FROM:

SUBJECT: Rate of Power Rise with Control Rod Removal

1. Removal of the control rod in 10 minutes is estimated to be a safe rate.

2. The rate at which the reactor power P increases with rod removal speed vr

is found to be always smaller than that predicted from the steady-state

power-rod position curve, ie

After a time delay characterized by a time

seconds at the middle of the range) where 1e is

the average neutron lifetime, [alpha] is the temperature coefficient of reactivity,

and To is the initial difference in temperature of solution and coolant,

the power rise rate approaches the predicted rate, .

Thus a test is provided for any pre-assigned rod speed. The maximum slope o

the curve above is

Thus at a speed such that the rod is removed in 10 min (600 sec), then

at other points on the curve dP/dx is smaller, of course, and thus dP/dt

is smaller.

The analysis loading to those conclusions is given in the Appendix.