FINAL DAY REVISION

Question 1

At what axial location in the core of an idealised cylindrical PWR is film boiling of the coolant most likely to occur if the power were to be increased?

Answer 1

At the core mid-plane

Question 2

The production of 1 GW (thermal) requires the fissoning of about how much Pu239 per day?

Answer 2

1 fission = 203 MeV = 3.25 E-11 J
1 GW for 24 hours = 8.64 E13 J
# fissions * 239 * 1.66E-27 = 1.05 kg

Question 3

Which is the order for spent fuel waste safety barriers in a repository, from inner to outer:

bentonite, crystalline rock, fuel cladding, fuel canister

Answer 3

fuel cladding, fuel canister, bentonite, crystalline rock

Question 4

Which list is in order of increasing maximum fuel cladding temperature?

Answer 4

BWR, PWR, Magnox, Sodium-cooled fast reactor, AGR

Question 5

What, approximately, are the dimensions of the active core of a PWR?

Answer 5

4m diameter, 4m height

Question 6

How to calculate the channel temperature rise?

Answer 6

Change in T = 2 * Peak linear rating * L * no. rods / mass flow rate * specific heat capacity * Pi

Question 7

The expression nvSigma_fv* gives _________

Answer 7

the local fission rate.

Question 8

Which value of fanning friction factor should be used to calculate the pressure drop?

Answer 8

normal (NOT DARCY WEISBACH)

Question 9

How to calculate the peak boundary layer temperature difference?

Answer 9

q’’ (peak) = h (T_s - T_infinity)

Question 10

Consider a typical fuel channel in a gas-cooled reactor (eg. an AGR). If the mass-flow rate of the gas and the reactor power were both decreased by 10%, the effect would be _______

Answer 10

The rate of cladding oxidation would be slightly decreased

Question 11

Which list is in ascending order of turbine entry temperature?

Answer 11

PWR, AGR, a modern coal fired power station

Question 12

In descending order, the main forms of energy release from fission of U235 are:

Answer 12

Fission fragment kinetic energy, fission product radiation, prompt
gamma rays, neutron kinetic energy

Question 13

Neutron current is

Answer 13

neutrons per unit area per unit time in a particular direction.

Question 14

What is the coolant pressure of a PWR?

Answer 14

150 bar

Question 15

What is the coolant pressure of an AGR?

Answer 15

40 bar

Question 16

What is meant by the reflood phase of (some) PWR accidents?

Answer 16

Slow bottom-up re-entry of water to the core

Question 17

What is the main physical phenomenon that contributes to the pressure drop in the core of an AGR?

Answer 17

Coolant frictional pressure drop

Question 18

Wigner energy is

Answer 18

neutron induced strain energy in the hexagonal lattice of graphite

Question 19

A typical PWR generates 1.4GWe. Approximately how many fissions per second does this correspond to:

Answer 19

1 fission = 203 MeV = … J
1.4 GWe / … J * Thermal efficiency

Question 20

Moderator heating is a mechanism which leads to

Answer 20

a change in reactivity, but there is insufficient information to determine whether it is an increase or decrease

Question 21

In a large-break loss of coolant accident the ‘bypass’ phase involves

Answer 21

Flow diversion around the baffle due to rapid steam flow from the core immediately following the break

Question 22

Xe-135 poisoning is thought to play a role in which nuclear accident?

Answer 22

Chernobyl

Question 23

Which of the following would not be used as a cladding
material in a nuclear reactor?

Answer 23

Gadolinium

Question 24

Which one of the following is the LEAST important economic
factor in the deployment of nuclear power

Fuel cost
Construction cost
Construction time
Wholesale electricity price

Answer 24

Fuel cost

Question 25

What might be used as the coolant and the moderator in a plutonium-breeding reactor?

Answer 25

Sodium, no moderator at all

Question 26

What is the most important of the following factors that influences the difference between coolant temperature and clad temperature in a typical PWR in normal operation?

Answer 26

Coolant density

Question 27

A prototype fusion reactor is able to maintain an ion density of 6E+20 ions/m3, at a temperature of 150E+6 K for 0.01 seconds. Which one of the following statements is true?

Answer 27

The reactor would fail to reach ignition

Question 28

In a supercritical water-cooled reactor, the coolant is

Answer 28

light water at ~230 bar

Question 29

In a PWR in which a large break loss of coolant accident occurs

Answer 29

the core depressurizes and the liquid water flashes to steam which exits through the break