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| a highly reactive unpaired electron |
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| Gastrointestinal tract syndrome |
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| blood leaking into the gastro tract & bacteria leaking out |
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| time to 1/2 the orginal activity using biological & physical |
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| organizes the cell and processes |
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| exposure over a long period of time (usually low dose) |
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| exposure over a short period (usually high dose) |
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| physical half-life, time to 1/2 of value |
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| charge deposited in air by photons (<3MeV) |
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| purple splotches, bust blood vessles |
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| 100 ergs of deposited energy per unit mass |
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| positive effect of radiation |
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| is a decrease in the number of circulating white blood cells (leukocytes) in the blood. |
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| LNT asserts that there is no threshold of exposure below which the response ceases to be linear |
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| positive effects of radiation |
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| the amount of radiation which would kill 50% of the population in 30 days with out treatment |
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cell cancer
1. life shortening
2. leukemia
3. other cancers |
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Total Effective Dose Equivalent
Deep Dose Equivalent
Committed effective dose equivalent |
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| Why is radiosensitivity indicator LD50/30, changed to LD 50/60 when discussing Human radiation effects. |
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Definition
| The last deaths in animals are observed by 30 days after radiation, however in humans the last deaths within the group occur within 60 days |
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Term
| Chromosome abberation dosimetry |
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Definition
| the dermination of an acute radiation dose received by a person by measuring rings, dicentrics, and deletions.(abnormal structures) |
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| name the four major components that make up human blood |
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Definition
| erythrocytes, lymphocytes, granulocytes, platlets |
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Definition
| the hypothesis that low radiation is beneficial to life while high doses are harmful |
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| As low as reasonably achievable |
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Term
| why is an ion chamber referred to as a counter? |
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Definition
| an ion chamber can not distinguish individual events, therefore it can not "count" just gather continuous readings |
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Term
| What causes the region of continuous discharge in the gas-filled detector characteristic curve? Why is the counter unusable for radiation detection in this region? |
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Definition
| The counter continues producing output despite the presence, or lack of, a radiation field at the detector. In this region the insulator becomes a conductor. |
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Term
| Why are some pocket dosimeters lined with plastic?...Boron? |
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Definition
Plastic makes it sensitive to fast neutrons.
Boron makes it sensitive to thermal neutrons. |
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Term
| Why does a proportional counter usually have a very thin wire for the collecting electrode rather than the rod characteristic of ion chambers? |
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Definition
| the wire increases the gas multiplication necessary for counter operation. |
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Term
| What is the instrument of choice for counting a mixed alpha-beta smear sample? Describe how it is possible to electrically distinguish between alpha-produced pulses and beta-produced pulses in this counter |
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Definition
Usually the gas flow proportional counter
by passing the electrical counter pulses through a pulse height discriminator, the difference in energy can be seen |
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Term
| what is a multichannel pulse height analyzer instrument used for in radiation protection technology? |
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Definition
| MPHA's are used for environmental sampling for unknown isotopes. |
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Term
| How can a proportional counter be made sensitive to thermal neutrons? to fast neutrons? |
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Definition
| Boron-10 atoms help detect thermals, while fast neutrons are detected when the counter is surrounded by a neutron moderator. |
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Term
| How is the pulse formation in a GM counter different from that in a proportional counter? How is the pulse terminated in the GM counter? |
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Definition
| The GM is characterised by a succession of avalanches, the proportional only has a single avalanche. The pulse is terminated by using a quinching gas. |
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Term
| Describe how the problem of "saturation" cn OCC UR IN A GEIGER TUBE. WHAT PRACTICAL COSEQUENCES might this pose for a radiation protection technologist? |
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Definition
| saturation is the production of miniature pulses below the reading threshold. In a field with many times the range of the instrument, the instrument might saturate and read nothing |
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Term
| Describe the various components used to fabricate a complete NaI scintillation counter and the operating principle of each. |
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Definition
| Crystal, photomultiplier tube and a housing for the crystal. the crystal converts a photon to an electron, the photomultiplier creates exponentially more electrons. |
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Term
| Why is it important to prevent a NaI crystal from contacting room air? |
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Definition
| the crystal will absorb moisture from room air and dissolve |
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Term
| Why must a scintillation counter be enclosed in a light-tight housing? |
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Definition
| the gamma rays produce no where near as much light as the environment. It is needed for detection purposes. |
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Term
| Name the two types of semiconductor counters discussed and give a practical application for each. |
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Definition
Surface Barrier diode detector - usedd to identify alpha emmetters
Germanium Counter - used to identify gamma emitting radio nuclides. |
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Term
| Name an advantage and a disadvantage of a germanium counter compared to a NaI scintillation counter |
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Definition
GM's have a higher energy resolution but have to be used at liquid nitrogen temperatures.
NaI are more efficient and can be operated at room temperatures. |
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Term
| What is the advantage of the HPGe detector compared to the lithium-drifted variety |
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Definition
| HPGe's do not need to be stored at liquid nitrogen temperatures. only while collecting data. |
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Term
| What is meant by "flat energy response" as applied to a personnel dosimeter? |
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Definition
| Flat energy response is the shape of the graph of the per-unit dose equivalent against the energy of incident radiation. It makes it so that the dosimeter is accurate. |
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Term
| Describe how fast and thermal neutrons can be detected by a film badge. What is meant by fading? |
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Definition
Fast neutrons knock protons off hydrogen atoms which exposes several grains in a row.
Thermal neutrons are detected by comparing a field region with cadmium to a constant region.
Fading refers to when the track shifts its position so you can no longer tell it from the other exposed grains |
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Term
| What use is a glow curve for a phosphor? In what sense are the phosphor fading characteristics dependent on the glow curve? |
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Definition
| The glow curve shows the location of the T.L traps. The glow curve predicts the fading of a phosphor. |
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Term
| What is the chief reason for the better energy response of common TLD phosphors than film? |
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Definition
| The atomic number of the phosphors is much closer to air than film is |
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Term
| HOw is the reusability of a TLD chip both an advantage and a disadvantage? |
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Definition
| this lowers the cost of the system as a whole. However, it would only be a temporary reading. |
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Term
| Define the parameters for deep dose equivalent and shallow dose equivalent. Describe how a personnel badge designed to read each of them. |
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Definition
Shallow dose - tissue depth of .007 cm
Deep dose equivalent - depth of 1 cm
both use filters to simulate overlying tissue |
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Term
| What are some conditions under which a criticality accident would likely occur? what changes could be made in these conditions to reduce the chance of such an accident |
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Definition
It occurs when there is an uncontrolled release of radiation cause by a nuclear fission.
You could preven this by regulation the size of uranium pieces. |
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Term
| How does a criticality dosimeter allow the neutron energy spectrum to be estimated? what are some practical problems in obtaining this information? |
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Definition
| They use different elements that respond to different neutron energies. However, some materials are not available for the intermediate range. |
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Term
| Name some of the usual metal elements likely to be found inside a gamma neutron film badge holder. |
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Definition
| aluminum, lead, copper, indium, gold, and cadmium |
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Term
| Briefly discuss the principle of operation of an albedo dosimeter. |
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Definition
| the albedo is a cadmium shielded dosimeter and detects thermal neutrons leaving the body of the wearer |
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Term
| Name two different types of procedures that are used to measure the amount of radioactivity internally deposited in a person. What are the advantages and limitations. |
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Definition
Bioassay - measure alpha, beta and gamma but only part of the burden
Invivo - measures the entire burden but only works on photons. |
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Term
| What kinds of body tissues or products are most often used for analysis |
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Definition
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Term
Define "bone seekers" and name some.
Why are they placed in a seperate category for internal dosimetry purposes? |
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Definition
radionuclides w/ high probability of attaching to bones
Pu-239, Ca-45
the are different because we have more data and experience with their long clearance time. |
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Term
| What is a reference adult? |
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Definition
| Reference adults are determined in ICRP Publication 23. |
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