2016 MCQ Flashcards
Equation to calculate average coolant speed?
u = mass flow rate / density x flow area
Equation to calculate average pin linear rating?
peak linear rating / average linear rating = PI / 2
Equation to calculate channel temperature rise?
Change in temperature = (2 * peak linear rating * L) / (mass flow rate * specific heat * PI)
What is the equation for local rate of neutron absorption?
= Macroscopic absorption cross section * neutron flux
What are the dimensions for the following:
Neutron flux
Neutron current
Microscopic absorption cross section
Macroscopic absorption
L-2 t-1
L-2 t-1
L2
L-1
If Pu239 is used to substitute U235, how do you calculate the multiple of neutron density needed?
Set fission rates equal to one another
What is the commonest form of reactor fuel?
Uranium oxide pellets, helium fill-gas, zircalloy cladding
True or false:
Fission products were easily able to escape into the surrounding rock of Oklo natural nuclear reactor.
False
One of the last steps in the manufacture of conventional reactor fuel is to pressurize each pin with which gas?
Helium
Approximately what percentage of the energy produced in a light water reactor is from the burning of Pu?
How is this calculated?
40%
2 % / 2+3 %
What is the neutron diffusion approximation?
dn/dt = vOE_d - OE_a - Laplace(DO)
Why does MOX fuel behave differently from conventional uranium fuel?
Pu releases slightly more neutrons per fission than U235
Fuel burnup in a PWR is typically first limited because:-
Fission product production and release to the plenum threatens pin integrity.
What is meant by a ‘delayed critical’ reactor?
One where criticality is achieved with >99% prompt neutrons, and <1% delayed
List in order of increasing maximum fuel cladding temperature:
AGR
BWR
Magnox
PWR
Sodium cooled fast reactor
BWR
PWR
Magnox
Sodium cooled
AGR
How to estimate the uranium mass needed for two different enrichments?
Divide enrichment percentages by one another (higher enrichment = less mass needed)
Which of the following does the power output of a critical nuclear reactor depend on?
Enrichment
Reactivity
Size of core
None
What is the reactivity of a critical reactor?
Zero
What is the value or R?
8.314
True or Untrue:
Even if a fuel storage pond leaks all its water ceramic UO2 fuel will not melt
untrue
Typical peak fuel-to-coolant heat fluxes in a water-cooled reactor will be
10 ^ 6
What is meant by a ‘critical’ reactor?
One where neutron number densities are unchanging
When calculating the time for decay heat to reach a fuel melting point, what must you ensure?
Time taken = (melting temp - average temp) / cooling rate
What is meant by ‘pellet – clad interaction’, and why does it matter?
Pellets can press against the clad and break it.