Problems After the 1986 Chernobyl disaster in Ukraine, the lodine-131 levels in

Question

Problems After the 1986 Chernobyl disaster in Ukraine, the lodine-131 levels in Romanian milk rose to 2900 Bq/L. Given that the half life of I/ is 8.04 days, how long of a wait was necessary for the level to reach a safety standard of 185 Bq/L? 1. 131 2. If a 70.0 kg person is exposed to 5.01/kg of x-rays (RBE-1), death usually occurs within a few days a. What is this lethal dose in Gy, rad, Sv, and rem b. How much total energy does this person absorb? If the 5.0J/kg dose came from a beam of protons (RBE-10), how do the answers in parts (a) and (b) change? c.

Explanation / Answer

1. given 1986 chernobyl disaster in UK

Ao = 2900 Bq/L

A1 = 185 Bq/L

T1/2 = 8.04 days

hence

A1 = Ao*e^(-lambda*t)

185 = 2900*e^(-t*ln(2)/T1/2)

hence

t = 31.922464024 days

hence it would take 32 days apx to get the radiation levels to back to normal

2. m = 70 kg

E = 5.0 J/kg

RBE = 1

a. from definition og gray

dosage = E = 5 J/kg = 5 Gy

in rad

1 rad = 0.01 Gy

hence dosage in rad = 500 rad

in Sv

dosage equivalent = E/RBE = 5 Sv

in rem

1 Sv = 100 rem

hence

dosage equivalent = 500 rem

b. energy absorbed = 70*5 = 350 J

c. for RBE = 10

dosage = E = 5 J/kg = 5 Gy

in rad

1 rad = 0.01 Gy

hence dosage in rad = 500 rad

in Sv

dosage equivalent = E/RBE = 0.5 Sv

in rem

1 Sv = 100 rem

hence

dosage equivalent = 50 rem

energy absorv=bed remains the same

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