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JAEA Reports

Operation and management of the high-pressure gas facility for the tandem accelerator; Maintenance, evaluation of the aging deterioration and action of reducing SF $_{6}$ gas emission

Tayama, Hidekazu; Nakanoya, Takamitsu; Otokawa, Yoshinori; Tsukihashi, Yoshihiro; Seki, Nobuo*; Onodera, Teruo*; Nisugi, Hikaru*

JAEA-Technology 2010-023, 42 Pages, 2010/09

JAEA-Technology-2010-023.pdf:4.81MB

The high-pressure gas facility for the tandem accelerator at nuclear science research institute is the facility to transfer SF $_{6}$ gas between the accelerator and gas storage tanks. The SF $_{6}$ gas is used to keep high voltage insulation of the tandem accelerator. This facility is one of the largest SF $_{6}$ gas handling facilities in research laboratories. This facility has been operated for 31 years. In addition to regular maintenance, we have evaluated the deterioration due to aging. SF $_{6}$ gas is regarded as a kind of green house gases that causes global warming and it is strongly required to reduce such gas emission into the atmosphere in recent years. In JAEA, the reduction of gas the emission is also an important problem. We have been continuously taking action for reducing the emission of SF $_{6}$ gas. In this article, we report the records of maintenance, evaluation of aging, and activity of reducing SF $_{6}$ gas emission.

JAEA Reports

Solution of large underestimation problem in the Monte Carlo calculation with hard biasing; In case with geometry input data created by CAD/MCNP automatic converter

Iida, Hiromasa; Kawasaki, Nobuo*; Konno, Chikara; Sato, Satoshi; Seki, Akiyuki

JAEA-Research 2008-050, 26 Pages, 2008/04

JAEA-Research-2008-050.pdf:1.98MB

An inconvenient experience was encountered, in which we have different answers depending on applied weight window values, in the nuclear analysis of the benchmark problem for CAD/MCNP interface programs, being developed under the ITER R&D task. Biasing can enhance calculation speed, but should not give different answers. Mechanism of this large underestimation is clarified. It is caused by the combination of the following two facts; (1) When one of particles in a history has got lost, MCNP cancels all tallies calculated during the history and all banked particles are thrown away (never tracked). (2) When we have distributed micro geometry errors in input data, important histories, which give significant contribution to tallies, will have many splitting and have "lost particle" with higher probability in the case of hard biasing. These two facts lead to selective canceling of important histories. An attempt to eliminate this inconvenience has been made, by modifying the subroutine "hstory" of MCNP. The modification has been done very successfully and eliminated the large underestimation, giving the same answer independently from applied weight window values.

JAEA Reports

The fabrication of FUGEN 32nd and 32nd (Part2) replacing fuel assembly; Fuel element fabrication Fuel assembly assembling

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JNC TN8440 2001-021, 54 Pages, 2001/11

JNC-TN8440-2001-021.pdf:2.29MB

This in the report about product quantity, product quality that Japan Nuclear Cycle Development Institue produced the Fugen 32nd and 32nd(Part2) replacing fuel elements and fuel assemblies in TOKAI WORKS (fabrication process : lower end plug welding, fuel pellet loading, upper end plug welding, assembling). The first process of 32nd replacing fuel assembly fabrication, that is lower end plug welding, was begun on September 4, 2000, and those fuel assemblies were inspected by METI on January 19, 2001. The quantity of product was 424 fuel elements or 15 fuel assemblies, and the fabrication yield was 99.1% on fuel elements and 100% on fuel assemblies. And the first process of 32nd (Part2) replacing fuel assembly fabrication, that is lower end plug welding, was begun on April 9, 2001, and was finished when those fuel assemblies were inspected by METI on November 22, 2001. The quantity of product was 254 fuel elements or 9 fuel assemblies, and the fabrication yield was 98.8% on fuel elements and 100% on fuel assemblies.

Journal Articles