PowerPointPrsentation

1
Some types of nuclear reactions
2
Nuclear resonances
3
Behaviour of reaction cross sections
(Segre, Nuclei particles)
4
Differential reaction cross section (CMS) for
12C? ? 14Nd (Segre, Nuclei
particles)
5
Energy spectrum of prompt neutrons in fission
(Krane, Introductory nuclear physics)
6
Neutron cross sections of uranium
envelopes to the resonances
7
Resonances (left 238U total neutron cross
section, right cross section for elastic
p-scattering off 12C)
(Mayer-Kuckuk, Kernphysik)
8
Scheme of a nuclear reactor
control rods
fuel elements
moderator
shielding and reflector
9
Nkeff
235U (n,? ) 236U neutron capture
238U (n,? ) 239U ? 239Np ? 239Pu
235U (n,f ) thermal fission
N?
fate of a neutron generation
238U (n,f ) fast fission
N?? fast neutrons
? (1-Ps) fast neutrons escape
N?? Ps are moderated

• (1-p) neutrons lost through
• 238U (n,? ) resonances

N?? Psp thermal neutrons are generated
? (1-Pth) thermal neutrons escape

• (1-f ) thermal neutrons absorbed
• in the moderator

N?? pfPsPth Nkeff thermal neutrons are available
10
Delayed neutron emission
11
Breeding reactions
neutrons
fast
next fission
fissile nuclide
breeding nuclide
thermal
next fission
fissile nuclide
breeding nuclide