Ionizing Radiation Protection Flashcards
Definition of Isotones
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Same number of neutrons, Different number of Protons (e.g. 3H, 4He)
Low LET for electrons set in motion by Co-60 vs. High LET alpha
Co-60 emits a 2 ~1.25 MeV gammas. Low LET for electrons set in motion ~ 0.25 Kev/micrometer. High LET alpha is 1000x that. So a 2 MeV alpha will set electrons in motion at 250 KeV/micrometer
Absorption by a medium of kinetic energy from a high energy charged particle through excitation and ionization
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Definition of “Dose”
Define ‘Secular Equilibrium’
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When the half life of the parent is very much greater than that of the daughter half life. After ~7 half lives, the activity of the daughter = activity of the parent
Radioactive decay is affected only by
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Conditions within the nucleus
Approximate diameter of an atomic nucleus
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1E-12 cm
Approximate diameter of an atom
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1E-8 cm
Most predominate constituent of primary cosmic radiation
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Protons
Cosmic radiation accounts for approximately ____ mrem per year at sea level?
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- This number roughly doubles for every 2000 meters increase in altitiude. e.g. Denver ~50 mrem
Numerical value of Quality Factor (Q) is based partly on:
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Biological effect and judgment. Q is not experimentally determined.
KERMA is the sum of the initial kinetic energy of all charged particles liberated by:
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Uncharged ionizing radiation
The Stopping Power for electrons _____ as the atomic number of the absorber _____
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decreases, increases. Stopping Power ~ hinderance
Bremmsstrahlung predominantly occurs at energies greater than:
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1 MeV
Average energy of a positron emitted during positron decay:
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2/5 or 0.4 of its max
For an alpha particle to penetrate the dead layer of skin, it must have an energy of at least:
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7.5 MeV
Define Internal Conversion as it related to an atom’s decay
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The nucleus transfers its energy to an orbital electron, which is then ejected
Name and list the multiple factor for the 3 naturally occurring decay series and the 1 artificially produced series
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Actinium (4n+3), Uranium (4n+2), Neptunium (4n+1) artificially produced, and Thorium (4n). Think A.U.N.T.
SI unit for energy
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Joule. English system is Erg
Isobar
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Same Atomic Mass Number e.g. 14C, 14N
Isotope
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Same number of Protons e.g. 32P, 33P
Isomer
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Same Mass and Atomic Number, different Meta-Stable states e.g. 99mTc and 99Tc
Definition of a Hot Particle
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Discrete radioactive fragment that is insoluble in water and is less than 1mm.
Minimum mass of material which sustains a nuclear chain reaction
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Critical Mass. Made up of fissile isotope, isotope enrichment, geometry, presence and types of moderator and reflector material.
Primary isotopes of natural uranium whose natural abundances are 99.23729, 0.7206, and 0.0057
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U-238, U-235, and U-234
Radioactive atoms that have a neutron to proton ratio that is too large will decay by
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Beta Minus Decay
Define elastic scattering in relation to photons
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No energy change of scattered photon. Photon may change direction, but not energy
Name the initial and final nuclide in the Thorium Decay series
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Th-232, Pb-208
Annual dose equivalent to the U.S. population from all man-made sources of radiation is given by the NCRP as:
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300 mrem/year. Total average annual exposure is 620 mrem:
What is the main factor determining the amount of energy that can be transferred to the electron during Compton scattering?
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Scattering angle. Scattering angle of incident photon is inversely proportional to the energy of the scattered photon
What is a neutrino?
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Massless particle- product of beta decay
The antineutrino is associated with what process?
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Beta Minus decay
In the energy range from 0.1 to 5 MeV in either air or water, the most predominant photon interaction is
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Compton Scattering
Process in which the parent radionuclide has a shorter half life than that of the daughter, but same order of magnitude:
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No equilibrium
Following electron capture, what processes may occur?
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Characteristic X-rays are emitted, Auger electrons emitted, Z deceases by 1
Average energy required to produce an ion pair in air by X or gamma radiation:
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33.7 eV - Also called the ‘W” value of air
All natural radioactive decay series have this in common (not neptunium)
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All end in a stable isotope of lead
A positron and an electron interact to produce 2 photons each with an energy of 0.511 MeV. What is this called?
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Annihilation reaction
What does an alpha emission consist of
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2 neutrons, 2 protons - essentially an energetic helium atom without the electrons
Radium-226 decays by alpha to Radium-
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- Alphas have an atomic mass of 4 (2 protons, 2 neutrons)
When ionizing energy ejects an electron from a water molecule, it makes an H2O+ ion. When an electron is added to a water molecule it makes H2O-. H2O- decomposes into
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Free radicals
This radionuclide in soil is a major contributor to genetically significant radiation exposure
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K-40
Most abundant radionuclide in the earth’s crust?
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Thorium 232. Followed by Nat U, then K-40
Secondary radiation following photoelectric interaction can include:
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Characteristic X-rays, Auger electrons
Controlling radon exposures in a building means that _______ of the building is to be avoided
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depressurization (negative pressure)
What would be a good approximation of the quality factor of the neutrino?
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- Neutrinos have essentially zero probability of interaction
The range of a 2 MeV alpha particle in air is about
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1 cm. Range = 0.5cm/MeV below 2.5 MeV
Range = 0.75 cm/MeV above 2.5 MeV
One of the processes that increases the proton/neutron ratio in a nucleus involves the conversion of a proton to a neutron. This process is called:
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Electron Capture
Eventually, charged particles give up their energy to the surrounding medium. In the case of the alpha particle, it becomes (a):
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Helium atom
When calculating for structural shielding, the occupancy factor can have a value of:
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1, 1/4, 1/16, 1/40. Full occupancy, T=1 consists of control space, living quarters, waiting rooms, and rest rooms for occupational workers. Partial occupancy, T=1/4, used for utility rooms, restrooms for non-occupational workers. Occasional occupancy T=1/16, stairways, closets. No occupancy T=1/40, parking lots
What is the mathmatical relationship between the decay constant and the half live?
Rev. 1
Inverse
The equivalent energy for the rest mass of a proton is about
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938 MeV. The ratio of the mass of the proton to the electron is 1837. The ratio of the energies must be the same (E=mc^2) so: 0.511 MeV*1837 = 938
Betas lose most of their energy at:
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2/3 max range
Underlying principal for measurement of radiation absorbed dose is:
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The Bragg-Gray principal. This principle relates absorbed dose in a medium to a measurement of a known amount of ionization in a small volume of a gas filled cavity (usually air).
Medical use of byproduct material falls under which 10 CFR?
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35
10CFR19
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Notices, Instructions, Reports to Workers
10CFR20
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Standards for protection against radiation
10CFR30
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Licensing of byproduct material
A positron has the same mass as a
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Beta particle
What happens to the incident photon in the compton process?
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Partial absorption of the photon energy. Photon and electron are scattered (share energy - binding energy of the electron)
Fraction of atoms which undergo decay per unit time is the
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Decay constant
Most common ionizing radiation hazard associated with anti-static devices
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Alpha particles
What is the “photoelectric effect” in regard to ionizing radiation?
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Total absorption of incident photon energy. Low energy photons collide with a bound orbital electron and eject it from the atom.
What happens to the incident photon in the pair production process?
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Conversion of a photon into mass. Occurs in photons that have greater than or equal to 1.022 MeV energy. energy is converted into a pair of electron masses (electron & positron). The positron annihilates with a free electron to produce two 0.511 MeV photons
Non-excreta licensed material can be put into the sewage system at a rate of ____ Ci/year/institution
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- An additional 1 curie of C-14 and 5 curies of H-3 is also allowed in the sewer per year.
Definition of a nuclide
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Nucleus with specific Z and A numbers. Specifies exact number of photons, neutron, energy state. Does not have to be radioactive.
When a charged particle strikes an electron knocking it out of its orbital, creating an ion pair, it is called
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Direct ionization
How does the NRC regulate materials produced in a linear accelerator? - Possibly Wrong Don’t Use -Sam
They don’t. It is regulated on a state level.
How does the NRC regulate X-ray machines
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They don’t. it is regulated on a state level.
Production of a positron is the result of the conversion of a _____ to a _____
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Proton, Electron
KERMA is expressed in what units?
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Joules/kg
Name the initial and final nuclides in the neptunium
Rev. 1 series
Np-237; Bi-209
How does a thermoluminescent dosimeter work?
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A crystal with an added impurity traps electrons during radiation exposure
A radionuclide that is constantly being released by cosmogenic action is
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C-14
Which effect predominates in the 100 keV - 10 MeV region for photons?
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Compton
How often should sealed sources be leak tested?
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Semi-annually
Sealed sources are exempt from leak testing if their half life is less than
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30 days
Sealed sources are exempt from leak testing if the byproduct material is in the form of:
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A gas
Sealed sources are exempt from leak testing if source contains _____ or less beta or gamma emitting material or _____ or less of alpha emitting material
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100 uCi, 10 uCi
Sealed sources are exempt from leak testing if it is a seed of Iridium-192 encased in
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Nylon Ribbon
Sealed sources are exempt from leak testing if they are in storage and not being used. T/F
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True dat
Name the initial and final nuclides in the actinium series
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U-235; Pb-207
Gamma rays get their energy from
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Nuclear disintegration
What is the Roentgen a measurement of?
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The amount of X or Gamma radiation that produces ionization in 1 esu of charge in 1 cc of dry air at STP
Which particle is considered to be radioactive by itself?
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Neutron. When removed from the nucleus of its atom, the neutron decays with a half life of about 10.4 minutes into a beta particle and a proton.
Sr-90 is a _____ emitter
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Beta. Sr-90 is a bone seeker. 546 keV max energy
Gamma radiation produces ionization by
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Photoelectric effect, Compton effect, and Pair Production
What is the rest energy equivalent of the electron?
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0.511 MeV
Radioactive decay is first order decay. it is also _____ of temperature
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Independent
The buildup factor, B, in radiation shielding is caused by
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Bad geometry aka broad beam conditions
What is Isomeric decay?
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Atomic number and Atomic Mass Number of the daughter is the same as that of the parent. e.g. Gamma ray emission, Internal conversion.
Regulations regarding excreta containing medically administered (in humans) radioactive materials:
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Exempt! Can be disposed of in ordinary sewage systems.
A buildup factor, B, equal to one in a radiation shielding equation occurs under
Good geometry aka narrow beam conditions
Radiation in the visible spectrum that results from the slowing down of charged particles in a medium
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Cerenkov Radiation. Occurs when a charged particles moves faster in a medium than the phase velocity of light in the same medium.
What is a use of a chelating agent?
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Chemically bind materials. Used to bind radioactive materials.
What effect predominates in the >10 MeV gamma radiation region?
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Pair production. Can happen with any gamma above 1.022 MeV, but not primary effect below 10 MeV.
Name the first and final member of the Uranium decay series
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U-238, Pb-206
Electromagnetic radiation produced by the rapid deceleration of charged particles is called _____
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Bremsstrahlung
‘Phantoms’ are:
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Material used to simulate tissue
Plutonium is very toxic
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Indeed
What is the inelastic scattering of a photon
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Decrease in energy of the scattered photon
What does the ‘Z’ represent in reference to an atom or an element or a nuclide?
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The Proton number or effective proton number
What effect predominates in the 10-100 keV range for photons?
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Photoelectric effect
The energy distribution of alpha emission is
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monoenergetic
Define ‘High Radiation Area’
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Any area with the dose rates greater than 100 mrem/hour at 30 cm from the source.
Define’ Very High Radiation Area’
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An area accessible to individuals in which radiation levels exceed 500 rad (5 gray) in one hour at 1 meter from the source. Requires preface of “GRAVE DANGER”
Define ‘Radiation Area’
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Any area with radiation levels greater than 5 mrem/hr at 30 cm from the source
Personnel dosimetry records must be retained:
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Until the NRC terminates the pertinent license.
Airborne Radioactivity Area must be posted at _____ DAC-hour(s) or _____ DAC-hour(s) to an individual in one week
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1, 12. 12 DAC-hours in a 40 hour week can be used to establish a posting threshold of .3 DAC
A chemical which as shown some success as an internal chelating agent for plutonium is:
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DTPA
Linear attenuation coefficient vs. the mass energy absorption coefficient
Funky answer - needs followup - Sam
Linear attenuation coefficient is the sum of absorption and scattering processes. The mass energy absorption coefficient will generally be smaller.
Dose limit to member of the public
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0.1 rem per year
Dose limit to embryo/fetus
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0.5 rem occupational (entire pregnancy)
Limit for sum of the deep dose equivalent and the committed dose equivalent to any individual organ or tissue other than the lens of the eye
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50 rem
annual limit for the lens of the eye
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15 rem
The “institutional monitoring period” for a low-level radioactive waste disposal site which utilizes near-surface disposal is:
Needs verification - Sam
100 years. After closure, the site is monitored for a period of five years by the operator. It is then turned over to the state for institutional monitoring for 100 years.
Target and filter material used in most x-ray MAMMOGRAPHY machines is,
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Molybdenum and Molybdenum.
Gamma interaction which is the greatest contributor the buildup factor
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Compton scattering
Leak test of sealed sources should be sensitive enough to detect
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0.005 uCi
Secondary protective barriers in medical x-ray facilities are designed to protect persons from
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leakage and scattered radiation only. Primary protective barriers are implemented for protection against the primary beam
Most to Least effective shielding materials for gamma radiation sources: Lead, iron, concrete, water
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Yes
Buildup factor typically increases with both the _____ and _____ of the shield
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Atomic number, thickness.
The minimum recommended face velocity for a fume hood is
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125 linear feet per minute.
NORM
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Naturally Occurring Radioactive Material.
TENORM
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Technologically Enhanced Naturally Occurring Radioactive Material
For diagnostic type x-ray machines, the leakage-radiation at a distance of 1 meter from the target cannot exceed
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100 mrad in 1 hour
For Therapeutic type x-ray machines operating in the 5-50 kV range, the max leakage rate at any point 5cm from the tube can not exceed
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100 mrad in 1 hour
For Therapeutic type x-ray machines operating in the 50-500 kV range, the max leakage rate at any point 1 m from the tube can not exceed
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1 Rad in one hour. Leakage rate at 5cm cannot exceed 30 rads/hr
For Therapeutic type x-ray machines operating in the 500+ kV range, the leakage rate in the region outside the useful beam but within 2m radius circular plane centered on the beam’s central axis does not exceed
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0.2% of the treated tissue dose rate. Except for this region, the dose rate at 1m from the path does not exceed 0.5% of the treatment dose.
Source material
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Uranium or thorium or any combination of the two in any physical or chemical form. Must be in natural isotopic concentrations. Depleted uranium is included as source material.
Reference Man’s breathing rate
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20,000 ml/min, 20 L/min 1ml = 1cc
