ABHP Part 2 Concepts

List three mechanisms by which tritium is produced in nuclear reactors.

a) Ternary fission of uranium

b) Neutron capture reactions with boron and lithium

c) Activation of deuterium in water

d) High-energy neutron capture reactions with structural materials

Select the incorrect statement(s) about protective action guide (PAG):

a) A PAG is the projected dose to an individual from a release of radioactive material at which a specific protective action to reduce or avoid that dose is recommended.

b) PAGs are guides that help officials select protection actions under emergency conditions.

c) PAGs do not establish an acceptable level of risk for non-emergency conditions.

d) PAGs do not represent the boundary between safe and unsafe conditions.

e) PAGs are meant to be applied as strict numeric criteria.

The correct answer is (e) – PAGs are NOT meant to be applied as a strict numeric criteria, but rather as guidelines to be considered in the context of incident-specific factors

What are the assumptions for using the Gaussian function for radioactive airborne release?

1) The source is a “continuous point source”.

2) Weather conditions do not vary over time or location.

3) The speed and the direction of the wind is considered to be constant.

4) The released material behaves as particulates.

5) The terrain is flat.

Based on the Protective Action Guidelines (PAGs) by Environmental Protection Agency, who, among the following, should receive KI based on a projected thyroid dose of 5 cGy? Explain.

a. 10 year old middle school student

b. Pregnant school teacher

c. 25 year old female volunteer teacher

d. 60 year old male teacher

e. One month infant

The following should receive KI:

a) 10 year old student

b) Pregnant school teacher

e) One month old infant

PAG for infants, children <10 years old, and pregnant/lactating women is >= 5 Gy

For adults: >= 10 cGy

For adults 40 years olf >= 500 cGy

List two properties of Cs-137 that makes it an important radionuclide of concern from a soil contamination perspective.

1) Long half-life of about 30 years.
2) Emits gamma radiation, which is penetrating and detectable.

3) Can accumulate in living organisms.

4) Highly soluble in water which makes it easy to bind and cycle through the food chains

Describe three ways cesium can move in the soil.

1) Leaching through soil layers due to water movement.

2) Root uptake by plants, entering the food chain.

3) Soil erosion and surface runoff transporting cesium to water bodies.

In addition to the extent and levels of contamination, what additional factors (list four) need to be considered for addressing the cleanup of contaminated soil?

1) Land use and future development plans.
2) Feasibility of remediation techniques

3) Regulatory Compliance

4) Cleanup cost comparisons of various methods

Name the interaction coefficient that each of the curves (A, B, C, D) represents. Be sure that you indicate the proper name for the interaction coefficient.

Curve A: Photoelectric effect mass attenuation coefficient

Curve B: Compton scatter mass attenuation coefficient

Curve C: Pair production mass attenuation coefficient

Curve D: Total mass attenuation coefficient

For curve A, explain why there is a sharp increase in the curve at about 2 keV.

At approximately 2 keV, there is a sharp increase in curve A due to the photoelectric effect becoming more dominant, as this energy range corresponds to the binding energy of inner-shell electrons in atoms. This results in a significantly higher probability of photon absorption and electron ejection, leading to increased attenuation.

For curve C, describe the process involved and explain why the curve does not exist below approximately 1.02 MeV.

Curve C represents pair production, this process cannot occur below approximately 1.02 MeV because that is the minimum energy required to create the mass of the electron-positron pair.

Explain why the two curves in Fig. 4.2 are very similar below 50 keV.

For lower energies, the total attenuation coefficient is almost identical to the photoelectric attenuation coefficient. Compton scattering contributes very little, and pair production is not possible below 1.02 MeV.

Explain why the two curves in Fig. 4.2 are different above 50 keV. Include a discussion of region in both curves.

Above 50 keV, the photons are no longer exclusively interacting with the matter via photoelectric effect. The total mass attenuation coefficient now includes the effects due to Compton scattering (dominant over 200 keV) and pair production (possible above 1.02 MeV; dominant above ~10 MeV).

List four symptoms that you would expect in a person exposed to a 2-Gy acute whole body dose without medical intervention.

Symptoms may include nausea, vomiting, fatigue, low white blood count, and hematopoietic syndrome.

Identify six factors that affect a tissue’s response to ionizing radiation.

Physical factors: 1) dose 2) dose-rate, 3) type of radiation

LET Biological factors: 4) age, 5) sex, 6) Circadian cycle during irradiation, 7) cell-cycle phase, 8) presence of oxygen, 9) mitotic rate of cells, 10) specialization of cell, etc.

Define Oxygen Enhancement Ratio (OER), and briefly explain what cause OER.

The OER is the ratio of dose without oxygen to the dose with oxygen needed to achieve the same effect.

OER describes how much more radiation is required without oxygen compared to with oxygen to achieve a certain biological effect, primarily due to oxygen's role in enhancing free radical formation and subsequent cellular damage.

OER for x-rays, gamma, and beta: 2.5-3

OER for alpha and neutrons: ~1

Explain why the dose equivalent calculated using air concentration and that calculated using urine bioassay may be different.

1) The measured room concentration may not be representative of the concentration of air breathed by the worker.

2) The air concentration measured by the flow-through ionization chambers may have been influenced by noble gas activity or residual gamma dose rates.

3) The assumption of all tritium in the form of HTO may be invalid.

4) The first void was not disregarded; and the urine sample may not reflect the equilibrium concentration.

5) The metabolism of the individual may not be the same as that of a Reference Man.

Identify two techniques that can be used for tritium air monitoring. Provide one advantage and one disadvantage of each technique.

1) Flow-through Ionization chambers
Advantage: Real-time measurement of tritium levels.
Disadvantage: Limited detection sensitivity at low concentrations.

2) Tritium bubbler:
Advantage: High sensitivity and ability to measure low levels.
Disadvantage: Not-real time

3) Use of desiccant media:

Advantage: Provides relatively accurate measurement

Disadvantage: Needs a lot of time for sample collection and not real-time

Assume an I-131 patient cannot be treated as an outpatient. State two restrictions that would allow you to release her from the hospital.

1) The Total Effective Dose Equivalent is not likely to exceed 500 mrem to any other individual

2) Written instructions shall be provided if the Total Effective Dose Equivalent is likely to exceed 100 mrem

What additional instructions for a released/outpatient I-131, if any, would you provide if the patient had:

1. A 15 month old child at home?

2. A 15 year old child at home?

1) Additional instruction would include guidance on the interruption or discontinuation of breast-feeding and information on the potential consequences of failure to follow the guidance.

2) No special instructions are required other than those mentioned above.

Calculations show an I-131 patient can be released as an outpatient. What three general requirements could you apply to minimize dose to members of her family?

1) Minimize time in proximity to family members.

2) Maintain distance from other person, including separate sleeping arrangements.

3) Take precautions to reduce spread of contamination, to include but not limited to, exclusive-use bathroom, sharing same bedding, towels, eating utensils, etc.

Based on the fetal dose estimate of 21.7 rad that you calculated, what are the risks to the unborn child?

NCRP Report 174, Preconception and Prenatal Radiation Exposure: Health Effects and Protective Guidance, provides detailed examination of the risks to the fetus from ionization radiation exposures.

1. No lethal effects are expected for 6-13 weeks post conception. LD50 > 2 Gy (200 rad)

2. Growth retardation is possible at 0.25-0.5 Gy (25-50 rad) for 6-13 weeks post conception but such effects are a low probability.

List four possible actions that your facility could have taken to reduce or eliminate exposure to x-rays and flouroscopy to the fetus had you known that an ER patient was pregnant.

1) Consider alternatives to x-ray imaging, such as ultrasound or MRI.

2) Use the lowest effective radiation dose if x-ray is necessary.

3) Minimize use of fluoroscopy and utilize lower intensity or pulsed approach to minimize exposure.

4) Limit the area exposed to radiation by employing shielding techniques.

4) Collimate the beam to reduce size of the effective area

As the RSO for the facility, list three other actions or notifications you should recommend if an emergency room patient has x-rays and fluoroscopy procedures done.

1) Notify the patient's physician about the potential fetal exposure risks.

2) Report the exposure incident to the appropriate regulatory body or personnel within the facility.

2) Document the radiation dose received and any pertinent information.

3) Train hospital personnel on the importance of questions about pregnancy or testing for non-emergency situations prior to diagnostic exposure.

Explain why the ratio of uterus dose to ESE increases as the HVL increases (as shown in NCRP 54 Table 4).

As the half-value layer (HVL) increases, less radiation is attenuated by the patient, leading to a higher dose of radiation being absorbed by the uterus relative to the entrance skin exposure (ESE), which results in an increased ratio.

List four factors that may influence plant uptake of uranium.

1) Soil chemistry and composition.

2) Plant species and their root structure.

3) Chemical form of Uranium

4) Environmental conditions

5) Irrigation methods

List five possible exposure pathways from an Uranium mill site

1) Inhalation and ingestion of airborne dust.

2) Ingestion of contaminated ground water.

3) Ingestion of contaminated plants grown in contaminated soil.

4) Consumption of milk and meat from animals that inhale and ingest dust

5) Consumption of milk and meat from animals that feed on contaminated vegetation or plants grown in contaminated soil.

Your organization is offering bioassay monitoring to residents concerned about their internal exposure from a uranium mill site. List two methods of determining the concentration of uranium in the body, and an advantage and disadvantage of each method.

1) Urine bioassay: A non-invasive method to measure uranium concentration through urine samples.

Advantage: Easy to collect and analyze.

Disadvantage: May not reflect long-term body burden due to excretion variability.

2) Fecal Analysis: A method to measure uranium concentration by analyzing fecal matter.
Advantage: Can provide information on recent exposure levels.
Disadvantage: Requires careful collection and may be less convenient for individuals.

3) In vivo monitoring: A method that involves using direct measurement techniques, such as gamma spectroscopy, to assess uranium concentration in the body.
Advantage: Has higher MDA compared to urine and fecal.
Disadvantage: Requires the individual to be present for on-site counting

Define DAC

DAC stands for Derived Air Concentration, which is the maximum allowable concentration of airborne radioactive material in air for reference man, doing light work, for 2000 hours which results in an intake of one Annual Limit of Intake.

List five conditions that could affect the accuracy of ion chamber measurements

1. Temperature

2. Pressure

3. Humidity

4. Electromagnetic Interference

5. Uniformity of radiation field

6. Degradation of ion chamber electronic components

Two samples were spiked with 50 dpm of 90Sr and processed by a technician undergoing training. Initial count results from both samples were higher than expected. Subsequent recount results were also higher than expected. Because of their unusual behavior, the samples were recounted repeatedly for a period extending over several 90Y half-lives, with the results on the following plots. In each case, provide the most likely explanation for the observed results.

Sample A: Incomplete separation of Y-90 is causing elevated initial counts of Sr-90 that would normalize when equilibrium is established.

Sample B: Incomplete separation of Y-90 plus an additional positive bias of excess Sr-90 error or underestimated counting efficiency due to excess precipitate mass.

You are the Senior Health Physicist at a commercial nuclear power plant. Plant management is considering a new demineralizer system and you are tasked with performing the radiological design review and ALARA evaluation.

Name four documents (i.e. Federal Regulations, facility documents, etc.) that will be needed to perform this evaluation.

1. Radiation Work Permits (RWPs)

2. Pertaining regulations such as 10 CFR 20 and 10 CFR 50

3. Technical specifications, and system design descriptions

4. ALARA Program, and previous ALARA evaluations

List and describe four items that you should consider when evaluating the demineralizer system at a commercial nuclear power plant from an ALARA perspective.

1. The contamination levels and dose rates on the demineralizer system

2. Estimated work load (person-hours)

3. Shielding and PPEs

4. Contamination monitors

List four methods you use to minimize exposure to plant personnel during maintenance of the demineralizer at a commercial nuclear power plant.

1. Use of remote handling techniques to reduce direct exposure.

2. Scheduling maintenance during low operation periods to limit personnel exposure.

3. Implementation of time restrictions on tasks to minimize duration of exposure.

4. Utilization of appropriate shielding to protect personnel during maintenance activities.

5. Use mockups to train individuals to become more proficient to reduce time spent near the source.

What do the letters AMAD stand for?

Activity Median Aerodynamic Diameter

Briefly describe the dosimetric significance of AMAD.

AMAD refers to the particle size distribution of aerosolized radioactive materials. It is significant in dosimetry as it helps predict the deposition and absorption of particles in the respiratory system, influencing radiation dose estimates.

What are the Emergency Classifications established by the US NRC for grouping off-normal events or conditions at nuclear power plants? List them in ascending order of severity.

1. Unusual Event 2. Alert 3. Site Area Emergency 4. General Emergency

What type of sampling medium(s) would be needed to determine radioiodine concentration independently of noble gas concentration?

Appropriate inorganic absorbed medium is needed to reduce adsorption of noble gases relative to radioiodine. Media such as silver zeolite and silver alumina have higher rejection efficiency for noble gases and higher retention efficiency for radioiodines. Media such as activated charcoal, while efficient at collecting radioiodine, also collect noble gases, so are not appropriate.

What is the best method to determine the dose to workers that will be entering the noble gas plume?

The best method to determine the dose to workers entering the noble gas plume is to use real-time dose rate measurements and personal dosimetry (OSL or TLD). These methods help assess both the exposure levels and ensure compliance with radiation safety regulations.

The release of I-131 is important in reactor accident emergency planning.

What is the critical pathway for iodine exposure, who is most at risk and why?

The critical exposure pathway for I-131 is ingestion through the food chain, particularly contaminated milk. Infants and young children are most at risk because they consume more milk relative to body weight, have smaller thyroid glands resulting in higher dose per unit activity, and have increased thyroid radiosensitivity.

How can KI be utilized and how does it help?

Potassium iodide (KI) is administered orally to saturate the thyroid with stable iodine, thereby blocking uptake of radioactive iodine such as I-131. This reduces thyroid dose and subsequent cancer risk. It is most effective when taken prior to or shortly after exposure and provides protection only to the thyroid.

According to the Protective Action Guidelines by the Environmental Protection Agency, what groups of individuals would be prescribed KI at a postulated thyroid dose of 5 rem?

According to the PAG, the intervention threshold of postulated thyroid dose of 5 rem applies to 1) pregnant and lactating women, and 2) infants, children and adolescent (birth – 18 years old)

According to the Protective Action Guidelines by the Environmental Protection Agency, what groups of individuals would be prescribed KI at a postulated thyroid dose of 5 rem?

NCRP 165 does not recommend a dose limit for emergency responders performing time-sensitive, mission critical activities such as lifesaving. Instead, the NCRP recommends the establishment of decision points by the incident commander based upon operational awareness and mission priorities. A decision point would be were the dose to an emergency responder reaches 50 rad (0.5 Gy). At 0.5 Gy, a decision whether or not to withdraw the emergency responder from the hot zone is made. The decision point of 50 rad (0.5 Gy) cumulative absorbed dose is a decision dose, not a dose limit.

The facility owner is contemplating a design goal of 0.1 mrem/hour for the office area across the hallway. Provide your justification as to why that is or is not appropriate.

The 0.1 mrem/hour design goal is not appropriate for a permanently occupied space for individuals who are not radiologically monitored. The average worker works approximately 2,000 hours per year and with a design goal of 0.1 mrem/hour would result in 200 mrem per year which is greater than the 10 CFR 20.1301 dose limits for individual members of the public of 0.1 rem in any one year.

The population groups that contributed to the development of risk models from external, whole body radiation to humans:

1. Life span survivor study (Atomic Bomb Survivors)

2. Medical worker studies after exposure to x-rays (early studies, typically pre-1940)

Define Relative Risk

Relative Risk (RR) is the ratio of the probability of an event occurring in the exposed group to that occurring in non-exposed group.

Define Excess Risk

Excess Relative Risk (ERR) is the portion of the RR accounted for by the particular risk factor under study, and is given as RR-1.

Define Attributable Risk

Attributable Risk (AR) is the risk of a specified health effect assumed to result from a specified exposure.