P. W. Lisowski

Nuclear energy generation and waste transmutation using an accelerator-driven intense thermal neutron source

We describe a new approach for commercial nuclear energy production without a long-term high-level waste stream and for transmutation of both fission product and higher actinide commercial nuclear waste using a thermal flux of accelerator-produced neutrons in the 1016 n/cm2s range. Continuous neutron fluxes at this intensity, which is approximately 100 times larger than is typically available in a large scale thermal reactor, appear practical, owing to recent advances in proton linear accelerator technology and to the spallation target-moderator design presented here. This large flux of thermal neutrons makes possible a waste inventory in the transmutation system which is smaller by about a factor of 100 than competing concepts. The accelerator allows the system to operate well below criticality so that the possibility for a criticality accident is eliminated. No control rods are required. The successful implementation of this new method for energy generation and waste transmutation would eliminate the need for nuclear waste storage on a geologic time scale. The production of nuclear energy from 232Th or 238U is used to illustrate the general principles of commercial nuclear energy, production without long-term high-level waste. There appears to be sufficient thorium to meet the worlds energy needs for many millenia.

Enhancement of persistent currents in Bi2Sr2CaCu2O8 tapes with splayed columnar defects induced with 0.8 GeV protons

Composite tapes of the superconductor Bi2Sr2CaCu2O8 on silver were irradiated with energetic light ions (0.8 GeV protons), creating extended splayed tracks ∼7 nm in diameter via fission of Bi nuclei. Magnetic hysteresis indicates large enhancements of persistent currents J, especially at high fields and temperatures, and substantial expansion of the irreversible regime. The technique may be suitable for large scale applications due to the long range (∼half meter) of fast protons.

A fission ionization detector for neutron flux measurements at a spallation source

Abstract The construction of a neutron flux monitor that can measure absolute neutron intensities in the neutron energy range from below 1 MeV to over 500 MeV is described. The detector consists of an ionization chamber with several thin deposits of fissionable material. The ionization chamber is thin enough that it does not significantly affect the neutron beam and may be left in the neutron flight path during experimental measurements to continuously monitor the beam flux. The use of this monitor at the continuous-energy spallation neutron source at the WNR target area at LAMPF is described.

Enhancement of transport critical current densities at 75 K in (Bi,Pb)2Sr2Ca2Cu3Oy/Ag tapes by means of fission tracks from irradiation by 0.8 GeV protons

The transport critical current density Jc of oxide‐powder‐in‐tube mono‐ and multifilamentary Bi‐2223/Ag tapes has been determined before and after irradiation by 0.8 GeV protons at fluences up to 7.0×1016 protons/cm2. Proton‐induced fission of the Bi nuclei produced up to 8.6×1013 fissions/cm3, creating long tracks at densities equivalent to matching fields up to 1.1 T. Relative to unirradiated tapes, Jc values at 75 and 64 K show no decrease in self field, indicating no breakdown of intergranular coupling, and show large, dose‐dependent enhancements in magnetic fields oriented parallel to the tape normal.

Broad range electron spectrometer using permanent magnets

Compact electron spectrometers have been designed and fabricated using permanent magnets. The design allows a very broad range of electron momenta (1 to 25 MeV/c) with resolutions dual to the greater of either 1% or 0.1 MeV/c. Two types of magnet material have been employed (SmCo and NdFe) to build two models of the spectrometer. Measurements of the spectrometer characteristics are compared to design calculations.

Observation of Fermi and Gamow-Teller strength in the 800 MeV(p, n) reaction

Abstract Angular distributions have been measured for the (p, n) reaction on targets of Li, C, C, and N at 800 MeV with an energy resolution of 2.7 MeV allowing observation of discrete nuclear levels. As is the case at lower energies, this reaction is very selective, emphasizing Gamow-Teller (GT) and Fermi transitions. Absolute cross sections of pure GT transitions are reproduced by impulse approximation calculations. The ratio |Jστ|2/|Jτ|2 was extracted from C and N measurements at 800 MeV and from a C measurement at 31

Fission cross section ratios for sup 233,234,236 U relative to sup 235 U from 0. 5 to 400 MeV

Neutron-induced fission cross section ratios from 0.5 to 400 MeV for samples of 233,234,236U relative to 235U have been measured at the WNR neutron Source at Los Alamos. The fission reaction rate was determined using a fast parallel plate ionization chamber at a 20-m flight path. Cross sections over most of the energy range were also extracted using the neutron fluence determined with three different proton telescope arrangements. Those data provided the shape of the 235U(n,f) cross section relative to the hydrogen scattering cross section. That shape was then normalized to the very accurately known value for 235U(n,f) at 14.1 MeV which will allow us to obtain cross section section values from the ratio data and our values for 235U(n,f).

The analyzing power Aγ(θ) for the elastic scattering of 12 MeV neutrons from deuterons

Abstract The analyzing power Aγ(θ) was obtained at 10° intervals between 30° (lab) to 120° (lab) for 2H(n, n)2H at 12.0 MeV. The polarized neutron beam employed in the measurement was obtained by using neutrons emitted at 0° from the polarization transfer reaction 2 H ( d , n ) 3 He . The accuracy in the Aγ(θ) values that was achieved ranged from ± 0.006 to ± 0.013. Comparison of the data to Aγ(θ) results obtained at 12 MeV for the charge symmetric reaction 2H(p, p)2H shows that the two Aγ(θ) distributions are equal to within the above accuracy.

Determination of the absolute efficiency of an organic scintillator for neutrons with energies between 0.5 and 800 MeV

Abstract We have determined the absolute efficiency of an NE-213 scintillator for neutrons with energies from 0.5 to 800 MeV. The detector was 5.1 cm in diameter and 2.5 cm deep. The efficiencies were obtained for detector thresholds of 0.011, 0.48, 1.12, and 4.48 MeVee. Our results are compared to predictions of the STANTON computer code.

Neutron Induced Charged Particle Reactions on 23Na

High resolution measurements of neutron induced charged particle reactions on 23Na have been performed. A NaI(T1) detector served as both target and detector, with pulse shape discrimination being applied for the separation of protons and alpha-particles from each other and from events involving gamma-ray detection. The neutron energy was measured by time-of-flight, using an 80 m flight path at the Los Alamos National Laboratory WNR facility.