Calculate the activity of nuclides, Chemistry

Calculate the activity of nuclides:

Problem:

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 in detail about the thermal oxidation The following reactions take place during thermal oxidation: During oxidation, Si - SiO 2 interface moves into silicon. A

Write the periods of periodic table have d-block element

introduction to chemical bonding

Preservatives: The preservatives avoid spoilage of food because of microbial expansion. The most common preservative employed is sodium benzoate; C 6 H 5 COON a It is metabol


Crystals and glasses   Unlike a complex ion or molecule, which is a finite (often small) assembly of atoms, a solid has no fixed shape and size but can add atoms indefinit

Number of unpaired electrons in  Mn 4+ is: (1) 3        (2) 5         (3) 6       (4) 4 Ans: 3

The shape of d xy orbital will be: (1) Circular (2) Dumb-bell (3)Double dumb-bell (4) Trigonal Ans: Double dumb-bell

An atom with atomic number 20 is most likely to combine chemically with the atom whose atomic number is: (1) 11         (2) 14      (3) 16                 (4) 10 An

what is the easy wet test of copper?