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Radiochemistry and Nuclear Chemistry self-test # 14

Comprises Chapter 14

This is a self grading test of your knowledge. It consists of 20 randomly chosen questions with single or multiple answers. The questions with single answers have round buttons and the questions with perhaps more than one correct answer have square buttons. Answer the questions by clicking on the corresponding button in the list of alternative answers. On questions with a single answer (round buttons to click on), it is only possible to mark one of the alternative answers as correct.
Grading of the completed test is automatic when you click on the button marked "GRADE MY ANSWERS" at the end of the test.
Correct answers can be read by clicking on the button having the same number as the question. You find these buttons at the end of the test. You can also refresh your memory first by jumping directly to the answer buttons and click on them to get answers and read relevant parts of the book before doing this test.
On the questions with one or more possible answers (squares to click on) only the first click on each button is recorded as an answer. Hence you must click on the reset button below the question before you can change the original answer(s). Failure to do this will probably make the answers on this question regarded as wrong in the grading process.
Please observe that your teacher may require a deeper understanding of the treated subject than reflected by this test. In case you have any valuable comments or questions regarding this self-test, explain them in an e-mail to: jol@nc.chalmers.se 


Question # 1 (One answer) The total energy release in thermal fission of uranium and plutonium isotopes is about

    A) 23.5 MeV
    B) 176.5 MeV
    C) 200 MeV
    D) 511 MeV
    E) 931.5 MeV

Question # 2 (One answer) Delayed neutrons are

    A) always emitted during the fission process itself
    B) emitted in the     b-decay of some fission products
    C) caused by     a-induced reactions with light elements
    D) typical for Rutherford's nuclear reaction
    E) emitted by all fission fragments

Question # 3 (One or more answers) In exoergic reactions between nuclei and neutrons

    A) the cross section will always increase with increasing neutron energy
    B) the cross section is often small because of the strong Coulomb repulsion
    C) the cross section with low energy neutrons decreases with increasing neutron energy
    D) there is no threshold energy for the reaction
    E) the threshold energy must be exceeded in order for a reaction to take place

In case of an error in the answers above, please click on this button before making any corrections 

Question # 4 (One answer) Macroscopic cross section has the dimension of

    A) barn
    B) barn/m2 
    C) m-1 
    D) m-2 
    E) m3/barn

Question # 5 (One or more answers) As part of the fission process itself there is always an emission of prompt

    A) a-particles
    B) electrons
    C)     g-quanta
    D) positrons
    E) neutrons

In case of an error in the answers above, please click on this button before making any corrections 

Question # 6 (One answer) The product Nv*x has a dimension of

    A) mole/liter
    B) m2 
    C) m2/atom
    D) atoms/m2 
    E) atoms/m

Question # 7 (One answer) What happens normally with the N/Z-value for the fission products?

    A) It remains exactly the same as in the fissioning nucleus - the UCD-rule
    B) It increases drastically in comparison with the value for the fissioning nucleus
    C) It decreases immediately after emission of the prompt     g-radiation
    D) It decreases stepwise through chains of successive     b-decays
    E) It decreases with about 20% through rapid emission of delayed neutrons

Question # 8 (One or more answers) Some partial reaction cross sections have got their own names. Which of the following are such names?

    A) the absorption cross section
    B) the activation cross section
    C) the fission cross section
    D) the capture cross section
    E) the scattering cross section

In case of an error in the answers above, please click on this button before making any corrections 

Question # 9 (One or more answers) A partial reaction cross section

    A) is usually given in barn
    B) is also called an activation function
    C) is a fraction of the total cross section
    D) always decreases with decreasing projectile energy
    E) always increases with decreasing projectile energy

In case of an error in the answers above, please click on this button before making any corrections 

Question # 10 (One or more answers) The inverse of the macroscopic cross section

    A) lacks physical meaning
    B) is called the mean free path
    C) is always << 1 barn
    D) corresponds to the average distance between two collisions with target atoms
    E) is near zero for a very thin target

In case of an error in the answers above, please click on this button before making any corrections 

Question # 11 (One or more answers) The mass-yield curve for fission products

    A) is independent of the neutron energy
    B) has often two maxima
    C) has nearly the same value at A=140 in fission of 233U and fission of 239Pu
    D) shows that the yield is the same for complementary masses
    E) suggests that fissible atoms are still spherical when they fission

In case of an error in the answers above, please click on this button before making any corrections 

Question # 12 (One or more answers) The Coulomb barrier is an obstacle that must be overcome in collisions between atomic nuclei and

    A) a-particles
    B) e- 
    C)     g-quanta
    D) neutrons
    E) protons

In case of an error in the answers above, please click on this button before making any corrections 

Question # 13 (One answer) Fission products are always

    A) instable with regard to electron capture
    B) instable with regard to neutron emission
    C) instable with regard to     g-transitions
    D) instable with regard to     b--decay
    E) isomeric states of the corresponding nucleus

Question # 14 (One or more answers) The wavelength of a neutron

    A) increases with its kinetic energy
    B) is always about the same
    C) decreases with its kinetic energy
    D) is of no importance when the neutron is at rest
    E) with high initial energy increases when it passes through heavy water

In case of an error in the answers above, please click on this button before making any corrections 

Question # 15 (One answer) One barn corresponds to a reaction cross section of

    A) 10-24 m2 
    B) 10-25 m2 
    C) 10-26 m2 
    D) 10-27 m2 
    E) 10-28 m2 

Question # 16 (One answer) By the most probable charge is normally meant

    A) the highest mass number in the center of a mass-yield curve
    B) the maximum in a charge distribution curve
    C) the charge where the probability of neutron emission is largest
    D) the expected energy release in a nuclear weapon explosion
    E) then nuclear charge of the most stable nuclides

Question # 17 (One answer) The reaction cross section for neutron induced reactions have strong maxima at certain energies. This is due to

    A) resonances with neutron levels in the compound nucleus
    B) dissonances between nucleons
    C) an increase in the partial cross section
    D) a decreasing mean free path
    E) an incomplete macroscopic cross section

Question # 18 (One answer) On order for a target to be regarded as thin one must assume that

    A) the projectile flux increases during its passage through the target
    B) the projectile flux is unchanged during its passage through the target
    C) the projectile flux decreases only a little during its passage through the target
    D) the projectile flux is zero on the other side of the target
    E) the irradiation is performed with neutrons

Question # 19 (One or more answers) A diagram showing the partial reaction cross section as function of projectile energy is usually called

    A) a cross section cut
    B) a reaction spectrum
    C) an excitation function
    D) the excitation gradient
    E) an excitation curve

In case of an error in the answers above, please click on this button before making any corrections 

Question # 20 (One or more answers) The kinetic energy of the fission fragments

    A) is caused by the Coulomb repulsion between them
    B) is mainly recoil energy from the emission of prompt neutrons
    C) increases dramatically when isomeric ground states decay
    D) is rapidly transformed into head in surrounding matter
    E) is always equal for both fragments

In case of an error in the answers above, please click on this button before making any corrections 

Correct answers to each question can be obtained by clicking on the corresponding button below

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(Updated 2001-08-23)