Ionising Radiation Flashcards
Types of ionising radiation
alpha, beta, gamma, neutron
Alpha radiation
particles, easily absorbed by clothing and outer layers of skin, travel short distances, safe outside of the body, dangerous if ingested
Beta radiation
high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic of an atomic nucleus. beta has medium penetrating power and medium ionising power
Gamma radiation
gamma radiation is high energy electromagnetic waves emitted from unstable nuclei; high penetrating power, gamma rays produce the least ionisation.
Neutron radiation
a free neutron, usually emitted as a result induced nuclear fission. Can travel hundreds/thousands of metres in air, they are stopped by concrete or water. They are absorbed into a stable atom, thereby making it unstable and more likely to emit ionizing radiation of another type. Neutrons are the only type of radiation that are able to turn other materials radioactive (activate them).
Activation products
Atomic nuclei that become radioactive because they have absorbed neutrons that change them into less stable nuclei that emit ionising radiation.
Uses of ionising radiation
Energy production, X Rays and CT scans, cancer treatment, sterilisation
Ionizing radiation average annual dose
The per capita radiation dose in a particular area. UK average annual radiation dose 2.7 mSv
What affects your annual radiation dose?
Where you live (e.g. granite bedrock), your job (e.g. airline pilot), your diet (contaminated food), your medical needs (e.g. cancer treatment), atomic weapons fallout.
Contamination
Pollution caused by the pollutant staying in contact or mixing with materials such as soil, atmosphere, water or living organisms.
Exposure
In ionising radiation control, this refers to an object or person receiving radiation, but not necessarily coming in contact with the source.
Sources of ionising radiation exposure
Cosmic radiation, gamma radiation for the lithosphere, radon gas emissions from the ground, Ingestion of contaminated food and water, medical exposure, occupational exposure, atomic weapons fallout, industrial discharges, consumer products (eg smoke detectors)
Half life
The time taken for half of the unstable parent atom to decay to a more stable daughter atom. Half life determines persistence.
Acute
Exposure to a substance or symptoms that appear rapidly.
Chronic
Exposure to a substance or symptoms that appear over long periods of time.
How much of the unstable parent isotope will remain after three half lives?
⅛ or 12.5%
Effects of ionising radiation
Damage to cell nucleus, DNA mutation, Damage to other parts of the cell, radiation sickness, death, cancer
Control of exposure to ionising radiation
Closed sources, materials to absorb radiation, protective clothing, distance from the source, reducing the period of exposure, decontamination
Closed sources
enclosing the radioactive source in a container, remote handling techniques used or workers in a sealed suit with separate air source.
Materials to absorb radiation
Barriers between the radioactive source and workers. Thickness and composition of material depends on the type of radiation.
Protective clothing
includes lightweight suits to protect against contaminated radioactive particulate matter.
Distance from the source
Increasing distance from the radioactive source reduces exposure.
Inverse square law
as distance from the radioactive source is increased, there is a more than proportional decrease in exposure, e.g. doubling the distance reduces exposure by three quarters. Dose received = 1/distance squared
Reducing the period of exposure
minimising the time workers are exposed to the radioactive source reduces exposure
Decontamination
washing, scrubbing and exfoliating scrubs remove contamination. Potassium iodide tablets prevents uptake of radioactive iodine
Low level nuclear waste
General equipment and clothing
Managing Low level nuclear waste
Thick polythene bags in steel drums, inside steel truck containers inside a concrete lined landfill site (LLWR, Low-level nuclear waste repository, at Drigg near Sellafield)
Intermediate level nuclear waste
Metal tubes surrounding fuel rods, filters from waste reprocessing
Managing Intermediate level nuclear waste
Mixed with cement and stored in stainless steel drums - currently stored at Sellafield
High level nuclear waste
Used uranium fuel rods
Managing High level nuclear waste
Vitrification, powdered waste is mixed with molten glass and poured into stainless steel containers, surrounded by concrete and cooled, stored at Sellafield
Encapsulation
a method of dealing with hazardous waste whereby the material is mixed with concrete and poured into a container so that the waste is immobilised.
Vitrification
a specialised encapsulation technique used for high level radioactive waste, powdered radioactive waste is mixed with molten glass and poured into stainless steel containers, the containers are placed in cylindrical passage in concrete which are ventilated. Even if the glass is shattered the powdered waste will remain encapsulated in glass
Monitoring workers exposure to ionising radiation
photographic film badges, dosimeters, air monitors, contamination monitors for workers leaving premises.
Dosimeter
a device that measures dose uptake of external ionizing radiation. It is worn by the person being monitored and is a record of the radiation dose received. Can give a continuous readout of cumulative dose and current dose rate, and can warn the wearer with an audible alarm when a specified dose rate or a cumulative dose is exceeded
Monitoring the environment for ionising radiation
Monitoring atmospheric dust, soil, water, meat fish and vegetables produced in the area.
Critical group monitoring (CGM)
A method of monitoring pollutants, particularly radioactive discharges. If the members of the public that are most at risk are safe, then so is everyone else.
Critical pathway analysis (CPA)
The prediction of the routes that an effluent will take in the environment, and where it may be deposited or become concentrated to assess pollution risk.
Grays
A measure of absorbed dose
Becquerel (Bq)
The Becquerel is the unit of activity of a radioactive source.
Sievert
A measure of absorbed dose taking into account the effects of different types of radiation (relative biological effectiveness)
Relative biological effectiveness (RBE)
This is a measure based on the amount of energy absorbed from ionising radiation which takes into account the damaging effects of the type of radiation.
ALARA - As low as reasonably achievable
An approach to control of pollution, especially ionising radiation, where levels are kept as low as is practically achievable, taking into account economic and technological factors.
BATNEEC - Best available technology not entailing excessive cost
An approach to pollution control where control technology is used that achieves the lowest emission levels, without costing so much that further marginal gains would risk their financial viability.
