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Radioactivity

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Safety engineering involving economic and ecological aspects ... 2.1 Experiment 1: Measuring the radioactivity of Co-60 ... discovered by Wilhelm Conrad R ntgen ... – PowerPoint PPT presentation

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Title: Radioactivity


1
Radioactivity

Basic Principles and Effects on the Human Body
2
Table of Contents
  • 1. Basic Principles of Radioactivity
  • 1.1 Alpha rays
  • 1.2 Beta- and beta- rays
  • 1.3 Gamma rays
  • 2. Experiments on Radiation
  • 2.1 Experiment 1 Measuring the radioactivity
    of Co-60
  • 2.2 Experiment 2 Effective penetration of
    Co-60
  • 3. Effects of Radioactive Radiation
  • 3.1 The radioactive catastrophe in Chernobyl
  • 3.2 Effects on the human body
  • 3.3 Long-term results caused by radiation
  • 3.4 Medical advances

3
Basic Principles of Radiation
4
1. Basic Principles of Radiation
  • the most well-known type of radiation is
    nuclear fission
  • when fission takes place two heavy atom nuclei
    fractionalise
  • the energy that is released causes the
    fragments to fly apart at great speed
  • a heavy atom nucleus can fractionalise by
    emitting ?-rays (?-radiation)
  • an unfavourable ratio between protons and
    neutrons can be compensated when beta- or
    beta rays are emitted
  • through this fission the resulting nucleus is
    more stable than the original atom nucleus

5
1. Basic Principles of Radiation
1.1 Alpha Rays
  • Special radionuclides (?- emitters) emit helium
    nuclei
  • These helium nucleii comprise 2 protons and 2
    neutrons
  • They reach a speed of around 15 000 km/h
  • Their decay often leads to the productin of
    gamma-rays
  • ?- rays give off all their energy after they
    have flown only a few centimetres


6
1. Basic Principles of Radiation
1.2 Beta- und Beta- Rays
  • When beta-radiation takes place a neutron is
    transformed into a proton when an electron is
    split
  • A new element is then formed, in this case
    Cs-137 becomes Ba-137
  • Depending on their strength beta rays are able
    to penetrate thin layers and cause damage to
    the human body

7
1. Basic Principles of Radiation
1.2 Beta- and Beta- Rays
  • When beta radiation occurs a neutron is
    transformed into a proton when a positively
    charged electron (positron) is split
  • A new element is formed, in this case Na-22
    becomes Ne-22

8
1. Basic Principles of Radiation
1.3 Gamma Radiation
  • discovered by Wilhelm Conrad Röntgen
  • like visible light it is electromagnetic but
    contains more energy
  • produced by nuclear transformation (alpha or
    beta decay)
  • is emitted in the form of gamma quanta
  • these quanta move at a speed of 300 000 km/s
    (speed of light)
  • its wave length (frequency) measures 0.5 nm
  • can also penetrate very dense materials such as
    lead

9
1. Basic Principles of Radiation
1.3 Gamma Rays
  • A great amount of energy is set free when alpha
    and beta rays fractionalise
  • During nucleus transformation the nucleus
    changes from a low state to a stable state

10
Experiments on Radioactivity
11
2. Experiments on Radioactivity
2.1 Experiment 1 Measuring the Radioactivity of
60 cobalts
To determine the intensity of a Co-60 emitter the
Becquerel values (impulse/time) are measured with
a Geiger counter at different distances.
Video 1
12
Video 1
13
Co-60
16
14
Co-60
16
4
15
Co-60
16
4
2
16
2. Versuche zur Radioaktivität
2.1 Experiment 1 Experiment to demonstrate
quadratic fall in gamma rays
Evaluation
- In this experiment the impulses per unit of
time (Becquerel Impulse/time) for the gamma
rays are measured at particular distances.
- It was noted that the longer the distance
(5cm 10cm 20cm 30cm and 40 cm) the more
the intensity of the gamma rays fell. A Geiger
counter showed that this fall is a quadratic
reduction.
- This observation is explained through the 1/r2
law.
17
2. Experiments on Radioactivity
2.2 Experiment 2 Effective penetration of 60
cobalts
To determine the surface density of materials,
these are bombarded with Co-60 rays. The emitted
?- rays are measured using a Geiger counter.
Video 2
18
Video 2
19
2. Versuche zur Radioaktivität
2.2 Experiment 2 Effective penetration of Co-60
Evaluation
- For this experiment the impulses per unit of
time (Becquerel) for gamma rays are measured
that are shielded by a particular material.
- It was noted that different materials
(Plexiglas, aluminium, lead and cement)
deflect or absorb the gamma rays due to the
varying properties of transmission,
reflection and absorption.
- This method is suitable to determine the
thickness of certain layers of known
materials.
20
Co-60
21
Effects of Radioactive Radiation
22
3. Effects of Radioactive Radiation
3.1 Radioactive catastrophe of Chernobyl
- 26th April 1986 Catastrophe of the century

- Source of this catastrophe Serious operating
errors, deactivated safety systems
- The catastrophe was triggered when an
incorrect experiment was carried out in
Reactor 4 of the nuclear power plant
23
3. Effects of Radioactive Radiation
3.1 Radioactive Catastrophe in Chernobyl
- Enormous amounts of I-131 and Cs-137
(radioactivity, formation of dangerous
aerosols) were emitted into the atmosphere

- these dangerous aerosols were carried hundreds
of kilometres
24
3. Effects of Radioactive Radiation
3.1 The Radioactive Catastrophe in Chernobyl
  • Result of this catastrophe 203 people were
    immediately taken to hospital, of these 31
    died

  • The surrounding area had to be evacuated at
    once and 135,00 people had to move to new
    homes

- The radioactive cloud comprising I-131 and
Cs-137 also reached Western Europe causing
the soil there to be contaminated with
radioactive substances
- In 1987 The number of people suffering from
cancer rose as a result of the catastrophe
in Chernobyl
25
3. Effects of Radioactive Radiation
3.2 Effects on the human body
  • 0,3 mSv/a
  • Limit for an effective dose of radioactive
    discharge to the population through water and
    air
  • 2,0 mSv/a
  • medical radiation
  • lt 3 mSv/a
  • natural radiation when living in a cement or
    granite building

250 mSv - first clinical measurable effects of
radiation when a patient has one session of
radiation to his/her whole body
26
3. Effects of Radioactive Radiation
3.2 Effects on the human body
  • ca. 1000 mSv
  • - temporary radiation sickness, one-off radiation
    of whole body


ca. 4000 mSv - serious radiation sickness, 50
mortality rate if victim remains untreated,
one-off radiation of whole body
  • ca. 7000 mSv
  • fatal dose, no medical treatment, one-off
    radiation of whole body

27
3. Effects of Radioactive Radiation
3.3 Long-term Effects of Radiation
- Liquidator committee 100,000 cleaning staff
died from long-term effects

- 31 official fatalities from international
organisations
- 1,800 children became ill with cancer of the
thyroid
- UNICEF and UNDP In the years after the
accident in Chernobyl the number of cases of
illness among children any adolescents rose to
8000 (Status January 2002)
28
3. Effects of Radioactive Radiation
3.3 Long-term effects of radiation
- Long-term consequence Number of cases of
breast cancer doubled

- Ukrainian scientists state Rise in the number
of tumour illnesses relating to urinary
tract, reproductive organs, lungs and colon
  • According to the UNDP and UNICEF the causes
    for this are Poverty, poor nutrition,
    unhealthy environment and psychological
  • consequences

- Result Number of cases of sickness are higher
in contaminated areas than in uncontaminated
regions
29
3. Effects of Radioactive Radiation
3.4 Medical Advances
Radiation Therapy to Treat Brain Tumours
  • there are different types of radiation
    treatment, external radiation treatment is
    the most widely used
  • the radiation dose is measured in Gray (GIy)
  • during each session of radiation treatment the
    patient receives a small individual dose of
    approximately 1.8 to 2.0 Gly

- radiation treatment works by using ionising
rays to damage fast growing cells -
nowadays one uses protons or, more recently,
heavy ions to treat brain tumours because
these can damage deep-seated tumours
30
3. Effects of Radioactive Radiation
3.4 Medical Advances
Radiation with fast Neutrons
  • in addition to x-rays fast (highly energy)
    neutrons will be used in future to kill
    tumour cells
  • neutrons (particle radiation) can damage
    slightly more tumour cells than x-rays

- damaged cells cannot regenerate completely and
the tumour cell is destroyed
31
Radioactivity
A presentation by - Daniel Demecz - Kevin
Grundke - Mira Arnold - Agnes Schimitzek -
(Corinna Engelhardt)
Any questions
?
32
THE END
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