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H.Araki*; T.Komab*; Sato, Kazujiro*; Y.Ozaki*; H.Inuzi*; K.Koday*; Y.Shino*
PNC TN941 81-114, 11 Pages, 1981/06
Some studies for confirmation of the usefulness of the measurements of boiling sound and fluctuations of sodium temperature, flowrate and neutron flux for detection of sodium boiling have been curried out in Japan. For the development of acoustic detection system, acoustic transmission decay and velocity change by fuel pins, gas plenum and neutron shield were measured. Acoustic transmission from the reactor core to the detectors which were installed in the upper core structure and the upper flange of reactor vessel were studied theoretically and experimentally using the reactor vessel mockup. Sodium boiling acoustic spectra which were dependent of detector positions were obtained in the out-of-pile experimental facility. Acoustic background caused by flow and electric noise were measured in the Experimental Fast Reactor. On the other hand, coolant temperature and flowrate fluctuations caused by the sodium boiling were measured by the Temp/Flow detector which were mounted on the outlet of fuel subassembly. Simulation tests by computer on the correlation method between neutronic and acoustic signals were carried out. Current status and future plans about these studies in Japan are summarized briefly in this paper.
J.Shima*; Y.Fujii*; Y.Shino*; H.Araki*
PNC TN941 81-116, 9 Pages, 1981/01
As a part of the work on the development of a diagnostic system for detecting anomalies in the core of a fast breeder reactor, a study is being made on the methods of detecting abnormal reactivity and coolant boiling on the basis computer simulation. The objective of the present simulation study is to obtain some basic information useful for developing sensitive method of signal processing suitable for boiling detection. Neutronic, acoustic and measurement noises as well as reactor kinetics and reactivity estimator are simulated on a hybrid computer and analyzed for various noise conditions using correlation, spectral and coherence analyses. It has been confirmed that the cross-spectral and coherece analyses between neutronic and acoustic signals are effective method for boiling detection provided that the void coefficient of reactivity is sufficiently large and that detection capability is slightly improved by using a discriminator of signal level before making spectral analysis. A simulated boiling detection experiment using a zero power thermal reactor is also planned in order to check the validity of computer simulation.
