3/2003 Rev 1 I.3.8&10 – slide 1 of 23 Part I Review of Fundamentals Module 3Interaction of Radiation with Matter Session 8&10Neutron Activation Session I.3.8&10 IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources

3/2003 Rev 1 I.3.8&10 – slide 2 of 23 Introduction  Neutron activation will be discussed  Students will learn about principles of neutron activation, the activation equation, concept of maximum or saturation activity, and solve a problem

3/2003 Rev 1 I.3.8&10 – slide 3 of 23 Content  Importance of neutron activation to health physics  Production rate of an isotope under neutron bombardment  Activation equation  Concept of maximum or saturation activity  Solve a problem

3/2003 Rev 1 I.3.8&10 – slide 4 of 23 Overview  Principles of neutron activation of stable isotopes will be discussed  Health physics significance of neutron activation will be discussed

3/2003 Rev 1 I.3.8&10 – slide 5 of Na (n,  ) 24 Na Neutron Capture in 23 Na

3/2003 Rev 1 I.3.8&10 – slide 6 of 23 Examples of Importance of Neutron Activation  Production of isotopes (for example 60 Co, 192 Ir, etc.)  Accident dosimetry (for example 24 Na in blood)  Crime detection in forensic medicine (for example Napoleon’s hair)

3/2003 Rev 1 I.3.8&10 – slide 7 of 23  Activation analysis for measurement of trace elements  Activation products in a reactor are major sources of radiation exposure to workers (for example 60 Co)  They can expose the public (for example direct gamma radiation from 16 N in steam in BWR) Examples of Importance of Neutron Activation

3/2003 Rev 1 I.3.8&10 – slide 8 of 23  Determination of fast neutron radiation component at Hiroshima  Accelerator mass spectrometry of 63 Ni (half-life = 100 years) produced by fast neutron  activation of copper in building materials  Reaction is 63 Cu (n, p) 63 Ni Examples of Importance of Neutron Activation

3/2003 Rev 1 I.3.8&10 – slide 9 of 23 Concept of Reaction Rate Neutron Bombardment

3/2003 Rev 1 I.3.8&10 – slide 10 of 23 =  n o - N dN dt Differential Equation for Neutron Activation

3/2003 Rev 1 I.3.8&10 – slide 11 of 23 N(t) =  n o (1 - e - t ) Equation for Radionuclide Production by Neutron Activation

3/2003 Rev 1 I.3.8&10 – slide 12 of 23 N(t) =  n o (1 - e - t ) A(t) = Activation Equation Expressed in Terms of Activity

3/2003 Rev 1 I.3.8&10 – slide 13 of 23 for t << 1 e (- t ) = 1 - t Useful Rule of Thumb for Simplifying Exponential Terms

3/2003 Rev 1 I.3.8&10 – slide 14 of 23 N(  ) =  n o Equation for Maximum or Saturation Activity

3/2003 Rev 1 I.3.8&10 – slide 15 of 23 Buildup of a Radionuclide Under Neutron Bombardment

3/2003 Rev 1 I.3.8&10 – slide 16 of 23 Buildup and Decay Following Neutron Activation

3/2003 Rev 1 I.3.8&10 – slide 17 of 23 Time to Reach Saturation Function of Product Half-Life

3/2003 Rev 1 I.3.8&10 – slide 18 of 23 Problem 1 One gram of cobalt is introduced into a neutron flux of 1 x neutrons cm -2 sec -1. Calculate:  the resultant activity of 60 Co in curies after one year and  the maximum (saturation) activity of 60 Co

3/2003 Rev 1 I.3.8&10 – slide 19 of 23 Problem 1 – Given Conditions Given: % abundance of 59 Co = 100% # of atoms in 1 mole of 59 Co = 6.02 x cross section = 19 barns 1 barn = cm 2 half-life of 60 Co = 5.2 years

3/2003 Rev 1 I.3.8&10 – slide 20 of 23 Solution to Problem 1 Activity of 60 Co is given by A =  n o (1 - e - t )  = neutrons cm -2 second -1  = 19 x cm 2 n o = 1 g * 6.02 x atoms mole -1 * = 1.02 x atoms t = * 1 y = 0.13 t = * 1 y = 0.13 (1 - e - t ) = (1 - e ) = ( ) = mole 59 g y

3/2003 Rev 1 I.3.8&10 – slide 21 of 23 Solution to Problem 1 Solving for A we have: (a) A = (10 14 ) * (19 x ) * (1.02 x ) * (0.12) = 2.33x dps of 60 Co = 2.33 TBq 60 Co (b)The maximum or saturation activity of 60 Co is given by:A(  ) = N =  n o since (1 - exp - ) = 1  n o = (10 14 ) * (19 x ) * (1.02 x ) = 1.94 x dps = 19.4 TBq 60 Co = 1.94 x dps = 19.4 TBq 60 Co

3/2003 Rev 1 I.3.8&10 – slide 22 of 23 Summary  Neutron activation was discussed  We learned about the health physics significance and principles of neutron activation, the activation equation, concept of maximum or saturation activity, and solved a problem dealing with radionuclide production by neutron activation

3/2003 Rev 1 I.3.8&10 – slide 23 of 23 Where to Get More Information  Cember, H., Introduction to Health Physics, 3 rd Edition, McGraw-Hill, New York (2000)  Firestone, R.B., Baglin, C.M., Frank-Chu, S.Y., Eds., Table of Isotopes (8 th Edition, 1999 update), Wiley, New York (1999)  International Atomic Energy Agency, The Safe Use of Radiation Sources, Training Course Series No. 6, IAEA, Vienna (1995)