[en] Purpose: To repair fuel elements that became failed during burnup in a reactor or during handling. Method: After the surface in the vicinity of a failed part of a fuel element is cleaned, a socket made of a shape-memory alloy having a ring form or a horseshoe form made by cutting a part of the ring form is inserted into the failed position according to the position of the failed fuel element. The shape memory alloy socket remembers a slightly larger inside diameter in its original phase (high-temperature side) than the outside diameter of the cladding tube and also a slightly larger inside diameter of the socket in the martensite phase (low-temperature side) than the outside diameter of the cladding tube, such that the socket can easily be inserted into the failed position. The socket, inserted into the failed part of the cladding tube, is heated by a heating jig. The socket recovers the original phase, and the shape also tends to recover a smaller diameter than the outside diameter of the cladding tube that has been remembered, and accordingly the failed part of the cladding tube is fastened with a great force and the failed part is fully closed with the socket, thus keeping radioactive materials from going out. (Horiuchi, T.)

[en] In a fuel assembly in which a water rod or water channel is disposed in the central portion of its arrangement, solid moderators are disposed in the water tube corresponding to an upper portion of the effective fuel length of the fuel assembly. In other words, the portion corresponding to the position of a conventional water tube where steams are generated is occupied with the solid moderators to exclude the presence of steams. In the axial segment of the water tube in which the solid moderators are disposed, the inside of the water pipe always has a composition of the solid moderators, and it does not change depending on the output and the flowrate. Accordingly, the reliability of the designed calculation for the change of the distribution of the enrichment degree and the distribution of burnable poisons due to burning, and the power distribution is not deteriorated even during operation at low flowrate and low output. (T.M.)

[en] The core stability measurements were taken during the cycle-9 startup of the 1,300 MWe BWR, Kernkraftwerk Kruemmel (KKK). The core contained advanced 9 x 9 type high burn-up design reload fuel with a higher enrichment than current 8 x 8 fuel. A design feature of the advanced 9 x 9 fuel assembly (FA) is a large square water channel for enhanced neutron moderation. The measurement data as a function of core flow and power showed almost the same stability characteristics as those of the past measurement during the cycle-3 startup of the KKK core with the 8 x 8 FA. The local power range monitors (LPRM) detected neutron flux oscillations in both core-wide in-phase and half-core out-of-phase modes. The frequency-domain stability analysis using the STAIF-PK code well reproduced the measurement result that the onset of unstable operation in KKK first occurs when about half of the reactor internal pumps are operating and the other half are stopped. The stability performance of the advanced 9 x 9 FA in the core was compared with the 8 x 8 FA by a design parameter analysis with respect to thermal-hydraulic and neutronic design. It has been demonstrated by the analysis that the stability performance of the advanced 9 x 9 FA is comparable with current 8 x 8 FA. (author)

[en] The Rhodotron TT300, installed in a customer site last year, has two electron beam output ports of 10 MeV and 5 MeV, and produces beam of 200 kW and 150 kW output power of 10 MeV and 5 MeV, respectively. With the X-Ray target in the 5 MeV port, it makes available a high irradiation of X-Ray on the customer's products. The system of Rhodotron TT300 is reviewed in this paper with including a viewpoint of its operation and maintenance. (author)

[en] Penetration range and depth-dose distribution of 10 MeV electrons within commercial packages of experimental animal feeds were examined with a high power electron accelerator for verification of the application of high energy electron beam irradiation to sterilize experimental animal feeds. Optimum packaging sizes were proposed based on the experimental results. The change of the vitamins and the efficacy of the sterilization by the irradiation were also studied. It is confirmed that the sterilization of experimental animal feeds by 10 MeV electron beam has been completely practical. (author)

[en] Acrylic fibers containing alumina-zinc silicate were irradiated by electron beams at doses of 3-24 kGy to sterilize them. Irradiation at the dose of 3-15 kGy stimulated the antibacterial activity of the acrylic fibers, and their bacteriostatic and bactericidal activity values became higher than those of non-irradiated fibers. At the dose of 24 kGy, however, antibacterial activity was not enhanced. Next, instead of fibers containing antibacterial agents, three different antibacterial agents were irradiated by electron beams to study the activation of antibacterial activity. However, none of the irradiated agents showed a significant difference from the non-irradiated ones. The mechanism of activation of antibacterial activity is thought not to be by the activation of metal ions themselves. This study showed that fibers irradiated by a certain amount of 10 MeV electron beams have greater antibacterial activity than non-irradiated fibers, and also clarified the optimum irradiation dose range for fiber products. (author)