Identification system by eye retinal pattern is introduced from the view-point of history of R & D, measurement, apparatus, evaluation tests, safety and application. According to our evaluation tests, enrolling time is approximately less than 1min, verification time is a few seconds and false accept rate is 0%.
Evaluation tests at Sandia National Laboratories in USA show the comparison data of false accept rates such as 0% for eye retinal pattern, 10.5% for finger-print, 5.8% for signature dynamics and 17.7% for speaker voice.
The identification system by eye retinal pattern has only three applications in Japan, but there has been a number of experience in USA. This fact suggests that the system will become an important means for physical protections not only in nuclear field but also in other industrial fields in Japan.

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A new method of the fuel burnup measurement using a shielded ion microprobe analyzer (SIMA) has been developed. This method is based on the direct isotope analysis of U, Pu and Nd in an irradiated fuel by means of the secondary ion mass spectrometry. The sample tests on the irradiated fuels up to 13a/0 burnup have shown an accuracy within 6%.
While the conventional isotope dilution method requires the acid-dissolution and the chemical separation of the irradiated fuel by handling samples in a glovebox, the new method can measure the burnup on a fuel in shielded apparatus remotely and directly. Consequently, the time for measurement was reduced to about one tenth of that of the conventional method, and a human radiation exposure became negligible.
A microarea surface analysis by the SIMA provides the local burnup distribution in small area. Using this technique, the radial profile of the burnup distribution due to a thermal neutron depression was obtained in the fuel pellet irradiated in JRR-2 reactor. The radial burnup distribution was also measured in the mixed-oxide fuel pellet of the experimental fast reactor "JOYO" MK-II, which revealed some effects of Pu redistribution on the radial burnup profile.

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A maintenance support system, which utilizes maintenance expert know-how and failure experience, is developed by applying the method of knowledge engineering. The system searches failure causes from failure symptoms by repeating forward and backward chaining. It then estimates the certainty factor of the failure causes by using the certainty factors of the symptoms and of the failure cause-consequence relation, and the occurrence probabilities of candidate causes. The system also provides a plant maintenance scheme based on maintenance priority. Application of the system to the diagnosis and maintenance scheme evaluation on BWR plant control rod drive systems demonstrates the system's usefulness.

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The core configuration of an axially heterogeneous core (AHC) for a 1, 000-MWe-class FBR has been dscussed with control rod maneuvering taken into account, aiming at further improving the core performance.
Current AHC designs in which a disk-shaped internal blanket (IB) with a radially changing thickness is located at the axial midplane are known to be superior to homogeneous core designs in thermal margin, fuel lifetime and safety. This paper proposes a further improved AHC design, in which the number of CRs inserted during operation is reduced by about a half in comparison with current AHC designs and a star-shaped thicker IB region extends between the sparsely arranged CRs. The improved AHC design, in comparison with a current AHC design, has the following advantages:
(1) The maximum linear heat rate is reduced by about 5%, allowing a more compact core design.
(2) Burnup reactivity is reduced by about 7%.
(3) Reactivity due to the up-and-down motion of CRs in seismic events is reduced by about 30%.

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A design method is described for the Fe compensational shield which is located around a straight duct in concrete shield wall against γ radiation to compensate the lowering of shielding efficiency caused by the duct. The method has been applied to the configuration, where the source area is not viewed through the duct from the detector point at the duct exit. The form of the compensational shield was determined depending on the wall thickness, the duct diameter, the incident angle of γ-ray beam to the wall, and the densities of the concrete and Fe. An experiment for the compensational shield was performed in the Dry Shielding Facility at JRR-4. The measured dose rates behind the wall were reduced effectively by the compensational shield, so that the maximum dose rates became only slightly higher than that of the bulk shield wall and the dose rates higher than the maximum dose rate for bulk shield wall were restricted only in the area near the duct exit. The experimental results have been analyzed using a multigroup γ-ray single scattering code G33YSN.

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