Purpose: Estimate the control rod withdrawal percentage at which reactor will become critical, using the inverse multiplication (1/M) method. Discussion:
Generally, the inverse multiplication method is an indirect method that uses count rate data from detectors located outside of the reactor, typically a BF2 or 3 He detector, suspended on a wall of the reactor building.
The multiplication M is:
M = CR, / CR.
where CR, = some count rate at a condition "n" CR. = initial count rate So that
1/M = CR / CR.
The relationship of kerf to 1/M is: Kerr = 1 – 1/M.
Assignment:
Use the TRIGA Pool Reactor simulator to generate data for a 1/M versus percent of rod withdrawal plot. Using this plot, estimate the percentage of rod withdrawal that will make the reactor critical by extrapolating the data points. Start from the reactor scrammed position. Then withdraw the rods 5%, 10%, 15%, 20%, 25%, and 30%.