Nuclear Power Plant, there is also a problem of
137 Cs having been concentrated by
treatment of contaminated water. Transmuting such nuclides into short-lived or
stable nuclides is one possible way to resolve this problem. Neutron capture
reactions have been proposed for transmutations of such fission products. However,
the neutron capture cross sections differ significantly from nuclide to nuclide, and
this transmutation method is not effective for nuclides with small neutron capture
cross sections such as
137 Cs.
Recently, photo-neutron (γ, n) reactions with laser Compton scattering γ-rays
have been suggested as an alternative method for nuclear transmutations [1, 2].
Figure 1.1 shows a schematic illustration of this transmutation. This transmutation
uses γ-rays generated by laser photons backscattered off GeV electrons and photonuclear reactions via electric giant dipole resonance (GDR) [3], which has a large
cross section for most nuclides. The GDR is a collective excitation of a nucleus that
decays mainly by the emission of neutrons, and its total cross section is a smooth
function of mass number. Therefore, this method is expected to be effective for
transmuting fission products regardless of isotopes.
So far, transmutation with laser Compton scattering for some nuclides has been
evaluated only in a simple manner. In this chapter, we investigate more quantitatively the effectiveness of the transmutation with laser Compton scattering, especially for
137 Cs.
1.2 Calculation Method
1.2.1 Reaction via Giant Dipole Resonance
Nuclear transmutation with laser Compton scattering uses photonuclear reactions
via GDR because the cross section of GDR is quite large and the total cross section
is a smooth function of mass number. GDR is a collective excitation of a nucleus
involving almost all nucleons, which is interpreted classically as a macroscopic
oscillation of a bulk of protons against that of neutrons. The total cross section
σ
tot
GDR , the resonance energy E R , and the width Γ R are given by [4]
σ
tot
GDR ¼ 60 1 þ κ
ð
Þ
NZ
A
mb Á MeV,
E R ¼ 31:2 A
À1=3
þ 20:6 A
À1=6 MeV,
Γ R ¼ 0:0026E
1:91
R MeV,
ð1:1Þ
where N and Z are the neutron and proton numbers, A ¼ N + Z is the mass number,
and κ, which is roughly equal to 0.2 for medium nuclides, is a correction coefficient
for the pion exchange.
When a target nucleus is irradiated with a photon and excited to GDR, it often
forms a compound nucleus with only a small contribution of a pre-equilibrium
reaction [5]. The compound nucleus is an excited state in which the energy brought
4
S. Takai and K. Hagino
137 Cs having been concentrated by
treatment of contaminated water. Transmuting such nuclides into short-lived or
stable nuclides is one possible way to resolve this problem. Neutron capture
reactions have been proposed for transmutations of such fission products. However,
the neutron capture cross sections differ significantly from nuclide to nuclide, and
this transmutation method is not effective for nuclides with small neutron capture
cross sections such as
137 Cs.
Recently, photo-neutron (γ, n) reactions with laser Compton scattering γ-rays
have been suggested as an alternative method for nuclear transmutations [1, 2].
Figure 1.1 shows a schematic illustration of this transmutation. This transmutation
uses γ-rays generated by laser photons backscattered off GeV electrons and photonuclear reactions via electric giant dipole resonance (GDR) [3], which has a large
cross section for most nuclides. The GDR is a collective excitation of a nucleus that
decays mainly by the emission of neutrons, and its total cross section is a smooth
function of mass number. Therefore, this method is expected to be effective for
transmuting fission products regardless of isotopes.
So far, transmutation with laser Compton scattering for some nuclides has been
evaluated only in a simple manner. In this chapter, we investigate more quantitatively the effectiveness of the transmutation with laser Compton scattering, especially for
137 Cs.
1.2 Calculation Method
1.2.1 Reaction via Giant Dipole Resonance
Nuclear transmutation with laser Compton scattering uses photonuclear reactions
via GDR because the cross section of GDR is quite large and the total cross section
is a smooth function of mass number. GDR is a collective excitation of a nucleus
involving almost all nucleons, which is interpreted classically as a macroscopic
oscillation of a bulk of protons against that of neutrons. The total cross section
σ
tot
GDR , the resonance energy E R , and the width Γ R are given by [4]
σ
tot
GDR ¼ 60 1 þ κ
ð
Þ
NZ
A
mb Á MeV,
E R ¼ 31:2 A
À1=3
þ 20:6 A
À1=6 MeV,
Γ R ¼ 0:0026E
1:91
R MeV,
ð1:1Þ
where N and Z are the neutron and proton numbers, A ¼ N + Z is the mass number,
and κ, which is roughly equal to 0.2 for medium nuclides, is a correction coefficient
for the pion exchange.
When a target nucleus is irradiated with a photon and excited to GDR, it often
forms a compound nucleus with only a small contribution of a pre-equilibrium
reaction [5]. The compound nucleus is an excited state in which the energy brought
4
S. Takai and K. Hagino