Radiation Protection Flashcards
How do neutrons cause ionisation and hence damage to living tissue
- Neutrons indirectly ionise atoms
- Neutron interaction depends on neutron KE
- Neutrons transfer some/all of there energy to the matter
- Neutrons lose energy as they pass through hydrogenous material (such as living tissue) via collisions with hydrogen nuclei which produces recoiling protons.
- Recoil protons cause biological damage by ionisation of atoms alongs the particle path
‘What’ is LET? (2x examples of each)
Linear Energy Transfer
Energy lost by a particle per distance travelled (dE/dl)
HET: Alpha (Wr = 20), Neutrons (Wr = 5-20)
LET: Proton/electron (Wr = 1)
Define ‘Acute’ and ‘Chronic’ doses
Acute:
- SMALL radiation dose received over a LONG period of time
- Harder for body to repair
- Observable effects e.g. vomiting, hair loss, fatigue
Chronic :
- Radiation dose received over a SHORT period of time
- Easier for body to repair
- No observable effects
What is a free radical?
- Product of primary interactions of radiation
- Neutron atom with an unpaired electron (X*)
- Diffuse into the body to damage critical biological structures
What is the primary production process of free radicals?
H20 + radiation –> H20+ + electron
H20 + electron –> H20-
H20+ –> OH + H+
H20- –> H + OH-
Biological effect of radiation (seconds to centuries)
10-18 - 10-8s: Initial reaction of radiation and tissue
10-7s to hrs: Generation of highly active chemicals resulting in biological damage
Days to weeks: Death of cells / death
Years: Biological changes leading to onset of cancers
Centuries: Generation of genetic defects
Define ‘Deterministic’ and ‘Stochastic’ Dose
Deterministic:
- Harmful tissue reactions above a certain dose threshold
- Effects increase with dose received
- Predictable effects
- Example = Erythema (redness of the skin)
Stochastic:
- Probability of illness depends on dose
- Severity independent of dose received
- Predictable effects for populations only
- Example = Cancerous tumours
