Decay Rates ,Radioactivity ,Half life easy question

  • Thread starter helpcometk
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  • #1
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Homework Statement


The radioactive nuclides released into the atmosphere by the Chernobyl nuclear accident
in 1986 included both 131I (t 1/2= 8 days) and 137Cs (t 1/2= 30 years). Given that 5 times as
many 137 Cs as 131 I are present in the reactor in steady state, and that 131 I is produced in
roughly 1% of all fissions, calculate
(a) the ratio of activities ACs/AI immediately following the explosion.
(b) how many days before the activities are equal.
(c) Given that the Chernobyl reactor produced 1000MW of power, estimate AI 4 days
after the explosion.


Homework Equations


it would take me considerable amount of effort to find what means 1% of all fissions produce I 131 .



The Attempt at a Solution




it is A level to find that λ= ln2/ (t1/2) and A= λΝ as is probably the whole exercise.
which gives Acs/AI easily since 5NI =Ncs is given,

b) N=No e^-λt should suffice

c) maybe among the other equations P=Po e^-λt has to be used once the power has been found 4 days after the accident , some other equation must be used to find AI ,note that AI initial is not given ,but only as a function of Acs.
 

Answers and Replies

  • #2
phyzguy
Science Advisor
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AI initial can be calculated given the reactor power level and the fact that "131 I is produced in roughly 1% of all fissions". I suggest you put in the "considerable amount of effort" to figure out what that statement means.
 
  • #3
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Ok
What about the other questions.Does anyone know the equation for power?
 
  • #4
phyzguy
Science Advisor
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Think of it this way. If the reactor is operating at a certain power level, there are a certain number of fissions/sec, which you should be able to calculate if you know how much energy is released in each fission. The problem tells you what fraction of the fission events produce I-131, so you should be able to calculate the production rate of I-131. In steady state, the production rate equals the decay rate, so you should be able to calculate the steady state activity of I-131. Does this help?
 
  • #5
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im afraid this confused me even more .Am i thinking correct for a) and b) ?
 

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