Phys6C Ch42 Nuclear Energy; Effects and Uses of Radiation

What is the principal difference between a hydrogen bomb and a uranium bomb? A hydrogen bomb converts mass into energy, whereas a uranium bomb does not. One results in radioactive fallout, and the other does not. A uranium bomb is an atomic bomb, and a hydrogen bomb is a nuclear bomb. A uranium bomb utilizes a fission reaction whereas a hydrogen bomb utilizes a fusion reaction. Both work on the same principle, but the hydrogen bomb has a higher yield.

A uranium bomb utilizes a fission reaction whereas a hydrogen bomb utilizes a fusion reaction.

A moderator is inserted into a fission reaction to absorb neutrons and prevent additional fissions. T or F?

False

The fuel for nuclear fusion in the center of the Sun is: O. H. He. U. any radioactive material.

H

What type of scan is used to find the areas of the body where glucose metabolism is most intense? MRI NMR PET scans CT scans radioactive iodine tracers

PET scans

In a nuclear power reactor of the type used to generate electricity, a neutron bombards a uranium nucleus, causing it to split into two large pieces (fission fragments) plus two or three neutrons. Energy is released in this process in the form of electromagnetic radiation and kinetic energy. Which of the following is an accurate statement concerning what happens in such a fission process? 1. The electrical energy generated comes from the kinetic energy of the incident neutrons. 2. The electrical energy generated comes from chemical energy stored in the electron bonds of the uranium atom. 3. Electrical energy is generated because the fission fragments are electrically charged, whereas the uranium was electrically neutral. 4. An intermediate step involves the fusion of protons to form helium nuclei, and energy is released in this process. 5. The total mass of the particles after fission is less than the total mass of the particles (uranium nucleus plus one neutron) before fission, and this decrease in mass Δm is converted into energy E, where E = Δmc^2.

The total mass of the particles after fission is less than the total mass of the particles (uranium nucleus plus one neutron) before fission, and this decrease in mass Δm is converted into energy E, where E = Δmc^2.

What is the meaning of the term "critical mass"? This is the material which is just on the verge of becoming radioactive. This refers to the minimum amount of fissionable material required to sustain a chain reaction. This refers to the mass of the "critical" elements in a reactor, i.e., the uranium or plutonium. This refers to the maximum amount of fissionable material required to sustain a chain reaction. This is the amount of mass needed to make a power reactor economically feasible.

This refers to the minimum amount of fissionable material required to sustain a chain reaction.

A fusion reaction generates energy by combining lighter nuclei into a heavier nucleus, plus additional particles. T or F?

True

Photons associated with the magnetic field used in magnetic resonance imaging have considerably less energy than the photons used in CT scans. T or F?

True

The Sun is powered by the proton-proton cycle. T or F?

True

The fuel for nuclear fission is: U. Li. H. He. any radioactive material.

U

Which Uranium isotope is the most commonly occurring isotope? U-239 U-238 U-235 U-237 U-236

U-238

Which of the following best describes the process in which energy is released in a conventional nuclear reactor? Uranium, when bombarded by neutrons, splits into fragments and releases two or three neutrons, and these neutrons in turn strike more uranium nuclei that split, thereby setting off a chain reaction that releases energy. Uranium is reacted with oxygen in a combustion process that releases large amounts of radioactivity and heat. Deuterium and tritium are joined together to form helium. The radiation given off by a naturally radioactive substance, uranium, is collected and used to make steam. A uranium nucleus is energized to an excited state by neutron irradiation, and it then decays by emitting beta rays and gamma rays that heat water and create steam.

Uranium, when bombarded by neutrons, splits into fragments and releases two or three neutrons, and these neutrons in turn strike more uranium nuclei that split, thereby setting off a chain reaction that releases energy.

When uranium fissions, the fission fragments are: about 1/5 and 4/5 the mass of the uranium nucleus. each about half the mass of the uranium nucleus. about 1/4 and 3/4 the mass of the uranium nucleus. about 1/3 and 2/3 the mass of the uranium nucleus. about 2/5 and 3/5 the mass of the uranium nucleus.

about 2/5 and 3/5 the mass of the uranium nucleus.

Which of the following is not used as a moderator material for nuclear reactors? boron graphite heavy water sodium These are all used as a moderator material for nuclear reactors.

boron

A series of fission reactions in which subsequent reactions are initiated by the neutrons produced in the previous reactions is called a: chain reaction. critical reaction. usion reaction. neutron catastrophe. chemical reaction.

chain reaction

All of the following are units used to describe radiation dosage in humans except: sievert. RBE. rad. rem. curie.

curie

The chief hazard of radiation damage to living cells is: due to heating. due to the creation of chemical impurities. due to ionization. the creation of new isotopes within the body.

due to ionization.

If the Q-value is less than zero for a nuclear reaction, the reaction is: endoergic. endothermic. exdoergic. exoergic. not possible.

endoergic.

If the Q-value is greater than zero for a nuclear reaction, the reaction is: exoergic. endothermic. endoergic. exdoergic. not possible.

exoergic.

The energy radiated by a star, such as the Sun, results from: fusion reactions. gravitational collapse. fission reactions. beta decay. alpha decay.

fusion reactions.

A nuclear reaction is said to be exothermic if the total kinetic energy is: equal both before and after the reaction. greater after the reaction than before. zero after the reaction. less after the reaction than before.

greater after the reaction than before.

A fusion reaction works because the binding energy of the resulting nucleus: is absorbed in the process. is greater than the binding energy of the original nuclei. is less than the binding energy of the original nuclei. is released in the process. is equal to the binding energy of the original nuclei.

is absorbed in the process.

How does the mass of the products of a nuclear fusion reaction compare to the mass of the original elements? greater the same less varies according to the reaction

less

How does the total mass of the products of a nuclear fission reaction compare to the mass of the original elements? the same greater less varies according to the reaction

less

A nuclear reaction is said to be endothermic if the total kinetic energy is: equal both before and after the reaction. less after the reaction than before. zero after the reaction. greater after the reaction than before.

less after the reaction than before.

Thermal neutrons are: neutrons that are used for heating. neutrons that are hot. neutrons that are cold. neutrons with a kinetic energy of about 1/40 eV neutrons that are used for cooling.

neutrons with a kinetic energy of about 1/40 eV

The process during which a heavy nucleus such as uranium splits into two intermediate-sized nuclei after being struck by a neutron is referred to as: nuclear fission. nuclear fusion.

nuclear fission.

The process during which small nuclei combine to form larger ones is referred to as: nuclear fusion. nuclear fission.

nuclear fusion

What is the source of the energy the Sun radiates to us? nuclear fusion reactions chemical reactions magnetic explosions cosmic rays nuclear fission reactions

nuclear fusion reactions

In a nuclear reaction, what value is conserved in addition to electric charge, energy, and momentum? neutron number atomic number nucleon number all of the given answers none of the given answers

nucleon number

PET is an abbreviation for: positron emission tomography. photon emission tomography. photon emission tunneling. photon-electron tunneling. pericranial electromagnetic technique.

positron emission tomography.

A unit that measures the effective dose of radiation in a human is the: Check all that apply. RBE. rad. sievert. curie. rem.

sievert rem

Controlled fusion has been difficult to achieve primarily due to: negligible proton cross section. the difficulty of slowing the fusion neutrons. the high temperatures required to overcome Coulomb repulsion. the weak interaction.

the high temperatures required to overcome Coulomb repulsion.

Fission fragments tend to be radioactive because they have: too many more neutrons than protons. the same number of neutrons as protons. more neutrons than protons. too many more protons than neutrons. more protons than neutrons.

too many more neutrons than protons.

A chain reaction can occur: when critical mass is exceeded. when critical mass is reached. in any uranium core. when the coolant is too hot. in the center of the Sun.

when critical mass is reached.