Week 2: Control Reactivity

Question 1

What factors have an impact on the net reactivity in the reactor core?

Answer 1

Rods
Boron
MTC
DTC
Voids
Burnup
Poisons

Question 2

What is the definition of Differential Boron Worth?

Answer 2

The rate of addition of reactivity per unit change in boron concentration in pcm/ppm.

Question 3

What is the definition of Integral Boron Worth?

Answer 3

The reactivity inserted by borating/diluting the RCS boron concentration from one concentration to another in pcm.

Question 4

What is the definition of Differential Rod Worth?

Answer 4

The change in reactivity resulting from a unit change of rod position in pcm/step.

Question 5

What is the definition of Integral Rod Worth?

Answer 5

The reactivity inserted by moving a RCCA from a reference position to any other position in pcm.

Question 6

What is Rod Bank Overlap and why is it used? What is the overlap value for a SNUPPS design?

Answer 6

An overlap is when a control bank begins to move prior to the preceding bank completing a full withdrawal. This overlap is used to provide a more uniform differential RCCA worth. Value for SNUPPS is 113 steps of overlap.

Question 7

What are the bases for Rod Insertion Limits?

Answer 7

To minimize the consequences of a rod ejection
To guarantee adequate shutdown margin
To produce an axial flux distribution that will prevent high local peak power levels

Question 8

What are the RIL alarms? What operator actions are required?

Answer 8

RIL Low
-10 steps above RIL
-Normal Borate until clear
RIL Low-Low
-At or below RIL
-Emergency Borate until clear