Lecture 6: Accidents Flashcards
What is the unit of radioactivity?
Becquerels (Bq)
Name the two isotopes that dominate environmental impact?
Iodine-131
Caesium-137
What does I-131 emit?
Alpha
What does Cs-137 emit?
Gamma
What is the half-life of I-131?
8 days
What is the half-life of Cs-137?
30 years
How is the effective dose calculated?
Radiation energy dose x Weighting factor
What are the weighting factors for gamma, beta, alpha, protons and neutrons?
Gamma: 1
Beta: 1
Alpha: 20
Protons: 2
Neutrons: 2 to 22
How is the total effective dose calculated?
Sum effective doses over all organs in the body (applying weighting factor for susceptibility)
How many Sieverts are fatal?
10 Sv
What is the effect of ~1 Sv?
Increase in long-term risk of fatal cancer
What is the % increase of cancer per Sievert?
5%
What two mitigating action are possible following an accident?
Population sheltering
Population evacuation
What is the criteria for sheltering and evacuation?
Sheltering > 10 mSv
Evacuation > 50 mSv
What is Wigner energy?
A build up of potential energy due to neutrons bombarding graphite.