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PNC TN9410 96-235, 258 Pages, 1996/03
The chemical decontamination technique has been developed in order to remove the crud adhering to the surface of the components constructing the primary coolant system, as a part of the measure to decrease the exposure in the annual inspection. The technique has been already applied to the prototype reactor "Fugen", in the core of which the fuel assemblies were not loaded. The chemical decontamination, for the core in which the fuel assemblies are loaded, has been planned for the purpose of improving the utilization factor. It is necessary to confirm, through the test before putting the plan into practice, that the decontamination reagent does not exert a bad influence upon the components constructing the fuel assembly. This report describes the test results which have been carried out so as to investigate the influence of the reagent on the components constructing the fuel assembly. The outline of the results is as follows: (1)The susceptibility to stress corrosion cracking of the chemical decontamination treatment and the residual decontamination reagent on the components constructing the fuel assembly is low enough. (2)The chemical decontamination treatment and the residual decontamination reagent do not exert a bad influence upon the integrity of the fuel assembly concerning the fuel rod holding function of the spacer and the characteristics of the fretting wear caused on the fuel claddings.
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PNC TN9410 94-052, 251 Pages, 1994/01
The structure of the pressure tube rolled joint portion for the ATR Demonstration Reactor is somewhat changed from that for Fugen, in order reduce the residual stress around the portion. Therefore, Constant Temperature Endurance Test and Thermal Cycle Endurance Test have been conducted under the reactor operating conditions except irradiation to examine the rolled joint integrity. (1)Constant Temperature Endurance Test. In fiscal 1988, Constant Temperature Endurance Test have been performed in the Component Test Loop for 2,033 hours under the reactor operating conditions (pressure 75kg/cm, temperature 280C) for the JP-3 specimen (total testing period 4,033 hours) and the JP-4, JP-5 specimens (total testing period 9,533 hours). After the endurance test it was found by the helium leak test that the rolled joint tightness was maintained enough. Therefore, it was confirmed that the reduction of the residual atress at the rolled joint portion which occurred at the initial stage of the operation did not affect the rolled joint tightness. (2)Thermal Cycle Endurance Test. The helium leak test and the ultrasonic flaw detection test were performed before and after Thermal Cycle Endurance Test (the unmber of thermal cycle increaced from 60 times to 140 times in fisical 1988), of which results showed the integrity of the rolled joint tightness and no crack propagation near the rolled joint portion. Therefore, it was confirmed that 140 times thermal cycle which was the design value for the reactor life of 30 years did not affect the rolled joint tightness and the initiation and propagation of a crack even for the specimen with 200 ppm hydrogen.