Radiation Quantities Flashcards

1
Q

1 amp = _____

A

1 amp = 1 Coulomb sec-1

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2
Q

1 watt = _____

A

1 watt = 1 Joule sec-1

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3
Q

1 eV = _____ ergs

A

1 eV = 1.6 x 10-12 ergs

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4
Q

1 eV = _____ Joules

A

1 eV = 1.6 x 10-19 Joules

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5
Q

1 Å (angstrom) = _____ m

A

1 Å (angstrom) = 10-10 m

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6
Q

1 inch = _____ cm

A

1 inch = 2.54 cm

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7
Q

1 ft = _____ cm

A

1 ft = 30.48 cm

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8
Q

1 u = _____ kg

A

1 u = 1.66 x 10-27 kg

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9
Q

1 u = _____ MeV

A

1 u = 931.5 MeV

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10
Q

1 Ci = _____ dps

A

1 Ci = 3.7 x 1010 dps

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11
Q

1 Ci = _____ dpm

A

1 Ci = 2.22 x 1012 dpm

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12
Q

1 R = ______ C kg-1

A

1 R = 2.58 x 10-4 C kg-1

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13
Q

1 rad = _____ J kg-1

1 Gy = _____ J kg-1

A

1 rad = 0.01 J kg-1

1 Gy = 1 J kg-1

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14
Q

1 rad = _____ MeV g-1

A

1 rad = 6.242 x 107 MeV g-1

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15
Q

1 rad = _____ erg g-1

A

1 rad = 100 erg g-1

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16
Q

1 R = _____ ergs g-1 of air

A

1 R = 86.9 ergs g-1 air

* based on 33.7 eV/ion pair

17
Q

1 R = _____ ergs g-1 of soft tissue

A

1 R = 98 ergs g-1 soft tissue

* based on 33.7 eV/ion pair

18
Q

1 dpm = _____ pCi

A

1 dpm = 0.45 pCi

19
Q

1 day = _____ sec

A

1 day = 86,400 sec

20
Q

1 day = _____ min

A

1 day = 1,440 sec

21
Q

1 year = _____ sec

A

1 year = 3.15 x 107 second

22
Q

What does exposure measure?

A

The ability of photons to produce ionizations in air.

23
Q

Three major limitations for the use of the roentgen

A
  1. The roentgen applies only to photons.
  2. The roentgen applies only in air.
  3. The roengten is defined only for E<3MeV
24
Q

Define

Absorbed Dose

A
  • Unit: rad (“Roentgen Absorbed Dose”)
  • Measures the energy which is actually deposited in some given mass.
  • One rad is equivalent to 100 ergs of energy deposited per gram of material.
25
_Define_ Quality Factor Radiation Weighting Factor
It is a modifying factor by which the absorbed dose at a point can be multiplied to determine the risk of biological injury corresponding to the irradiation conditions. Values are a function of LET. _NRC / DOE / NCRP_ * Symbol: Q * Unit: rem rad-1 _2007 ICRP_ * Symbol: wR * Unit: Sv Gy-1
26
_Define_ Dose Equivalent Equivalent Dose
Biologically weighted absorbed dose. Takes absorbed dose (in rad/Gy) and converts to a risk factor. _NRC / DOE / NCRP_ * "Dose Equivalent" * Symbol: HT * Unit: rem, Sievert * Equation: HT = D Q _2007 ICRP_ * "Equivalent Dose" * Symbol: HT * Unit: Sievert * Equation: HT = ΣwRD
27
_Define_ Tissue Weighting Factor (wT)
Takes into account the reduced risk of cancer mortality and genetic effects when only some body organs receive a dose.
28
_Define_ Effective Dose Equivalent Effective dose
Whole body dose equivalent of partial exposure. _NRC / DOE / NCRP_ * Symbol: HE * Unit: rem, Sievert * Equation: HE = ΣwTHT _2007 ICRP_ * Symbol: E * Unit: Sievert * Equation: E = ΣwTHT
29
_Define_ Committed Dose Equivalent (CDE) Committed Equivalent Dose
_Pre-2007 ICRP_ * Symbol: HT,50 or CDE * Unit: rem, Sievert * 50 year organ dose from internal emitters _2007 ICRP_ * Symbol: HT(50) * Unit: Sievert * 50 year organ dose from internal emitters
30
_Define_ Committed Effective Dose Equivalent (CEDE) Committed Effective Dose
_Pre-2007 ICRP_ * Symbol: HE,50 (CEDE) * Unit: rem, Sievert * Equation: HE,50 = ΣwTHT,50 * 50 year body dose from internal emitters _2007 ICRP_ * Symbol: E(50) * Unit: Sievert * Equation: E(50) = ΣwTHT(50) * 50 year body dose from internal emitters
31
_Thumb Rule_ When can you treat a line source as a point source for calculation purposes?
As long as the distance away from the source is at least three times the longest dimension of the source, then inverse square law calculations will give the correct answer to within one percent.
32
_Equation_ Calculate Dose Rate using the Bragg-Gray equation
Through the use of this equation, an exposure or exposure rate measurement in air can be converted into an accurate dose or dose rate in tissue. * S = stopping power * W = erg/ion pair * e = Coul/ion pair
33
_Define_ Relaxation length
* The thickness of a shield for which photon intensity in a narrow beam is reduced to 1/e (0.368) of its original value. * One relaxation length is the mean free path (1/µ) * µx = # of mean free paths
34
How do absorbed fractions compare between α/β and X/γ-rays?
_Charged particles (α/β)_ * AF(T←S) = 1 if T = S * AF(T←S) = 0 if T ≠ S _X-ray and γ-rays_ * 0 \< AF(T←S) \< 1
35
What is the ICRP 26 risk factor for stochastic effects?
1×10-4 rem-1
36
Explain why the equation I = I0e-µx does not apply in relation to photon shielding for broad beam conditions or for very thick materials.
* Primary interaction of photons is Compton scattering which leads to scattered secondary photons referred to collectively as buildup. * The given equation does not include the variable B and therefore only accounts for initial/uncollided photons