Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
; ; Koyama, Shinichi
JNC TN9400 2002-001, 155 Pages, 2002/01
JNC-TN9400-2002-001.pdf:13.36MB
Uranium-plutonium mixed nitride, (U,Pu)N, has been developed as advanced fuels for fast reactors. Compare with MOX fuel, it has an advantage of larger fissile density and higher thermal conductivity. In order to investigate the irradiation behavior under a fast reactor condition, post irradiation examinations were conducted for (U,Pu)N fuels as a part of the JAERI-JNC joint research program entitled "Basic Irradiation Test of Carbide and Nitride Fuels for Fast Reactors". The (U,Pu)N fuels were irradiated up to 40GWd/t at maximum linear power of 76kW/m in the fast test reactor JOY0. In the center part of fuels, the porosity and the pore size were increased compared with the peripheral region. But there were not observed the drastic structure change such as the formation of central hole and columnar grains. It was shown that the concentration of retained FP gas in any region was extremely high by the measurements of Xe radial distribution in the fuels. These results mentioned above indicated that the fuel temperature was low because of high thermal conductivity of (U,Pu)N.
; ; ;
JNC TN9400 2001-077, 114 Pages, 2001/06
JNC-TN9400-2001-077.pdf:4.32MB
Bundle duct interaction (BDI) caused by expansion of fuel pin bundle is a main factor to limit the fuel lifetime. Therefore, it is important for the design of fast reactor fuel assembly to understand the fuel pin deformation behavior under BDI condition. In order to understand the fuel pin deformation behavior under BDI condition, out-of-pile compression tests were conducted for FBR fuel pin bundle by use of X-ray CT equipment. In these compression tests, two kinds of fuel pin bundles were conducted. 0ne was the fuel pin bundle with the short wire-pitch and the other was the fuel pin bundle with the short wire-pitch and large diameter claddings. The general discussions were also performed based on the results of out-of-pile compression tests obtained by use of X-ray CT equipment in the previous work. Following results were obtained. (1)The occurrence of the pin-to-duct contact depends on the wire-pitch. In the fuel pin bundle with large wire-pitch, the pin-to-duct contact occurred at the early stage of BDI. The reason of this result is due to the low bowing rigidity of the fuel pins with long wire-pitch. (2)The value of the ovalation stiffness strongly depends on the geometry of cladding (diameter, thickness) and especially on wire-pitch. This result in this work revealed that the occurrence of the pin-to-duct contact depends on the value of the ovalation stiffness. (3)The occurrence of wire dispersion and dispersive displacement of pins depends on the wire-pitch strongly. In the fuel pin bundle with the long wire-pitch, the occurrence of the above-mentioned suppression mechanism to BDI is remarkable. (4)The suppression mechanism to BDI of the fuel pin bundle with the long wire-pitch is elastic oval deformation of cladding, wire dispersion and dispersive displacement of pins. 0n the other hand, the elastic and plastic oval deformation of cladding is the major suppression mechanism to BDI in the fuel pin bundle with the short wire-pitch. (5)The appearance ...
; ; ;
JNC TN9400 2001-022, 130 Pages, 2000/10
JNC-TN9400-2001-022.pdf:9.09MB
Bundle duct interaction (BDI) caused by expansion of fuel pin bundle becomes one of the main limiting factors for fuel life times. Then, it is important for the design of fast reactor fuel assembly to understand the BDI behavior in detail. In order to understand the BDI behavior, out of pile compressive tests were conducted for FFTF type bundle by use of X-ray CT equipment. In these compressive tests, two type bundles with different accuracy of initial wire position were conducted. The objective of this test is to evaluate the influence of the initial error from standard position of wire at the same axial position. The locations of the pins and the duct flats are analyzed from CT image data. Quantitative evaluation was performed at the CT image dada and discussed the bundle deformation status under BDI condition. Following results are obtained. (1)The accuracy of initial wire position is strongly depends on the pin-to-duct contact behavior. In the case of bundle with large error from standard position, pin to-duct contact is delayed. (2)The BDI mitigation of the bundle with small error from standard wire position is following: The elastic ovality is the dominant deformation in mild BDI condition, then the wire dispersion and pin dispersion are occurred in severe BDI condition. (3)The BDI mitigation of the bundle with large error from standard wire position is following: The elastic ovality and local bowing of pins with large error from standard wire position are occurred in mild BDI condition, then pin dispersion is occurred around pins with large error from standard wire position, finally wire dispersion is occurred in severe BDI condition. (4)The existence of pins with large error from standard wire position is effective to delay the pin-to-duct contact, but the existence of these pins is possible to contact of pin-to-pin.