RN 1

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

1. Alpha particles (α): Helium nuclei (2 protons, 2 neutrons). Heavy, low penetration.

2. Beta particles (β): High-speed electrons (β⁻) or positrons (β⁺). Medium penetration.

3. Gamma rays (γ): High-energy electromagnetic radiation. Deep penetration.

4. X-rays: Electromagnetic radiation, similar to gamma but lower energy. Deep penetration.

U = Uran (symbol)

235 = mass number (number of proton and neutrons in nucleus)

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

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.

The Exposure X is a measure for the ability of the radiation to ionize the surrounding air.

X = Q / m³ of air

produced charge per unit mass of the air

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

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.

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).

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.

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 (at least initially).

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.

1. Aircraft travel:

   • Flying at high altitudes:

     0.005–0.01 millisieverts (mSv) per hour.

2. X-rays:

   • A typical chest X-ray:

     0.1 mSv.

   • A dental X-ray :

     0.005 mSv.

3. Bananas:

   • Eating a single banana:

     0.0001 mSv

4. Nuclear tests

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).

Nuclear Device

1. Regular Nuclear warhead

2. Improvised Nuclear Device

Radiological Dispersal Device (RDD)

1. explosive RDD

2. non-explosive RDD

Radiological Exposure Device

1. Sealed Radioactive Source

2. Non-Sealed Radioactive Source

   (similar to neRDD)

1. 2,000 Ci of Sr-90 in ceramic form (one pellet is about the size of an ice cube)

2. A radium needle was found in a Prague playground in 2011, radiating 500 µSv/h @ 1m

3. A bunch of radiotherapy sources for brachytherapy (e.g. Ra-226 up to about 1 Ci)

1. Aerosol Deposition

2. Debris Deposition

3. Inhalation (including from resuspension)

   (alpha, beta)

4. Skin (beta)

5. Ground/Cloud shine (gamma)

1. 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.

1. Gaussian Puff Model:

   • Type: Dispersion model

   • Input Data Needed: Wind speed, direction, emission rate, cloud cover

   • 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.

1. 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.

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

no

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).

No. Its dependent on factors like form, neutron shielding and volume. Also consider enrichment %.

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.

Direct Effects

• Nuclear Blast

• Thermal Radiation or Heat Flash

- UV light

- visible light

- IR light

• (Ionizing) Initial Radiation

- Neutrons

- Gamma Radiation

Indirect Effects

• (Ionizing) Residual Radiation or Fallout Radiation

- Alpha Radiation

- Beta Radiation

- Gamma Radiation

• Nuclear Electromagnetic Pulse (NEMP)

• Transient Radiation Effects on Electronics (TREE)

• Disruption in the electromagnetic spectrum (radio propagation)

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.

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.

High-Altitude Electromagnetic Pulse

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

In personal dosimetry, the radiation dose is measured at a representative position on the surface of the human body for the present radiation field.

The measured operational quantity is a good estimate for the effective dose the person was exposed in the radiation field.

Usually not available for alpha-radiation because it doesnt penetrate. Ingested or otherwise incooperated radionuclides can also not be measured.

Definition: Dose equivalent H in tissue in 10mm depth in the person at the location where the dosimeter is worn

• 10mm is minimal depth of most of the organs Hp(10) ≥ E (for homogeneous irradiation)

• The person is part of definition and required for measurement

In this application high-volume detectors with a large efficiency are needed to get the necessary time resolution, especially when the detectors are used in fast vehicles or helicopters.

We are talking more about quantitative detection and not about a proper metrological measurement of the gamma- or neutron dose rate.

To detect radioactive particles on surfaces of for example vehicles, equipment, clothing and personnel.

Generally two-dimensional probes with a large active probe area of about 100 to 300 cm2 are used for this purpose.

The measured value is basically displayed as a simple count rate.

The simplest way is to analyze the gamma radiation of a radionuclide. This identification by photons is called gamma spectroscopy.

There are already hand-held gamma spectrometers available (less accurate than lab testing).

Because of the broad energy distribution of beta radiation a classical beta spectroscopy is not possible. Rough nuclide identification sometimes is achieved by determining the so called end point energy of the broad beta spectrum.

When a gamma photon completely transfers its energy to an electron in the detector, the photon is absorbed. This produces a photopeak in the spectrum, which represents the specific energy of the gamma ray and is crucial for identifying the isotope.

Additionally we have to look out for:

1. Compton Effect (Compton Scattering):

   • In this interaction, the gamma photon transfers only part of its energy to an electron and is scattered. This creates a range of lower-energy signals, known as the Compton continuum in the spectrum, which can complicate analysis but provides insights into photon interactions within the detector.

2. Pair Production:

   • When gamma rays have very high energy (over 1.02 MeV), they may create an electron-positron pair upon interacting with the detector material. When the positron eventually annihilates, it produces two 0.511 MeV photons, which can also appear as signals in the spectrum.

This means that energy calibration is necessary for clear results!

Hand-held gamma spectrometers are generally equipped with NaI(Tl)-detectors (energy resolution not smaller than 6%). Laboratory gamma spectroscopy systems mainly use high resolution HPGe (high purity germanium) - detectors (energy resolution about 0.15%)

Gamma Spectroscopy = Nuclide Identification

Gamma Spectrometry = Activity Measurement (nuclide specific)

gas-filled detectors

semi conductors

scintillators and light conversion devices

miscellaneous detectors

Depending on supplied voltage -> 3 different modes:

1. Ionization chamber (lowest voltage)

   The voltage on ionization chambers is just sufficient to separate the positive (ions) and negative charges (electrons) produced in the consequence of the interaction of the radiation particles with the detector gas and to avoid their recombination.

   Used for accurate dosimetry measurements (e.g. for calibrating radiation fields) and for the measurement of pulsed radiation

2. Proportional counters

   The voltage applied to a proportional counter is of that magnitude that the produced charged particles get accelerated towards the anode and the cathode respectively. On their way through the counting gas of the tube, the primary charged particles are able to ionize further gas atoms or molecules which results in an amplification of the separated charge

   Therefore proportional counters are well suited for the discrimination between alpha- and beta particles for example in contamination monitors.

3. Geiger-Müller tube (highest supply voltage) (most common):

   Independent from energy of the penetrating radiation particle a charge avalanche is generated in the tube because of the high voltage conditions. Therefore amplification factors in the range of 106 to 108 are possible

   
   

   ! Dead time of the GM-counter: This dead time usually is in the range of 10 to 100 µs and describes the time period the detector is not able to process another radiation event after a successful avalanche generation.

HPGe, MOSFET

Advantages:

-> proportionality

-> passive measurements

Disadvantages

-> degrades over time (permanent radiation damage)

Because neutrons do not possess any electrical charge, they cannot be detected directly on the basis of electrical methods. So in an electrically working neutron detector, the neutrons must interact with the detector material to produce charged particles in a first step, which are electrically detected in the end.

(Detector types for fast neutrons:

• Ionization chambers

• bubble detectors

• special Si-PIN Diodes)

3 reasons of TREE:

• Total Dose Effect (neutron + gamma)

• Dose Rate Effect (prompt gamma)

• Neutron Fluence Effect

RN-Protection Slide 17

Free Field Dose

divided by

Dose inside equipment

Radioactive particles can not be destroyed or transformed into less harmfull products by means of mechanical or chemical decontamination measures.

Radioactive contamination can only be removed from a surface and at the best collected together with the decontamination solution as radioactive waste

1. The aim of RN-decontamination for military and first responder issues is to reduce radioactivity from surfaces for- reducing external irradiation- minimizing contact hazard and spreading- preventing re-aerosolization

1. The effectivness of RN-decontamination depends on the interaction with the surface structure: nuclide type, chemical compounds, particle size, solubility, humidity, temperature, structure, mechanical and chemical properties of the surface

It falls rapidly. See Slide 7

Nuclear explosions on or near the ground will drag large masses of soil, dust and debris into the fireball. Fission products of the explosion will condense, adhere or chemically react on or into particles.

Physical and chemical properties of the fallout will mainly be determined by the inactive parts.

Particles > 300 µm will accumulate near Ground Zero (GZ).

Particles < 20 µm will mainly remain in higher air levels -> continental or worldwide fallout

Particles are mainly insoluble and are deposited quite loosely on equipment and vehicles -> mechanical brushing or washing with water, optionally under increased pressure

At relative air humiditiy above 70% it is assumed that rain will be induced by a nuclear detonation. It is assumed that up to 20% of the radioactive load of the rain will be present in aqueous solution

• Dry Contamination:

- start with mechanical means to remove -> brushing, sweeping, vacuuming, compressed air blowing

- use of water with high pressure cleaner -> immediate removal of the radioactive particles

- A longer contact of the dry contaminant with the water may lead to a leaching process of radioactive nuclides out of the particles or solving the particles themselves

Wet Contamination:

- nuclides reach the surface in ionic, molecular or colloidal form and will adhere or bound to the surface

- in general a decontamination agent will be needed

• Soiled Surfaces:

- soil generally acts as protection for the surface

- the contaminant is deposited on the soil layer and removing the soil means eliminating most of the contamination as well

- conventional surfactant-based cleaners will serve to some extent as decontaminants

No perfect agent.

… can only be the best compromise concerning

• Nature of the surface to be decontaminated

• Kind of contaminant and the presumed type of strongest bond between contaminant and surface

• Required decontamination efficiency

• Economic, safety and health protection aspects

Surfactants generally consist of a hydrophobic portion (usually long alkyl chain) attached to hydrophilic (water solubility enhancing) functional groups.

Prinzip -> Seife

Chelating agents are substances that can form multiple bonds with a single metal ion, effectively "binding" or "sequestering" the metal and making it less reactive. They are commonly used to remove heavy metals from the body, soil, or water.

1. SPRAYING / EXTRACTION TECHNIQUE

Aqueoussolution of cleaners and RN decontaminants are sprayed onto the surface under elevated pressure and vacuued off in the same working step

1. SURFACE ABLATION TECHNIQUES

Removal of the upper layer of the surface together with the penetrated radioactive contamination.

For example dry ice blasting and laser cleaning.

• total dose effect (gamma + neutrons)

• dose rate effect (promt gamma)

• neutron fluence effect (neutrons)

• total dose effect -> irradiation facility

• dose rate effect -> X-flash facility

• neutron fluence effect -> neutron generator (2MeV)

• Sea (Submarines) -> most survivable

• Land (ICBMs) -> most responsive

• Air (Bombers) -> most flexible and visible (show of force)