Download presentation

Presentation is loading. Please wait.

Published byAshlyn Foster Modified over 3 years ago

1
IAEA International Atomic Energy Agency Radioactivity - 1 Radioactive Decay Day 1 – Lecture 4

2
IAEA Objective To discuss radioactive decay principles and some pertinent terms To define the units to measure radioactive decay 2

3
IAEA Content Activity Law of Radioactive Decay Half-Life Mean Life Decay Constant Units 3

4
IAEA Radioactivity Radioactivity is the property of some atoms that cause them to spontaneously give off energy as particles or rays. Radioactive atoms emit ionizing radiation when they decay 4

5
IAEA Naturally Occurring Elements In nature there are about 300 nuclides Majority of naturally occurring elements aye stable But A few of high atomic weight, from polonium (Z =84) onward Radium (88), Thorium (90), Uranium (92) consists entirely of unstable nuclides The unstable substances undergo spontaneous change, radioactive disintegration or radioactive decay at definite rates. 5

6
IAEA 1 Bq = 1 disintegration per second Activity The amount of a radionuclide present SI unit is the Becquerel (Bq) 6

7
IAEA Multiples & Prefixes (Activity) MultiplePrefixAbbreviation 1-------Bq 1,000,000Mega (M)MBq 1,000,000,000Giga (G)GBq 1,000,000,000,000Tera (T)TBq 1 x 10 15 Peta (P)PBq 7

8
IAEA International Atomic Energy Agency Units Curie (Ci) = 3.7 x 10 10 dps Becquerel (Bq) = 1 dps 1 Ci = 3.7 x 10 10 Bq

9
IAEA Non-SI Units QuantityOld UnitSI UnitConversion Activitycurie (Ci)becquerel (Bq)1 Ci=3.7 x 10 10 Bq Absorbed Doseradgray (Gy)1 rad = 0.01 Gy Equivalent Doseremsievert (Sv)1 rem = 0.01 Sv 9

10
IAEA The Decay Constant is denoted by NOTE: Units on are Typically or sec -1 or “per second” Decay Constant 1time 1sec 10

11
IAEA A = N where “A = activity” has units of disintegrations per second (dps or Bq) Activity Activity 11 If we have N atoms of a given radioisotope and the radioisotope has a known decay constant, the activity of this sample is given by the simple product of the number of atoms and the decay constant.

12
IAEA The relationship between half-life and decay constant is: Half-Life and Decay Constant T ½ = 0.693 12

13
IAEA Half-Life 13

14
IAEA Half-Life RadionuclideHalf-Life Phosphorus-3214.3 days Iridium-19274 days Cobalt-605.25 years Caesium-13730 years Carbon-145760 years Uranium-2384.5 x 10 9 years 14

15
IAEA Sample Problem A criticality accident occurs in a Uranium processing facility. 10 19 fissions occur over a 17-hour period. Given that the fission yield for 131 I is 0.03 and its half-life is 8 days, calculate the 131 I activity at the end of the accident. Neglect 131 I decay during the accident. 15

16
IAEA Solution to Sample Problem Activity = N = x x ( 10 19 x 0.03) = 3 x 10 11 Bq 131 I 0.693 8 days 1 86,400 sec day -1 3 x 10 11 Bq 3.7 x 10 10 Bq/Ci = 8.1 Ci 131 I 16

17
IAEA Differential Equation for Radioactive Decay = - N(t) dN dt 17 Rate of decay at a certain time is directly proportional to the number of radioactive atoms present at that time -ve sign is because of decay (decrease)

18
IAEA Radioactive Decay Equation N(t) = N o e - t 18

19
IAEA Expressing the equation in terms of activity: Radioactive Decay Equation N(t) = N o e - t A(t) = A o e - t where A(t) = activity at any time t and A o = the initial activity at time t = 0 or 19

20
IAEA Radioactive Decay The amount of activity decayed away after “n” half-lives is given by A AoAo 1 - 20

21
IAEA The amount of activity “A” remaining after “n” half-lives is given by Radioactive Decay A AoAo 1 2n2n = 21

22
IAEA International Atomic Energy Agency Mean Life T M = 1.44 T 1/2 For some applications, as in the case of dosimetry of internally deposited radioactive material, it is convenient to use the average life of the radioisotope.

23
IAEA A radionuclide has a half life of 10 days. What is the mean life? Sample Problem 23

24
IAEA Solution to Sample Problem Mean Life = 1.44 T 1/2 = 1.44 x 10 days = 14.4 days 24

25
IAEA Where to Get More Information Cember, H., Johnson, T. E, Introduction to Health Physics, 4th Edition, McGraw-Hill, New York (2009) International Atomic Energy Agency, Postgraduate Educational Course in Radiation Protection and the Safety of Radiation Sources (PGEC), Training Course Series 18, IAEA, Vienna (2002) 25

Similar presentations

OK

Fourth lecture. Radioactivity was the first nuclear phenomenon to be discovered, the credit for this discovery goes to the French physicist Henri Becquerel.

Fourth lecture. Radioactivity was the first nuclear phenomenon to be discovered, the credit for this discovery goes to the French physicist Henri Becquerel.

© 2018 SlidePlayer.com Inc.

All rights reserved.

To ensure the functioning of the site, we use **cookies**. We share information about your activities on the site with our partners and Google partners: social networks and companies engaged in advertising and web analytics. For more information, see the Privacy Policy and Google Privacy & Terms.
Your consent to our cookies if you continue to use this website.

Ads by Google

Ppt on conciliation arbitration adjudication Ppt on sigma and pi bonds Ppt on tcp/ip protocol suite presentation Ppt on global warming in hindi Ppt on ledger and trial balance Interactive ppt on ipad Ppt on rainwater harvesting techniques Ppt on current account deficit and exchange Ppt on interview skills training Ppt on sales closing techniques