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Juli

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activity / dose rate
« on: May 29, 2006, 07:47 »
Hello,
how can I calculate the activity of an injected Po solution which emits alpha-particles when I now the energy of the alpha particles, the initial dose rate and the weight of the animal the Po was injected to? Can someone help me? Thanks!
Best wishes, Juli

wlrun3@aol.com

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Re: activity / dose rate
« Reply #1 on: May 29, 2006, 09:29 »
if dose rate is from solution prior to injection, R=6cen, solve for c...if dose rate is from outside animal, I=IoB^ux, then R=6cen, solve for c.

Juli

  • Guest
Re: activity / dose rate
« Reply #2 on: May 30, 2006, 06:33 »
Thanks for the answer but I still not know what to do. My task is the following:

A small animal of weight 2 kg was injected with a (210 84) PO solution that emits alpha-particles of energy 5.3MeV. Calculate the activity of the injected solution if the initial dose-rate was 4.4 mGy*hr^-1.

alphadude

  • Guest
Re: activity / dose rate
« Reply #3 on: May 30, 2006, 09:48 »
ICRP 10 may help if you can find a copy, or ICRP 53. The previous formulas are applicable for gamma emitters. notice the dose is in Rads.
« Last Edit: May 30, 2006, 09:52 by alphadude »

atomicarcheologist

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Re: activity / dose rate
« Reply #4 on: May 30, 2006, 11:07 »
Thanks for the answer but I still not know what to do. My task is the following:

A small animal of weight 2 kg was injected with a (210 84) PO solution that emits alpha-particles of energy 5.3MeV. Calculate the activity of the injected solution if the initial dose-rate was 4.4 mGy*hr^-1.

I am not a medical radiopharmaceutical tech, but I'd like to play on on TV.  Since the factor for Sv/hr per GB/g of Po210 is 1.66E5, it should be a simple plug and chug to get the answer for this problem.

alphadude

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Re: activity / dose rate
« Reply #5 on: May 30, 2006, 01:26 »
wouldnt that skew the results. Since the problem is in Rads or Gy using the 4.4 as a measurement of gamma (Sv) would lead you in a different direction. the assumption since it is Gy or Rads is that you know the energy imparted in joules then back calculate from there. If you can ratio the Sv/Gy it should work that way. 

atomicarcheologist

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Re: activity / dose rate
« Reply #6 on: May 30, 2006, 02:45 »
If you are unable to ratio the Sv/Gy, then you shouldn't have this level of problem to worry about.  I think the reason the initial dose rate was given in mGy was to preclude any erroneous back calculation of alpha shielding due to the container.  However, since I have already stated what I am not, I didn't feel it was necessary to go to this level of concern in my initial reply.  Obviously, I have erred.

alphadude

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Re: activity / dose rate
« Reply #7 on: May 30, 2006, 04:06 »
well thinking about it a little we may use the formula H =D QF  to give you Sv or

joules/sec = (dps) (mev x 1.6 E-13 joules/mev)   SOLVE FOR DPS
« Last Edit: May 31, 2006, 08:53 by alphadude »

wlrun3@aol.com

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Re: activity / dose rate
« Reply #8 on: May 30, 2006, 07:05 »
was this dose rate taken in contact with the solution container or in contact with the animal...from Radiation Monitoring Handbook, J.T. Voss, Los Alamos-Po210, 5.84E-5 R/hr per Ci@ 30 cm...

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Re: activity / dose rate
« Reply #9 on: May 30, 2006, 08:42 »
Thanks for the answer but I still not know what to do. My task is the following:

A small animal of weight 2 kg was injected with a (210 84) PO solution that emits alpha-particles of energy 5.3MeV. Calculate the activity of the injected solution if the initial dose-rate was 4.4 mGy*hr^-1.

yinz a buncha high falluting kalcoolators!  ain't the question what is the activity?  juli ain't lookeen fer the dose rate to the critter, is she?
quando omni flunkus moritati

dubble eye, dubble yew, dubble aye!

dew the best ya kin, wit watt ya have, ware yinze are!

wlrun3@aol.com

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Re: activity / dose rate
« Reply #10 on: May 31, 2006, 02:51 »
i think specific activity is what is being asked for...Herman Cember, Introduction to Health Physics, third edition, page 94, bottom of page...sincerely, good luck with your studies.

atomicarcheologist

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Re: activity / dose rate
« Reply #11 on: May 31, 2006, 06:48 »
i think specific activity is what is being asked for...Herman Cember, Introduction to Health Physics, third edition, page 94, bottom of page...sincerely, good luck with your studies.

I agree.  BTW, is there a site where your reference is available online?  I tried to Google it, but they only show snippet views, not very good for looking up specific references.  Thanks.

alphadude

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Re: activity / dose rate
« Reply #12 on: May 31, 2006, 08:52 »
well, using the formula i supplied it gives you joules which the gray is based upon. solve for x.

wlrun3@aol.com

  • Guest
Re: activity / dose rate
« Reply #13 on: May 31, 2006, 05:27 »
the Cember text is the classic in this field...$30 used on amazon...the example in the text is SA=lamdaxN=(ln2/T1/2)(Avogadro contant/atomic weight)=(.693../1.2E7sec)((6.02E23atoms/mol)/(210grams/mol))=1.7E14atoms/gram/sec...thankyou for asking...sorry for the simple math but i think it will help juli...

alphadude

  • Guest
Re: activity / dose rate
« Reply #14 on: May 31, 2006, 05:41 »
hmmmm I think that is another problem..  how does that tell you how much is in the syringe?  Specific activity is Curies/gram or Bq/Kg. The problem is set up to give the student some hints- MEV, Dose, varmit weight and isotope   The weight of the varmit can be use to further calculate the dose per kg delivered. (distractors)
« Last Edit: May 31, 2006, 06:07 by alphadude »

wlrun3@aol.com

  • Guest
Re: activity / dose rate
« Reply #15 on: May 31, 2006, 10:21 »
i used the conversion 6.24E7MeV/gram=1rad and given 5.3MeV/dis, 4.4E-3Gy/hr, 2kg/animal...2.9E6Bq/animal

atomicarcheologist

  • Guest
Re: activity / dose rate
« Reply #16 on: Jun 01, 2006, 05:48 »
Wlrun 3, thanks for that sourcing.  I'll have to take a look at it, although I do have a preference for Gollnick.  While we are tracing ourselves back to our roots in this problem, my conversion was taken from Tom Voss's "Radiation Measurement & Protection Notebook" as distributed by Thermo Electron Corporation.  I used it as it fits in my pocket and is good here in the field.  The numerical value that I used was based on the GBq/g formulation of 1.324E7/(t1/2 x atomic mass).  I didn't go the rest of the way, as I don't do others' homework for them.  My kids used to complain about that also.  However, as I used to explain to them, my ego is big enough without having to be right about this too!
I blew off the animal mass and associated assumptions as superfulous data designed to confuse the student.  The activity of the injected solution has nothing to do with these.  It is activity/g and matters little how many grams of solution nor of the area the injection affects.  Should the problem have stated a time line post needle insertion, and sought an answer for the radiation dose to tissue or concentration in the animal system,then the other data may have been pertinent.  I didn't see that in the problem and so I didn't address it in my reply.  Sorry, Juli.  I'll buy you a coffe to make it up to you. ;)
« Last Edit: Jun 01, 2006, 08:13 by Atomic Archeologist »

 


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