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Isozaki, Kazunori; ; Ito, Hideaki; ; Chatani, Keiji; ;
PNC TN9520 93-006, 198 Pages, 1992/11
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*; Maekawa, I.*; Sato, Kazujiro*
PNC TN9410 87-056, 139 Pages, 1987/03
The mass transport version (ver.MT) of three-dimensional thermal-hydraulic analysis code, COMMIX-PNC, has been developed to evaluate gas blow -down effects in the annulus between the MONJU closure head and plug port. The ver.MT has been validated through the analysis of the fundamental experiment of KCl transport and gas blow-down mock-up experiment. The fundamental experiments were carried out using a water cavity with 500 mm 
500 mm 50 mm in size. The experiments began pouring KCl solution into the inlet of the cavity. The calculated histories of the KCl concentration transient agreed well with the experiment. For the mock-up gas blow-down experiment, three gas flowrate cases, 0.05m
/min, 0.02m/min and 0.1m/min were calculated. Noble gas were predicted to reach the top part of the annulus only in the case with 0.1m/min flowrate. Through the application of the code to the MONJU configuration, the follwing have been effects of gas blow-down as obtained : [Normal gas blow condition] F.P. gases didn't enter into the annulus. [Half gas blow condition] The gases with 10
% concentration reached the location of 3905 mm above the bottom of shielding plug, and [Gas blow trip condition] The gases with 13% concentration reached the door valve in 1000 sec. simulation. From the above results and their consistency with the evaluation of gas blow-down effects by the experimental correlation derived from the gas blow-down experiments, the correlation can be applicable to a complicated annulus like that of the MONJU.
*; *; Sasaki, Makoto; *
PNC TN941 81-239, 62 Pages, 1981/12
This report describes the presumption about the causing mechanism of the power Coefficient Anomaly in JOYO, which occurred in 75 MW Power Ascension Test, summer 1979. After the previous report, the new information about the results of the post irradiation examination and the analyses about JOYO power coefficient could be obtained. The causing mechanism of the anomaly could be presumed from these information as follows. [Step 1]-50 MW Power Operation Period- The fuel burn-up reached about ten thousand MWD/ton at the end of 50 MW duty 2nd cycle, and the produced fission gas was almost retained in the fuel pellets. [Step 2]-Fission Gas Release during Initial Power Ascension from 50 MW to 75 MW- On the occasion of the initial power ascension from 50 MW to 75 MW, the fission gas release began suddenly at the power level of some above 50 MW. [Step 3]-Rising of Fuel Pellet Temperature and Appearance of Pellet Crack due to Fission Gas Release- The fission gas release reduced the gap conductance and caused the rising of fuel pellet temperature and appearance of pellet crack. These phenomina induced the fuel stack length to elongate abruptly. [Step 4]-Abnormal Behavior of Power Coefficient- The fuel temperature rising and the fuel stack length elongation induced the fuel expansion reactivity effect and Doppler reactivity effect to enlarge, and caused the anomaly behavior of power coefficient. [Step 5]-Power Coefficient Changing and Reactivity Loss of 40 cent- After the initial 75 MW, the fuel stack length didn't respond nomaly to the reactor power change by some reason. Therefore, the magnitude of power coefficient became smaller and the power level dependency changed after 75 MW. At the shut down of reactor, the core average stack length elongated a few mm and the reactivity of about 40 cent was lost from the core after the power coefficient anomaly. As mentioned above, it is presumed that the causing mechanism of the power coefficient anomaly in JOYO was the ...
*; Kawata, Tomio*; Yumoto, Ryozo; *; *; *
PNC TN243 81-02, 15 Pages, 1981/10
no abstracts in English
