Thermal neutrons utilized to induce U-235 fission possess a kinetic energy of _____________ eV?
Show answer Hide answer
Answer: A. < 0.025
Explanation
Thermal neutrons utilized to induce U-235 fission possess very low kinetic energies of less than 0.025 eV. These slow-moving neutrons are in thermal equilibrium with their surrounding moderator molecules. Low kinetic energy maximizes the probability that a neutron will cause a uranium nucleus to undergo fission. Thermal neutrons have speeds comparable to gas molecules at room temperature, roughly two kilometers per second. Fission cross-sections for U-235 are significantly higher for slow thermal neutrons than for fast neutrons. Energy is measured in electron-volts, where one eV represents energy gained by a single accelerated electron.
Nuclear reactors use moderators specifically to thermalize fast fission neutrons down to these low energy levels. Controlling thermal neutron populations allows operators to regulate power output in commercial reactors. Neutron energy distributions directly influence the criticality and efficiency of thermal nuclear reactors. Neutrons with energies greater than 1 eV are classified as epithermal or fast rather than thermal neutrons. Energy ranges from 1 to 25 eV exceed standard thermal neutron energies found in moderated reactor cores. High energies above 200 eV describe fast neutrons that require moderation before efficiently causing fission.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. Natural uranium is predominantly composed of the isotope___________________?
Show answer Hide answer
Answer: A. 92U238
Natural uranium is composed predominantly of the uranium-238 isotope, designated as ninety-two U two-thirty-eight. This specific isotope makes up over ninety-nine percent of all uranium found naturally in the Earth's cru...
Q2. A radioactive element has a 100-day half-life. After 400 days, one gram of this element decays down to ______________ grams?
Show answer Hide answer
Answer: D. 1/16
Dividing the total elapsed time of 400 days by the 100-day half-life calculates four half-life periods. Raising the base fraction of one half to the fourth power results in a remaining fraction of one sixteenth. Starting...
Q3. The spatial dimension of a typical atom is on the scale of one __________________?
Show answer Hide answer
Answer: A. °Angstrom
The spatial dimension of a typical atom is on the scale of one angstrom. An angstrom equals one ten-billionth of a meter, providing a convenient unit for atomic scales. Electron cloud diameters establish this characteris...
Q4. The rate of radioactive disintegration for a given element _______________?
Show answer Hide answer
Answer: B. Progressively decreases
The rate of radioactive disintegration for a given element progressively decreases over time. As unstable parent nuclei decay into daughter products, fewer radioactive atoms remain available to disintegrate. This declini...
Q5. The standard unit for quantifying radioactivity is_________________?
Show answer Hide answer
Answer: D. Curie
The Curie is a traditional unit of radioactivity defined originally based on the decay rate of radium. One Curie represents exactly thirty-seven billion radioactive disintegrations occurring per second. This standard uni...
Q6. The combined mass of the two daughter nuclei produced during fission compared to the parent nucleus is_____________________?
Show answer Hide answer
Answer: A. Less
The combined mass of the two daughter nuclei produced during fission is less than the parent nucleus. This missing mass is converted directly into immense amounts of energy according to mass-energy equivalence. Nuclear b...