Mass yield distributions of fission products from photo-fission of 238U induced by 11.5–17.3 MeV bremsstrahlung

Abstract

The yields of various fission products in the 11. 5, 13.4, 15.0 and 17.3 MeV bremsstrahlunginduced fission of 238 U have been determined by recoil catcher and an off-γ-ray spectrometric technique using the electron linac, SAPHIR at CEA, Saclay, France. The mass yield distributions were obtained from the fission product yields using charge-distribution corrections. The peak-to-valley (P/V) ratio, average light mass and heavy mass and average number of neutrons in the bremsstrahlung-induced fission of 238 U at different excitation energies were obtained from the mass yield data. From the present and literature data in the 238 U(γ, f) and 238 U(n, f) reactions at various energies, the following observations were obtained: i) The mass yield distributions in the 238 U(γ, f) reaction at various energies of the present work are double-humped, similar to those of the 238 U(n, f) reaction of comparable excitation energy. ii) The yields of fission products for A = 133-134, A = 138-140, and A = 143-144 and their complementary products in the 238 U(γ, f) reaction are higher than other fission products due to the nuclear structure effect. iii) The yields of fission products for A = 133-134 and their complementary products are slightly higher in the 238 U(γ, f) than in the 238 U(n, f), whereas for A = 138-140 and 143-144 and their complementary products are comparable. iv) With excitation energy, the increase of yields of symmetric products and the decrease of the peak-to-valley (P/V ) ratio in the 238 U(γ, f) reaction is similar to the 238 U(n, f) reaction. v) The increase of 〈υ〉 with excitation energy is also similar between the 238 U(γ, f) and 238 U(n, f) reactions. However, it is surprising to see that the 〈A L 〉 and 〈A H 〉 values with excitation energy behave entirely differently from the 238 U(γ, f) and 238 U(n, f) reactions.

Fission product yield measurements using monoenergetic photon beams

“…The photon-induced FPY values for both isotopes are very close to the neutron-induced data. In 2013, Naik et al [9] studied mass-yield distributions of fission products from photofission of 238 U induced by 11.5-17.3 MeV bremsstrahlung. Figure 5 compares our 13 MeV monoeneregtic photofission data with 13.4 MeV end-point bremsstrahlung-induced fission data of 238 U [9].…”

“…In 2013, Naik et al [9] studied mass-yield distributions of fission products from photofission of 238 U induced by 11.5-17.3 MeV bremsstrahlung. Figure 5 compares our 13 MeV monoeneregtic photofission data with 13.4 MeV end-point bremsstrahlung-induced fission data of 238 U [9]. As can be seen, the FPYs for almost all of the fragments of 238 U are consistently lower than our data.…”

Project New Orion: Pulsed Nuclear Space Propulsion Using Photofission Activated by Ultra-Intense Laser

“…The established photofission energy yield per input of ultra-intense laser energy ratio assumes a photofission event produces 200 MeV, approximating the energy yield of uranium-235 fission [2] [7]. Noted by Naik et al the determination of photofission energy yield for uranium-238 is an evolving scientific subject pending convergence [15]. The photofission energy yield ratio developed by LeMoyne and Mastroianni utilizes the experimental findings that 7 × 10 4 fissions per joule of the ultra-intense laser are feasible [2] [10] [12].…”

Fundamental Architecture and Performance Analysis of Photofission Pulsed Space Propulsion System Using Ultra-Intense Laser

“…The characterization of the mass yield distribution for photofission of uranium-238 is still an active and evolveing subject [19]. In order to derive performance parameters for a pulsed space propulsion system, the energy yield for photofission of uranium-238 is approximated to the equivalence of neutron induced fission of uranium-235, which has been thoroughly characterized over course of a half century of experimental physics.…”