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; *; Yoshida, Eiichi; Aoto, Kazumi
JNC TN9400 2000-011, 33 Pages, 1999/03
JNC-TN9400-2000-011.pdf:13.45MB
The damage was observed in rupture disk for the A-loop superheater of sodium-water reaction products releasing system for MONJU on March 3, 1998. Low temperature creep and stress corrosion cracking tests were carried out as the causes investigation of the damage. As the result, the followings are clarified. (1)The possibility that low temperature creep is the principal damage is small. (2)The stress corrosion cracking under NaOH environment due to the reaction of Na vapor and moisture condensed on the surface of glass beads as remains is the most probable cause on the damage. (3)Comparatively many glass beads remained in damaged surface. The gap between rupture disk and vacuum support was narrower than other parts, and they were not directly exposed to the Na vapor for a long time. The above factors caused the perfect intergranular cracking by stress corrosion. Since NaOH was chemically changed into the harmless Na
O on the location except for damaged zone by full Na vapor, the stress corrosion cracking was not generated.
*; *; *; *; *; *; *
PNC TJ9164 94-006, 133 Pages, 1994/03
This report gives an applicability of SWAT-3 facility and contents of the reconstruction in order to confirm a DBL (Design Basis Leak) for the demonstration reactor SG. (1).Test Cndition and test case. Evaluation of the wall temperature for adjacent heat transfer tubes under the sodium-water reaction event was performed. (a)As the effect of tube rupture due to overheating, failure of upper part of the helical coil was severer than one of the lower part. (b)The wall temperature depends on the water side condition. (c)Reference test condition, whici is water leak rale about 1 kg/s, failure of upper part of the helical coil and 30% partial load, was selected. A total of ten test cases were decided. (2).System and Components Design. (a)Large leak sodium-water reaction analyses including water injection rate analysis and quasi-steady pressure analysis were performed. The maximum water leak rate of 1 DEG was 7.2 kg/s and the water leak rate at the quasi-steady state was 3.1 kg/s. The maximum pressure was 18.1kg/cm
a at the piping between the reaction vessel and IHX, the pressure was within the design condition of SWAT-3 facility. (b)Based on the results of the large leak sodium-water reaction analyses, a reaction vessel, water heaters and a dump tank were designed and their design specification were clarified. The reaction vessel was a scale of one third of the demonstration reactor SG and it was designed to be able to conduct the water injection test twice with one test unit. (c)A system and piping diagram, and many kinds of list (Piping list, Valve list, instrumentlist) were made up. (3).Reconstruction scope and arrangement plan. The reconstruction scope and a layout for the components and piping were clarfied and the arrange ment plans were made up. (4)Reconstruction period. The recoastruction period and man power for the design, fabrication, inspection and installation were studied and the reconstruction schedule was made up.
Ohtaki, Akira
PNC TN9410 90-062, 145 Pages, 1990/04
It is important to control an operation to avoid water flow in which cause of SCC for a superheater which is made by astinetic stainless steel. During the superheater war㎜ing operation at the 50MW Steam Generator Test Facility, temperature fluctuation at the inlet tube sheet are easily occurred, and existence of saturated water with in warmming steam is regarded as the cause of it. A test simulating operating conditions of "Monju" superheater warmming was carried out to comfirm start up condition of "Monju". Test results show that a part of war㎜ing steam was cooled down to saturated temperature in main steam pipe which temperature is still lower than the saturated temperature, then the saturated water flows in the tube sheet which temperature is as high as sodium inlet temperature, and cause the temperature fluctuation. In order to confirm the effect of pre-heating the main pipe using trace line, a trace line was adapted at the main steam pipe, and the same superheater warmming simulation test was performed. Test results show that trace line was effective to pre-heat the main steam pipe exceeding temperature, and the temperature fluetuation was considerably decreased.