FEYNMAN-ALPHA CORRELATION-ANALYSIS BY PROMPT-PHOTON DETECTION

Two-detector Feynman-a measurements were carried out using the UTR-KIN KI reactor, a light-water-moderated and graphite-reflected reactor, by detecting high-energy, prompt gamma rays. For comparison, the convent ional measurements by detecting neutrons were also performed. These me asurements were carried out in the subcriticality range from 0 to $1.8 . The gate-time dependence of the variance-and covariance-to-mean rati os measured by gamma-ray detection were nearly identical with those ob tained using standard neutron-detection techniques. Consequently, the prompt-neutron decay constants inferred from the gamma-ray correlation data agreed with those from the neutron data. Furthermore, the correl ated-to-uncorrelated amplitude ratios obtained by gamma-ray detection significantly depended on the low-energy discriminator level of the si ngle-channel analyzer. The discriminator level was determined as optim um for obtaining a maximum value of the amplitude ratio. The maximum a mplitude ratio was much larger than that obtained by neutron detection . The subcriticality dependence of the decay constant obtained by gamm a-ray detection was consistent with that obtained by neutron detection and followed the linear relation based on the one-point kinetic model in the vicinity of delayed critical. These experimental results sugge st that the gamma-ray correlation technique can be applied to measure reactor kinetic parameters more efficiently. (C) 1997 Elsevier Science Ltd.