07_physical_agents_2_radiation_20140117153059

Question 1

Radiation is

Answer 1

energy in transit in the form of high speed particles and electromagnetic waves

Question 2

Radiations are produced by

Answer 2

the acceleration or sudden movement of electrons, which results in an interlocked pair of electric and magnetic fields oscillating at the frequency of the electron current. The electric field is created by the charge on the electrons. The magnetic field is produced whenever charges move and is proportional to the size of the current.

Question 3

Electromagnetic energy can be described by

Answer 3

frequency, wavelength, or energy

Question 4

Frequency is

Answer 4

the number of cycles or waves per second, measured in Hertz (Hz)

Question 5

Wavelength is

Answer 5

the distance between crests of the wave, measured in metres (m)

Question 6

Energy increases as

Answer 6

the wavelength shortens. An electron volt (eV) is the amount of kinetic energy needed to move an electron through one volt potential.

Question 7

Radio and microwaves are usually described in terms of

Answer 7

frequency (Hz)

Question 8

Infrared and visible light are usually described in in terms of

Answer 8

wavelength (m)

Question 9

X-rays and gamma rays in terms of

Answer 9

energy (eV).

Question 10

Non-ionising radiation

Answer 10

has enough energy to move atoms in a molecule around or cause them to vibrate, but not enough to remove electrons. Examples of non-ionising radiation include visible light, and microwaves.

Question 11

Ionising radiation

Answer 11

has enough energy to remove tightly bound electrons from atoms, thus creating ions. Ionisation is the process in which a charged portion of a molecule (usually an electron) is given enough energy to break away from the atom. This process results in the formation of two charged particles or ions: the molecule with a net positive charge, and the free electron with a negative charge. Each ionisation releases approximately 33eV of energy which is absorbed into the material surrounding the atom. The 33eV from one ionisation is more than enough energy to disrupt the chemical bond between two carbon atoms.

Question 12

The International Commission on Radiological Protection (ICRP)

Answer 12

Since 1928, the ICRP has developed, maintained, and elaborated the International System of Radiological Protection used world-wide as the common basis for radiological protection standards, legislation, guidelines, programmes, and practice.

Question 13

Health Protection Agency (HPA)

Answer 13

The HPA identifies and responds to health hazards and emergencies caused by infectious disease, hazardous chemicals, poisons or radiation. It gives advice to the public on how to stay healthy and avoid health hazards, provides data and information to government to help inform its decision making, and advises people working in healthcare. It also makes sure the nation is ready for future threats to health that could happen naturally, accidentally or deliberately. The HPA has a statutory responsibility for advising UK government departments, and those with responsibility for using ionising and non-ionising radiation, on the associated risks to human health (these were formerly the responsibilities of the National Radiological Protection Board (NRPB) before it merged into the HPA in 2005).

Question 14

Environment Agency

Answer 14

The Environment Agency (EA) enforces the Radioactive Substances Act 1993 (RSA93) in England and Wales. The primary purpose of which is to control radioactive substances and in particular radioactive waste. It requires:  registration with the Environment Agency for the keeping and use of radioactive materials and mobile radioactive apparatus  authorisation by the Environment Agency for the accumulation and disposal of radioactive waste.

Question 15

Non-ionising radiation (NIR) is the term used to describe the part of the electromagnetic spectrum covering two main regions, namely:

Answer 15

 optical radiation (ultraviolet (UV), visible and infrared.  electromagnetic fields (EMFs) (power frequencies, microwaves and radio frequencies).

Question 16

UVR is sub-divided into three bands, depending on wavelength:

Answer 16

 UVC is very short-wavelength UVR and is theoretically the most harmful to humans; however UVC radiation from the sun is filtered out in the atmosphere. In practice human exposure is only available from artificial sources, such as germicidal lamps.  UVB is mid wavelength and is the most biologically damaging UVR which causes sunburn and other biological effects.  UVA has the longest wavelength and is normally found in most lamp sources. Although UVA can penetrate deeply into tissue, it is not as biologically damaging as UVB.

Question 17

The most significant artificial sources of UVR are:

Answer 17

Industrial arc weldingIndustrial UVR lampsBlack lights Medical treatment Germicidal UVR lamps Cosmetic tanningGeneral lighting

Question 18

Infrared radiation is located between microwaves and visible light. It is subdivided into three bands, based on wavelength and the absorption characteristics of IR in tissue and the resulting different biological effects.

Answer 18

 IRA is the shortest wavelength - from 780 nm to 1.4 μm  IRB (from 1.4 μm to 3 μm )  IRC - the longest wavelength (from 3 μm to 1 mm).

Question 19

Metal working What key measures need to be considered?

Answer 19

 provide face shields, coveralls and gloves  protect others using screens / curtains / restricted access  provide information and training  display appropriate warning signs  monitor and enforce use of control measures  if any workers are over-exposed, provide medical examination and consider whether follow-up health surveillance is appropriate

Question 20

Pharmaceuticals and research What key measures need to be considered?

Answer 20

 provide protective eyewear and make sure other areas of skin are not exposed (i.e. provide lab coats and gloves)  protect others using screens / curtains / restricted access  provide information and training  display appropriate warning signs  monitor and enforce use of control measures  if any workers are over-exposed, provide medical examination and consider whether follow-up health surveillance is appropriate

Question 21

‘Hot industries’ What key measures need to be considered?

Answer 21

 engineered measures – remote controls, screening, interlocks, clamps to hold material Provide face shields, goggles or other protective eyewear, coveralls and gloves  enforced maximum working periods – routine change of activity  protect others using screens/curtains/restricted access  provide information and training  display appropriate warning signs  monitor and enforce use of control measures  if any workers are over-exposed, provide medical examination and consider whether follow-up health surveillance is appropriate

Question 22

Printing and paint (motor vehicle repairs) What key measures need to be considered?

Answer 22

 engineered measures – screening, automation, remote control  provide face shields, goggles or other protective eyewear and ensure other areas of skin are not exposed by providing coveralls and gloves  protect others using screens/curtains/restricted access  provide information and training  display appropriate warning signs  monitor and enforce use of control measures  if any workers are over-exposed, provide medical examination and consider whether follow-up health surveillance is appropriate

Question 23

An ion is

Answer 23

an atom that has gained or lost electrons

Question 24

If an atom gains electrons it is

Answer 24

negatively charged (anion)

Question 25

If an atom loses electrons it is

Answer 25

positively charged (cation)

Question 26

There are three main sources of man-made ionising radiation:

Answer 26

 Medical diagnosis and treatment, for example: X-rays used in radiography and radiotherapy.  Industrial uses, for example: Non-destructive testing (NDT) and electricity production. (Note: both medical and industrial uses of radiation produce radioactive waste).  Fallout from nuclear weapon explosions and nuclear accidents such as Chernobyl and Fukushima.

Question 27

Occupational exposures may be significant for workers who deal with radiation in the following activities:

Answer 27

 nuclear power industry  medicine and dentistry  research laboratories  general industry.

Question 28

The stability of the nucleus depends on

Answer 28

the relative numbers of protons and neutrons present

Question 29

The main types of ionising radiation are:

Answer 29

 Alpha particles  Beta particles  Neutrons  Gamma rays  X-rays.

Question 30

The ability of ionising radiation to cause harm is a function of

Answer 30

mass and penetrating ability. Alpha particles have the greatest effect, gamma rays the least.

Question 31

Alpha particles

Answer 31

Alpha particles are emitted from the nuclei of the radioactive atoms and consist of two protons and two neutrons. They are heavy, slow moving and carry a double positive charge. They are potentially the most damaging type of ionising radiation (if ingested or breathed in, for example) but are fairly easy to stop with barriers. They will not penetrate human skin and can only travel a few centimetres in air. Alpha particle emitters are used in smoke detectors and as static eliminators.

Question 32

Beta particles

Answer 32

Beta particles are high energy negatively charged particles. Each particle is actually an electron emitted from the nucleus. They have an electrical charge of -1 and a mass of approximately 1/2000 of the mass of a proton or neutron. Beta particle electrons do not come from the electron shells around the nucleus, they are formed when the ratio of neutrons to protons in the nucleus is too highm, and an excess neutron transforms into a proton and an electron. The proton stays in the nucleus and the electron is ejected energetically. Beta particles can travel further than alpha particles and can penetrate human skin, but are not as harmful as alpha particles. Examples of beta emitters include: phosphorous-32; tritium (H-3); carbon-14; strontium-90; technetium-99; iodine-129 and -131; caesium-137 and lead-210. Beta emitters are used in industrial thickness gauges and as medical radioactive tracers; carbon 14 is used in carbon dating.

Question 33

Neutrons

Answer 33

Neutrons may be emitted from nuclear fusion or nuclear fission, or from any number of different nuclear reactions such as from radioactive decay or reactions from particle interactions (such as from cosmic rays or particle accelerators). Large neutron sources are rare. Neutron radiation is termed ‘indirectly ionising radiation’. Because neutrons have no charge they do not ionise atoms by exciting an electron. However, neutron interactions can result in gamma emission and subsequent removal of an electron from an atom, or a nucleus recoiling from a neutron interaction is ionised and causes more traditional subsequent ionisation in other atoms. Because neutrons are uncharged, they are not affected by electrical fields and are therefore more penetrating than alpha radiation or beta radiation. They are also more penetrating than gamma radiation in materials of high atomic number.

Question 34

Gamma rays

Answer 34

Gamma rays are very high-energy electromagnetic waves. They have very short wavelengths ranging from 3/100ths to 3/1,000ths of a nanometer (nm). Gamma photons have about 10,000 times as much energy as the photons in the visible range of the electromagnetic spectrum. They travel at the speed of light and can cover hundreds to thousands of meters in air before spending their energy. They can pass through many kinds of materials, including human tissue. Very dense materials, such as lead, are commonly used as shielding to slow or stop gamma photons. Gamma radiation is often emitted following release of a Beta particle, when the nucleus still has too much energy and needs to release it to become more stable. Gamma emitters such as Cobalt 60, Caesium 137 and Technetium 99m have a range of medical and industrial uses including steel thickness testing, medical sterilisation, medical diagnostics, food pasteurisation and cancer treatment.

Question 35

X-rays

Answer 35

Whereas gamma rays originate in the nucleus, X-rays originate in the electron fields surrounding the nucleus (See Figure 7.4) or are machine-produced. X-rays sit between ultra violet and gamma rays in the electromagnetic spectrum. X-rays have a wavelength in the range of 0.01 to 10 nanometers. X-ray machines are used universally, for example: in airport security; in industry for non-destructive testing (NDT); and in medicine for examinations and radiotherapy treatment.

Question 36

Routes of exposure

Answer 36

People can be exposed externally, to radiation from a radioactive material or a generator such as an X-ray set, or internally, by inhaling or ingesting radioactive substances. Wounds that become contaminated by radioactive material can also cause radioactive exposure.

Question 37

Acute exposure and effects

Answer 37

Acute exposure is exposure to a large, single dose of radiation, or a series of moderate doses received during a short period of time. Acute exposure to radiation may cause both immediate and delayed effects. A large dose of radiation can cause rapid development of radiation sickness, evidenced by gastrointestinal disorders, bacterial infections, haemorrhaging, anaemia, loss of body fluids, and electrolyte imbalance. An extremely high dose of acute radiation exposure can result in death within a few hours, days, or weeks. Delayed biological effects include: cataracts, temporary or permanent sterility, cancer, mutagenic (inheritable genetic effects); or teratogenic (interferes with embryonic development) effects.

Question 38

Chronic exposure and effects

Answer 38

Chronic exposure is continuous or intermittent exposure to low doses of radiation over a long period of time. With chronic exposure, there is a delay between the exposure and the observed health effect. The effects of chronic exposure include: cancer, benign tumours, cataracts, and mutagenic or teratogenic effects.

Question 39

Somatic effects

Answer 39

are the symptoms produced in the irradiated person which result from direct damage to body cells. They are divided into ‘early’ and ‘late’ effects which broadly correspond to acute and chronic effects.

Question 40

Genetic effects

Answer 40

are those arising from damage to reproductive cells. Irradiation of reproductive organs increases the risk of genetic malformation and disease in offspring and subsequent generations of offspring.

Question 41

Stochastic effects

Answer 41

are associated with long-term, low-level (chronic) exposure to radiation. Stochastic effects are effects that occur on a random basis, independent of the size of dose. The effect typically has no threshold and is based on probabilities, with the chances of seeing the effect increasing with dose. Cancer is a stochastic effect. Ionising radiation’s ability to break chemical bonds in atoms and molecules makes it a potent carcinogen. Damage at the cellular or molecular level can disrupt the natural processes which control the rate at which cells grow and replace themselves. Cancer is the uncontrolled growth of cells. Radiation can cause changes in DNA, or mutations, which the body may not be able to repair. The mutations may be mutagenic – which can be passed on to future generations, or teratogenic which affect the developing foetus in the uterus and affect only the individual who was exposed.

Question 42

Non-stochastic effects

Answer 42

(also known as deterministic or threshold effects) can be related directly to the dose received. The effect is more severe with a higher dose, i.e., the burn gets worse as dose increases. It typically has a threshold, below which the effect will not occur. A skin burn from radiation is a non-stochastic effect. Non-stochastic effects appear in cases of short term exposure to high levels of radiation (acute exposure) and become more severe as the exposure increases. Acute health effects such as burns and radiation sickness usually occur quickly. Radiation sickness can cause premature aging or even death. If the dose is fatal, death usually occurs within two months. The symptoms of radiation sickness include: nausea, weakness, hair loss, skin burns or diminished organ function. Medical patients receiving radiation treatments often experience acute effects, because they are receiving relatively high ‘bursts’ of radiation during treatment.

Question 43

Non-stochastic effects are specific to each exposed individual and are characterised by:

Answer 43

 A minimum dose being exceeded before the particular effect is observed (the threshold may differ from individual to individual).  The magnitude of the effect increases with the size of the dose received by the individual.  There is a clear relationship between exposure to radiation and the observed effect on the individual.

Question 44

Measuring exposure There are two basic types of instruments used for its detection:

Answer 44

 Particle counting instruments.  Dose measuring instruments.

Question 45

Radioactivity is measured in units called

Answer 45

becquerel (Bq). One becquerel = one atomic disintegration per second.

Question 46

The half-life of a radioisotope describes

Answer 46

how long it takes for half of the atoms in a given mass to decay

Question 47

The SI unit for absorbed dose of ionising radiation is

Answer 47

the gray. One gray (Gy) is the absorption of one joule of energy by one kilogram of matter: 1Gy = 1J / 1kg

Question 48

sievert - Sv

Answer 48

As the effects on human health vary with the type and energy of radiation and the tissues affected, the absorbed dose is multiplied by a factor to calculate the dose equivalentFor beta particles, gamma rays and X-rays the factor is 1 (i.e. the dose equivalent = the absorbed dose), for alpha particles the factor is 20 (1 Gy of alpha particles = 20Sv).

Question 49

The three main factors that can be controlled to reduce radiation exposure are:

Answer 49

 Shielding  Time  Distance.

Question 50

ShieldingThe type and amount of shielding needed to achieve a safe working level varies with the type and quantity of radioactive material used. Gamma rays and X-rays are more penetrating than alpha or beta particles and will require a few inches of lead or several feet of concrete to stop them (see Figure 7.7).

Answer 50

GAMMA Rays andX-RaysStopped by several feet ofconcrete or a few inches ofleadBETA ParticlesStopped by layer of clothingor by a few millimeters of asubstance such as aluminiumALPHA ParticlesStopped by a sheet of paper

Question 51

Time Because radiation is roughly emitted at a constant rate from its source, the radiation dose will be proportional to the amount of time spent in proximity to the source. Good practices designed to reduce the time spent exposed to radioactive materials as much as possible include:

Answer 51

 Dry running activities, without any radioactive material, to get used to the procedures; then performing the actual activity in minimal time after becoming familiar with the procedures.  Storing the bulk of the radioactive material away from the work area or behind shielding and only using the minimum necessary amount of radioactive material for the task in hand.

Question 52

Dose levels must be kept as low as is reasonably practicable. Dose limits, as shown in Table 7.7, are maximum permitted levels and to exceed them is an offence.

Answer 52

Employees (18y +) Trainees (< 18y) Other Persons Whole Body Effective Dose 20 mSv 6 mSv 1mSv Lens of eye 150 mSv 50 mSv 15 mSv Skin 500 mSv 150 mSv 50 mSv Hands, forearms, feet & ankles 500 mSv

Question 53

The word laser is an acronym, which stands for

Answer 53

Light Amplification by the Stimulated Emission of Radiation

Question 54

A laser beam is electromagnetic radiation just like the light from a lightbulb, but unlike the lightbulb: 4

Answer 54

 the beam of light is monochromatic, i.e. it emits light of a single wavelength (or small number of wavelengths)  the beam may be in the infrared, visible or ultraviolet regions of the spectrum depending upon the active medium  the individual waves of a laser beam are ‘in phase’ – the laser beam is coherent  the beam is usually highly collimated (i.e. has low angular divergence and does not ‘spread out’ significantly with distance).

Question 55

Laser products are classified to take account of

Answer 55

the amount of laser beam which can be accessed when the product is in normal use or during routine user maintenance.

Question 56

Class 1

Answer 56

Safe under reasonably foreseeable conditions of operation.

Question 57

Class 1M

Answer 57

As Class 1 but not safe when viewed with optical aids such as eye loupes or binoculars.

Question 58

Class 2

Answer 58

(Visible laser beams only) The eye is protected by the aversion responses, including the blink reflex and head movement.

Question 59

Class 2M

Answer 59

As Class 2 but not safe when viewed with optical aids such as eye loupes or binoculars.

Question 60

Class 3R

Answer 60

More likely to cause harm to the eye than lower class lasers but do not need as many control measures as higher class lasers.

Question 61

Class 3B

Answer 61

Eye damage likely to occur if the beam is viewed directly or from shiny reflections.

Question 62

Class 4

Answer 62

Eye and skin damage likely from the main laser beam and reflected beams. These lasers may cause fires.

Question 63

Laser health effects Potential health hazards are dependent upon a range of variables, including: 4

Answer 63

 Laser light wavelength  Beam intensity  Distance from the laser  Power of the laser: - average power over long intervals - peak power produced in a pulse.

Question 64

The wavelength of the laser radiation is significant because

Answer 64

only light within the retinal hazard region (wavelength range of approximately 400 to 1400 nm) can penetrate the eye sufficiently to damage the retina.

Question 65

Radon 222 is

Answer 65

a radioactive ( particles) gas which comes from uranium and occurs naturally in many rocks and soils. Radon can seep out of the ground and build up in houses and indoor workplaces.

Question 66

The health effects of radon

Answer 66

Breathing in radon is the second largest cause of lung cancer in the UK (after smoking). It accounts for 3-5% of all lung cancers in the UK and around 2000 fatal cancers per year. The risk from radon is approximately 25 times higher for cigarette smokers than for non-smokers. Most radon gas breathed in is immediately exhaled and presents little radiological hazard. However, the decay products of radon (radon daughters) behave more like solid materials than a gas and are themselves radioactive. These solid decay products attach to atmospheric dust and water droplets which can then be breathed in and become lodged in the lungs and airways. Some decay products emit alpha particles which cause significant damage to the sensitive cells in the lung.

Question 67

Radon is present in all buildings: the average level in the UK is

Answer 67

20 becquerels per cubic metre of air. Some workplaces have been found to have measured radon levels significantly in excess of the 400 Bq/m3 action level. Worst cases have shown levels over 17,000 Bq/m3.

Question 68

Practical control of radon levels in buildings

Answer 68

New buildings can be protected during construction by installing a ‘radon proof barrier/ membrane’ within the floor structure. In existing buildings the best approach is to prevent radon entering the building by altering the balance of pressure between the room and the ground. Pressure inside the building can be increased by blowing air from the roof space with a small fan and pressure under the floor is reduced by connecting a low power fan to a small sump and extracting the air.

Question 69

It is good practice to set a timescale after which re-measurement of the radon levels will occur. The HSE suggests the following guidelines: 3

Answer 69

 where initial levels were significantly less than 400 Bq/m3 re-measurement should occur once every 10 years  where initial levels were just below 400 Bq/m3 re-measurement should occur before 10 years  where initial levels were above 400 Bq/m3 and measures have been taken to reduce radon exposures (such as engineered systems or occupancy restrictions), the re-measurement periods may need to be significantly more frequent in order to verify their continuing effectiveness.