1. NE 301 - Introduction to Nuclear Science Spring 2012 Classroom Session 1: Homework #0 Radioactive Types Radioactive Decay and Growth Isotopes and Decay Diagrams Nuclear Reactions Energy of nuclear reactions Neutron Cross Sections Activation Calculations

2. Solution to Homework #0 Please bring clickers to class. We will start next session to collect points. Please bring calculators. Get in pairs, feel free to talk across tables. Time on task please. I want everybody working to get answers. 2

3. 1. What is atomic and molecular weight? What is the difference between the two concepts? Weight of an atom vs. weight of a molecule. Both can be given in: AMU or grams/mole 3

4. Example: What is the molecular mass of Uranil Sulfate (UO 2 SO 4 )? M(UO 2 SO 4 )= M U +6*M O +M S M(UO 2 SO 4 )= M U +6*M O +M S = = 238.029 g/mol + 6* 15.999 g/mol + 32.066 M(UO 2 SO 4 ) = 366.089 g/mol or amu 4 REMEMBER: If nothing else is said, masses are natural isotope mixtures.

5. 2. Define the Avogadro’s number according to your own understanding. Think of a dozen, but 6.022e23 instead. What is the weight of a mol of H 2 molecules? What is the weight of a mol of H atoms? What is the weight of a mol of electrons? 5

6. 3. Explain the difference between mass density (  ) and atom density (N)  = m / V N = # atoms / V 6 Why atomic density is important in nuclear engineering? Nuclear reactions are a collision Rxn. Rate = N  

7. 4. What is the atom density of oxygen in water? (  = 1 g/cm 3, M = 18 g/mol). What is the atom density of hydrogen in water? 7 Density of oxygen atoms: Density of hydrogen atoms: What is the density of water molecules in water?

8. 5. Cylinder with a diameter and height of 10 cm weights 15.16 kg. What is it likely made out of? Google it! 8 10 cm

9. 6. What is the classical formula for kinetic energy? How much kinetic energy has a baseball traveling at 100mph in Joules? How much would it cost to buy that amount of electrical energy (assume 10¢/kW-h) Google mass of baseball = 5oz Quad-Lock Unit Converter (or some such) 9 =0.0004 ¢ J  W.s

10. 7. How much energy in Joules is there in a proton if we could convert it entirely in energy using Einstein equation (E=mc 2 )? How much is that in KW-h? Either kg  mc 2  J  kW-h Or MeV  J  kW-h 10 How many protons Callaway convert by fission a day (3,700 MW of installed capacity)?

11. 8. The average mass of potassium in the human body is ~140g. What is the activity (Bq) of 40 K in the body? 11 A=N. T 1/2 =1.27e9 y The natural abundance of 40 K is: 0.0117 %, so N for 40 K

12. 9.The activity of a radioisotope is found to decrease by 35% in one week. What are the values of its: (a) decay constant (days -1 ) (b) half life (days) (c) mean life(days)? 12

13. 11. How many atoms are there in a 1.00 MBq source of (a) 24 Na (b) 238 U 13 Notice that equally active sources can have vastly different masses (14 orders of magnitude) depending on half-life. Short-lived isotopes are a lot more active than long-lived ones. 24 Na T 1/2 =15.020 h 238 U T 1/2 =4.468x10 9 y

14. Nuclear Science 14

15. 15 Atomic and Nuclear Nomenclature X element symbol (H, He, Na, Xe, U, etc.) represents the number of charges in the nucleus (thus electrons, thus chemical behavior). A = Mass number = protons + neutrons = Nucleons. Z = atomic number = protons. X and Z are redundant and normally we only write A X. e.g. 235 U, 16 O, 3 H, 14 C

16. 16 Chart of the Nuclides Z N Isobars Isotopes Isotones

17. 17

18. Isobars = A 18