Calculate the activity of nuclides, Chemistry

Calculate the activity of nuclides:


100 mg piece of a gold ornament containing 10% copper as impurity was irradiated with thermal neutrons at 2.1×1011 n/cm2/s for 2 days producing 198Au (t½ = 2.7 d) and 64Cu (t½ = 12.7 h). Calculate the activity of these nuclides in terms of counts/s at the end of irradiation and after a delay of 2 d and 4 d. How long will it take for the decay of activity due to 64Cu to 0.1% of its original activity? 197Au is monoisotopic and its thermal neutron absorption cross section (σ) is 99 b whereas 63Cu is 30.9% abundant and its σ value is 4.4 b.

Answer: 100 mg piece of gold ornament will contain 90 mg gold or 197Au and 10 mg of copper or 0.309×10 = 3.09 mg 64Cu

Using the Eq. (13.8) Activity due to 198Au at the end of irradiation

=   90×10-3 × 6.02×1023 ×2.1×1011(1- 0.5985)/197

=   22.96×108 cps

Activity after a delay of 2 d   = 22.96×108×e(-0.693×2/2.7)

=          13.74×108 cps

Activity after a delay of 4 d   =      22.96×108×e(-0.693×4/2.7)

=          8.22×108 cps

Activity due to 64Cu at the end of irradiation = 3.09×10-3×6.02×1023×4.4×10-24\(1-0.073)

= 2.53×107 cps

Activity after a delay of 2 d            = 2.53×107×e(0.693×48/12.7)

= 18.4×105 cps

Activity after a delay of 4 d            = 2.53×107×e (0.693×96/12.7)

= 13.4×104

Using the formula    t = 1/λ lnNo/N

After substitution, time interval = 12.7/0.693 ln 2.53×107×0.1/100

= 185.8 h = 7.74 d

Posted Date: 1/2/2013 6:35:51 AM | Location : United States

Related Discussions:- Calculate the activity of nuclides, Assignment Help, Ask Question on Calculate the activity of nuclides, Get Answer, Expert's Help, Calculate the activity of nuclides Discussions

Write discussion on Calculate the activity of nuclides
Your posts are moderated
Related Questions
Explain the Gibbs Phase Rule for Multicomponent Systems? The Gibbs phase rule for a pure substance was written F = 3 - P. We now consider a system of more than one substance an

how hyperconjugation accued in branched molecules?

what groups comprise each block of elements in the periodic table?

Compounds and IUPAC names

I think you are talking about aniline(Nitrogen containing compounds) . If so then no, they do not undergo friedel craft as nitrogen donates its lone pair to form a complex and do

If magnetic quantum number of a given atom represented by -3, then what will be its principal quantum number: (1) 2                (2) 3        (3) 4                (4

what are differences and similarities between covalent bond and electrovalent bond

Beckmann rearrangement Ketoxime while treated with acid at 0° C it goes through rearrangement termed as Beckmann rearrangement. So, acid catalysed conversion of ketoximes t

Uses of Starch - Biomolecules (a) Starch are used as the most useful constituent of food as rice, bread, potato and corn-flour, etc. (b) Starch are used in the creation of d