Flashcards in Calculations Deck (13):
Given a uniform disk source of radiation, at what minimum distance from the disk source would the point source formula have only about 1% difference from the disk source formula?
The average distance a photon will travel will be the _____ of the linear
reciprocal. e.g. photon linear attenuation coefficient of 0.0023cm
Semi-infinite cloud of gamma-emitting noble gas estimation of absorbed dose rate (D):
D=.25(Energy)(concentration in uci/cc) D is in Rad/sec
Formula to estimate exposure rates
6CEN=X. 6(Activity in Curies)(Energy in MeV)(Photon Fraction per disintigration). Gives R/hr at 1 ft.
= ln(2)/attenuation coefficient (u)
B=All primary photons and secondary photons/primary photons. e.g. at a point outside a thick photon radiation shield the exposure due to primary photons is 0.25 of the exposure from secondary photons. What is the buildup factor at that point? B=1.25/.25=5
1/10th life ratio
3.32 - Multiply by half life to get 1/10th life
Equation for specific activity
Decay constant * Number of atoms in a gram (activity/gram)
The DAC is calculated based on the average airborne concentration that a person would receive in what period of time?
2000 hours/year. DAC = (ALI/(1.2 m^3/hr)*2000 hr)
1.2 m^3/hr = reference man breathing rate
What is the mathematical relationship of the wavelength of a photon to its frequency?
1 Relaxation length
the thickness of shield that will attenuate a narrow beam to 1/e of its original intensity.
Secular Equilibrium before 7 half lives
A daughter = A parent (1-e^(-lambda(t))