Fission neutrons are thermalized in a pure Beryllium moderator at 427 oC. Determine the number of...

Fission neutrons are thermalized in a pure Beryllium moderator at 427 oC. Determine the number of collisions (scattering reactions) needed to thermalize these neutrons, the macroscopic slowing down power, and the moderating ratio. The density of Beryllium is 1.82 g/cm3

Solutions

Expert Solution

Beryllium A= 7

microscopic cross sections _s = 7.63 b

_a = 0.0076 b

density = 1.82 g/cc

macroscopic cross section _s = * N_a/A *_s = 1.82 * 0.602 E+24 * 7.63E-24 /7

= 1.194 /cm --- scattering

_a = 1.82 * 0.602 E+24 * 0.0076E-24 /7

= 0.0012 /cm

slow down decrement = 1+ (/ 1- )ln where = (A-1)² /(A+1)² = 9/16

= 0.26

slow down power = *_s = 0.26 * 1.194 = 0.3104

Moderating ratio = *_s/_a = 0.26 * 1.194/0.0012 = 258.7

is the average logarthmic energy loss ratio per collision

n = 1/ ln(E_o/E_n ) is number of collisions required for slowing down the neutrons

E_o = 2 Mev - fast neutron from the reactor.

E_n - thermal energy of neutrons at 427^oC = 3/2 kT 3/2 * 8.617E-5 *(273+427) ev

= 0.009 ev

n = 1/0.26 * ln(2.0E+6/0.009) = 73.92

about 74 collisions are required to thermalise the fission neutrons to the moderator temp.

genius_generous answered 1 year ago

Next > < Previous

Related Solutions

In a nuclear reactor, in the fission process, neutrons are emitted at high energies. Neutrons are...

In a nuclear reactor, in the fission process, neutrons are emitted at high energies. Neutrons are to be thermalized, i.e., their kinetic energies have to be significantly reduced, so that you can increase the probability for the new fission processes. You have a choice of a number of materials such as, say, heavy, water, iron and lead. The neutrons experience elastic collisions with the atoms of these materials and lose their energies. Assuming the target atoms are at rest initially,...

Given that the average number of fast neutrons emitted following the thermal-neutron induced fission of 235U...

Given that the average number of fast neutrons emitted following the thermal-neutron induced fission of 235U is 2.42 per fission event; use the following data to calculate the mean number of fission neutrons produced per initial thermal neutron in a large volume sample of (a) pure 235U (b) natural uranium 238U, and (c) uranium enriched to 3% in the 235U isotope. Note: The microscopic absorption cross section for 235U is 694 barns. The cross section for 238U is 2.71 barns....

Determine the number of protons, neutrons and electron for the element Sodium. The mass number for...

Determine the number of protons, neutrons and electron for the element Sodium. The mass number for the isotope of this element is 25. You must show your work for each determination: _______________ Diamond has a density of 3.52 g/mL. What is the volume in mL of a diamond with a mass of 4.6 g? Show your work. ______________________ Diamond has a density of 3.52 g/mL. What is the volume in mL of a diamond with a mass of 4.6 g?...

Nuclear fission reactors consist of three main components: the fuel rods, control rods and the moderator....

Nuclear fission reactors consist of three main components: the fuel rods, control rods and the moderator. Draw a diagram of typical reactor and give a brief description of each of the main components. Why are fusion reactors considered ‘cleaner’ than fission reactors?

Neutrons are born out of fission at a high energy and must be slowed down to...

Neutrons are born out of fission at a high energy and must be slowed down to the low energy region, called the “thermal energy” region, to cause another fission. A material called a “moderator” is used to slow the neutrons down, or “moderate” them, by elastic scattering collisions.The average neutron energy coming out of fission of thermal neutrons is 1.98 MeV in kinetic energy. What is the number of collisions required to bring its average kinetic energy to 0.1 eV...

Show how you would determine the number of neutrons in a Chlorine atom that has a...

Show how you would determine the number of neutrons in a Chlorine atom that has a mass number of 37 ? Another atom of Chlorine has a mass number of 35. How does it compare to the atom of Chlorine in the above question ?

1. Determine the number of electrons, protons and neutrons in each isotope of titanium based on...

1. Determine the number of electrons, protons and neutrons in each isotope of titanium based on the table below. Determine its atomic mass. Isotope Mass (Da) Natural Abundance (%) Electrons Protons Neutrons Atomic Mass 46Ti 45.9526294 8.25 47Ti 46.9517640 7.44 48Ti 47.9479473 73.72 49Ti 48.9478711 5.41 50Ti 49.9447921 5.18 2. For each compound listed below write down the correct formula and calculate the formula mass. • Iron(III) sulfide • Aluminum nitrate • Carbon tetrachloride • Perchloric acid • Ammonium hydroxide...

47. Suppose that 1 kg of U235 undergoes fission by thermal neutrons. Compute the masses (or...

47. Suppose that 1 kg of U235 undergoes fission by thermal neutrons. Compute the masses (or mass equivalents) in grams for the following, which are produced: 1. neutrons, 2. γ-rays, 3. β-rays, 4. neutrinos, 5. kinetic energy, 6. fission products.

Moderating a Neutron In a nuclear reactor, neutrons released by nuclear fission must be slowed down...

Moderating a Neutron In a nuclear reactor, neutrons released by nuclear fission must be slowed down before they can trigger additional reactions in other nuclei. To see what sort of material is most effective in slowing (or moderating) a neutron, calculate the ratio of a neutron's final kinetic energy to its initial kinetic energy, Kf/Ki, for a head-on elastic collision with each of the following stationary target particles. (Note: The mass of a neutron is m=1.009u, where the atomic mass...

Determine the number of neutrons, protons, and electrons for a bromide ion that has a mass number of 76, and a charge of -1.

Determine the number of neutrons, protons, and electrons for a bromide ion that has a mass number of 76, and a charge of -1. number of neutrons: number of protons: number of electrons:Determine the element symbol, number of protons, and number of electrons for an ion that has a mass number of 56, 30 neutrons, and a charge of +3. element symbol: number of protons: number of electrons:Determine the element symbol, m number, and charge for an atom or ion that has a 49 neutrons, 38...

Subjects