Advanced Physics Essay Dissertation Help

Advanced Physics

1. Using the Maxwell-Boltzmann distribution for thermal neutron energies, derive the expression for the most probable energy, Emp.
2. From the Chart of the Nuclides, what are the values for these five cross sections:
σth for: 115In + n → 116mIn (t1/2 = 54.2 min) σRI for: 115In + n → 116mIn (t1/2 = 2.165 s) σf for: 235U (thermal) σf for: 238U (thermal) σγ for: 135Xe
3. What is the most important neutron reaction for boron, and why? Write its reaction equation and calculate the Q-value.
4. Boral is an aluminum boron carbide alloy used as a shield against thermal neutrons. If the density of boral is 2.7 g cm-3, the boron content is 35%, the carbon content is 2% and the aluminum content is 63% by weight, calculate the half-value layer of boral for thermal neutrons at room temperature. The absorption cross sections are: B = 755 b, Al = 230 mb, C= 3.2 mb.
5. Calculate the absorption cross section for aluminum given that a thermal flux of 2.91×108 neutrons/cm2 sec is incident on a 4.8 mm thick aluminum foil, and that after passing through the foil the beam contained 2.89×108 neutrons/cm2 sec. Assume all neutrons are of the defined thermal energy (i.e., E = 0.0253 eV).
6. The (n,γ) reaction in 113Cd using thermal neutrons (E = 0.0253 eV) produces 114Cd.
Calculate the energy of the emitted (prompt) photon. Do you think this absorption reaction has a high or low probability of occurrence (relative to other thermal neutron absorption reactions)?
7. The cross section for the 6
Li(n,α)
3
H reaction is 941 barns for a thermal neutron (E = 0.0253
eV) and 6
Li is a 1/v absorber. A distribution of thermal neutrons (at 30° C) are incident on a thin (1 mm) lithium target. Calculate the number of alpha particles created given a uniformly incident fluence of 3×1015 n/cm2 on the 2 cm x 2 cm target.
8. Determine the macroscopic absorption cross section (Σa) for thermal neutrons (a distribution of energies) at room temperature in paraffin (C22H46, density = 0.87 g/cm3).
9. At room temperature (20° C), a source produces thermal energy neutrons (distribution) with an intensity of 2.1×107 n/sec. If the source is inside a spherical lead shield 3.5 cm thick and then covered by 35 cm of paraffin, what would be the intensity of neutrons (a) at the lead/paraffin interface and (b) just outside the paraffin sphere? Assume no interactions in air
gaps, and assume absorption reactions only.
10. An aluminum foil of 1.5 cm2 area and 0.02 cm thick is exposed to a flux of thermal neutrons for 20 minutes (E = 0.0253 eV). During exposure, a total of 7×105 prompt gammas are recorded by a counting system with 3.4% absolute efficiency. What is the flux of neutrons?