What are the absolute activities Bq for the H 3 and C 14 in the mixture 30

# What are the absolute activities bq for the h 3 and c

This preview shows page 2 - 4 out of 5 pages.

What are the absolute activities (Bq) for the H-3 and C-14 in the mixture? (30 marks) (B) You are provided with 1 g ATP (M.W. 551) solution in which some of the terminal phosphates are labelled with P-32. If the strength of the sample is 3.7 MBq, what fraction of the ATP molecules are labelled? (t 1 for P-32=14.2 days; 1 mole=6.02x10 23 molecules) 2 (30 marks) 2. (A) Assuming that for sodium in fish, the critical organ is the whole body, design an experiment which could be carried out to determine the biological half -life for sodium. Describe it in detail including the principle of the procedure, equipment needed, choice of radionuclide, type of data obtained and operational procedures. Na-22 t!=2.60 yrs, Decay Bmax 0.54; y 1.28 MeV t,=15.0 hrs, Decay B 1.39; y 2.75, 1.37 MeV 2 max (30 marks) Na-24 (B) Consider a Co-60 point source of 1.85x10 11 Bq set up for demonstrating the inactivation of an enzyme by radiation. The dose required for the reaction is 25 rriiy and the irradiation is carried out at a distance of 0.5 m from the source. (i) Calculate the thickness required for a lead shielding wall to be built at 2 m from the source such that outside surface dose rate is 25 ~Gy per hr. (ii) Determine the exposure time required to give the necessary reaction dose both when the source is new and when it is three years old. (Half-value thickness for Co-60=138.6 kg.m- 2 ; density of Pb= 1 .13x10~ kg.m- 3 ; 1 Coulomb.kg- 1 =33.7 Gy in air; 1 Coulomb.kg- 1 = 38.76 Gy in water; half-life of Co-60=5. 3 yr· and specific gamma ray constant for Co-60=9.2x10- 15 Coulomb.kg- 1 .h-J .Bq- 1 at 1 m) (30 marks)
3. (A) (i) 2 You have plated a sample which, on the G.M. counter, shows a count rate of 200,000 counts/5 min. The counter has a dead-time of 400 ~sec. What is the correct count rate? (ii) After one month the same planchet shows approximately 10,000 cpm before dead-time correction. What is the isotope you are measuring? (Hint: half-life of the isotope should be calculated!) {iii) As this represents an appreciable percent correction, what is a better way of counting your sample with the same G.M. counter?

#### You've reached the end of your free preview.

Want to read all 5 pages?

• Fall '17
• R
• Scintillation counter