Lecture 4

Question 1

The neutron spectrum averaged cross sections in a fast reactor are substantially _____ than those in a thermal system

Answer 1

smaller

Question 2

In a fast reactor, the spatial distribution of the flux will be ____ across the cross section of the cell

Question 3

K infinite equation as a function of enrichment for fast reactors

Answer 3

Question 4

In the thermal and intermediate neutron energy ranges, cross sections generally are ___ than for higher energy neutrons.

Answer 4

larger

Question 5

Thermal reactor coolant and moderator region dimensions are typically ___ than those of the coolant channels in fast reactors

Answer 5

larger

Question 6

In thermal reactors the flux (will/will not) differ significantly

Answer 6

will

Question 7

k infinite for thermal reactors

Answer 7

Question 8

What is the four factor formula?

Answer 8

k infinite = εpfη

Question 9

Define ε

Answer 9

fast fission factor, the ratio of fast neutrons produced by fissions at all energies to the number of fast neutrons produced in thermal fission

Question 10

ε =

Answer 10

1 + probable number of collisions in fast neutron spectrum * nu / probable number of collisions in thermal neutron spectrum * nu

Question 11

define p

Answer 11

the probablity that a neutron will be slowed to thermal energy and escape resonance capture

Question 12

p =

Answer 12

numer of neutrons that reach thermal energies/numer of fast neutrons that start to slow down

Question 13

Increasing the temperature ____ the self-shielding at the resonance peak, and this _____ the absorption as temp increases

Answer 13

decreases

increases

Question 14

The resonance integral eqn

Answer 14

integral of absorption probablity in fuel/scattering dE

Question 15

Seperation of fuel from moderator causes resonance escape probablity to

Answer 15

increase

Question 16

f =

Answer 16

f = thermal utilization = number of thermal neutrons absorbed in fuel/ number of neutrons absorbed in all material

Question 17

what is ς

Answer 17

thermal disadvantage factor

Question 18

define η

Answer 18

Thermal fission factor; the number of fussion neutrons produced per thermal neutron absorbed in the fuel

Question 19

η =

Answer 19

Question 20

in a PWR, as the ratio of moderator to fuel (VmNm/FvNf), p ____, f _____

Answer 20

increases, decreases

Question 21

In a PWR, increasing the fuel radius ______ the multiplication

Answer 21

increases