Radiations
(MeV)
,
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,
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Indoor radon is believed by many to be a serious radiological protection problem. The questions below address various aspects of radon quantities, units, and measurements.
| Nuclide |
Principal Radiations |
Energies
(MeV) | Half-life |
| 222Rn |
| 5.5 | 3.82 day |
| 218Po |
| 6.0 | 3.10 min |
| 214P | , |
1.0 max ()
| 27 min |
| 214Bi | ,
|
3.3 max ()
| 19.9 min |
| 214Po |
| 7.7 | 164 µs |
| 210Pb | | 0.061 max | 22.3 yrs |
| 5 | A. | Define the working level (WL). | |
| 20 | B. | If an atmosphere contains 600 Bq/m3 of 218Po, what is the working-level concentration due to the 218Po? Show all work. | |
| 20 | C. | A person is exposed in his home to an average concentration of 0.02 WL for 14 hours per day for 30 weeks. What is his cumulative exposure in working-level months during this time? Show all work. | |
| D. | In various models, the dose delivered by radon/radon progeny to the lung depends on properties of both the inhaled aerosol and the physiology of the respiratory tract. | ||
| 8 | 1. | List 2 important Rn/Rn progeny aerosol properties. | |
| 12 | 2. | List 3 important physiological characteristics of the respiratory tract. | |
| 5 | E. | The best estimate listed below for lung dose from
exposure to radon progeny is:
| |
| F. | Radon and radon progeny measurements can be categorized into three types: instantaneous (grab); integrated; and continuous. | ||
| 15 | 1. | Define each of the 3 types listed above. | |
| 15 | 2. | Give one example of a method or instrument that exemplifies each type of measurement (list the type along with the corresponding method or instrument). Do not use manufacturer and model number; rather, specify each instrument generically. | |
You work for the large business conglomerate International Industrial Innovations (I3). As part of their multi-disciplinary health and safety department, you are participating as a member of a team performing hazard assessments throughout the company. The team leader has asked you to look specifically at the non-ionizing radiation hazards present within several of the laboratories.
In the biomedical research wing, a UV light box has just been installed. It is used to view and photograph electrophoresis gels stained with ethidium bromide and operates at a peak wavelength of 300 nm. This laboratory also uses a biological safety cabinet (BSC) containing a bulb with a peak wavelength of 280 nm. Gel manipulation requires about 20 minutes each day. Work in the BSC requires about 30 minutes each day; the bulb in this cabinet is left on at all times.
h = 6.6262x10-34 J-sec
1 J = 6.24x1012 MeV
| Ultraviolet Radiation Exposure TLV and Spectral Weighting Function | |||
| Wavelength (nm) | TLV (mJ/cm2) | TLV (mJ/cm2) | Relative Spectral Effectiveness, S  |
| 250 260 270 280 290 300 310 |
70 46 30 34 47 100 2000 |
7.0 4.6 3.0 3.4 4.7 10 200 |
0.430 0.650 1.000 0.880 0.610 0.300 0.015 |
| A. | The manufacturer reports in its operating manual that the irradiance at 2 ft from the light box is 1 µW/cm2 and at 6 inches from the BSC the level is 0.6 µW/cm2. | ||||
| 15 | 1. | Assuming the entire irradiance is at the peak wavelengths given, is the TLV exceeded? | |||
| 5 | 2. | Is the assumption of irradiance at the peak wavelength accurate? Justify your answer. | |||
| 5 | 3. | Briefly describe a better means of assessing the exposure to an individual working with this equipment. | |||
| 10 | B. | What are the two biological tissues at risk from excessive UV light exposure? How would excessive exposure be manifest for each of these tissues, i.e., what symptom would be present in each case? Number your responses. Only the first 2 will be graded. | |||
| 10 | C. | List two steps you would recommend to lower the exposure to UV light in this lab. Number your responses. Only the first 2 will be graded. | |||
| D. | Another laboratory has acquired a surplus microwave transmitter that it intends to use for microwave health effect experiments. The device operates with the following parameters: | ||||
| Frequency: Peak power: Pulse width: Pulse rep rate: Antenna gain: | 10 GHz 2000 W 1 msec 200 pps 16 dB | ||||
| Maximum horn antenna dimension: 0.2 m | |||||
| 4 | 1. | List two precautions that could be followed to prevent harm to the technicians. Number your responses. Only the first 2 will be graded. | |||
| 10 | 2. | The device's horn antenna transmits into the room and the closest human access distance is 3 meters away. Assuming far-field conditions, calculate the maximum equivalent plane-wave free space power density at this distance in units of milliwatts per square centimeter. Show all work. | |||
| 6 | 3. | The staff are not permitted in the test room when the device is energized. However, on this day a lab worker ignores the warning sign on the door, enters the room, and remains inside for an estimated 2 minutes before leaving for the day. Measurements in the room indicate the lab worker was exposed to a free-space power density of 25 mW/cm2. No levels could be detected outside the room. Was the lab worker exposed in excess of the ACGIH or ANSI microwave recommendations? Show all work and justify your response by stating the appropriate exposure limit recommendations. | |||
| E. | The laboratory has purchased a microwave device used to cure a particular form of adhesive. The device operates at a frequency of 2400 MHz. Workers are concerned about possible health effects including cancer induction. | ||||
| 15 | 1. | Can the radiation emitted by this source cause ionization and subsequent damage to DNA? Justify your answer quantitatively. | |||
| 10 | 2. | What is the primary effect of this type of radiation on tissue? Describe why it causes this effect. | |||
| 10 | F. | The ALARA principle is generally applied to radiation exposure controls while most of the above hazards are limited by TLVs . What is the basis for the difference between these two concepts? | |||
You are a health physicist at a power reactor during a refueling outage.
| 60Co Information Gamma emissions:  1.17
MeV @ 99.9%1.33 MeV @ 100%
 Co-60 = 3.7 x 10-4
mSv/hr-MBq @ 1 m µCo-60 for lead = 0.679 cm-1 µCo-60 for H2O = 0.0707 cm-1 µCo-60 for air = 7.75 x 10-1 cm-5 | 137Cs Information Gamma emissions: 0.662
MeV @ 89.8%µen Cs-137 for H2O = 0.0327 cm-1 µ Cs-137 for H2O = 0.0894 cm-1 |
| Additional Information: 1 MeV = 1.6 x 10-6 erg Pb blanket specs: 31 cm x 62 cm x 2.5 cm, 10.4 kg  Pb
= 11.4 g/cm3 |
| R(mfp)* | Water | Air | Lead |
| 0.5 | 1.47 | 1.47 | 1.20 |
| 1 | 2.08 | 2.08 | 1.38 |
| 2 | 3.62 | 3.60 | 1.68 |
| 3 | 5.50 | 5.46 | 1.95 |
| 4 | 7.68 | 7.60 | 2.19 |
| 5 | 10.1 | 10.0 | 2.43 |
| 6 | 12.8 | 12.7 | 2.66 |
| 7 | 15.8 | 15.6 | 2.89 |
| 8 | 19.0 | 18.8 | 3.10 |
| 10 | 26.1 | 25.8 | 3.51 |
| 15 | 47.7 | 47.0 | 4.45 |
| 20 | 74.0 | 72.8 | 5.27 |
* mean free paths
| 20 | A. | The dose rate from a small bucket of activated metal bearings in the fuel pool is 3 rad/hr at one meter underwater. Assume all activity in the bucket is due to 60Co. Calculate the dose rate in the overhead crane cab 10 meters above the water surface directly above the bucket when the bucket is lifted above the water surface (i.e., the source-to-operator distance is 10 m). State any assumptions used in the calculation. Show all work. | |
| 30 | B. | The dose rate in air from a small sealed source containing 137Cs is 100 mGy/hr at 30 cm. Calculate the activity of the source in Bq for the shipping documents. Show all work. | |
| 25 | C. | The dose rate from a long, thin-walled, 2.5 cm diameter pipe is 900 mrad/hr at one meter. Calculate the activity per unit length in the pipe. Assume all activity in the pipe is 60Co which uniformly coats the pipe interior. State any assumptions used in the calculation. Show all work. | |
| 25 | D. | The dose equivalent rate at one meter from a small valve is 150 mrem/hr, due to 60Co. Calculate the minimum layers of lead-wool blankets (PVC covered lead-wool used for shielding) needed to reduce the area around the valve to below the regulatory high radiation criteria. State the criteria for a high radiation area and any assumptions used in the calculation. Show all work. | |
The following questions relate to a university radiochemistry facility. A cyclotron produces large activities of radioactive gases with short half lives (11C, 13N, 15O and 18F). These nuclides are transported via a carrier gas through plastic tubing into a laboratory hood. Radiochemical processing occurs in a shielded reaction vessel in the hood. An accident occurred when a ceiling tile dislodged and knocked loose the gas line, allowing 15O to be released at a constant rate into the laboratory room air.
Assume instant and complete mixing of 15O with room air.
Room ventilation occurs only through hood exhaust, and volume exhaust rate is 30
m3/min.
Room size is 6 m x 6 m x 3 m
15O release rate = 2.6 x 109 atoms/s
15O half life = 12.2 s
| 10 | A. | Will room ventilation or radioactive decay be the dominant removal mechanism? Justify your answer | |
| 30 | B. | What is the room activity concentration of 15O (in Bq/m3 ) after 4 minutes of release? Show all work. | |
| 20 | C. | Flow was terminated after 6 minutes and the technician left the room. She is concerned because she calculated the room's 15O concentration to be much greater than the DAC (4000 Bq/m3 for submersion) at the time she exited. Give two reasons why exceeding this DAC does not necessarily mean that an overexposure to 15O has occurred. Number your responses. Only the first 2 will be graded. | |
| 10 | D. | NRC licensed materials are also used in this laboratory and airborne radionuclide concentrations of these materials occasionally exceed the DAC inside the hood. The hood is posted with a sign bearing the radiation symbol and the words "CAUTION, AIRBORNE RADIOACTIVITY AREA". Is this posting necessary? Justify your answer. | |
| 10 | E. | What type of radiation do 11C, 13N, 15O and 18F emit? | |
| 10 | F. | Identify two health physics concerns which would result from the use of plastic transport lines for 11C, 13N, 15O and 18F. Number your responses. Only the first 2 will be graded. | |
| 10 | G. | Monitoring is being
considered for the laboratory hood exhaust stack. Monitoring needs to be able
to detect releases of these radionuclides (11C, 13N,
15O and 18F) and yet be rather insensitive to common
activities of most other radioactive materials used in university research (3H,
14C, 32P, and 125I). Which of the following
instrument and sampling combinations would be most appropriate?
| |
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