During an annual survey of a general purpose X-ray machine, the data in the table below were collected for machine output in mR as a function of kVp and the accompanying mAs and SID settings.
Conditions and results of survey measurements:
| kVp | 55 | 65 | 75 | 85 | 95 | 105 | 115 | 125 |
| mR | 58 | 81 | 112 | 145 | 183 | 223 | 264 | 305 |
| Additional information: | |
| Anterior-posterior (AP) abdominal exam: table top exam with SID
of 40 inches Posterior-anterior (PA) chest exam: horizontal beam with SID of 72 inches. | |
| 15 | A. | For an AP abdominal exam on a standard patient, the technique settings are 75 kVp and 60 mAs. The standard patient abdominal thickness is assumed to be 10 inches. The screen-film speed is 250 and a 10:1 grid is used. What will the patient entrance skin exposure (ESE) be? | |
| 20 | B. | For a PA chest exam on the standard patient, technique settings of 115 kVp and 5 mAs are used. Assume the distance from the chest board surface to the cassette can is zero and the patient abdominal thickness is 10 inches. The screen-film speed is 250 and a 10:1 grid is used. What will the patient entrance skin exposure (ESE) be? | |
| 20 | C. | Recommend two procedural changes which could reduce the ESE for these procedures. State the effect each change would have on image quality. Number your responses. Only the first 2 will be graded. | |
| 10 | D. | A technologist stands about 1 meter from the patient during an AP abdominal exam and is not wearing a lead apron and is not behind a control room wall. What is the approximate exposure from scatter to the technologist from one exposure? Show how you derived this exposure value. | |
| 12 | E. | Provide three design features of the room containing the control panel that are required to minimize the technologist's dose during X-ray exposures. Number your responses. Only the first 3 will be graded. | |
| 8 | F. | An X-ray technologist performs only mammographic procedures in a large hospital X-ray department. In June, the technologist's monthly whole body film dosimeter read 80 mrem. Is this dose equivalent typical of the average monthly occupational dose one would expect of this radiation worker? Explain your answer. | |
| 15 | G. | Identify three design characteristics of a general purpose X-ray system and the associated image receptor system which are required to minimize patient dose. Number your responses. Only the first 3 will be graded. | |
An incident occurred when a 137Cs source was accidentally processed in a metal smelter. Subsequent investigation revealed that this incident resulted in a release of 137Cs from the smelter stack over an 8 hour period.
Maximum 137Cs deposition on soil at 135 degrees and 2 km: Ds = 14,000 pCi/m2
| Meteorological Conditions: | |
| Wind at 5 m/s from the NW Pasquill Stability Class C. | |
Nominal deposition velocity: Vd = 0.002 m/s
Effective stack
height: H = 40 m
Breathing rate: R = 0.8 m3/h
Gaussian Plume dispersion equation for particles:
where: (x,0,0) = | ground level downwind concentration in air (pCi/m3), | |
| Q = | release rate (pCi/s), | |
| u = | wind speed (m/s) |
Charts of 
y and
z attached
| 20 | A. | What is the inhalation intake to a person present at the given point of maximum 137Cs deposition (2 km, 135 degrees) during the 8 hours that the release occurs? Show all work. | |||
| 20 | B. | Assume that you calculated the 8-hour average air concentration at the soil sampling site to be 300 pCi/m3. On that basis, how much 137Cs was released from the stack? Show all work. | |||
| 10 | C. | What additional information would you request in order to confirm the release scenario and reduce the uncertainty in the release estimate? | |||
| 10 | D. | An analytical instrument is set up to count environmental samples taken as a result of this incident. List five tasks that should be routinely performed to assure the quality of the counting system. Number your responses. Only the first 5 will be graded. | |||
| E. | A 100-minute background is run on the system in part D. Five 1-minute counts are performed on a NIST traceable standard. The sample is then counted for 50 minutes. Show all work for each part below. | ||||
| Data: | Background Count: | 123 counts | (100 minutes) | ||
| Sample Count (gross): | 225 counts | (50 minutes) | |||
| NIST Standard activity: 89570 ± 789 dpm NIST Standard counts (gross): 9263, 9607, 9242, 9681, 9524 (1 minute each) | |||||
| 20 | 1. | What is the counter efficiency and the error associated with this efficiency? | |||
| 20 | 2. | What is the sample activity and its associated error? | |||
You are a health physicist at a 100 MeV particle accelerator. The 4He+2 beam and thick target combination produces two primary products in the following reactions with equal cross sections:
X (4He,n)A X(4He,2n)B
GIVEN:
The radioactive reaction products A and B have the following properties:
| A: t½ = 1 d |  A
= 0.5 R-m2(Ci-h)-1 |  A = 7.8 g/cm3 |
| B: t½ = 5 d | B= 1.0 R-m2(Ci-h)-1 |
B = 3.3 g/cm3 |
1 mA = 6.2x1012 electrons/sec
1 e- = 1.6x10-19
C
Cell Volume = 100 m3
Cell Ventilation Rate = 7 m3/sec
| A. | From an initially cold target the 100 MeV 4He+2 beam is applied and held at a steady state. What is the ratio of the exposure rate from the decay of A to the exposure rate from the decay of B at the following times? (Assume no attenuation between target and point of measurement.) Show all work. | ||
| 10 | 1. | After 1 day of operation. | |
| 10 | 2. | After 2 months of operation | |
| 10 | 3. | 2 days after shutdown, after operating for 2 months. | |
| 10 | B. | The 100 MeV 4He+2 beam from this accelerator is pulsed with a duty factor of 10-3. The peak electrical beam current intensity during the 1ms pulse is measured to be 1 mA. How many beam particles per second are available to interact with the target? Show all work. | |
| 30 | C. | Assume that the O3 concentration in the cell achieves a steady state value of 10 ppm. Calculate the delay time after beam shutdown for the O3 concentration to reach a safe level of 0.1 ppm. Assume that the mean life of O3 is 2000 sec. Show all work. | |
| D. | What is the most likely problem each of the following instruments could experience when operating in the vicinity of the beam interaction area with the beam described in part B? | ||
| 5 | 1. | A Geiger-Mueller instrument. | |
| 5 | 2. | A standard portable ion chamber instrument. | |
| 5 | E. | What half-life would you expect the neutron field in part A to die off with when the beam is turned off? Explain your answer | |
| 10 | F. | List 5 sources of industrial hazards associated with the operation of a facility such as this. Number your responses. Only the first 5 will be graded. | |
| 5 | G. | List 5 ionizing radiations that can be produced during the operation of this machine. Number your responses. Only the first 5 will be graded. | |
You have been tasked to investigate a urine bioassay sample that was collected upon termination of a worker. There were no radionuclides detected in his last routine urine sample. The worker had been assigned to process and prepare radioactive waste for shipment. Upon questioning, the worker acknowledged that a drum containing dry resin contaminated with 137Cs vented some of its contents due to gas buildup while he was in the process of tightening the lid and he remained in the area for 30 minutes after it vented. The event occurred approximately 20 days prior to collection of the termination bioassay. The worker was not wearing respiratory protection during the waste preparation.
The ventilation system in the waste preparation room delivers one room air change every 2 hours.
Reference Man breathing rate = 1.2 m3/h
Sample collection time = 24 hr
Sample volume = 1500 mL
Analyzed
portion of sample = 500 mL
137Cs activity in analyzed portion =
0.43 mCi
The following is an excerpt from the cesium table in NUREG/CR-4884:
CLASS D
AMAD
= 1 MICRON
HALFLIFE = 1.10E+04 DAYSCESIUM- 137
| FRACTION OF INITIAL INTAKE IN | ||
| TIME AFTER SINGLE INTAKE | __________________________________ | |
DAYS | 24-HOUR URINE |
ACCUMULATED URINE |
| 1.00E+00 2.00E+00 3.00E+00 4.00E+00 5.00E+00 6.00E+00 7.00E+00 8.00E+00 9.00E+00 1.00E+01 2.00E+01 3.00E+01 4.00E+01 |
1.35E-02 1.33E-02 1.10E-02 8.87E-03 7.16E-03 5.89E-03 4.97E-03 4.32E-03 3.85E-03 3.51E-03 2.59E-03 2.41E-03 2.26E-03 | 1.35E-02 2.68E-02 3.78E-02 4.67E-02 5.38E-02 5.97E-02 6.47E-02 6.90E-02 7.28E-02 7.63E-02 1.04E-01 1.29E-01 1.52E-01 |
| 20 | A. | What is the estimated intake for the worker, in µCi? Show all work. | |||
| 30 | B. | Assume the intake for the worker was 1.5 mCi. What is the estimated initial concentration of 137Cs in air to which the worker was exposed? Show all work. | |||
| Your facility also processes naturally occurring uranium. Your duties require conformance to regulatory requirements pertaining to worker safety, including protection of workers from airborne radioactive materials and personnel contamination. Answer the following questions: | |||||
| 10 | C. | Naturally occurring uranium consists of 234U, 235U, and 238U. By weight, the distribution is: | |||
| U-234 U-235 U-238 | 0.013 g/mole-total U 1.71 g/mole-total U 236.4 g/mole-total U | T1/2 = 2.5E5 y T1/2 = 7.0E8 y T1/2 = 4.5E9 y | |||
One µg of uranium typically has a total activity
of 0.66 pCi. Assuming equilibrium conditions, approximately what percentages of
the total activity can be attributed to 234U, 235U, and
238U, respectively?
| |||||
| 10 | D. | ANSI Z88.2, "Practices
for Respiratory Protection," gives recommendations for the use of supplied
breathing air. This manual references other standards and specifications from
other organizations such as the Compressed Gas Association. Choose the best
answer that agrees with the recommendations of ANSI Z88.2.
| |||
| 20 | E. | 10 CFR Part 20 provides
respiratory protection factors for standard types of approved respiratory
protection devices as listed in items 1 through 4 below. State the maximum
allowable protection factors for the given respiratory protection devices.
Assume that the airborne hazard is radioactive particulate material. Choose from (a) 10, (b) 50, (c) 1000, or (d) 10000.
| |||
| 10 | F. | Describe one type of hand-held instrument routinely used for the detection of uranium contamination on personnel as they leave contaminated areas. Your description should include the types of radiation detected, any special constraints, and advantages or disadvantages of the instrument. | |||
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