The potential of CO₂ emission reduction is analyzed by the MARKAL model for the Japanese energy system in the time horizon 1985-2030, taking into account such reduction measures as energy conservation, fuel switching, and technology substitution. Among them, nuclear energy utilization is found to have a large CO₂ reduction potential, i.e. from 10% reduction of the total emission in 1990 to the levels of 16%, 21% and 42% in years 2000, 2010 and 2030, respectively, through electric power generation and process heat application.

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This is a progress report on the activities of the Japanese Nuclear Data Committee (JNDC) in the period of April 1989 to March 1991. In this period, JENDL-3 (the Japanese Evaluated Nuclear Data Library, version 3) and the JNDC FP Nuclear Data Library-Version 2 have been released for users after completion of extensive checking and integral tests of the data therein. New activites have been initiated to meet the wider range of new requirements for nuclear data. As special topics, the followings are presented here; (1) the completion of the JENDL-3 FP File, (2) the current status of the Special Purpose Nuclear Data FileS, and (3) international cooperation on nuclear data evaluations.

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Alloy design, manufacturing and evaluation testing have been conducted to apply the ferritic/martensitic steel with superior swelling resistance for FBR core materials. This development was carried out with emphasis on the improvement of irradiation stability and high temperature strength of 12Cr type ferritic/martensitic steels.
The optimized composition for ferritic/martensitic steel is Fe-0.12C-11Cr-0.5Mo-2W-0.4Ni-0.2V-0.05Nb-0.05N. To satisfy the requirements for cladding and wrapper tubes, the most suitable heat treatment for normalizing and tempering are 1, 100°C/780°C and 1, 050°C/700°C, respectively. This steel named PNC-FMS exhibits the highest level of high temperature strength among the ferritic/martensitic steels applicable to FBR core, and maintains a superior characteristics under the conditions of fast neutron exposure and high-temperature flowing sodium.

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A cryopump system for JT-60 neutral beam injector (NBI) is composed of 14 cryopumps with the largest total pumping speed of 20, 000m³/s in the world, which are cooled by liquid helium through a long-distance liquid helium transferline of about 500m. An automatic control method has been developed and tested of the 14 cryopumps in cool-down and steady-state modes. Features of the automatic control method are as follows:
(1) Suppression control of the thermal imbalance in cooling-down of the 14 cryopumps.
(2) Stable cooling control of the cryopump due to liquid helium supply to six cryopanels by natural circulation in steady-state mode.
(3) Stable liquid helium supply control for the cryopumps from the liquid helium dewar in all operation modes of the cryopumps, considering the helium quantities held in respective components of the closed helium loop.
In the automatic operation of the cryopumps by the newly developed control method, the cool-down of 14 cryopumps was completed in 16h from the start of cool-down of the system and the cryopumps was stably cooled by natural circulation cooling in steady-state mode.

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Heated turbulent gas flow in an annular duct is numerically analyzed using the k-kL-uv 3-equation turbulence model. Special attention is paid to the laminar-turbulent transitional region. In the case of outer tube only heated, heat transfer coefficient in downstream becomes constant and a new correlation, which is independent of the heat flux, is proposed. The similar result is obtained in the case of inner tube only heated. In the case of both inner and outer tubes heated, laminarization does not occur under the condition of the heat flux less than a certain magnitude on one tube and it does not depend on the heat flux magnitude on the other tube. The flow regime of heated annular duct is classified into the following four regions based on heated conditions of inner and outer tubes: (1) TT region (heat transfer coefficients in both tubes are expressed by St_b∝Re_b^-0.2), (2) LT region (heat transfer coefficient in inner tube becomes constant), (3) TL region (heat transfer coefficient in outer tube becomes constant) and (4) LL region (laminarization occurs).

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