week 4- ionising radiation Flashcards
name 2 sources of ionising radiation
natural
artificial
list natural sources of radiation
Cosmic Radiation, Animals, Rocks, Buildings, Soil, Plants, Food, Water,People, Radon Gas
list artificial radiation sources
X-Ray Machines [ Medical Imaging ], Nuclear Power, Nuclear Missiles,Nuclear Weapons Testing
name characteristics of ionising radiation
Penetrating [ absorbed and scattered in a medium ]
Invisible [ to the eye ]
Reduces in intensity [ I ] with Half-Value Layer and Inverse Square Law
Can cause radiation-induced tissue damage / biological effects
Radioactive materials [ isotopes ] have activity [ half-life]
what is half value layer
is the thickness of a substance which will transmit one ½ of the intensity of the radiation incident upon it
define half lfe
The time taken for half of the atoms todecay is known as the half-life
state radiation safety principles
Time= The amount of radiation exposure depends directly (linearly) on the time spent near thesource of radiation. The radiation dose can be reduced by limiting exposure time.
Distance= The amount of radiation exposure depends on the distance from the source of radiation.
Shielding= If the radiation source is too intensive (and the time or distance do not provide sufficientradiation protection) then shielding can be used.
what is radon gas
It is a radioactive, colourless, and tasteless gas
It is formed by the radioactive decay of small amounts ofuranium that occur naturally in all rocks and soils.
Every building contains radon but the levels are usually low
what is alpha decay
Alpha decay [α-decay] is the spontaneous emission of an alpha particle from a nucleus. Itconsists of two protons and two neutrons tightly bound together [ a helium nucleus ]
what is radioactive decay
Radioactive decay is the process by which an unstable atomic nucleus loses energy byemitting radiation, such as an alpha particle, a beta particle, or a gamma ray
what is beta decay
Beta decay [ β-decay ] is the spontaneous emission of a fast-moving particle with the mass ofan electron from a nucleus
Negative and positive beta particles are produced by the decay of either a proton or a neutron
name 2 types of radiation induced tissue damage
direct
indirect
what is direct radation induced tissue damage
action or damage – ionisation of macromolecules
DNA, RNA, Proteins, Enzymes
what is indirect radation induced tissue damage
action or damage – free radicals produced by ionisation of water
H+ OH very radioactive
free radicals can recombine to form what?
hydrogen peroxide and a hydroperoxyl radical, both of which are highly reactive and produce biological damage
what will the transferrerl of excess energy do
break chemical bonds of other molecules
when is strand break problematic
usually repaired
if not repaired, effect is dependent upon where the damage has occurred
Protein Production [Okay]
Cell Division [Problematic]
double strand break inhibits tumour supressor gene
what does breakage of macromolecules lead to
breakage of chemical bonds
-inappropriate chemical reactions
-abnormal replication/ cell death
-damagte to reproductiove cells
what is Linear Energy Transfer
how much energy is transferred per unit length
name 2 biological effects of ionising radiation
Deterministic Effects
Non-cancer damaging effects that will definitely result fromhigh dose radiation
Stochastic Effects (Chance / Probabilistic)
Cancer and genetic effects that may result or develop
if a somatic cell is iorridated, what is there a chance of
radiation induced malignancy (cancer) to develop
what is an absorbed dose
Absorbed Dose is the energydeposited per unit mass and ismeasured in joules per kilogram[J.kg-1]
It is given the special name ofgray with the SI unit symbol Gy
what is an equivalent dose
Equivalent Dose is a measure of the radiation dose to tissue with an allowance for the different relative biological effects for different types of ionising radiation
Sv
give an equation to work out equivelent dose
Equivalent Dose =Absorbed Dose ×Radiation Weighting Factor (WR
how do we work out absorbed dose
times by photons (1)
how do we work out absorbed dose
tissue or organ times alpha particles
what is the effective dose
he effective dose is used to compare the stochastic risk of non-uniform exposure to radiation. Body tissues react differently to radiation and cancer induction occurs at a different rate of dose in different tissues.
Effective dose is measured using the sievert (Sv)
Effective Dose =Σ [ Equivalent Dose ×Tissue Weighting Factor (WT)
what does alpha radiation consist of and what is it stopped by
helium-4 nucleus and iseasily stopped by a sheet of paper
what does beta radiation consist of and what is it stopped by
high-energy electrons orpositrons is halted by an aluminium plate
what does gamma radiation consist of and what is it stopped by
high-energy photon emitted by thenucleus which can eventually be absorbed as it penetratesa dense material, such as lead [Pb]
