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; ; Tamura, Seiji*
PNC TN941 83-54, 53 Pages, 1983/04
In order to develop one of the on-line plant anomaly monitoring system, applying reactor noise analysis technique, a modeling of transfer function for the indisial response and spacial dependent neutron fluctuation in the core was studied using WS (weight sequence) model technique. It was proven that the reactor kinetics and space dependent neutron fluctuation Were well identified by means of the WS model technique and also the WS model may detect the anomaly experienced in JOYO. The WS model method has advantages, if compare to the ordinary frequency analysis technique. The access time is shorter and the volume of program is smaller. The results suggested that the WS model has a potential to be utilized in the on-line anomaly monitoring system.
Muramatsu, Toshiharu; ; ; ; ;
PNC TN941 82-176, 90 Pages, 1982/08
The eddy current type flow meters were installed above the center of the core in "JOYO", in order to study their feasibiliey under high temp and high energy neutron flux condition. The characteristics of flowmeter placed at the center are as followings, (1)The unbalance signal of flow signal drifted-40%, compared with result at 4th oyde operation of 75MW power. (2)The lineality of flow signal at sensor 1 VS. main flow was obtained as
5% of full scall in each test case. (3)The lineality of temperature dependency of flow signal. at 1 sensor was obtained as 4% of 600
C full scale. (4)The lineality of temperature signal at sensor 1 VS. Thermocouple (TC-1) was obtained as 1% of full scale 600C on each test cycle. (5)Change of each coil resistance was very in significant at neutron flux level of about 4.06
10
n/cm
for 130days.
Muramatsu, Toshiharu; ; ; ; Tamura, Seiji*
PNC TN941 81-75, 53 Pages, 1981/04
Eddy current type flow meter has been installed above center of the core in "JOYO", to measure outlet sodium velocity of center channel. This information is applied, together with outlet sodium temperatures subassemblies, in monitoring the malfunction of the center subassembly. This paper presents a study of flow measurements from the initial 50 MWt power ascention to the third cycle operation of 75 MWt power. The results of the tests are as followings. (1)If an unbalance of the secondary coils is adjusted to zero, lineality of velocity vs. primary main flow and temperature dependency above the temperature of 350C are obtained within error of 6%. (2)The unbalance signal must be adjusted prior to every cycle operation, because of its drift during the power operation. (3)On constant power operation, the flow signal drifts 2% of full scale. (4)It was confirmed that added signal detected temperature change with almost zero delay time. (5)The flow velocity obtained by cross-correlation method was approximately 20% less than the flow signal reading.
; ; Tamura, Seiji*
PNC TN941 81-03, 82 Pages, 1981/01
Reactor noise tests were carried out in 75 MW Power Up Test. The main purpose of this analysis is to investigate the existance of the peak in APSD of neutron flux signal and the low correlations of neutron flux signals from different position power range flux monitors in the frequency range 5 10
7 10
Hz. The anormalous reactivity phenomenon, observed at the first 75MW power-up, accompanied the power coefficient change of 50 MW power level, thereby it was predicted that reactor noise characteristics have aloso changed. These changes were investigated, and the phenomena of neutron flux signal were examined. The primary points of the results are as follows. (1)By the quantitative analysis and the investigations of reactor noise characteristics changes, it became almost clear that the phenomena of the low correlation between different locations is caused by the spacial dependency effect of neutron flux fluctuations. (2)Coherence functions of neutron flux signals and transfer functions of reactor inlet temperature - neutron flux have changed with the power coefficient changes, thereby it became almost clear that the intensity of spacial dependency effect have also changed with the anormalous reactivity phenomenon. (3)It was estimated that the peak in APSD of neutron flux signal is the inherent phenomenon of the reactor and caused by the movements of core composition elements. Based on these estimation, it was assumed that the peak is a resonant phenomenon between thermal bowing of the subassembly wrapper tube and the neutron flux, which accompanies the movements of core subassemblies.
; ; Tamura, Seiji*
PNC TN941 80-146, 60 Pages, 1980/08
In the experimental fast reactor "JOYO", in-core acoustic monitoring has been continued, in order to detect in-core abnormal condition like sodium boiling at an early stage. Three in-core acoustic detectors are situated in the core addressed [5A2], [5C2] and [5F2]. The following facts were derived from the measurements and the monitoring by these detectors through the first 75 MW duty cycle operation. (1)The background noise at several ten kHz range, which is suitable range for sodium boiling detection, is mainly composed of electromagnetic noise from the primary sodium flow control system. The power spectral density of the noise has a broad peak at about 22 kHz. The signal level of the noise are independent of reactor power and primary sodium flow (primary sodium pump in operation). (2)Since this in-core acoustic detection system has poor SN ratio, the analogy of the result of the local sodium boiling test conducted at off-site may resulted in difficulty for detection of local sodium boiling by this system. (3)Insulation resistance of the detectors became lower as sodium temperature became higher. Over about 330C, however, the resistance of [5A2] in-core acoustic detector suddenly increased more than 300 times of its normal value. (4)Abnormal core condition has not been found until now according to the in-core acoustic monitoring system.
; Tamura, Seiji*; ; ; Muramatsu, Toshiharu
PNC TN941 80-145, 60 Pages, 1980/08
Anomaly reactivity monitoring program which is one of functions of Joyo data reduction system was tested under various plant conditions during power ascension testing period. The program is based on a reactivity balance of measured reactivity and known reactivity, and is to detect unknown (or anomaly) reactivity. As consequences of the testings, following results were obtained. For each change of power level and coolant temperature, reactivity change of more than 10cent was induced, the program, however, indicated no trace of any anomaly reactivity. While for change of coolant flowrate of 20%, approximatly 3cent error reactivity was detected due to, probably, mismatch of thermal constants in the program. Through these testings, it was cleared that the modeling of the program is well simulating the reactor kinetics within 2cent of error except for the change of flowrate. In normal operation, since flowrate is held constant, the error due to flowrate is insignificant.
; ; ; Tamura, Seiji*; Sanda, Toshio*; Yamamoto, Hisashi*
PNC TN941 80-02, 70 Pages, 1980/01
Neutron flux, control rod (CR) load cell signals, CR acoustic signals and reactivity signal were measured and analyzed to study the effect of CR vibration induced by primary sodium flow during the low power and the power ascension tests of the Experimental Fast Reactor "Joyo". The measured signals were recorded by a multi-channel data recorder under various operating conditions of primary sodium flow, CR position and reactor power. Then the recorded signals were analyzed by a spectrum analyzer to obtain their power spectral density functions (PSD), coherence functions and r.m.s. values. Following characteristics were determined. (1)Impact sound detected on housing of CR drive mechanism became obvious as the sodium flow rate reached 100%. Its frequency was about 2Hz. (2)The auto PSDs of the fluctuation of the measured signals had evident spectra at about 2Hz. Also the coherence functions between them showed more significant at about 2Hz. (3)The r.m.s. value of the fluctuation of reactivity signal decreased as a control rod was withdrawn. The r.m.s. value at 50Mw was about 0.1 cent. Based on these results, the frequency of CR vibration due to the flow was about 2Hz. The r.m.s. value of reactivity fluctuation at 50MW mainly caused by the vibration was about 0.1 cent.
; ; ; Tamura, Seiji*
PNC TN941 79-237, 27 Pages, 1979/12
Reactor noise tests were carried out in the second operating cycle at 50MW power level. The aim of this reactor noise analysis was to examine the correlations of fluctuations of temperature, flowrate and neutron flux in reactor vessel and in the primary coolant loop. The primary points of the results are as follows. (1)In APSD of neutron signal, the peak at 2.53.010 Hz exists. This peak seems to be produced by the neutron penetration fluctuation, caused by sodium temperature fluctuation in the blanket region. (2)Neutron fluctuations of l.05.010 Hz seem to be reactivity fluctuations, produced by reactor inlet temperature fluctuations. On the other hand, those of 5.010 2.010Hz seems to be neutron penetration fluctuations, caused by sodium temperature flucturations in the blanket region. These results were obtained, by analyzing coherence functions between neutron signals. (3)Core and blanket subassemblies can be divided into two regions, A and B region, with respect to the spacial motion of temperature in the reactor core, The A region means the region in which sodium temperature fluctuations in subassembly are affected by the A loop reactor inlet temperature significantly, and the B region means the region in which sodium temperature fluctuations in subassembly are affected by the B loop reactor inlet temperature. (4)The fluctuations of the A loop reactor inlet temperature are greater than the fluctuations of the B loop reactor inlet temperature. This reason seems to be that the fluctuations of the coolant flow rate may affect the fluctuations of the reactor inlet temperature directly at A loop, and this tendency does not exist at B loop.
; Muramatsu, Toshiharu; Yamamoto, Hisashi*; Sanda, Toshio*; ; ; Tamura, Seiji*
PNC TN941 79-227, 50 Pages, 1979/12
A great interest exists in developing the reliable rapid malfunction detection system for the safe and economic operation of LMFBR. In the experimental fast reactor "Joyo", the acoustic detection technique was adopted to monitor the reactor core as one of malfunction detection techniques. According to this technique, power spectral density and rms value of the signal from the in-core acoustic detector are monitored. If they vary greatly rrom their normal pattern and value, the inspection is held to assure the failure part. Two in-core acoustic detectors are inserted above the reactor core (address [5A2] and [5C2]). The data from them at normal reactor condition were collected during the low power test and the power up test up to 50MW. Some conclusions were derived from the analysis of the data. (1)The characteristies of [5A2] and [5C2] in-core acoustic monitoring systems are different. The [5C2] in-core acoustie monitoring system is affected by acoustic noises of the rotating plug. While the signal amplitude or [5A2] in-core acoustic signal was reduced by half at high sodium temperature. (2)A S/N ratio or this system is poor quality, therefore the amount of information detected from sodium by the in-core acoustic detectors is not known yet. (3)CRD housing acoustic detector is more sensitive to the impact sound caused by control rod vibration than the in-core acoustic detectors. (4)Abnormal condition has not been found until now according to this monitoring system.
Sanda, Toshio*; ; ; ; ; Muramatsu, Toshiharu; Sekiguchi, Yoshiyuki*
PNC TN941 79-218, 99 Pages, 1979/12
As part of dynamics tests in the experimental fast breeder reactor "JOYO", reactor noise tests were carried out. At some power levels, up to 50MW, fluctuations of the flux, the outlet, temperatures of fuel assemblies and temperatures of primary and secoudary main cooling loops were measured. The power spectral density, correlation function, transfer function and coherence function of these signals were obtained and reactor characteristics were analyzed. The major results are as follows. (1)It was confirmed that no unstable phenomenon exists in JOYO. (2)At low frequency region, fluctuations of these signals are larger and give better correlations. At this region, the primary contributors to fluctuations of the flux and the reactor outlet temperature were investigated. (3)In power spectral density of the flux, the noticeable peaks exist at about 1.8Hz and 0.025Hz. The former peak is due to control rod vibration effect and the latter peak has reactor power dependency and the neutron detector position dependency. (4)By the correlation functions of the secondary cooling loop temperatures, coolant transport delay times were obtained, which showed good agreement with the times calculated by flow velocity and the pipe length.
Sanda, Toshio*; ; ; ; ; ; Yamamoto, Hisashi*
PNC TN941 79-160, 64 Pages, 1979/10
As a Part of dynamics tests in the experimental fast breeder reactor "JOYO" pile oscillator tests were carried out. At some power levels, from zero power to about 50 MW, the transfer functions between sinusoidal reactivity change wich a pile oscillator equipment and the response of the neutron flux, the outlet temperatures of fuel assemblies, reactor outlet temperatures and etc., were measured. Measurements were made in the range from 0.001 Hz to 3Hz. Major results are as follows. (1)The agreement between the measured and calculated zero-power transfer function was satisfactory. (2)By the measurements of the at-power frequency responses, the stability of JOYO was confirmed and the large and negative feedback effects were obseved. (3)The feedback transfer function and the transfer function between the flux and the response of the outlet of the temperature of the center fuel assembly are approximately expressed by a first-order lag with the same time constant (about 3 seconds). (4)In those measurements, in which the reactivity change inserted in the reactor was about 7 cent (peak-to-peak), the effect of the coolant temperature controller in the secondary cooling loop was reflected only in so far as the measurements were made at so low frequency, around 0.001 Hz. (5)The time constant of the thermocouple of the center fuel assembly was about 3.2 seconds.
