2014 MCQ Flashcards
Name three two-phase regimes that occur in vertical two-phase flow?
Bubble flow
Slug flow
Annular flow
What is the typical enrichment for a PWR fuel?
5%
What would happen to a sub-critical satellite nuclear reactor after it plunges into seawater?
Neutron reflection by the seawater would make the reactor more reactive
What would be the effect on the thermal efficiency of a plant if the fuel enrichment of AGR were increased?
Little changed
A new rib design for an AGR increases its heat transfer coefficient. If nothing else is changed, as a result:
Cladding temperature will be reduced.
Order the following in decreasing energy release of U235:
Neutron kinetic energy
Fission fragment kinetic energy
Prompt gamma rays
Fission product radiation
Fission fragment kinetic energy
Fission product radiation
Prompt gamma rays
Neutron kinetic energy
Wigner energy is
Neutron induced strain energy in the hexagonal lattice of graphite
What is the fuel for Magnox?
U-metal
What is the moderator and coolant for AGR?
Graphite
CO2
What is the moderator and coolant for Magnox?
Graphite
Coolant
List the following in ascending order of CO2 release per unit of electricity:
Coal
Nuclear
Oil
Gas
Nuclear
Gas
Oil
Coal
Why are delayed neutrons so important in reactor control?
They increase the average neutron lifetime
What does the microscopic cross section provide?
The properties of an individual nucleus
A sub-critical multiplying assembly can ________ the number of neutrons beyond the number introduced
increase
Do fission neutrons have a higher or lower KE than fission fragments?
Lower
What charge are fission neutrons?
Uncharged
The ‘activation energy’ to permit fission comes largely from
the binding energy of the neutron that causes the fission
What does the absorption cross section comprise of?
absorption cross section = capture cross section + fission cross section
What is the reactivity of a sub-prompt-critical nuclear reactor?
N/A
Following a period of normal full power operation, a reactor suddenly loses coolant to the extent that the fuel rod may be considered to be adiabatic, and the fission reaction ceases. As a result the fuel pellet edge temperature will
Rise.
Fuel burnup in a PWR is typically first limited because:
Fission product production and release to the plenum threatens pin integrity
What does the second and fourth term in the differential equation give?
(ii) local fission neutron production rate
(iv) local divergence of neutron current
Name four material effects as a consequence of radiation damage?
embrittlement
Phase changes
creep
hardening
Unit for neutron current?
neutrons per square metre per second
What moderator is used in a gas cooled fast breeder reactor?
No moderator
What coolant is used in CANDU?
Heavy water
List the following in increasing order of operating pressure:
CANDU
AGR
PWR
RBMK
AGR
RBMK
CANDU
PWR
A fast reactor typically requires a fissile concentration of plutonium around ___
20%
List the following in increasing coolant heat transfer coeffieicnt:
Water
Liquid sodium
High pressure CO2
Boiling water
High pressure CO2
water
liquid sodium
boiling water
True or false:
There is a decrease in the number of Frenkel defects as a result of radiation damage.
False
Which gas is used to pressurize reactor fuel pins?
Helium
Why is this statement inaccurate:
In a fast breeder reactor fuel is converted into energy rapidly, resulting in a shortened fuel cycle.
While fast breeder reactors are designed to produce energy more efficiently by using fast neutrons to convert fertile material (like uranium-238) into fissile material (like plutonium-239), they don’t necessarily convert fuel into energy more rapidly.
During a small break loss of coolant accident (LOCA) in a PWR, the core can remain uncovered for a significant time because ____
the reactor vessel remains pressurised and inhibits ingress of ECCS water
As the size of nuclei increases, the neutron to proton ratio
increases (gets larger)
