Modification of the evaluation model for Pu redistribution phenomena

; *;

JNC TN9400 2000-045, 64 Pages, 2000/03

JNC-TN9400-2000-045.pdf:2.47MB

During the irradiation, the Pu redistribution phenomena would occur in the FBR MOX fuel pellets. The phenomena would considerably affect on the thermal properties of the fuels, therefore, it is need to establish the evaluation method for Pu redistribution phenomena. ln JNC, the efforts for development of the evaluation model for the phenomena had been continued and the simple evaluation model was constructed in 1992. In this work, the modification of the simple model developed in JNC has been done and the following results were obtained. (1)Based on the recent data of the MOX fuel irradiation tests, the evaluation model for Pu redistribution phenomena constructed in l992 is modified. And the model is included into the fuel performance analysis code "CEDAR". (2)To calibrate the modified CEDAR code, it is confirmed that the uncertainty in the Pu concentration evaluation for the center of the fuel pellet at EOL is about 3wt.%. (3)Based on the results of the evaluations using the modified CEDAR code, it is found that, in the early stage of the irradiation, the Pu redistribution is controlled by the vapor transportation mechanism via pores, and after that, the Pu redistribution is kept in progress due to the thermal diffusion mechanism with the change of the Pu concentration due to the degradation of U and Pu by fissions. And it is also found that the O/M ratio dependence of the U-Pu inter diffusion coefficients would affect on the Pu redistribution mechanisms, in especial, in the early stage of the irradiation.

Radionuclide migration analysis in porous rock

Ijiri, Yuji; ; *; Watari, Shingo; K.E.Web*; *; *

JNC TN8400 99-092, 91 Pages, 1999/11

JNC-TN8400-99-092.pdf:6.62MB

JNC has been developed the performance assessment approaches for both fractured rock and porous rock. An equivalent continuum model is incorporated for solving the radionuclide migration in porous rock, while a discrete fracture network model is incorporated for solving the radionuclide migration in fractured rock (see more detail in Sawada et al. [1999]). This report describes the methodology, the data and the results of the performance assessment of porous rock. From the results of radionuclide migration analyses that were based on the hydrogeological properties obtained from the Neogene sedimentaly rock at the Tono mine, it was found that the release rate of selenium-79 and cesium-135 are dominant in porous rock. The sensitivity analyses using one-dimensional porous model revealed that hydraulic conductivity has more influences on the results than porosity does. In addition, it was found that smaller distribution coefficients of sandstone yield higher release rate than mudstone and tuff, and smaller distribution coefficients of saline water conditions yield higher release rate than fresh water conditions. The radionuclide migration in Neogene sedimentaly rock, where flow in rock matrix as well as in fractures are significant, was evaluated by superposing the results of porous model and fracture model. Since fracture model tends to yield more conservative results than porous model, it is obvious that the performance of Neogene sedimentary rock can be conservatively assessed by fracture model alone. The nuclide migration analyses performed in this report were based on the hydrogeological properties obtained at the depth between 20 meters and 200 meters frrom the ground surface. Therefore, it should be noted that the release rate at the depth of a future repository in Neogene sedimentary rock, 500 m, will be smaller than that shown in this report due to peemeability decrease from 200 m to 500 m.

Hydrogen absorption of titaniam for nuclear waste container in non-oxidizing condition

Tomari, Haruo*; *; Shimogori, Kazutoshi*; Wada, Ryutaro*; ; Taniguchi, Naoki

JNC TN8400 99-076, 100 Pages, 1999/10

JNC-TN8400-99-076.pdf:45.74MB

Effects of bentonite clay, applied potential, pH, of solution and cathodic polarization time on hydrogen absorption into titanium, which is one of the candidate materials of overpack for high-level radioactive waste container, have been investigated in artificial underground water. Considering the result at various test time and assuming the hydrogen absorption is ruled by the paraboric law, the amount of hydrogen after 1000 years exposure calculated to about 17ppm, which will be absorbed at the applied potential of -0.51 vs. SHE corresponds to equilibrium potential of hydrogen. It seems the assumption of the parabolic law and the test period are proper, because the linear relations were obtained between the amount of absorbed hydrogen and the logarithm of the averaged cathodic current and between the slopes of the lines and a square root of the test time. Titanium seems to have a life over 1000 years in deep underground repository according to assumption that about 500ppm absorbed hydrogen is critical for hydrogen embrittlement of titanium.

None

*; *; *; *; Morooka, Koichi*; *

JNC TJ1400 99-025, 483 Pages, 1999/02

JNC-TJ1400-99-025.pdf:20.57MB

no abstracts in English

None

PNC TN1410 97-032, 468 Pages, 1997/08

PNC-TN1410-97-032.pdf:10.35MB

no abstracts in English

None

Ikeda, Takao*; *; Chiba, Tamotsu*

PNC TJ1281 97-002, 182 Pages, 1997/03

PNC-TJ1281-97-002.pdf:6.29MB

None

Implementation of an MRACnn System on an FBR Building Block Type Simulator

Ugolini; Yoshikawa, Shinji; Ozawa, Kenji

PNC TN9410 95-253, 13 Pages, 1995/10

PNC-TN9410-95-253.pdf:0.5MB

This report presents the implementation of the a model reference adaptive control system based on the artificial neural network technique (MRAC) in a fast breeder reactor (FBR) building block type (BBT) simulator representing the Monju prototype reactor. The purpose of this report is to improve the control of the outlet steam temperature of the three evaporators of the Monju prototype reactor. The connection between the MRAC system and the BBT simulator is achieved through an external shared memory accessible by both systems. The MRAC system calculates the demand for the position of the feedwater valve replacing the signal of a PID controller collocated inside the heat transport system model of the Monju prototype reactor. Two series of simulation tests havc been performed, one with one loop connected to the MRAC system (leaving the remaining two connected to the original PID controller), and the other with three loops connected to the MRAC system. In both simulation tests the MRAC system performed better than the PID controller, keeping the outlet steam temperature of the evaporators closer to the required set point value through all the transients.

None

Mano, Tadashi; Ishikawa, Hirohisa; Fujita, Tomoo; Sugita, Yutaka

PNC TN8020 95-001, 50 Pages, 1995/01

PNC-TN8020-95-001.pdf:1.48MB

None

None

Sasage, Kenichi; ; Ouchi, Jin

PNC TN8100 94-003, 337 Pages, 1994/02

PNC-TN8100-94-003.pdf:11.55MB

no abstracts in English

Corrosion tests of cladding inner surface coating

*

PNC TJ9605 91-001, 28 Pages, 1990/10

PNC-TJ9605-91-001.pdf:1.81MB

The present report describes the results of studies performed sa a part of the results of "CORROSION TESTS OF CLADDING INNER SURFACE COATING" during a period of Feb. 20 - Mar.30, 1990. In the present study, corrosion tests have been carried out with CsOH to evaluate corrosion resistance of ferritic stainless steel and coated stainless steel. The following results were drawn from the present study (1)Corrosion tests of austenitic and ferritic stainless steel with ScOH were made at temperatures of 500-700C. After corrosin tests, intergranular attack was found to occur in the austenitic steel, however, there was no intergranular attack in the ferritic steel. Ferritic steel appears to have corrosion resistance to liquid CsOH superior to austenitic steel. (2)Corrosion tests between Ni-Ti, Ti, Al coatings on stainless steel and CsOH were made at temperature of 500-700C. Ni-Ti and Al coated stainless steel showed no intergranular attack, though the coatings were locally detached from the stainless stell substrates. Intergranular attack was observed in the Ti coated stainless steel. Ni-Ti and Al coating seem to be useful for reduction of intergranular attack of stainless steel cladding.