

, many of the neutrons are released do not hit other nucleis and the reaction does not get faster and faster. For a chain reaction to happen there must be a minimum amount of the nuclei (critical mass)

what is the easiest way to get the half life on a graph

. Read the original count rate at zero days.On our graph the reading is 1640 counts. 2. Go down to half the original count rate (820 counts)and draw a horizontal line to the curve.Then draw a vertical line down from the curve.You can read off the half-life where the line crosses the time ax On our graph the half-life is 20 days.

how does the The Geiger-Muller tube work?

1) It is a glass tube with an electrically conducting surface on the inside. 2) The tube has a thin window made of mica (naturally occurring mineral that can be split into thin sheets). 3) The tube contains a special mixture of gases at very low pressure. 4) In the middle of the tube, electrically insulated from conducing surface, there is an electrode. This electrode is connected, via a high-value resistor to a high voltage supply, typically 300-500V When ionising radiation enters the tube it causes the low pressure gas inside to form ions. The ions allow a small amount of current to flow from the electrode to the conducting layer. This is detected by an electronic circuit. ions enable the tube to conduct. current produced in the tube for a short time. The current produces a voltage pulse. (Each voltage pulse, one ionising radiation) The voltage pulse is amplified and counted. The greater the level of radiation, the more ionisation in the tube so the greater the number of counts.

Practical: investigate the penetrating powers of different kinds of radiation

1) We have to measure the background radiation with the Geiger-Muller tube to a counter. Write down the number of counts after 5 minutes. Repeat this 3 times and find the average background radiation count 2) Take a source of alpha radiation and set it up at a measured distance (between 2 and 4cm) from the GM tube 3) Measure the counts detected in a 5 minute period. Repeat the count with sheet of thick paper in front of the source. You should find that the counts have dropped to the background radiation count. This shows that alpha radiation does not pass through paper. 4) Now replace the alpha source with beta source. After measuring the new count for 5 minutes place thin sheets of aluminium between the source and detector. When the thickness of the aluminium sheet is 1-2mm thick you will find that the count has dropped to the background radiation level. This shows that beta radiation is blocked by just a few millimetres 5) Carry out the same steps using gamma radiation source. Now you will find that gamma radiation is only blocked when a few centimetres of lead are placed between the source and the detector. Count rate will significantly decrease if radiation is stopped.

what is a chain reaction

A chain reaction occurs in a nuclear reactor when each fission event causes further fission events.

what are the dangers of alpha?

Alpha particles have a great ionsing effect, but cannot pass through many materials, this means that an alpha source presents little risk, as alpha particles do not penetrate the skin. The problem of alpha radiation is much greater if the source of alpha particles is taken into the body.

Describe atomic structure

Atoms are made up of electrons, protons and neutrons.

what are isotopes?

Atoms of an element with different number of neutrons are called isotypes of the element. The number of neutrons in a nucleus affects the mass of the atom. Different isotopes of an element will all have the same atomic number, but different mass numbers

what is background radiation

Background radiation is low-level ionising radiation that is produced all the time. This background radiation has a number of sources. Some of these are natural and some are artificial.

function and effects of nuclear weapons

Blast, thermal radiation, and prompt ionizing radiation cause significant destruction within seconds or minutes of a nuclear detonation. The delayed effects, such as radioactive fallout and other environmental effects, inflict damage over an extended period ranging from hours to years.

what are the dangers of ionising radiation

Can damage moleules that make up the cells of living tissue. Cells suffer this kind of damage all the time for many different reasons. Cells can repair themselves but they can get killed. This can also cause mutations.

what is alpha radiation?

Consists of fast-moving particles that are thrown out of unstable nuclei when they decay. These are called alpha particles. Alpha particles are helium nuclei - helium atoms without their orbiting electrons.

Consider the suitability of an isotope for a particular use based on type of decay and half life

Isotopes with a long half-life decay very slowly, and so produce fewer radioactive decays per second; their intensity is less. Istopes with shorter half-lives are more intense. the more penetrating the more used in industry etc

difference between control rods and moderator?

Moderator slows the neutrons down so that they are more likely to be absorbed into a nearby fuel rod. Control rods - these are raised and lowered to stop neutrons from travelling between fuel rods and therefore change the speed of the chain reaction.

reactants and products of fission

Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission.

parts of the nuclear reactor:

Nuclear fuel - the uranium or plutonium isotope that will split when triggered by an incoming neutron. The fuel is held in rods so that the neutrons released will fly out and cause nuclear fission in other rods. Moderator - graphite core - a graphite core, for example, slows the neutrons down (produced in fission) so that they are more likely to be absorbed into a nearby fuel rod. water can be used Control rods - absorb the nuetrons themselves to control the rate of fission, to absorb any excess neutrons Coolant - this is heated up by the energy released from the fission reactions and is used to boil water to drive turbines in the power station. Concrete shield - the daughter products of the fission reaction are radioactive and can be a hazard.

basic overview of the nuclear reactor

Nuclear reactors are designed to sustain an ongoing chain reaction of fission; they are filled with a specially designed, solid uranium fuel and surrounded by water, which facilitates the process. When the reactor starts, uranium atoms will split, releasing neutrons and heat. Those neutrons will hit other uranium atoms causing them to split and continue the process, generating more neutrons and more heat. This heat is used to create the steam that will spin a turbine, which powers a generator to make electricity.

why can't the fusion in our stars not be harnessed on earth

On Earth it is very difficult to start nuclear fusion reactions that release more energy than is needed to start the reaction. The reason is that fusion reactions only happen at high temperature and pressure, like in the Sun, because both nuclei have a positive charge, and positive repels positive.

uses of radiation: thickness detection

Radiation is absorbed as it passes through materials. This allows it to be used to gauge the thickness of a material by measuring the amount of radiation that passes through. This is commonly used with beta minus emitters in industry, for paper milling and the production of aluminium foil. If the foil is too thick it absorbs more beta particles. The detector receives less beta particles and then sends a signal to the rollers to increase the force on the foil, making it thinner. If the foil is too thin it absorbs less beta particles. The detector receives more beta particles and then sends a signal to the rollers to decrease the force on the foil, making it thicker.

what is ionising radiation? how is this brought about ?

Radiation that knocks electrons off atoms, creating positive ion. When unstable nuclei decay, they give out ionising radiation

how is radioactivity used in tracers?

Radioactive isotopes are used as tracers to help doctors identify diseased organs ( like kidneys or the liver). A radioactive tracer is a chemical compound that emits gamma radiation. The tracer is taken orally (swallowed) by the patient or injected. Its journey around the body can be traced using gamma ray camera.

how to calculate halflife

The activity of a sample of a certain isotope is found to be 200Bq If the isotope has a half-life of 20 minutes, what will the activity of the sample be after one hour? After 20 minutes the activity will have halved to 100Bq After 40 the activity will have half to 50Bq. After 60 minutes it will be 25Bq What is it after 3 hours? Three hours= 9x20 nine half-life periods. This means the activity will have halved nine times. The level of activity ( and the amount of radioactive remaining) will be: ½ x ½ x ½ x ½ x ½ x ½ x ½ x ½ x ½ or 1/2(9) so 1/512 of the original activity or amount.

background radiation from living things?

The atoms that make up our bodies were formed in the violent reactions that take place in stars that exploded (supernovae) billions of years ago. Some of these atoms are radioactive so we carry our own personal source of radiation around with us. as we breath we take in tiny amounts of the radioactive isotope of carbon, carbon-14. Because carbon-14 behaves chemically just like the stable isotope, carbon-12 we continuously renew the amount of the radioactive carbon in our bodies. Carbon-14 and other radioactive isotopes are eaten by humans (and animals which are in turn eaten by humans) because they are present in all living things.

where does the electron come from in beta radiation?

The stability of a nucleus depends on the proportion of protons and neutrons it contains. The results of radioactive decay is to change the balance of protons and neutrons in the nucleus to make it more stable. Beta minus decay involves a neutron in the nucleus splitting into a proton and an electron. The proton remains in the nucleus and the electron is ejected at high speed as a beta minus particle

what is half life

The half-life of a radioactive sample is the time taken for half of the original mass of the sample to decay, if the amount of radioactive matter has halved then the activity of the decay halves - this activity is what is measured in finding the half-life of an isotope. The half-life is different for different radioactive isotopes.

what makes a atom stable and unstable?

The presence of neutrons in the nucleus affects the balance between the forces between protons (nuclear force) . Too many or too few neutrons will make the nucleus unstable. An unstable nucleus will eventually decay. When the nucleus of an atom decays it gives out energy and may also give out alpha or beta particles.

what is an ionising power?

The process in which an electron is given enough energy to break away from an atom is called ionisation. Ionising radiation causes uncharged atoms to lose electrons. An atom that has lost (or gained) electrons has an overall charge. It is called an ion. The three types of radioactive emission can all form ions.

what is the force that holds protons together

The protons are held in the nucleus by the nuclear force. This force is very strong and acts over a very small distance. It is strong enough to hold the nucleus together against the electric force repelling the protons away from each other. (protons carry positive electric charge and alike charges repel).

how is radioactivity used in industry?

Tracers 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 detected · have a half-life of several days, to allow the emissions to build up in the soil · not be poisonous to humans because it will form part of the water supply

example of fusion

Two isotopes of hydrogen, deuterium (H-2) and tritium (H-3) collide at very high speed. The result is the formation of a helium nucleus, a neutron and a large amount of energy. The fusion process is the energy source of our sun and all stars. they have to collide with enough energy to overcome the repulsive (pushing away) force between the positive electric charge in the nuclei of each isotope

how is radioactivity used in treatment

Very high doses of radiation will kill living cells. we can kill cancerous cells by chemicals containing radioactive isotopes. However, it also kills healthy cells. To reduce the damage to healthy tissue, chemicals are used to target the location of the cancer in the body. They may emit either alpha or beta radiation. Both these types of radiation have a short range in the body, so they will affect only a small volume of tissue close to the target.

background radiation from space?

Violent nuclear reactions in stars and exploding stars called supernovae produce cosmic rays (very energetic particles) that continuously hit the Earth. Lower energy cosmit rays are given out by the sun. our atmosphere gives us fairly good protection from cosmic rays but some still reach the Earth's surface.

what is nuclear decay?

a process that occurs when an unstable atomic nucleus changes into another more stable nucleus by emitting radiation

What are the three types of ionising radiation?

alpha, beta, gamma

what is beta radiaiton?

are very fast moving electrons that are ejected by a decaying nucleus. Beta minus decay involves a neutron in the nucleus splitting into a proton and an electron. The proton remains in the nucleus and the electron is ejected at high speed as a beta minus particle

what is the background radiation from the earth?

comes from rocks in the Earth's crust (hard outer layer) why? around 4.5 billion years ago, it contained many radioactive isotopes. Some decayed very quickly but others are still producing radiation

what is the difference between contamination and irradiation

contamination:Coming from the source is hitting you and you are absorbing it Irradiation: The radioactive source must be on you, or in you.

what is the big advantage of a nuclear power station

do not produce carbon dioxide or acidic gases do does not contribute to global warming or acid rain.

what are nuclear reactions a source of?

energy Nuclear reactions involve a change in the quantities of atoms. Heavy atoms may split into lighter atoms - fission Lighter atoms may be forced to join together to make heavier atoms fusion In either processes the mass of the starting atoms is greater than the mass of the products. This missing mass has been converted into energy.

how is radioactivity used in sterlization

gamma radiation can kill bacteria and viruses. It is therefore used to kill these microorganisms on surgical instruments and other medical equipment. The techniquw is called irradiation. The items to be sterilized are placed in secure bags to ensure that they cannot be re-contaminated before use. The gamma radiation will pass through the packaging and destroy bacteria without damaging the item. food can also be used in this way

what is a nuclear reactor?

generates electricity by controlled fission reactions

The rate of decay corrected for background radiation

is proportional to the amount of radioactive isotope present. If we plot a graph corrected count rate against time. We can measure the half-life from the graph

how should radioactive sources be stored?

lead-lined boxes, metal cupboard with a radiation warning label. The source must be held with tongs away from the body.

what are the properties of gamma?

mass -> As they are waves, they have no mass charge-> no charge. ionising power -> They are weakly ionising and interact only occasionally with atoms in their paths. penetration-> They are extremely penetrating and pass through all but the very densest materials with ease. It takes several centimetres thickness of lead, or a metre so of concrete to stop gamma radiation.

properties of beta

mass- > are very light charged? -> B- is -1 (it is a electron) ionising power? -> medium (smaller than alpha because they are smaller and carry less charge.) range? -> greater range than alpha, travel long distances through air, pass through paper easily and are only absorbed by denser materials like aluminium. A millimetre or two of aluminium foil will stop all but the most energetic beta particles.

what are the properties of alpha particles?

mass- > relatively large mass. They are made up of four nucleons and so have a mass number of 4. charged? -> yeah charged because of the two protons that the carry. The relative charge of an alpha particle is +2. ionising power? -> strong range? -> have a short-range. Alpha particles can only travel a few centimetres in air and cannot penetrate more than a few millimetres of paper

what is a becquerel (Bq)

measure of how many unstable nuclei are disintegrating (breaking up) per second. eg: one becquerel means a rate of one disintegration per second. The becquerel is a very small unit. More practical units are the kBq (an average of 1000 disintegrations) and the MBq ( an average of 1000000 disintegrations per second)