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Buxton & District
Science Discussion
4
Types of ionising radiation
X-raysGamma rays
Alpha particlesBeta particles (or radiation)
Neutrons, protons etc.
Buxton & District
Science Discussion
5
Types of ionising radiation
X-raysGamma rays
Alpha particlesBeta particles (or radiation)
Neutrons, protons etc.
Buxton & District
Science Discussion
6
Fear and the Perception of riskEating a banana Going to Cornwall on holiday
for a fortnight
Living within 50 miles of a nuclear power plant for a year
Having a PET scan of the head
Working as an airline pilot for a year
Having a dental x-ray
Having a CT scan of the head Working in a nuclear power station for a year
Standing in the grounds of Chernobyl for an hour
Living in Buxton for a year
Buxton & District
Science Discussion
7
Estimated doses in mSvLiving within 50 miles of a nuclear power plant for a year
0.00009 Working as an airline pilot for a year
2.2
Eating a banana 0.0001 Having a CT scan of the head
2.3
Having a dental x-ray 0.005 Living in Buxton for a year 3.1
Working in a nuclear power station for a year
0.18 PET scan of the head 5
Going to Cornwall on holiday for a fortnight
0.3 Standing in the grounds of Chernobyl for an hour
6
Buxton & District
Science Discussion
8
History
1895 X-rays Röntgen
1895 Radioactivity Becquerel
1898 Radium Curies
Buxton & District
Science Discussion
10
The pioneering daysSome conditions recommended for
treatment with radium in 1906
Lupus vulgarisEczemaAcne
Psoriasis Pain
ArthritisInfectious diseases
x-rays Radium
Buxton & District
Science Discussion
12
Legislation1960 Radioactive Substances Act
(Updated in 1993)Keeping, storage, disposal of waste
1978 The Medicines (Administration of Radioactive Substances) Regulations
Administration of radioactivity to patients
1985 Ionising Radiation Regulations(Updated in 1999)
Work
2001 Ionising Radiations (Medical Exposures) Regulations
Medical exposures
2001 Radiation (Emergency Preparedness and Public Information) Regulations
Emergency Preparedness
2004 Justification of Practices involving Ionising Radiations
Justification
Buxton & District
Science Discussion
13
Radiation Dose
Internal : from unsealed radioactive substances
Modes of exposure to ionising radiation
External : from x-rays & sealed radioactive substances
Buxton & District
Science Discussion
14
Protecting yourself from ionising radiation
TimeDistanceShielding
And, to reduce internal irradiation you needGood housekeeping
Buxton & District
Science Discussion
16
Radiation can only cause harm if at least some of its energy is
absorbed within the body
Type of radiation Outside the body Inside the body
Alpha Stopped by thin sheet of paper
Imparts all its energy to a tiny area
Beta Stopped by a few mm aluminium
Almost all of the energy is absorbed
close to the site
Gamma(sim. X-ray)
Shielding needs may be substantial
depending on energy
A sizeable proportion may escape the body, depending on energy
Buxton & District
Science Discussion
18
What sort of damage can radiation do to humans?
Acute effects (Radiation sickness)
Skin reddening, cataracts (Tissue reactions)
Increased probability of certain kinds of cancer – avoidance is main aim of radiation protection
(Stochastic effects)
Buxton & District
Science Discussion
19
There is hard evidence for radiation sickness and the so-called tissue reactions
(were called deterministic and, before that, non-stochastic)
Buxton & District
Science Discussion
20
Stochastic effect – Increased probability of cancer
Overall, it is estimated that more than one in three people will be
diagnosed with some form of cancer during their lifetime.
Buxton & District
Science Discussion
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At 200 mSv, we have reasonably good evidence that death from cancer as a result of radiation exposure is under
9000 in a million to add to underlying incidence of 250,000
Buxton & District
Science Discussion
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Linear No Threshold Model
0
Dose (mSv)
Relative increase in risk Linear-No-Threshold (LNT)
Supralinear
Sublinear Threshold
HormesisRelative benefit
www.llrc.org
Buxton & District
Science Discussion
23
Units of effective radiation dose
Rem/Sievert(1 Sievert = 100 Rem)
Whole body or part
Buxton & District
Science Discussion
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Rolf Maximilian Sievert
Doses talked about so far are whole body effective dose. This is
the energy absorbed per mass taking into account the type of
radiation and the part of the body irradiated – a measure of harm
Buxton & District
Science Discussion
25
There are many assumptions that go into effective dose estimations
1. Energy deposited per unit mass – accurate measure
2. What kind of radiation – α particles are 20 times more damaging than x or γ
3. Which part of the body – gonads more sensitive, liver less so
Buxton & District
Science Discussion
26
Tissue weighting factorsGonads 0.20 Red bone
marrow 0.12 Colon 0.12
Lungs 0.12 Stomach 0.12 Bladder 0.05
Breast 0.05 Liver 0.05 Oesophagus 0.05
Thyroid 0.05 Skin 0.01 Bone surfaces 0.01
Buxton & District
Science Discussion
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The basic assumption behind all the radiation protection precautions we take these days is that all radiation is
harmful. Even if it is naturally-occurring like Radon, we seek to
limit it as far as possible.
Buxton & District
Science Discussion
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Control of exposure is based on 3 tenets
1. Justification (Risk v Benefit)2. Optimisation3. Limits (but ALARP)
ALARP = as low as reasonably practicable
Buxton & District
Science Discussion
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Data from the NRPB – National Radiological Protection Board (which became part of the HPA - Health Protection Agency and is now, from April 2013, part of Public Health England)
Buxton & District
Science Discussion
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Annual dose limits
Classified workers (must be over 18) 20 mSv
Unclassified workers and trainees 6 mSv
All others (including members of the public*)
1 mSv
* There are no specified limits for patients or ‘carers’
Buxton & District
Science Discussion
38
Why does the radiographer go behind a lead screen when an x-ray is taken? It
must be dangerous so why isn’t it dangerous for me as the patient ?
It’s true of course - the patient will get more dose than the member of staff for that one exposure
But the member of staff will be present at many such exposures over the year and the only benefit they receive is that it is their job. There is no
justification for irradiation of the member of staff when it can be avoided by standing behind a lead screen.
Buxton & District
Science Discussion
3939
Ex-Russian agent Alexander Litvinenko died in a London hospital on 23 November 2006 from poisoning with Polonium 210
Buxton & District
Science Discussion
40
Polonium 210 absorbed into the body cannot be detected from the outside – the way to check for it is
to monitor the urine