Neutron Energies, Velocity & ThermalNeutrons Abdul Rizwan (Reg# 2007-Mech-2616) Waleed Mumtaz (Reg# 2007-Mech-2615) Adnan ...
Neutron Sub atomic particle No charge and greater mass Free neutrons are unstable High penetrating power Essential in...
Neutron Source    Different sources of neutrons are:   Radioisotopes which undergo spontaneous fission   Radioisotopes w...
Neutron Energies   Neutron energy indicates a free kinetic energy,    usually given in electron volts   En= mnV2/(2*gc) ...
Prompt Neutron Energy Spectrum U235
Classification of Neutrons• neutrons are classified according to their energy• thermal neutrons have an energy of about  ~...
Neutron Energy DistributionRanges   Fast neutrons          > energy approximately 1 MeV   Slow neutrons          > energ...
Thermal Neutrons   Slow neutron having energy 0.025 eV   Results from scattering   Moderator mediums are H , D , BeO, B...
Most Probable Neutron Velocities• Most probable neutron velocity is given by•          Vm=(2kT/m)0.5=128.39 T0.5    v=most...
Thermal Neutron Speeds & EnergiesTemperature 0C   Vm ( m/sec)   Em (eV)20               2200          0.0252260           ...
Velocity Distribution At TwoTemperatures
Interaction of Neutrons   Neutrons are uncharged and can travel    appreciable distances in matter without    interacting...
Inelastic Scattering• A part of the kinetic energy that is transferred  to the target nucleus upon collision• The nucleus ...
Elastic scattering• Interaction between fast neutrons and low atomic number Z• For slowing down neutrons• Responsible for ...
Interaction of Neutrons   .......E o , M, V → m.......     (before collision).......E, M, V1 → m, ν 1 .......      (after ...
Continued…• total kinetic energy and momentum are conserved and we have:             1             2                 MV 2 ...
Continued…           1      E 0 = MV for incident neutron              2           2        1 and E = MV12 we get        2...
Continued…            1      2   1     2        4mME  Emax = MV -            2          2   MV1   =            2          ...
presentation uploaded by anwershifa
presentation uploaded by anwershifa
presentation uploaded by anwershifa
Upcoming SlideShare
Loading in …5
×

presentation uploaded by anwershifa

224 views

Published on

power plant presentation

Published in: Technology, Business
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
224
On SlideShare
0
From Embeds
0
Number of Embeds
2
Actions
Shares
0
Downloads
6
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

presentation uploaded by anwershifa

  1. 1. Neutron Energies, Velocity & ThermalNeutrons Abdul Rizwan (Reg# 2007-Mech-2616) Waleed Mumtaz (Reg# 2007-Mech-2615) Adnan Rasheed (Reg# 2007-Mech-2557) Adnan Khan (Reg# 2007-Mech-2620) Suhaib Ilyas (Reg# 2007-Mech-2595)
  2. 2. Neutron Sub atomic particle No charge and greater mass Free neutrons are unstable High penetrating power Essential in Fission process
  3. 3. Neutron Source Different sources of neutrons are: Radioisotopes which undergo spontaneous fission Radioisotopes which decay with alpha particles  Radioisotopes which decay with high energy photons co-located with beryllium or deuterium Plasma focus and plasma pinch devices Light ion accelerators
  4. 4. Neutron Energies Neutron energy indicates a free kinetic energy, usually given in electron volts En= mnV2/(2*gc) = 5.227*10-13 V2 ( eV) Fission neutron energy range is (0.075……..17 ) MeV Prompt neutron vs delayed neutron Prompt neutrons have average energy of about 2 MeV.
  5. 5. Prompt Neutron Energy Spectrum U235
  6. 6. Classification of Neutrons• neutrons are classified according to their energy• thermal neutrons have an energy of about ~ 0.025 eV• epithermal neutrons, resonance neutrons, slow neutrons have energies between 0.01 MeV and 0.1 MeV• fast neutrons - 0.1 MeV and 20 MeV• relativistic neutrons
  7. 7. Neutron Energy DistributionRanges Fast neutrons > energy approximately 1 MeV Slow neutrons > energy less than or equal 0.4 eV Epithermal neutrons > energy 1 eV to 10 keV Hot neutrons > energy about 0.2 eV Thermal neutrons > energy of about 0.025 eV Cold neutrons > energy 5x10−5 eV to 0.025 eV Very cold neutrons > energy 3x10−7 eV to 5x10−5 eV Ultra cold neutrons > energy less than 3x10−7 eV Continuum region >energy 0.01 MeV to 25 MeV Resonance region >energy 1 eV to 0.01 MeV Low energy region > energy less than 1 eV
  8. 8. Thermal Neutrons Slow neutron having energy 0.025 eV Results from scattering Moderator mediums are H , D , BeO, Be Neutrons at a given temp posses wide range of energies and corresponding speeds Maxwell-Boltzman distribution: 2π f (E ) = e − E / kT E 1/2 ( πkT )3/2
  9. 9. Most Probable Neutron Velocities• Most probable neutron velocity is given by• Vm=(2kT/m)0.5=128.39 T0.5 v=most probable velocity of neutron (m/sec) k=Boltzmans constant (1.3805*10-23 J/ K) T=absolute temperature in degrees Kelvin ( K) m =mass of neutron 1.66 x 10-24gram• The energy corresponding to Vm is given by Em= kT = 8.617*10-5 T (eV ) At T = 20 0C Vm = 2200 m/sec Em =0.025 eV
  10. 10. Thermal Neutron Speeds & EnergiesTemperature 0C Vm ( m/sec) Em (eV)20 2200 0.0252260 2964 0.0459537.8 3656 0.06991000 4580 0.1097
  11. 11. Velocity Distribution At TwoTemperatures
  12. 12. Interaction of Neutrons Neutrons are uncharged and can travel appreciable distances in matter without interacting Neutrons interact mostly by inelastic scattering or elastic scattering
  13. 13. Inelastic Scattering• A part of the kinetic energy that is transferred to the target nucleus upon collision• The nucleus becomes excited and a gamma photon/photons are emitted
  14. 14. Elastic scattering• Interaction between fast neutrons and low atomic number Z• For slowing down neutrons• Responsible for neutron – slowing in reactors• Fast neutrons lose K.E. As A result of scattering collisions with nuclei which act as moderators
  15. 15. Interaction of Neutrons .......E o , M, V → m....... (before collision).......E, M, V1 → m, ν 1 ....... (after collision)
  16. 16. Continued…• total kinetic energy and momentum are conserved and we have: 1 2 MV 2 = 1 MV12 + 1 mv 1 2 2 2 and MV = MV1 + mv 1•Solving for V1 and substituting into: (M - m) V1 = V (M + m)
  17. 17. Continued… 1 E 0 = MV for incident neutron 2 2 1 and E = MV12 we get 2 2 M−m E = E0   M +m• The energy transferred to target nucleus is:   M - m 2  E 0 - E = E 0 1 -     M +m   
  18. 18. Continued… 1 2 1 2 4mME Emax = MV - 2 2 MV1 = 2 (M + m )• when: M = m; E = Emax•for neutrons in a head on collision with hydrogen all the kinetic energy can be transferred in onecollision since the mass of neutrons and protonsare almost equal.

×