Obsidian/.archive/300s School/NUCE 2100 - Fundamentals of Nuclear Engineering/2024-09-10 Module 3.md

title	allDay	startTime	endTime	date	completed
NUCE 2100 Class 2	false	18:00	20:30	2024-09-10	null

Module 3.1 - Radiation Terminology and Units

[!note] Radiation Activity Units Activity is measured in disintegrations per unit time.

• Historical Unit: The Curie
  • 1 Curie = 3.7 x 10^10 disintegrations per second = 2.22 x 10^12 disintegrations per minute
• SI Unit: The Becquerel
  • 1 Bq = 1 disintegration per second

1. Ionization is what causes all observable effects of radiation.
   1. Breaks chemical bonds, disturbs chemical processes
2. The number of ionization events a single particle of radiation can cause is dependent on energy
   1. Number of ionization DENSITY is determined by the linear energy transfer, in units of energy per unit length
      1. Alpha SUPER high
      2. Beta mid
      3. Gamma low
   2. But different rays can only penetrate certain materials
      1. Ionization density is inversely proportional to penetration

[!note] Exposure: The \gamma and x ray radiation field incident on a body. Measured by the specific ionization produced by it in the neighboring air. Measured in photon flux. Amount of energy transferred from the photons ot a unit mass of air. Traditional unit for exposure is the roentgen (R) 1 R is the amount of radiation required to liberate positive or negative charges of one electrostatic unit of charge (esu = 3.33E-10 Coulomb) in 1 cm^3 of dry air at STP. 1 R = 1 esu/cm^3 where \rho = 1.293 kg/m^3 An old unit. First attempt and standardizing field of radiation measurement

[!note] Absorbed Dose Actual damage to matter depends on how much energy is absorbed. SI unit: rad ("Radiation Absorbed Dose"): 1 rad = 100 ergs/gm

[!attention] SI Units for Radiation Quantities • Decay rate: Becquerel (Bq): 1Bq = 1 disintegration/second (dps), whereas 1 Curie = 3.7 x 1010 dps • Deposited energy: Gray (Gy): 1 Gy = 100 rads = 1 joule/kg * • Biological radiation effect: Sievert (Sv): 1 Sv = 100 rem

• Recall 1 erg = 10-7 joule

Concentrations of ionizations within a single cell are more damaging then spread out ionization over many cells. Biological damage is proportional to absorbed dose, as well as LET for that type of radiaiton.

[!note] Relative Biological Effectiveness (RBE) Compares biological effects of different types of radiation.

\text{RBE} = \frac{\text{Dose of 250 keV X-rays producing an effect}}{\text{Dose of reference radiation for same effect}}

RBE is highly dependent on the type of radiation. The upper limit of the RBE for a specific type of radiation is called the quality factor. Multiplying the absorbed dose by the quality factor gives the effective or equivalent dose (QF x rad = rem)

Module 3.2 - Radiation Damage in Biological Systems

Ionizing radiation in the body can cause problems in multiple ways. One way is by creating highly reactive free radicals. Water for example breaks down into hydrogen peroxide. Which is really not good for life. Interactions happen pretty fast. 1 millionth of a second the toxic products are formed. Doseage - Chronic and acute. Acute is generally worse because the body can't repair itself. LD50/30: Dose of radiation expected to cause death to 50 percent of an exposed population within 30 days.

Module 3.3 - Radiation Protection Standards

Background radiation is normally pretty low. mSv range. Radon is the most potent natural cause. We have no idea what low dose radiation does. No observable effects below 25 rem per year

[!tip] Dose Reduction Principles

1. Time: Restrict Proximity
2. Distance: 1/r^2 loss
3. Shielding

Module 3.4 - Estimating Radiation Dose Rates

Good example problems on calculating dosage. Different particles have different dose calculations. Internal Exposure Charged particles can be ingested -- this can be a massive problem. High LET particles can wreak havoc on internal tissues if ingested, as opposed to being blocked by dead skin.

• Ingesting is referred to as radiation intake.
• Uptake is when the radionuclides cross the biological barrier. Once a radioactive atom is in the body, it'll keep being radioactive until it decays completely, or the body removes. Two things can be done - Prevention, and promotion of excretion.

Module 3.5 - Radiation Shielding

Three main techniques:

1. Absorb primary radiation
2. Turn primary radiation into secondary radiation that's easier to absorb
3. Absorb secondary radiation. Alpha and beta are super easy to absorb. Gamma and x ray, well not so much. Need an insane amount of shielding, and usually composite shielding at that. Tenth thickness Approximate amount of shielding of a specific material required to reduce a radiation dose by a factor of ten.

\frac{I}{I_0} = \left(\frac{1}{10}\right)^{\left[\frac{x} {x_{1/10}}\right]}

I is intensity, x is thickness.