Study of the Open Loop and Closed Loop Oscillator Techniques
Dr. George Imel
Department of Nuclear Engineering and Health Physics
Idaho State University
the years 2008-2014 we undertook a careful study of the theory and
operation of absorbing samples of very low reactivity worth oscillated
in our AGN-201 reactor. In this study both the open loop and closed
loop techniques were directly compared, with the objective being to
prove that the open loop technique (no feedback control) can achieve
the same low degree of uncertainty as the technically more complicated
closed loop system (requiring reactor control of power via a low worth
control rod as well as a feedback control system). That is, the lower
limit of uncertainty in either method is limited by reactor noise.
the years 2008 and 2009 undergraduates at Idaho State University
completed two senior design projects: the first to design and build a
simple open loop oscillator, and the second to design and build a
simple closed loop oscillator (capable of maintaining reactor power
constant through a small worth experimental rod using feedback control).
the years 2010 to 2013 our team refined the two oscillators regarding
actuator control and data acquisition. Additionally through this period
the important reactor parameters (λi, βi, generation time) were
quantified and uncertainties carefully studied. This phase is extremely
crucial to the success of the open loop system which relies on inverse
kinetics to unfold the reactivity of a small worth sample. Finally in
this phase a controlling “pilot rod” of low worth (to provide
reactivity resolution) had to be designed, fabricated, and calibrated.
the last years of this project, which officially ended December, 2014,
many experiments were performed, and the prime objectives were met: a
clear demonstration of the equivalency of the open and closed loop
techniques as well as showing that both were only limited by reactor
noise regarding achievable uncertainties.
Finally, two simple
designs were produced to implement the open loop system in a thermal
reactor (a TRIGA) and a generic fast reactor.
In summary, we
will present all of the important steps that we had to make in order to
successfully meet our objectives. We will present some of the
surprises, as well as some of the mistakes we made along the way. We do
this in the hopes that the simpler open loop technique will be
implemented elsewhere in support of measurements for the advanced