Resonant Photonuclear Reactions for Isotope Transmutation

Abstract

Coherent photonuclear isotope transmutation (CPIT) produces exclusively radioactive isotopes (RIs) by coherent photonuclear (γ,n) and (γ,2n) reactions via E1 giant resonances. Photons to be used are medium energy (E(γ) ≈ 12-25 MeV) photons produced by laser photons backscattered off GeV electrons. The cross sections are as large as 0.2 -0.6 b (10 −24 cm 2 ), being independent of individual nuclides. A large fraction (∼ 5%) of photons is effectively used for the photonuclear reactions, while the scattered GeV electrons remain in the storage ring to be re-used. CPIT with medium energy photons around 10 12−15 /sec provides specific/desired RIs with the rate of 10 10−13 /sec and the RI density around 0.05-50 G Bq/mg for nuclear science, molecular biology and for nuclear medicines.Key wards: RI productions, laser photons, Compton backscattering, GeV electrons, photonuclear reactions, EI giant resonance, nuclear medicine,The present letter aims to report that CPIT (coherent photonuclear isotope transmutation) is quite powerful for exclusive RI (radio isotope) productions (transmutations). Nuclear reactions used for CPIT are coherent photonuclear reactions through giant resonances (GR) by means of laser electron photons, i.e. medium energy photons produced by laser photons backscattered off energetic GeV electrons in a storage ring. CPIT is shown to be a very efficient and realistic way to provide various kinds of RIs to be used for nuclear physics, molecular biology, nuclear medicine and for other basic and applied science.So far, (n,γ) reactions and nuclear fissions have been extensively used for RI productions and transmutations. They are caused by the strong (nuclear) interaction, while the photonuclear reactions are by EM interactions. Thus the photonuclear reaction cross section is in general much smaller than typical nuclear cross sections because of the small EM coupling constant.Low energy thermal neutrons used for (n,γ) reactions and/or nuclear fissions are easily obtained by using intense medium energy protons and/or high flux nuclear reactors. On the other hand medium energy photons required for photonuclear RI productions are hardly obtained by conventional methods.RIs produced by (n,γ) reactions and those by nuclear fissions are limited to those with large neutron capture cross sections and those with large fission branches, respectively. Many kinds of fission product RIs, however, are produced in addition to the specific isotope of interest, and thus chemical separation is indispensable for extracting the desired isotope.Laser electron photons for RI productions have been discussed, as given in re- * ) ejiri@rcnp.osaka-u.ac.jp typeset using PTPT E X.cls Ver.0.9

Nuclear Transmutation of Long-Lived Nuclides with Laser Compton Scattering: Quantitative Analysis by Theoretical Approach

“…Because the transmutation with laser Compton scattering can almost exclusively generate desired nuclides, this method will be useful for the generation of isotopes for medicine [1]. …”

“…The scattering cross section of laser Compton scattering is given by the KleinNishina formula: To have a situation in which (γ, n) reactions occur, the photon beam with energy at B(n) E γ < B(2n) is desired. In case of the free electron laser, we may assume/ expect to get the total photon flux N γ % 2 Â 10 12 /s/500 mA for E e ¼ 1.2 GeV [1]. From Eq.…”

“…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.…”

Feasibility studies towards future self-sufficient supply of the ⁹⁹Mo-^99mTc isotopes with Japanese accelerators

“…3) Together with world-wide efforts, new methods to produce the 99 Mo isotopes have been explored and proposed using Japanese accelerator facilities through photonuclear reactions (γ, n), 4) neutron-induced reactions (n, 2n) 5) and (n, γ), as well as proton-incident reactions (p, pn) and (p, 2n).…”

Shielding design of laser electron photon beamlines at SPring-8

“…Various experiments using the laser electron photons have been carried out such as Kaon physics and penta-quark physics [1], transmutation experiments such as the production of useful radio-isotopes of Mo-99 [2], and nondestructive inspection [3] etc.…”