What is ionizing radiation?
Subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them
Particles generally travel at > 1% of light speed
Alpha particles (α): Helium nuclei (2 protons, 2 neutrons). Heavy, low penetration.
Beta particles (β): High-speed electrons (β⁻) or positrons (β⁺). Medium penetration.
Gamma rays (γ): High-energy electromagnetic radiation. Deep penetration.
X-rays: Electromagnetic radiation, similar to gamma but lower energy. Deep penetration.
What is U-235?
U = Uran (symbol)
235 = mass number (number of proton and neutrons in nucleus)
What type of shielding is effective against different types of ionizing radiation?
Alpha -> Paper
Beta -> Thin plates (wood, aluminum etc)
Neutron -> Water, concrete
X-ray -> Lead, Iron or other thick metal plates
Gamma-ray -> Lead, Iron or other thick metal plates
What are the risk vectors for different radiation types?
Alpha radiation is mainly an incorporation risk.
Beta radiation is mainly a contamination risk.
X-rays are a risk for external exposure.
Gamma radiation is mainly a risk for external exposure.
Neutron radiation is a risk for external exposure.
What is exposure and what unit is used to describe it?
The Exposure X is a measure for the ability of the radiation to ionize the surrounding air.
X = Q / m of air
produced charge per unit mass of the air
What is the absorbed dose and what unit is used to describe it?
D is a dose quantity which is the measure of the energy deposited in matter by ionizing radiation per unit mass.
1 J/kg = 1 Gy (Gray)
Absorbed dose D depends on material composition for silicon:
D = 2.5 Gy(Si) for human tissue:
D = DT = 12.5 mGy(TE) = 12.5 mGy
What is the equivalent dose and what unit is used to describe it?
H measures the stochastic health effects of low levels of ionizing radiation on the human body which represents the probability of radiation-induced cancer and genetic damage.
It is derived from the physical quantity absorbed dose, but also takes into account the (long term) biological effectiveness of the radiation, which is dependent on the radiation type.
[H] = 1 J/kg = 1 Sv (Sievert)
Weigthing factor used in formula dependent on energy and range of radiation type.
What is the effective dose and what unit is used to describe it?
E is the tissue-weighted sum of the equivalent doses in all specified tissues and organs of the human body and represents the stochastic health risk to the whole body.
[E] = 1 Sv (Sievert)
Takes into account what organs/tissue or similar are affected (Tissue weighting factor).
What dose quantity concepts do you know?
Physical quantities (gray, Fluence)
Operational quatities (Ambient dose equivalent, Personal dose equivalent):
These are measurable and used for practical eval. of dose for regulation and assessment. Are calculated with the absorbed dose of simple phantoms (spheres or slabs).
Protection quantities (Organd absorbed dose, Effective dose):
Not measurable, calculated using observed health effects. Used to set exposure limits.
Protection and operational quantities are linked.
Physical quantities are the basis for the other two.
What different exposure types do you know?
External exposure:
Radiation sources (radioactive material) outside the body.
Subtype: Body surface contamination
Often whole-body exposure.
Internal exposure:
From a wound.
Inhalation or ingestion of radioactive materials.
Tends to be localized (atleast initially).
What is the committed effective dose for intake?
Long-term internal radiation dose from internal contamination (ingestion/inhalation of radioactive material).
For adults calculated over 50 years.
For children calculated over 70 years.
Unit: Sieverts
Accounts for different orangs/tissue by integrating the effective dose over time. Also considers where the radioactive materials accumulate.
Give examples of radiation exposure in our daily life.
Aircraft travel:
Flying at high altitudes:
0.005–0.01 millisieverts (mSv) per hour.
X-rays:
A typical chest X-ray:
0.1 mSv.
A dental X-ray :
0.005 mSv.
Bananas:
Eating a single banana:
0.0001 mSv
Nuclear tests
Deterministic vs. Stochastic effects? Explain.
Deterministic Effects:
- Effects that occur after reaching a threshold dose.
- Severity increases with dose.
- Predictable, immediate effects (e.g., burns, sickness).
Stochastic Effects:
- Random effects that can occur after any radiation dose.
- Risk increases with dose but not predictable.
- Long-term effects (e.g., cancer, genetic mutations).
What types of radiological or nuclear weapon types do you know?
Nuclear Device
Regular Nuclear warhead
Improvised Nuclear Device
Radiological Dispersal Device (RDD)
explosive RDD
non-explosive RDD
Radiological Exposure Device
Sealed Radioactive Source
Non-Sealed Radioactive Source
(similar to neRDD)
Examples of radioactive sources suitable for radiological weapons. No pictures (see slide 7 RNP2)
2,000 Ci of Sr-90 in ceramic form (one pellet is about the size of an ice cube)
A radium needle was found in a Prague playground in 2011, radiating 500 µSv/h @ 1m
A bunch of radiotherapy sources for brachytherapy (e.g. Ra-226 up to about 1 Ci)
What attack vectors does an explosive radiological dispersal device have?
Aerosol Deposition
Debris Deposition
Inhalation (including from resuspension)
(alpha, beta)
Skin (beta)
Ground/Cloud shine (gamma)
What is the dispersal model “Gaussian Plume Model“? What input data is needed? What does it specifically describe and how high is the accuracy?
Gaussian Plume Model (widely used):
Type: Combined meteorology and diffusion model
Input Data Needed: Wind speed, direction, emission rate, cloud cover
Application: Point, area, volume source
Accuracy: Gives concentration estimates within an order of magnitude for continous release over homogenous terrain.
What is the dispersal model “Gaussian Pluff Model“? What input data is needed? What does it specifically describe and how high is the accuracy?
Gaussian Puff Model:
Type: Dispersion model
Application: Dispersion under time varying meteorological conditions, continous short term releases under emergency situations
Accuracy: Better than Gaussian Plume model for time varying meteorology. Not satisfactory under strong wind shear.
What is the dispersal model “Particle trajectory model“? What input data is needed? What does it specifically describe and how high is the accuracy?
Particle Model:
Type: Particle trajectory model, Lagrangian model (follows air parcels).
Input Data Needed: Atmospheric stability, wind velocity, turbulence.
Application: Best for complex terrain and non-homogeneous environments.
Accuracy: Good for complex terrain and long-range dispersion.
On what factors does the final size distribution of a dispersed radioactive material (of a RDD) depend?
Stress and initial Particle size. Also type of radioactive substance:
Powders: 20-80% aerosolised
Ceramics: 2-40% aerosolised
Metals(Cobalt): <0.2% aerosolised
Liquids: almost full aerosolisation possible
Graph RNP2 slide 18
Are Radiological Weapons WMD?
no
Explain the cannon type of nuclear weapons.
A simple design where two sub-critical masses of fissile material are brought together by firing one mass into the other using conventional explosives, forming a supercritical mass. This initiates a nuclear chain reaction (nuclear chain reaction should be clear).
Is the critical mass of fissile material set?
No. Its dependent on factors like form, neutron shielding and volume. Also consider enrichment %.
What is boosting in nuclear weapons?
Boosting increases a nuclear weapon's power by adding tritium and deuterium (fusion fuel) to the core. The fusion reaction releases extra neutrons, making the fission reaction more efficient and powerful.
What are direct effects of nuclear weapons?
Direct Effects
• Nuclear Blast
• Thermal Radiation or Heat Flash
- UV light
- visible light
- IR light
• (Ionizing) Initial Radiation
- Neutrons
- Gamma Radiation
What are INdirect effects of nuclear weapons?
Indirect Effects
• (Ionizing) Residual Radiation or Fallout Radiation
- Alpha Radiation
- Beta Radiation
• Nuclear Electromagnetic Pulse (NEMP)
• Transient Radiation Effects on Electronics (TREE)
• Disruption in the electromagnetic spectrum (radio propagation)
What types of nuclear detonation do you know (location dependent) and what effect does it have?
Here’s a breakdown of the types of nuclear detonations based on their location and effects:
1. High Altitude Burst:
- Location: Above 60 km in the atmosphere.
- Effects: Strong EMP (Electromagnetic Pulse) effect, minimal blast and thermal damage on the ground.
2. High Air Burst:
- Location: < 60 but above 10 km.
- Effects: Larger blast radius, reduced fallout, but less damage on the ground compared to lower altitude bursts.
3. Air Burst:
- Location: Detonated within a few kilometers of the surface.
- Effects: Maximizes blast and thermal damage over a large area, limited fallout due to no ground contact.
4. Low Air Burst:
- Location: Very close to the surface, but not touching it.
- Effects: Increased localized blast damage, moderate fallout due to some ground contact.
5. Surface Burst:
- Location: On or near the ground.
- Effects: Severe local damage, high levels of radioactive fallout as debris is drawn into the explosion.
6. Underground Burst:
- Location: Below the surface.
- Effects: Limited surface damage but creates significant underground shockwaves, causing earthquakes or craters, and potential release of radioactive material depending on depth.
What is the yield?
The Yield is the total spontaneously released energy of a nuclear explosion, not only the kinetic energy. For nuclear explosions the kinetic energy can – in contrast to conventional explosions – be significantly smaller than the total energy.
What does HEMP stand for?
High-Altitude Electromagnetic Pulse
What 3 distinct phases of a HEMP event do you know?
HEMP consists of 3 components
1. Early-Time Pulse (TREE)
most interesting for military equipment
2. Subsequent Pulse
mainly covered by lightning protection measures
3. Continuing Pulse
EMP coupling to long overhead power lines with the danger of damaging power stations and substations
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