Isothermal Temperature Coefficient

Question 1

Define:

Isothermal Temperature Coefficient

Isothermal Temperature Defect

Answer 1

ITC - incremental change in reactivity due to an incremental change in moderator and fuel temperatures (pcm/ ºF)

ITD - total change in reactivity due to given change in moderator and fuel temperatures (pcm)

Question 2

Describe how ITC (isotheramal temperature coefficient) changes with:

core age

temperature

boron

Answer 2

ITC is dominated by MTC therefore however MTC changes, ITC will also change

core age - ITC gets more neg, buildup of Pu-240, P goes up because more resonant absorbers

temp - ITC gets more neg, at greater temp, density changes are greater for given change in temp

boron - ITC gets more neg, as [B] decreases, less competition

Question 3

Describe the following terms in the six factor formula

P (resonance escape probablility)

f (thermal utilization factor)

Answer 3

P - the probablilty of a neutron escaping the resonance peaks and reaching thermalization (any increase in this value, adds positive reactivity)

f - neutrons that reach thermalization, do not leak out of the core and have a chance of causing thermal fission (any increase in this value, adds positive reactivity)

Question 4

How does the following affect the:

P (resonance escape probability)

f (thermal utilization factor)

increase in fuel / moderator temp?

increase in core age?

increase in [B}?

Answer 4

inc fuel/mod temp -