Radioactivity Basic Principles and Effects on the Human Body
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
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 apartat 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
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 flownonlya few centimetres
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
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
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
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
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
Co-60 16 4
Co-60 16 4 2
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.
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
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.
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
3. Effects of Radioactive Radiation 3.1 Radioactive Catastrophe in Chernobyl -Enormous amounts ofI-131 and Cs-137 (radioactivity, formation of dangerous aerosols) were emitted into the atmosphere - these dangerous aerosols were carried hundreds of kilometres
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
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 • < 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
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
3. Effects of Radioactive Radiation 3.3 Long-term Effects of Radiation - Liquidator committee: 100,000 cleaning staff died from long-term effects - 31official 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)
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
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
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
Radioactivity A presentation by: - Daniel Demecz - Kevin Grundke - Mira Arnold - Agnes Schimitzek - (Corinna Engelhardt) Any questions ?