2016 MCQ

Question 1

Equation to calculate average coolant speed?

Answer 1

u = mass flow rate / density x flow area

Question 2

Equation to calculate average pin linear rating?

Answer 2

peak linear rating / average linear rating = PI / 2

Question 3

Equation to calculate channel temperature rise?

Answer 3

Change in temperature = (2 * peak linear rating * L) / (mass flow rate * specific heat * PI)

Question 4

What is the equation for local rate of neutron absorption?

Answer 4

= Macroscopic absorption cross section * neutron flux

Question 5

What are the dimensions for the following:

Neutron flux
Neutron current
Microscopic absorption cross section
Macroscopic absorption

Answer 5

L-2 t-1
L-2 t-1
L2
L-1

Question 6

If Pu239 is used to substitute U235, how do you calculate the multiple of neutron density needed?

Answer 6

Set fission rates equal to one another

Question 7

What is the commonest form of reactor fuel?

Answer 7

Uranium oxide pellets, helium fill-gas, zircalloy cladding

Question 8

True or false:
Fission products were easily able to escape into the surrounding rock of Oklo natural nuclear reactor.

Answer 8

False

Question 9

One of the last steps in the manufacture of conventional reactor fuel is to pressurize each pin with which gas?

Answer 9

Helium

Question 10

Approximately what percentage of the energy produced in a light water reactor is from the burning of Pu?

How is this calculated?

Answer 10

40%

2 % / 2+3 %

Question 11

What is the neutron diffusion approximation?

Answer 11

dn/dt = vOE_d - OE_a - Laplace(DO)

Question 12

Why does MOX fuel behave differently from conventional uranium fuel?

Answer 12

Pu releases slightly more neutrons per fission than U235

Question 13

Fuel burnup in a PWR is typically first limited because:-

Answer 13

Fission product production and release to the plenum threatens pin integrity.

Question 14

What is meant by a ‘delayed critical’ reactor?

Answer 14

One where criticality is achieved with >99% prompt neutrons, and <1% delayed

Question 15

List in order of increasing maximum fuel cladding temperature:

AGR
BWR
Magnox
PWR
Sodium cooled fast reactor

Answer 15

BWR
PWR
Magnox
Sodium cooled
AGR

Question 16

How to estimate the uranium mass needed for two different enrichments?

Answer 16

Divide enrichment percentages by one another (higher enrichment = less mass needed)

Question 17

Which of the following does the power output of a critical nuclear reactor depend on?

Enrichment
Reactivity
Size of core

Answer 17

None

Question 18

What is the reactivity of a critical reactor?

Answer 18

Zero

Question 19

What is the value or R?

Answer 19

8.314

Question 20

True or Untrue:

Even if a fuel storage pond leaks all its water ceramic UO2 fuel will not melt

Answer 20

untrue

Question 21

Typical peak fuel-to-coolant heat fluxes in a water-cooled reactor will be

Answer 21

10 ^ 6

Question 22

What is meant by a ‘critical’ reactor?

Answer 22

One where neutron number densities are unchanging

Question 23

When calculating the time for decay heat to reach a fuel melting point, what must you ensure?

Answer 23

Time taken = (melting temp - average temp) / cooling rate

Question 24

What is meant by ‘pellet – clad interaction’, and why does it matter?

Answer 24

Pellets can press against the clad and break it.