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HW16-6page1

# HW16-6page1 - 9-6 Radiation Doses and Hazards Chap.9 6 A...

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9-6 Radiation Doses and Hazards Chap. 9 6. A rule of thumb for exposure from point sources of photons in air at distances over which exponential attenuation is negligible is as follows: -"- 6CEN x= 2' r where C is the source strength (Ci), E is the photon energy (MeV), N is the number of photons per disintegration, r is the distance in feet from the source, and X is the exposure rate (R h -1). 1. Reexpress this rule in units of Bq for the source strength and meters for the distance. 2. Over what ranges of energies is this rule accurate within 20%? Solution: 2 (a) The approximate formula can be transformed thusly: X ( R / h) = 6C(Ci)E(MeV)N approx [r(ft)]2 C(Bq) ~ = 6(3.7 x lOlO(BQ/Ci)) / (O:3~7"ft)) -1.507 x 10-11C(Bq)E(MeV)N -(r(m)]2 (b) Now calculate the exact exposure rate. The uncollided flux density of
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