Equivalency of open loop and closed loop reactivity measurement techniques

There is a need for integral physics data on reactivity worth of minor actinides (transmutation studies) and fission products (burn-up credit) for validation of differential data. In France, the MINERVE facility has been used to determine low-worth reactivity measurements using a closed-loop oscillator technique. However, it has been deemed unfeasible to perform such measurements in a simulated fast reactor spectrum in MINERVE as was done in the past. We propose that reactivity worth measurements could be directly performed in the fast reactor MASURCA using an open loop oscillator technique. Theoretically, these two methods should be equal in how well a measurement can be known. This paper compares open loop techniques (pile oscillator method analyzed with harmonic analysis and inverse kinetics) with the closed loop technique (reactivity oscillator method). Open and closed loop techniques are defined in the classic control sense - closed loop utilizes feedback while open loop has no imposed feedback. Experiments were performed to show variations based on frequency and power as well as the determination of a small worth sample on the order of 0.04 cents with standard deviations on the order of 0.003 cents. All techniques were shown to produce results that were limited only by reactor noise.