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How surface-feeding albatrosses feed on deep-sea squids has long been a mystery. We investigated foraging behavior during daylight hours of 20 Laysan albatrosses Phoebastria immutabilis breeding in Hawaii using GPS- and camera-loggers. The birds traveled to the North Pacific Transition Zone up to 600 km north of their breeding site. The camera images showed that Laysan albatrosses fed on large (～ 1 m body length), intact floating dead squids (6 events) and floating fragmented squids (10 events) over deep oceanic water (>2000 m) while they flew in a straight path without sinuous searching. Feeding events on squids were not observed during trips when fishing vessels were photographed and seemed to be distributed randomly and sparsely. Thus, this study suggests that Laysan albatrosses found large, presumably post-spawning, squids opportunistically while they were traveling during daylight hours. Although we did not find cetaceans in our surface pictures, we could not rule out the possibility that birds fed on squids, especially fragmented specimens, in the regurgitates of cetaceans at depth. This study demonstrates the usefulness of combining animal-borne GPS- and camera-loggers on wide-ranging top predators for studying the distribution of little known deep-sea squids and their importance in the diet of marine top predators.

In order to perform the parametric survey for an accelerator-driven system (ADS) core with the subcriticality adjustment mechanism, a new calculation code system, ADS3D, was developed on MARBLE which is a comprehensive and versatile framework for reactor analysis. The application of ADS3D was also demonstrated on the neutronics design of ADS operated by control rod (CR) movement. Through the neutronics calculation, it was shown that the maximum proton beam current was decreased from 20.5 to 11.6 mA due to the switch from beam-operated to CR-operated core.

The conceptual design study of the beam window of the spallation target is one of the critical issues in the R&D of the accelerator-driven system (ADS). In this study, the investigation to create a feasible concept of the beam window for the ADS was performed by changing the proton beam profile from the Gaussian distribution to the parabolic and the flat distributions. Detailed analyses were performed by considering the particle transport of protons and neutrons in the spallation target region, the thermal hydraulics of lead bismuth eutectic (LBE) around the beam window, and the structural strength of the beam window. The calculation results showed that the difference in the temperature between the inner and outer surfaces at the top of the beam window was reduced by changing the beam profile from the Gaussian to the parabolic and the flat distributions. By this reduction, in the parabolic case, the thermal stress at the top position was also reduced and the buckling pressure increased by about 20%. On the other hand, in the flat case, the thermal stress at the peripheral region instead of at the central position increased and the buckling pressure slightly deteriorated. The buckling mode was also changed in the flat case. From these calculation results and discussions, it was confirmed that all three cases, the Gaussian, the parabolic, and the flat, were feasible and it was concluded that the concept with the parabolic distribution would be the most feasible under the current ADS design condition.

An accelerator-driven system (ADS) has been investigated to transmute minor actinide (MA) included in high-level waste. In the neutronic design of the ADS, the accuracy of nuclear data for MA and lead bismuth (LBE) which is the candidate material for coolant and spallation target, is important. To know the current accuracy of nuclear data libraries, this study aims to compare representative nuclear data libraries, JENDL-4.0, 3.3, ENDF/B-VII.1 and VII.0 through the neutronic calculation of the ADS geometry proposed as the IAEA benchmark problem. The calculation results showed that about 1.1%dk, 0.7%dk and 2.7%dk differences were observed between JENDL-4.0 and ENDF/B-VII.1, ENDF/B-VII.0 and JENDL-3.3 at the beginning of cycle, respectively. These results mean that the current nuclear data libraries are still insufficient for the neutronic design of the ADS. The enhancement of nuclear data libraries by cross section measurement is required and, moreover, integral experiments with MA and LBE isotopes are essential. Received: 29 June 2012; Revised: 22 August 2012; Accepted: 30 August 2012