week 4- ionising radiation

Question 1

name 2 sources of ionising radiation

Answer 1

natural
artificial

Question 2

list natural sources of radiation

Answer 2

Cosmic Radiation, Animals, Rocks, Buildings, Soil, Plants, Food, Water,People, Radon Gas

Question 3

list artificial radiation sources

Answer 3

X-Ray Machines [ Medical Imaging ], Nuclear Power, Nuclear Missiles,Nuclear Weapons Testing

Question 4

name characteristics of ionising radiation

Answer 4

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]

Question 5

what is half value layer

Answer 5

is the thickness of a substance which will transmit one ½ of the intensity of the radiation incident upon it

Question 6

define half lfe

Answer 6

The time taken for half of the atoms todecay is known as the half-life

Question 7

state radiation safety principles

Answer 7

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.

Question 8

what is radon gas

Answer 8

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

Question 9

what is alpha decay

Answer 9

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 ]

Question 10

what is radioactive decay

Answer 10

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

Question 11

what is beta decay

Answer 11

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

Question 12

name 2 types of radiation induced tissue damage

Answer 12

direct
indirect

Question 13

what is direct radation induced tissue damage

Answer 13

action or damage – ionisation of macromolecules

DNA, RNA, Proteins, Enzymes

Question 14

what is indirect radation induced tissue damage

Answer 14

action or damage – free radicals produced by ionisation of water

H+ OH very radioactive

Question 15

free radicals can recombine to form what?

Answer 15

hydrogen peroxide and a hydroperoxyl radical, both of which are highly reactive and produce biological damage

Question 16

what will the transferrerl of excess energy do

Answer 16

break chemical bonds of other molecules

Question 17

when is strand break problematic

Answer 17

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

Question 18

what does breakage of macromolecules lead to

Answer 18

breakage of chemical bonds
-inappropriate chemical reactions
-abnormal replication/ cell death
-damagte to reproductiove cells

Question 19

what is Linear Energy Transfer

Answer 19

how much energy is transferred per unit length

Question 20

name 2 biological effects of ionising radiation

Answer 20

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

Question 21

if a somatic cell is iorridated, what is there a chance of

Answer 21

radiation induced malignancy (cancer) to develop

Question 22

what is an absorbed dose

Answer 22

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

Question 23

what is an equivalent dose

Answer 23

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

Question 24

give an equation to work out equivelent dose

Answer 24

Equivalent Dose =Absorbed Dose ×Radiation Weighting Factor (WR

Question 25

how do we work out absorbed dose

Answer 25

times by photons (1)

Question 26

how do we work out absorbed dose

Answer 26

tissue or organ times alpha particles

Question 26

what is the effective dose

Answer 26

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)

Question 26

what does alpha radiation consist of and what is it stopped by

Answer 26

helium-4 nucleus and iseasily stopped by a sheet of paper

Question 26

what does beta radiation consist of and what is it stopped by

Answer 26

high-energy electrons orpositrons is halted by an aluminium plate

Question 26

what does gamma radiation consist of and what is it stopped by

Answer 26

high-energy photon emitted by thenucleus which can eventually be absorbed as it penetratesa dense material, such as lead [Pb]