[in Japanese]

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This is a progress report on the activities of the Japanese Nuclear Data Committee (JNDC) in the period of April 1993 to March 1995. In this period, the latest version of the Japanese Evaluated Nuclear Data Library, JENDL-3.2, has been released for users after benchmark tests of data therein. Preparation of the special purpose nuclear data files has been also progressed. As special topics, the followings are presented here: (1) the completion and benchmark tests of the JENDL-3.2, (2) progress in evaluating special purpose nuclear data, (3) progress in studying high energy nuclear data, and (4) utilization of nuclear data by means of internet.

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The authors studied the influence of solution depth on the amount of hydrogen released from non-stirred aqueous nitric acid solution with a laboratory-scale 60</sup>Co<sub> γ-ray irradiation apparatus. In the experiment, dose rate was 1.3-6.3kGy/h, nitric acid concentration 1-5M, temperature 10-60°C, and solution depth 5-105cm.
The number of molecules of hydrogen released per energy absorption of 100eV, G(H₂)', decreased with an increase in the solution depth; 0.036(5cm depth), 0.012(25cm), 0.0075(45cm) and 0.0059(65cm) for the case of a dose rate 1.8kGy/h, nitric acid concentration 2.5M, temperature 30°C. The concentration of hydrogen dissolved in irradiated solution measured immediately after completing irradiation increased through a maximum at approximately 20 cm depth, and then decreased with an increase in the solution depth. Moreover, G(H₂)' in case of same solution depth, increased both with a decrease in the dose rate, and with an increase in the solution temperature.

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One of important problems of a current operation support system for a nuclear power plant is that the credibility of its resultant suggestions is not always high sufficiently. The authors have proposed an efficient remedy called "Diversity Criteria" for this issue in the previous works. It employes a variety of information resources and reasoning mechanisms for the system to enhance its entire credibility. Within this framework, a complementary combination of the resources and mechanisms is desired. The work presented here proposes systematic and quantitative measures determining the appropriate combinations. First, concrete and systematic guidelines are proposed for the detailed criteria of "Information Diversity" and "Methodology Diversity". Next, two concepts of "Orthogonality of Identified Result" and "Orthogonality of Utilized Symptom" are presented together with their quantitative measures. These guidelines and measures have been applied to an example of failure diagnosis of a nuclear power plant, and their efficiency has been clearly confirmed.

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The present paper aims at studying the contribution of the second-ordered spatial derivative term to the well-posedness of the two fluid model with single pressure. A numerical experiment based on Hadamard's condition demonstrates that the second-ordered spatial derivative in the momentum equation can make the system well-posed for an initial value problem without regard to the magnitude of the term. Consideration on the eigenvalues has an advantage of knowing the movement of the system from being ill-posed to well-posed. It is derived analytically that the maximum of the real part of eigenvalues is intensively dependent on the wave number and is inversely proportional to the coefficient of the second-ordered derivative.

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