NSE 481 Midterm Review

You call it a MID term for a reason.

Where do heavy charged particles deposit most of their energy?

At the end of its path.

What is dosimetry?

An attempt to quantitatively relate specific radiation measurements to chemical/biological changes that could be produced.

What do secondary electrons do?

Produces additional ionizations and excitations, and all energies are expended.

What is exposure?

The quantity of photon radiation that produces 1 C/kg in air.

True/False: Exposure only applies to electromagnetic radiation; the charge and mass refer only to air.

True

What are the old units of exposure?

Roentgen (R)

What is the value of a roentgen?

The amount of photon radiation that produces 1 esu of charge in 1 cm³ of air at STP.

What is one way we can measure exposure?

Using a free air chamber.

How do free air chambers work?

Photons enter chamber and interact with fixed quantity of air, where the ions from are are collected by plates.

What is electronic equlibrium?

Where if equal number of electrons are coming in from the outside of the sensitive volume as they are going out. You do not gain or lose information.

Why aren’t free air chambers used more readily?

They are huge and they need a laboratory.

What is an alternative to an air chamber?

Air Wall Chamber.

How do Air Wall Chambers Work?

They are built as a capacitor, where you have a central anode, insulated from the rest of the chamber. When exposed to photons, electrons neutralize the charge and lower the potential between the anode and the wall.

What is the equation for specific energy imparted?

z = ε/m (energy imparted per mass (J/kg))

What is the absorbed dose equation?

D = (d\bar{ε})/(dm) (Mean energy imparted per mass) (j/kg (gray)) (10000 erg/g) (100 rad)

What is absorbed dose?

Measures energy absorbed per mass.

What is KERMA?

Sum of the initial Kinetic Energy Released per unit MAss of all charged particles produced by uncharged ionizing radiation (J/kg).

As you go in depth inside of a material, how do absorbed dose and KERMA relate?

As we reach equilibrium thickness, KERMA and absorbed dose trend in the same direction very closely to each other.

What is the region early in the depth of the material where the absorbed dose is approaching equilibrium?

Build up region.

What is Dose Equivalent?

The product of absorbed dose in tissue and the radiation weighting factor (H_T = SUM_R w_R D_T,R).

What is the Committed Dose Equivalent (H_T,50)?

The dose equivalent to organs or tissues of reference that will be received from an intake of radioactive material by an individual during the 50-year period following intake (Integrate dose equivalent over t to t+50 years).

What is the Effective Dose Equivalent (H_E)

The sum of the products of the dose equivalent to the organ or tissue and the weighting factors applicable to each of the organs or tissues irradiated (H_E = SUM_T w_T H_T).

What is the Tissue Weighting Factor (W_T)?

A measure to provide a common scale relative to stochastic risk (W_T = (risk for tissue T) / (Total Risk))

What is the Committed Effective Dose Equivalent (H_E,50)?

The sum of the producsts of the committed dose equivalent to the organ or tissue and the weighting factors applicable to each of the organs that are irradiated (H_E,50 = SUM_T w_T H_T,50)

What is the Total Effective Dose Equivalent (TEDE)?

The sum of the effective dose equivalent (for external exposures) and the committed effective dose equivalent (for internal exposures) (TEDE = H_E (external)+ H_E,50 (internal)).

What are the basic foundations of radiation protection introduced in ICRP 26/30?

Justification (Risk benefit), Optimization (ALARA), and Limitation (don’t exceed limits).

What is ALI?

Annual Limit on Intake

How is ALI calculated?

I_s = (0.05 Sv/year)/(Sum_T w_T H_50,T (p.i.u.a)) (WHOLE BODY)

I_N ≤ (0.5 Sv/year)/(H_50,T (p.i.u.a)) (ORGAN DOSE)

What is DAC?

Derived Air Concentration, the concentration of a radionuclide in air, which if breathed for one working year would result in one ALI by inhalation:

DAC (Bq /m³) = ALI/((2000 h/year)(1.2 m³/hour))

How can we relate ALI to DAC?

2000 DAC - hours (Bq/m³ hr) = ALI

How can we calculate total dose?

Dose = SEE * U_s
U_s = number of nuclear transformations (integrated activity)
SEE = physical properties (ICRP 38 and ICRP 23)

What is ALARA?

As Low As Reasonably Achievable.

It is an important safety principle for minimizing radiation dose.

What is the current economic considerations for ALARA?

5100/person-rem in 2015

What is the Cost per dose?

Value of a statistiacal life ($9 M) * 5.7E-4 per rem = $5100 per rem

What are the NCRP 116 ALARA Guidance?

Justificaion: The need to justify radiation dose (for benefit)
Optimization: Make sure benefits are maximized
Limitation: Make sure to apply dose limits.

List the Hierarchy of Controls (Top to Bottom, most effective to least effective).

Elimination, Substitution, Engineering Controls, Administration Controls, PPE.

What is an example of an Engineering Control?

Glove boxes, shields, etc.

What is an example of an Administration Control?

Training, and notificaiton

What are the 3 main postings and signs for radiation?

Radioactive materials (10 times 10 CFR 20 App. C), radiation area (5 - 100 mrem in 1 hr at 30 cm), and high radiation area (100 mrem - 500 rem in 1 hr at 30 cm).

Why do we care about records?

Regulatory requirement, good practice, provies ALARA feedback, and provides dose reconstruction.

What is substitution in the Hierarchy of Controls?

Replacing the hazard.

What is elimination in the Hierarchy of Controls?

Physically removing the hazard.

What is PPE in the Hierarchy of Controls?

Protect the workers with personal protection equipment.

True/False: Cells which do not divide will be reistant to radiaton damage.

True

List the acute radiation syndroms and when they first appear (in rads or rem)

Prodomal: +1000 rem
Hematopietic: 300 - 800 Rads
Gastrointestinal: +800 Rads
Central Nervous System: +5000 Rads

What can happen to irradiated cells?

Immediate death, DNA Damage, or no effect.

When are cells most sensitive to radiation damage?

Mitosis Stage

Definition: What are genetic effects?

Those which occur in the offspring of exposed persons.

Definition: what is Somatic Effects?

Those which occur in the person exposed.

for CEDE, what is the basic limits for exposure introduced in ICRP 26?

CEDE ≤ 0.05 Sv (5% sievert)

for CDE, what is the basic limits for exposure introduced in ICRP 26?

CDE ≤ 0.5 Sv (50% sievert)

What is considered a non-stochastic effect of radiation?

Cataracts at 0.15 Sv/yr

How were the limits on ICRP 26/30 made?

Made using the linear dose response relationship.

What does the Bragg-Gray Prinicple relate?

It relates ionization measurements in a gas to absorbed dose in some material.

What is the Bragg-Grey Cavity Theory?

It is a way to measure absorbed dose by measuring ionization and approximating dose.

Why is calorimetry so difficult?

To accurately measure it, you need grays of dosage, which leads to death.

What is one assumption we can make for the Bragg-Grey Cavity Theory?

Assume our cavity is really small, small enough that it does not disrupt the electron spectrum.

What dose does the risk for cancer become significant for adults?

>100 mSv

What dose does the risk for cancer become significant for children?

>10 mSv

Are there any genetic effects for radiation exposure?

No convincing links to exposure and heritable diseases have been found, and <0.2 Gy doses are unlikely to double the risk of untoward pregnencies.

Where did we get the most amount of data from for radiation exposure?

Hiroshima & Nagasaki, medical exposures, as well as Chernobyl, Mayak workers, Hanford, etc.

What are bystander effects?

Effects extends to unirradiated cells, increasing the target cell population.

What are genomic instabilities?

Puts all genes at a higher risk for mutagenesis and impacts carcinogenesis when mutations arise in certain critical genes.

What are adaptive respones?

Radiation priming dose protects cells from susequent radiation doses.

What are threshold and/or hormesis?

Anecdtotal evidence but usually in ecological studies with low power.